Recent Research on Geotechnical Engineering, Remote Sensing, Geophysics and Earthquake Seismology

This article intends to present the advantages of including activities of a practical nature, in curricular units of Soil Mechanics and Rock Mechanics, both in undergraduate and master’s degrees in Civil Engineering, or in the development of master’s theses. The creation of a reduced scale physical model of a reinforced soil structure with tires is presented. The didactic aspects of the development of a work within the service carried by ISEP’s Construction Studies Center (NEC) are also described. In addition, a coastal geotechnical study, developed by an undergraduate Civil Engineering student in ERASMUS mobility, is reported. The examples described involved several students and the results achieved, evidenced by the permanent interest they showed throughout the development of their studies and the excellent marks they obtained in their final evaluations, attest to the effectiveness of this teaching strategy with a strong practical component.

Surface coal mining involves excavating the overburden material, typically dumped in massive spoil heaps; appropriately managing and reclaiming these areas is a global priority. Time-dependent settlements are a crucial challenge to any efficient reclamation, such as renewable energy systems or civil infrastructure. Several studies examined the geotechnical stability of spoil heaps, but very few include characterization of the spoil material, and none a time-dependent settlements’ analysis. This work simulated time-dependent settlements as self-load 1D consolidation settlements to model the spoil response and predict their completion time and magnitude. The Finite Element Method was used for the consolidation analysis implementing the Hardening Soil model for the spoil. The calibration of the model parameters was based on a multipoint settlement gauge with two-year measurements from a massive spoil heap of 136 m in Northern Greece. Validation of results has been primarily based on secondary in situ measurements of surface markers spanning a larger period and on in situ and laboratory geotechnical testing. The numerical simulation fitted the multipoint settlement gauge measurements well, while the parameters were within the range of the geotechnical testing results. The simulation results agreed well with the validation measurements, further supporting the model’s parameters. The settlement completion time was calculated at 22 years, denoting the heap’s massive nature and the material’s fine-grained nature. Overall, the consolidation analysis of the spoil heap’s time-dependent settlements, serving as a paradigm for similar cases, provides valid lessons and results according to the available measurements and can serve as a design basis, at least on a preliminary evaluation.

In this study, a procedure to perform a time-domain deconvolution in nonlinear elastoplastic materials has been proposed. The aim is to develop accelerograms at the base of a finite element model (FEM) from surface records to perform soil-structure interaction analyses. This procedure is based on finding a relationship between the surface response and the surface target spectrum, modifying the input signal at the base through a spectral matching technique until obtaining a surface response compatible with the target spectrum. To this end, a FEM of a soil deposit, considering its nonlinear properties and ground motion records from the L’Aquila earthquake, was used to validate the methodology; a Eurocode 8 design spectrum was used as the target. It was found that the procedure produces input signals at the base that generate surface spectra similar to the target spectrum, with errors lower than 10% for all considered periods. Results obtained demonstrate the usefulness of the proposed methodology.

Investigations carried out on pottery in the Draa-Tafilalet (DT) region have shown that this activity is subject to many constraints linked particularly to the depletion of natural resources, lack of workforce, and the quality of the final products. This study contributes to the recognition, characterization, and valuation of clay materials in the DT region in order to control a sustainable supply for local potters. To do this, various analyses are carried out, particularly at the lithological, mineralogical, chemical, and technological characteristics of the clays exploited in pottery, as well as data relating to the estimated reserves in the supply zones. The clays are harvested in different geological contexts from four provinces covering different Saharan structural domains. The analyses generally show a loamy to sandy-loamy composition with a clay fraction not exceeding 14%. Most materials have a plastic character (15 < PI < 40). The identified minerals are dominated by quartz, total clay, goethite, calcite and feldspars. The clay fraction is composed of illite, chlorite, kaolinite, smectite, and palygorskite. The collected data are processed in chemical, mineralogical and granulometric diagrams to test the suitability of these materials for use in ceramics. Medium-quality samples were balanced in formulations to improve their pottery making ability. It shows that, despite qualitative fluctuations, DT clays can be used in pottery, subject to adjustments relating to manufacturing processes and firing conditions. The amount of clay consumed annually by potters remains very modest (~ 3000 tons/year) compared to potential clay reserves estimated at 30 million tons.

The subject of this paper is the way, in which the amount of cement and the curing time influences the parameters of shearing resistance of clay soil obtained through the direct shear experiment that is routinely conducted in geotechnical laboratories. The direct shear test was performed on silty clay soil samples compacted according to the standard Proctor test, with the compaction degree equal to 95% of the maximum achievable compaction. The shear strength of samples containing 0, 3, 5, 7, and 9% of added cement was tested, and for curing times of 3, 7, and 14 days. The drained shear strength parameters ϕ′ and c′ were obtained by processing the results in Excel. The drained cohesion increases with increasing the percentage of cement and curing time. The internal friction angle increases with the increase of the percentage of cement up to a certain limit, while a decrease in the internal friction angle value is recorded between 5 and 7% of added cement. In contrast to cohesion, the internal friction angle decreases with the extension of the curing time of the samples.

This study investigates the changes in the strength of Nigde marble irradiated by microwave energy. The uniaxial compressive strength (UCS) and the Brazilian tensile strength (BTS) tests were carried out on the untreated samples and on the samples which were microwave treated at 6 kW for a duration of 5 min. The tests were carried out on both dry, semi-saturated and saturated samples. After the irradiation of the samples by microwave at 6 kW power for 5 min, while the temperature reached about 215 °C for the dry specimens, the temperatures of the semi-saturated and fully saturated specimens raised to about 230 °C and 250 °C, respectively. The strength decrements in the UCS samples are 10.9% and 35.4% for the dry and saturated conditions, respectively. The strength decrements in the BTS samples are 30.4% and 37.7% for the dry and saturated conditions, respectively. The UCS value of the treated dry specimen decreases slightly. On the other hand, the UCS values of the treated samples decline steadily with the increasing saturation degree. The BTS value of the irradiated dry specimen decreases rapidly. The BTS value of the saturated specimens after the treatment declines slowly with the increasing saturation degree that the UCS and the BTS specimens show different behavior under the microwave treatment is probably due to the size effect. Concluding remark is that the microwave treatment has important effect on the strength of Nigde marble.

Numerous land protection techniques are available but all of them are not always suitable due to various factors such as resource limitations, cost-effectiveness and environmental impacts. This research work aims to focus on the protection of char land (small river islands) which are highly erodible and unstable due to high tidal flow and flood actions. Bioengineering technique is effective in increasing bed roughness. In this context, vetiver grass (Chrysopogon zizanioides) has been selected for its special characteristics such as fast growth, submergence tolerance and long root system. Even though there has been studies on the roughness coefficient (n) of vegetated soil, there is still gap in study on char land. For this purpose, a small-scale physical model-based experiment and theoretical studies were conducted. A rectangular wooden model with a dimension of 3.0 m × 0.7 m × 0.6 m filled with char soil and a mild bed slope of 1:60 was constructed. Vetiver tillers were planted with a spacing of 20 cm c/c in both directions. Model tests were conducted after 140 days of vetiver plantation varying the discharge in the range of 0.000111–0.000138 m3/s to determine n. The vetiver root system grew to a depth of 50 cm and anchored the bed soil. Vetiver shoots grew up to 127 cm and retarded the flow velocity and also increased the surface roughness and flow depth. Theoretical relationships have been established using Manning’s roughness equation, and Strickler’s formula for determining the Manning’s Roughness Coefficient, n of the char land for a discharge range of 0.002–0.004 m3/s. Manning’s roughness coefficient was found to be in the range of 0.03–0.07 for different roughness heights. It is concluded that vetiver grass plantation is effective in char land protection and reclamation by increasing roughness, retaining soil and reducing erosion.

The study of earth movements and their occurrence factors contributes positively to the reduction of damages resulting from disasters caused by landslides, falls or alluvium. The investigation of early warning systems for landslide events that is developed for this case uses main variables for the generation of movement. In this case, the main conditioning factor is the slope, and the triggering factor is the precipitation, measured through the daily precipitation history of the mountain town of San Jose de Maipo, Chile. Using fuzzy logic rules, an algorithm capable of establishing logical relationships between variables with a prediction accuracy ratio of over 88% is developed, which implies that the applied model is efficient at the time of detecting a real warning signal.

High soil retaining walls as well as deep water berths of solid construction need to be anchored in order to provide structures’ stability and required bearing capacity. Traditional anchor systems for such facilities in many cases are resource demanding and costly. An innovative (patented) design of the anchor system is worked out. Anchor bearers are made of “comb” type as several small anchor plates fixed along the rigid core. Anchor force is taken by all plates of the comb simultaneously. Distance between anchor plates on the rigid core may be regulated to achieve the maximal positive effect from the point of view of anchor system bearing resistance. Other adjustable parameters are angle between the plate and the core axis and plate sequence (if plates are of different height). Study of the innovative anchor system included both physical (in laboratory conditions by use of soil box in scale of 1:20) and numerical modelling. Based on the executed study, the basic factors that determine the bearing capacity of both the anchor device and the whole structure (the depth of the anchor bearers, the angle of anchor plates’ inclination, the number of plates, the height of the various plates in the “comb” and the order of their location in the device) are analysed. As it was demonstrated by our research, proposed design approach provides increasing bearing capacity both of the anchorage and of the soil retaining structure in whole (keeping the same material consumption for the anchorage as at the traditional solutions with one large anchor plate or with anchor sheet pile wall). On the other hand, proposed structure may provide decreasing of the material consumption (keeping the same structure’s bearing capacity as at the known facilities).

With the development of great depths of the sea and the need to drill deep wells from stationary platforms, the issue of using an anchor fastening design with a large bearing capacity became acute, and for this purpose, a combined type design was proposed. The design feature is that a metal pipe driven into the upper layer of weak soil of the sea bottom, through which a well is drilled to the required depth, forms an ordinary bored pile in the lower part, followed by filling the entire internal cavity with cement mortar to the level of the platform, inside which the platform is installed tubular metal anchor. The purpose of this design was to reduce the length of the anchor fastening in the ground with the same bearing capacity due to additional pouring with cement mortar. At the same time, to assess the bearing capacity of such a structure, a calculation model is used, which consists of the fact that the cement slurry, before hardening, produces lateral pressure on the walls of the wells, similar to hydraulic pressure, and the reaction from the soil is taken equal to this pressure, and it remains unchanged in magnitude even when the cement slurry hardens. As for the bearing capacity of the butt, the solution of the problem obtained for a round stamp pressed into an elastic–plastic body is used for it. Taking into account also the bearing capacity of the clogged part of the structure, calculation formulas were obtained to determine the bearing capacity of the combined anchor fastening. According to the regulations on environmental protection, drilling works are carried out with seawater and a solution made from natural clay, the resulting slurry does not contain harmful toxic substances and it is allowed to be thrown to the bottom of the sea as it does not pollute the environment. Pouring this solution to the bottom of the sea does not violate the requirements of the legislation on protecting the economic importance of water bodies and the natural local conditions inhabited by living organisms from an ecological point of view.

The rapid economic growth of the town present the matter of water issue as very important problem in terms of human life, construction life, agriculture, etc. … This study is to predict techniques of foundation construction through the displaying of the water table at the flow direction in the town of Kumba and GIS. It is characterized by a significant research question which is the level of fall and rise in groundwater levels within the town of Kumba and this influence on choice of types of foundation in construction. This study is directed to decision-makers and technicians of the construction field to develop policies facilitating the supervision when building construction foundation by informing about water level depth and its flowing direction in the town. To achieve this, depths of static water levels were measured in over 200 randomly selected hand-dug wells in Kumba, after their geolocation and data were collected during the dry season (November and March 2017) and during the rainy season (between April and October 2017). Data were analyzed and treated using Microsoft Excel and GIS software us as Golden Surfer, Global Mapper, and ArcGIS. The results show us the water table contours of the city in dry and rainy seasons which vary between 26.1 and 2.0 m. Quarters such as Kumba-Mbeng and Meboka Streets have water levels ranging between 0 and 4 m in the rainy season and deeper above 5 m in the dry season. This variation of water level in the areas of Kumba may threaten foundation construction that why in those areas shallow foundation are not advice if the constructed structures is important only deep foundation is suitable. In Kumba Station, Mile 1, Bulletin Street (Fongong Quarter), and parts of Fiango show that water table is to deep water and proper for the shallow foundation but very hard for water supply through borehole. Groundwater flow direction was revealed to be toward the south and southeastern parts of Kumba. The significance of the study is to propose to the technician the direct application on the field of chosen types of foundations according to the quarter and proposed groundwater supply possibilities.

Since dams are built on rivers generally to store water, they also store solid materials from floods. These materials settle and consolidate to create enormous quantities of mud, hampering the normal functioning of the structures and threatening the safety of the dam and surrounding populations. In addition to preventive solutions reducing this siltation phenomenon, dam managers often opt for desilting reservoirs as a curative solution. This solution produces enormous quantities of mud to be stored in landfills so far from the watercourse and dam reservoir, causing enormous environmental damage and considerable loss of land. Given the increasing scarcity and rising costs of various raw materials, the utilization of this mud as a valuable resource in diverse sectors including civil engineering, agriculture, crafts, and environmental applications has become imperative. An optimal approach to recover the mud extracted from dam reservoirs is designed and presented in the present article. This approach, which is the result of our research on mud valorization experiences around the world, is based on the definition of the characteristics to be studied, the tests to be carried out on the mud and the limit values to be observed, and on a diagram of the procedures to be followed in the valuation process. To show the canvas for using this approach, the present research work summarizes a case study carried out in the Moroccan context. This case study is based on the inventory of the experiences of some Mediterranean basin countries to define the possible uses of mud and on the laws and regulations of Morocco to choose the laboratory tests to accomplish and the limit values not to be exceeded. As a result, a guide for valuing mud extracted from dam reservoirs has been developed. It is composed of three elements: A grid of tests to accomplish on mud and limit values to observe, a matrix of characteristics to study for each intended use, and a diagram of the optimal approach to follow. It is a framework that Moroccan dam managers can follow to gain part of the cost of desilting operations. The guide can be adapted to other countries by replacing the limit values of the standards used in Morocco with those of the country in question.

Around 30 Mt of phosphogypsum are generated annually in Morocco. It is a by-product from the phosphoric acid industry where the majority is stockpiled by Jorf Lasfar and Safi plants. The purpose of this study is to characterize Moroccan phosphogypsum on the physico-chemical, mineralogical, morphological, geotechnical, and environmental level in order to assess its suitability as a road material. To this end, several techniques have been implemented, namely: X-ray fluorescence and X-ray diffraction (XRF/XRD), laser granulometry, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), proctor and oedometer tests as well as radioactivity and leaching tests. The results showed that Moroccan phosphogypsum has a pH of about 3.45, a fine grain size (< 200 μm) marked by the presence of parallelepipedic crystals. Chemical and mineralogical analyzes showed that phosphogypsum is mainly composed of dihydrate gypsum (86%), but contains impurities such as quartz, heavy metals, and radioelements from phosphate rock, in addition to some acid residues due to the transformation process. These impurities constitute the main source of pollution linked to the storage of phosphogypsum insofar as heavy metals can migrate from the heap to the groundwater and the radionuclides can decompose and pose risks to human health. From a geotechnical point of view, phosphogypsum is a low-density material with compressive behavior and low resistance to immersion due to the solubility of gypsum which further increases owing to its acidic nature. Although the radiological indices relating to phosphogypsum allow its use in road engineering, this is not possible given its sensitivity to water variations which could impact its bearing capacity as well as the risk of leaching of contaminating elements. Thus, for phosphogypsum to be valorized in road engineering, it requires a treatment in order to stabilize its behavior, in particular the improvement of its resistance to compression and immersion. Lime–fly ash treatment is a promising solution for a use as a road base material.

This paper concerns the development of a new protection technique to improve simultaneously the waterproof or the impermeability, the thermal insulation, and the bearing capacity of flexible pavement structures. The technique consists on the introduction of a layered system composed of three different materials into the pavement structure, in this case: Foamglas material, XPE foam laminated Alufoil, and geotextile Terram 2000. The new protection technique is believed to limit frost penetration in the frost susceptible subgrade soil, reduce significantly road network damages associated to differential heaving and bearing capacity loss during seasonal temperature variations, restrict water infiltration, and thus reduce considerably the associated damage and the rehabilitation costs. Furthermore, a procedure was developed for the determination of the thicknesses different layers of the improved flexible pavement structure.

Weathering processes due to heating and cooling, wetting and drying cycles, salt decay, and acidic rains (atmospheric pollution) can affect the durability and long-term behavior of rock masses and aggregates. The resistance of rocks to weathering can be described using a durability parameter referred to as slake durability index. The main purpose of this study is to evaluate the influence of weathering processes simulated by heating and cooling and wetting and drying on the durability of fine-grained and porphyritic granites rocks from Ado-Ekiti, southwestern Nigeria. Petrographic and physical tests were carried out on the rocks using appropriate international standards. The slake durability test followed the procedure stipulated by ASTM D4644 standard was performed. The test cycles were conducted in wet (with distilled water) and dry (without water) conditions. The granites contain minerals such as quartz, microcline, hornblende, biotite, and muscovite. The fine-grained granite has lower water content, water absorption capacity, and porosity compared to porphyritic granite. The rate of mass loss decreases as the number of slaking cycles increased. This rate of mass loss is found to be higher at the early cycles than the final cycles. The maximum mass loss was observed in samples used for wet slake durability test. Slake durability indices of the granitic rocks decreased as number of slaking cycles increases and is higher in dry test than in wet test. Comparison between the results of dry and wet slake durability tests show that the effect of water on the rate of rock degradation differs in both rocks. The porphyritic granite is sensitive to water in terms of their slake durability compared to fine-grained granite. This may be attributed to the variation in physical properties of the granitic rocks.

Over-excavation in underground opening is one of the most significant geo-mechanical hazards in mining and civil projects with potential consequences including cost overruns, time delays, increased rehabilitation, grade dilution, equipment damages, injuries, loss of human lives, and social or environmental consequences. The main objective of this study is to detail study the role of non-controllable parameters, namely rock type, geometrical, topological, kinematical and geo-mechanical properties of the discontinuity network, and in-situ stress on over-excavation around a tunnel of El Teniente Mine. To this end, we investigate the role of each of these parameters on the over-excavation around tunnel using cause–effect approach. We performed extensive sensitivity analysis using Monte Carlo simulation techniques of discrete fracture network and carry out the rigid block failure analysis to capture contribution of the non-controllable parameters on the kinematic state of the rock blocks. It is worth to mention that we assume that the constant value of in-situ stress around tunnel due to low coefficient of variation of the in-situ stress around tunnel (less than 5%). The rock type does not show a significant impact on the over-excavation. The mutual interaction between the induced stress around tunnel and discontinuities shows a significant correlation with observed over-excavation around tunnel. We used the microseismic data to study the potential correlation between over-excavation, fracturing process, and the non-controllable factors. According to the results of this study, the pre-existing discontinuities and their mutual interaction with induced stress around tunnel are the key factors on variational trend of the over-excavation along tunnel at El Teniente mine.

Geological and geotechnical studies have been usually based on experimentation, analytical analysis, graphical representations, and numerical modeling. However, with the development of the artificial intelligence field and the sharp increase of its applications, using machine learning and deep learning methods has gained a significant importance in these studies. Within this context, this paper presents, first, an overview about recent research articles that studied the application of machine learning approaches to rock mass studies. Second, a case study of rock mass joint sets identification at Draa Sfar mine in Morocco is presented. Based on a database of 400 measurements of dips and dips directions for different rock mass discontinuities such diaclases and schistosity, a comparative study between stereographic projection as a classical method and K-means clustering as an unsupervised machine learning method is established, to identify the mine’s main joint sets. The results show that the clustering of the joints sets through both two methods is concordant. However, the use of stereographic projection for joints sets identification does not need prerequisites while K-means clustering presents the limitation of requiring the initial number of clusters as an input. In this case, the use of pre-analysis methods, such as the elbow method or the silhouette score, is mandatory. In addition, both of the methods need sufficient number of inputs in order to give accurate values of joint sets’ spatial orientation characteristics. To sum-up, our comparative study shows the advantages of classical modeling for rock mass joint sets identification, but also introduces the potential and the limitations that have one of the clustering algorithms within this topic. The challenge now is to train and test more sophisticated artificial intelligence methods that will allow advanced analysis of geotechnical and geological data, to confirm if these tools can partially or entirely substitute classical modeling.

Coal surface excavations create wastes, typically dumped in nearby areas forming massive spoil heaps. Several reclamation options have been proposed, including constructing linear civil infrastructure. Evaluations on this reclamation type have not been presented in the literature as the necessary geotechnical characterization of the spoil material is generally lacking, and various literature, design standards, and regulations are included. In this work, the potential of constructing a railroad or a highway on a massive spoil heap in Greece is assessed based on the geotechnical characterization of the spoil material. The soil body is highly heterogeneous due to the extraction and deposition processes related to the heap’s construction. Thus, the soil mass was considered one unified spoil material with significant uncertainty for a preliminary assessment. The representative material of the spoil heap is high plasticity silt (MH for USCS). The mean values of the constraint modulus (Es) for 100–200 kPa, the compression (cc), and recompression (cr) indices were determined through 1D consolidation tests as 2.7, 0.216, and 0.37 MPa, respectively. The most significant property of the subgrade’s suitability for road or railroad construction is stiffness, quantified through an elastic modulus (e.g., the resilient modulus). Each country’s regulations specify the minimum subgrade stiffness requirements for railroads; spoil stiffness is significantly smaller than the minimum requirements. Moreover, based on soil classification, worldwide standards qualitatively characterize the highway subgrade and its potential; high plasticity silt—the representative spoil material—is generally unwanted as a subgrade material for highways. Additionally, considering the resilient modulus and the CBR, the spoil results are far below the minimum requirements. Overall, the spoil material is too soft to withstand linear infrastructure without ground improvement.

The ever-increasing global energy consumption leads to a rise in demand for renewable energy sources and storage solutions. Nevertheless, in several cases energy is not sufficiently stored and dissipates unused (e.g., waste heat from air conditioning systems). This results in increasing the air temperature, especially in urban areas. Underground thermal energy storage (UTES) systems can be used to utilize underground soil to store unused energy for use when needed (e.g. district heating). The objective of this paper is to investigate the implementation of a UTES system in the 2D finite element software PLAXIS. Furthermore, the modelling approach used for thermally insulating the storage tank by using improved diaphragm walls was evaluated. In case of a UTES system, it is necessary to model a heating phase in which the storage stores energy for later use. For this purpose, different modelling approaches were investigated. Each analysis aimed to heat the storage reservoir to 90 °C. Afterwards, the difference in temperature distribution in the soil was investigated. Moreover, the influence of the thermal properties of the diaphragm walls on the temperature distribution was reviewed. Concrete with a density of 2400 kg/m3 was compared to a lightweight concrete developed at the Institute of Structural Concrete at Graz University of Technology. The thermal properties of the lightweight concrete were determined based on laboratory tests. The lightweight concrete had a thermal conductivity of 1.026 W/m K, which led to a significant reduction in heat losses from the storage.

Impervious surfaces change the natural hydrology due to lower levels of water infiltration, increasing stream peak flows and flood risks. Concentrated storm water runoff over the landscape can contribute to pollutants and contamination of drinking water, streams and aquifers. In the past decade (2010–2020), the North Central Province of Sri Lanka has experienced a series of anomalously severe flash flood events during annual monsoon rain from December to January. While regional paddy production has experienced successes and failures, the failures have dominated due to adverse climate conditions. This study aims to develop supervised machine learning-based geospatial analytics models to classify spatial and temporal impervious surface cover changes. Following the literature on remote sensing in conjunction with machine learning, we deploy Google Earth Engine-based machine learning algorithms under the localised climate zone (LCZ) classification workflow approach to predict the imperviousness of surfaces in the northern part of Sri Lanka during 2013–2020. The ground truth for the training data set is established via Google earth images and field survey data extracted from urban areas such as the Anuradhapura and Polonnaruwa districts of the North Central Province. Random forest (RF) and classification and regression tree (CART) classifications were used to train and test the data extracted from the Landsat imageries. CART classification gives promising results. Performance measures (F1 scores) for impervious, vegetation, water, agriculture and bare lands are 0.71, 0.96, 0.96, 0.91 and 0.91, respectively. The predictive model with a pixel density analysis conducted at the lowest level of local administrative divisions appears practically and conceptually appealing to aggregated and disaggregated urban systems.

The analysis of the structural health response of the Beirut port silos, two years after August 4, 2020 explosion, is presented in this chapter. This work evaluates the structural response of the remaining standing silos caused by the blast loading using 3D laser scan measurements, performed every couple of months, and live monitoring of the silos’ tilt changes carried out using four ultraprecise triaxial inclinometers installed in strategic locations on the North and South silos’ blocks. The tilted silos are then modelled using Abaqus to test the status of the silos under different earthquake loadings. Therefore, the objective of the performed study is not only to assess and monitor the real condition of the remaining standing silos, but also to check their status and prevent their catastrophic failure under seismic conditions. The results indicate that till March 2022; the North block silos have been rotating vertically by a rate of 0.85 mm/day since the day of the explosion while the South block got stabilized. This rate varies with bad weather and sharp changes in temperature. Moreover, the triaxial inclinometers’ results indicate that the displacements of the monitored silos have increased in the last couple of months to reach 45 cm on silo#84 in July 2022. The obtained results show that the remaining standing silos will exhibit serious damage and possible failure in case of moderate intensity earthquakes.

The Mediterranean Region of Turkey has simultaneously witnessed intense wildfires throughout the summer seasons, resulting in many fatalities and injuries, linked to global warming and climate change. In the region, Antalya is one of the most vulnerable provinces to forest fire activities due to its climatic and anthropogenic conditions. In this chapter, three ensemble-based machine learning algorithms, including Extreme Gradient Boosting (XGBoost), Random Forest (RF), and AdaBoost (AB) were applied to model wildfire susceptibility of the Antalya province situated in the southern coastal zones of Turkey. For this aim, an inventory map was initially constructed by using the publicly available MODIS data retrieved from NASA’s Fire Information for Resource Management System between 2001 and 2020. Also, a total of 13 causative factors (temperature, precipitation, wind speed, elevation, slope, aspect, plan curvature, profile curvature, curvature, TRI, NDVI, LULC, and TWI) were selected by considering the main characteristics of the study area and previous studies conducted in this region. According to the results, the XGBoost algorithm produced the highest accuracy of 85.4%, followed by the RF (84.6%) and AB (78.9%). Considering the estimated AUC values, XGBoost and RF outperformed the AB algorithm by about 6%. McNemar’s statistical significance test results showed that RF and XGBoost algorithms produced similar performances, but their results significantly differ from that of the AB algorithm. According to the Shapley additive explanations (SHAP) strategy, elevation was found the most effective parameter for the occurrence of wildfire events, while curvature was the least effective one. SHAP analysis also showed that topographic (e.g., elevation and aspect) and climatic (e.g., temperature, precipitation, and wind speed) parameters had a larger impact on wildfire susceptibility. When all susceptibility maps were thematically interpreted, approximately 20% of the study area was covered by a very high fire susceptibility category. To be exact, the highest potential forest fire risk was mainly situated around the center and shoreline zones of the Antalya province. Taking all the results into consideration, producing a reliable wildfire susceptibility map could be used as an early warning system by decision-makers to manage, prevent, and mitigate potential fire risks and protect wildlife.

At the Northern Black Sea coast of Bulgaria, large numbers of active landslides are located. The situation has changed in the last 30 years since large technogenic load was put on it caused by construction activities in that area. For this reason, tracking activation of the landslides and surface movements in them is a critical task that must be carried out. This is the reason to perform a pilot investigation for a single landslide using synthetic aperture radar (SAR) from ESAs’ Sentinel-1 mission. As main advantages of said data pointed out should be the uninterrupted time series, the unrestricted access, and the compatibility with other data operating in the radar C-band.In the recent years, the landslide found in the residential area “Fish-fish” has been the subject of our research by making terrain observations, geodetic and geologic investigations. In the last years, two surveys by unmanned aerial system (UAS) were done spanned in one and half year period focused at studying the deformations that took place in its area. The first one has the task to create precise digital elevation model of the zone, while with the second the surface motions were registered. For this research, SAR data were used to establish the magnitude of the geodynamic processes in the area of the landslide for the period 2015–2022. To complete this task, seven uninterrupted time series covering the time span from late autumn to early spring were created using the small baseline approach (SBAS). The period was limited to the said one, because in the researched area large parts are vegetated, which causes spatial decorrelation in the interferograms. As a result of our research produced were 42 interferometric images using SAR data in SLC format allowing creation of deformation maps for the zone of “Fish-fish” landslide. The analysis of the obtained results confirmed that the applied technique provides sound information and is solid basis for systematic monitoring of the area.

Remote sensing imagery enables large coastal areas to be mapped effectively. In particular, in low-lying sandy coasts exposed to high energetic wave conditions, where rapid and significant morphological changes can occur, the development of satellite-derived bathymetry methodologies represent a cost-efficient technique to estimate water depths. This work presents a satellite-derived bathymetry map of Figueira da Foz coastal stretch in Portugal, using Sentinel-1 synthetic aperture radar (SAR) data. The results are obtained with the application of a wavelet methodology where the nearshore bathymetry is inferred from the observed swell wave patterns captured by the satellite imagery. The results are compared with data extracted from Coastal Nautical Charts and from the Portuguese COaStal Monitoring Program (COSMO). The results indicate a good agreement to map water depths up to 30 m. However, errors increase close to the shore and are practically of the same order of the morphologic feature elevations such as longshore bars or rip channels. Improved results require higher imagery resolution to provide more accurate estimates.

Agricultural drought has become a major global problem due to its severe impact on rain-fed crop yield and indirect impact on employment and per capita income. Evaluating agricultural drought risk effectively is critical to properly manage current water resources and ensure food security. The current study aims to evaluate the effectiveness of GIS and remote sensing tools for monitoring the spatial and temporal extent of agricultural drought by applying different drought indices for the lands at the high and middle Moulouya basin. The annual weather data from 1978 to 2017 was used to analyze the extent of meteorological drought using a standardized precipitation index (SPI) across the basin. Remote sensing images in 1984, 1995, and 2022 from Landsat 4–5 Thema Tique Mapper (TM) and Landsat 9 operational land image (OLI) were utilized to monitor agricultural drought using the NDVI-based vegetation condition index (VCI). The extreme drought in upper Moulouya occurred during 1983/1984 with an average SPI value of − 1.97. The largest areal extent of agricultural drought conditions was recorded in 2022 compared to 1984 and 1995. Results show that VCI tracks agricultural droughts more effectively than the SPI indices employed in this study. This identification will help to build an effective planning and drought management tool for the agriculture sector over time.

The process of topographic maps updating in the Moroccan Agency for Land Registration, Cadaster and Cartography (ANCFCC) is essentially performed by manual 2D or 3D plotting based on aerial or satellite images. In this chapter, we use data from airborne LiDAR to automatically extract some map features for the purpose of speeding up the map updating process. We processed LiDAR data with both ArcGIS and QGIS Grass software to automatically generate some map data layers like contour lines and hydrography streams. The obtained features were compared by overlapping other data such as orthoimages, manually stereoplot map and contour lines generated after automatic photogrammetric correlation in the same area. The comparison of all datasets showed that LiDAR can bring a significant advantage in some areas like shaded areas of aerial images or areas of complex topographic structures like cliffs as well as in dense forest zones or even relatively urban areas where classic stereoplotting often presents difficulties. However, automatic processing of LiDAR data requires adapted parameters to avoid poorly or over detailed maps, particularly with hydrographic features even if the automatically obtained hydrographic streams present the advantage of being ordered following the stream size. We conclude that automated LiDAR data processing is of high value in terms of accelerating map updating and the extracted features like contours and hydrographic streams are of better quality than traditional methods.

The goal of the presented research was to establish sound basis for studying the current geodynamic processes at single landslide area located between the villages of Topola and Bozhurets at the Bulgarian Black Sea coast. The investigated zone has been under high anthropogenic pressure in the last decade by constructing several touristic and holiday properties some of them already collapsed because of lack of preliminary monitoring of the surface motions in it. In order to register past and ongoing surface motions, we used data from satellite-based synthetic aperture radar (SAR), which is the main instrument of the Sentinel-1 (S-1) mission. To this end, created was local geodatabase (LGDB) into which collected all available information concerning this specific zone including, geological and techtonic maps, hydrology inventories, geodetic data from local geodynamic GNSS networks, information for land use/land cover in the said coastal zone, optical imagery from unmanned aerial systems and satellites, to name a few, besides the SAR data. Currently, such detailed and well-organized information for the studied region is not available in centralized repository for public use. Other objective of this study was to create and keep updated the mentioned LGDB using free and open source processing tools, such as QGIS, ingesting publicly available data from different sources e.g. Copernicus data and products. Key element of this research was to harmonize the already available data and to create methodology for their integration into the LGDB as well as to establish a protocol for future data acquisition from the mentioned sources and their integration into the geodatabase. The established LGDB allowed synergetic interpretation of the data thus providing better modelling of the studied geodynamic processes by large number of experts in different application domains. The authors are confident that the resulting information product is of high quality and allows seamless integration the produced LGDB into regional datacubes that are gaining popularity for machine learning applications in Earth sciences and even are used to offer products for the wide public.

This study focuses on the recognition and analysis of fracturing in the coastal basin of Tarfaya located in southwestern Morocco, through the extraction of lineaments using the remote sensing method. This extraction was carried out by processing and interpretation of the Landsat-8 OLI satellite image. For a more in-depth analysis of the spatial distribution of the lineaments, we opted for a comparison of the average lengths and directions of the lineaments in the four zones of the basin using Kruskal–Wallis test. The Ascending Hierarchical Classification (AHC) was designed, in our study, to group individuals (lineament directions) that represent the same directions. The lineament analysis carried allowed to highlight a network of 1603 lineaments oriented in three directions: NNE-SSW, NE-SW and WNW-ESE. These directions suggest that the bedrock fracturing of the Tarfaya coastal basin results from several tectonic phases. The application of the tests (ANOVA) proved the absence of an interaction between the length and the orientation of the lineaments. The Ascending Hierarchical Classification (AHC) of the directions of the lineaments allowed the study of their spatial distribution in the basin and subsequently the identification of the fracturing which impacted the layout of the hydrographic network of the basin.

In this chapter, a per-pixel trend analysis approach and the temporal variance of drought risk were used to compare the seasonal dynamics of the multivariate risk level of agricultural drought in two hydrological systems (Tensift and Moulouya watersheds in Morocco). The multivariate risk level is calculated from the time series of the enhanced composite model for agricultural drought monitoring constructed from anomalies in precipitation, evapotranspiration, soil moisture, NDVI and land surface temperature (LST). These five factors of agricultural drought are obtained from multi-sensor remote sensing data (MODIS, CHIRPS) for the period 2004 to 2022. In both watersheds, the results show a significant upward trend in the level of extreme and moderate risk and a very contrasting seasonal variance. At the same time, over the past two decades, risk levels (normal and low) have shown a marked downward trend. The multivariate frequency of generalized extreme risk is identical in both hydrological systems. Over the data period, the seasonal occurrence of multivariate risk is 6/19 (extreme risk), 7/19 (moderate risk) and 6/19 (low to normal risk). The recent spatio-temporal dynamics of the level of extreme risk have significant negative correlations (−0.6 at Tensift and −0.62 at Moulouya) with cereal yield anomalies. Multivariate risk is positively correlated with the SPI index at the seven-month scale of the growing season. The maximum correlation is 0.86 with a p-value of 0.0000 at Tensift and 0.74 with a p-value of 0.0004 at Moulouya. Depending on the year, the multivariate extreme risk can vary from 0 to 100% in terms of exposed areas in both the Tensift and the Moulouya watersheds. It is generalized over all the spatial extents of these watersheds for the years 2022, 2020, and 2016 and non-existent for the years 2004, 2006, 2009, 2010, 2013, and 2015.

Assessing the surface water balance of mountains is a real challenge given notably the extreme variability of meteorological conditions and the sparsity of in-situ monitoring. While mountains are recognized as water towers feeding the surrounding plains, there is only unconsolidated knowledge about the individual water balance components especially the evapotranspiration (ET). Satellites land surface temperature (LST) along with air temperature (Ta) and incoming solar radiation (Rg) can be used to assess the energy budget and provide a reasonable estimation of instantaneous ET. Nevertheless, over mountains, the Ta and Rg, respectively, undergo strong topographical changes due to elevation and sun exposure effects. Moreover, upscaling the instantaneous ET to its daily value is expected to be uncertain in mountains as the evaporative fraction (EF, defined as the ratio of ET to available energy ratio) of a given pixel can no longer be considered constant during daytime until proven otherwise. In this context, this contribution focuses on a topography-based estimation of ET using the two-source energy balance (TSEB) model. We also examine the variability of hourly and daily EF estimates through both satellite and in-situ monitoring. An eddy covariance tower was installed at 3850 m.a.s.l over the High Atlas Mountains in central Morocco and has been operating since September 2020 to present. The 30 m resolution LST is derived from thermal data collected by Landsat-7, 8, and 9 on clear sky days. Rg is estimated at the Landsat (30 m) resolution from the SRTM’s digital elevation model (DEM) and two different topography-based approaches: a physically based model (DART) and a simplified semi-empirical model. The 9 km resolution ERA5-Land’s air temperature product is spatialized at the same (30 m) resolution by applying the environmental lapse rate (ELR) retrieved at the Landsat overpass time over a 9 km2 area including the eddy covariance tower. Satellite-derived estimates of ET and EF are compared to instantaneous station measurements for three and nine dates in 2020 and 2021, respectively. The variability during daytime of the in-situ EF is also assessed to evaluate the potential for upscaling instantaneous remotely sensed ET to a daily scale.

Apple company recently started to include lidar sensor in iPhone 12, 13 Pro, and iPad Pro system devices. Lidar was introduced by Apple to improve camera focusing and support augmented reality (AR) applications. However, Apple lidar attracted app developers and users to start scan indoor and outdoor environments within the specified range configurations. Although Apple has not revealed the type of the 3D scanner used, some scholars believe Apple’s lidar is based on direct time of flight (DToF) lidar. It is a mobile handheld scanner that provides greater flexibility and control when scanning close objects, and therefore, more affordable and much cheaper than TLS devices in very close ranges. This study aims to assess the positional accuracy of the new lidar sensor in the iPhone 12 Pro Max in outdoor environment, particularly for scanning building façades. Sitescape app was used for scanning objects using this device where it is primarily concerned with extracting 3D point clouds following specific scanning pattern. The study is carried on the façade of a selected building, where a number of artificial targets are affixed and observed using three different laser-based remote sensing techniques (total station, iPhone lidar, and TLS). The research study is divided into two stages where total station measurements used as reference ground-truth dataset. The first stage compares mobile DToF to static TLS sensor in terms of precision. The data are collected in the same range and environmental conditions to analyze the level of accuracy. The result showed that the accuracy of the iPhone lidar and TLS are comparable. The RMSE of TLS data was 3.44 mm, while the iPhone lidar delivered 4.89 mm. In the second stage, the sensor accuracy was tested over various ranges starting from 0.25 to 5 m to show range dependency on the positional accuracy. The accuracy shows convergent results; however, errors increased slightly as range increased. The data acquisition time was generally short and directly proportional to the scene size. Results are later analyzed and studied for future conservation applications.

Floods have caused severe consequences on the environment in different areas of the world and also in Italy. Therefore, this study explores the opportunity of combining the Earth Observation data (both radar and optical images) for flood mapping in the Po River, located in the north part of Italy. Based on a multi-temporal approach, synthetic aperture radar Sentinel 1 images between August and November 2016 were used in the period. The methodology adopted is semi-automatic method using GEE to detect a flooded area. We selected images before and after flood event using VH band flood detection. It was concluded that the use of synthetic aperture radar (SAR) data produces results with low accuracy especially in building areas due to the spectral signatures of urban features. To deal with this, we used an optical image (Landsat 8 OLI) based on automatic threshold using Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) for change detection to accentuate changes likely caused by flooding. The results were calibrated by hydraulic model using HEC-RAS software. Thus, the approach developed in this study could be a crucial step toward adequate flood risk mitigation and management strategies.

Ecosystem services are a complex relationship between humans and nature. Interactions among these ecosystems are self-sustainable if they are unaltered. But, due to rapid urban expansion, changes in land use land cover (LULC), and anthropogenic activities, these ecosystem services (ES) are exerted under tremendous pressure. In the Mangaluru urban agglomeration, a coastal region of Karnataka, this study examined changes in land use and land cover (LULC). In order to categorize the spatiotemporal changes in LULC over the course of five decades, 1980, 1990, 2000, 2010, and 2022, the study used the object-based image analysis (OBIA) technique. Deriving knowledge about various LULC classifications is the primary goal of this work. The study area is divided into five categories using the OBIA technique: built-up area, water body, forest area, agricultural land, and barren land. The categorization accuracy is assessed using images from Google Earth, SoI Topo maps, and on-the-ground confirmation. We discover that between 1980 and 2022, the area used for agriculture has decreased, the area used for forests has increased, the area used for buildings has dramatically increased, while the area used for water bodies and arid land has primarily remained the same. The results of the accuracy evaluation demonstrate that the LULC variations discussed in this work are legitimately correct and applicable to subsequent uses. In order to expand the city in the future, decision-makers may find the study's findings helpful in determining the best course of action. This study also demonstrates GIS and remote sensing (RS) in LULC applications, particularly in the coastal regions.

The work proposes a salinity recovery method for the Sea of Azov based on implementation of a general regression compiled from archival in situ data and regional biooptical parameters obtained from standard MODIS L2 products. The observational data from the open Internet services were acquired directly from data providers. The authors’ procedures for quality control and merging were implemented for these data. We researched the following biooptical parameters: aph(678) is the absorption coefficient by phytoplankton at 678 nm, Tchl is the sum concentration of chlorophyll-a and pheophetin-a, atot(438) is the total absorption coefficient by all optically active components at 438 nm, aCDM(438) is the absorption coefficient by colored detrital matter at 438 nm, and bbp(438) is the particulate backscattering coefficient at 438 nm. We chose these variables because they are the operational satellite ocean color products of the MODIS (NASA). Each measurement of satellite data with 1 km spatial resolution processed to spatial maps of five biooptical parameters on a regular grid of the Sea of Azov. Based on the linear regressions satisfying the condition R ≥ 0.5, general equations of the following form were compiled y = (aaver ± σ1) ⋅ x + (baver ± σ2), where aaver and baver—averaged linear coefficients a и b, σ1 and σ2—standard deviations, x—regional biooptical products, y—salinity (‰). The results of the study showed the possibility of using different approaches to building generalized empirical regressions for the spring and summer. The result is merged regressions for spring and summer designed for reconstruction of salinity and obtaining the data sets for spatiotemporal variability analysis of salinity. Average values of salinity recovered indirectly using our proposed method are within the 95% confidence bands for the long-term average seasonal trends for periods 1986–2018 and 2000–2018 from in situ data. The main result is merged regressions for spring and summer seasons designed for reconstruction of salinity and obtaining the data sets for spatiotemporal variability analysis of salinity in the Sea of Azov. In addition, the values of salinity reconstructed from aCDM(438) are found to reflect its changes most realistically within the observed salinity range (1–18‰). These results allow us to use in the future reconstructed salinity datasets in the assimilation procedures of the 3D hydrodynamic model and for retrospective salinity recovery.

The aim of the current study is to monitor sand and dust storm events, which are one of the key environmental apprehensions over the Kingdom of Saudi Arabia, using MODIS satellite data. A new approach, Saudi Dust Detection Index (SDDI), is presented based on spectral characteristics of sand and dust features to monitor SDS events. The index-based results are validated by using MODIS combined dark target (DT) and deep blue (DB) aerosol optical depth (AOD) product and AOD product from AERONET station data. The accuracy of the SDDI is determined by using probability of false-positive detection (POFD), probability of correct positive detection (POCD), and algorithm accuracy approach. Results of the study show that SDDI can identify SDS events based on various threshold values (between 0 and 0.5) with high accuracy. This research is at a preliminary stage, and the future objectives are further improvements and validation of the developed index.

Due to population growth and urbanization, high-rise residential strata have developed in Malaysia's big cities. People from diverse socioeconomic backgrounds must share a ground parcel and use the same common utilities. Strata tenants must deal with several management issues to maintain an attractive, standardized living environment. Poor strata administration caused several problems for owners. Unlike conventional housing, residential strata require an executable model for proactive management. This research aims to identify the temporal management issues in 3D residential strata and join them with the existing Land Administration Domain Model (LADM) in the form of the management package in the LADM. A conceptual domain model in unified modeling language (UML) is developed in this research. Temporal management issues, actors involved, and management procedures for residential strata are identified by literature review from 2000 to 2021. Furthermore, it is concluded that proactive and preventive management is required to increase the residential strata’s market value and life span. The developed generic conceptual domain model for temporal management of residential strata can further be used by the management bodies worldwide to perform proactive management by developing database management systems and software based on this model.

Traffic noise causes 90% of urban noise pollution. Visualizing noise is challenging. Three-dimensional (3D) space noise visualization reflects natural movement or acoustic dispersion. However, improving traffic noise visualization is hardly addressed. This review paper aims to fulfill the gap mentioned earlier. Noise models such as the Federal Highway Administration (U.S.), RLS-90 Model (Germany), Road Traffic Noise Prediction (U.K.), Stop and Go model (Thailand), and Henk de Kluijver model are compared and described. Noise is visualized using hotspots, contours, and building facades. The shape and direction of building facades do not affect 3D noise visualization. Traffic volume, composition, speed, road gradient, surface, ground covering, and distance to traffic sources affect noise. Green spaces absorb noise and provide acoustic relief. The 2D and 3D propagation should address noise screening and diffraction. Interpolating noise for visualization uses IDW, Kriging, and TIN. TIN outputs correct noise contours. Flat triangles must be avoided to remove unpredictable oscillation of interpolated noise levels in 3D space. For 2D noise visualization, raster cell size and noise level accuracy are essential. Noise interpolation requires 2 m minimum observation points. Plus, this review identifies the IDW distance weighted factor and the optimal Kriging variogram. Furthermore, this review suggests purple instead of red to denote high noise levels.

The LouMu Project is an ongoing collaboration between the Laboratory of Instrumentation and Experimental Particle Physics (LIP), the Institute of Earth Sciences—University of Évora and the Lousal Ciência Viva Center which is evaluating the muography potential in the Lousal Mine, with the general aim to create the conditions to use muography as a novel method for geophysical surveys in Portugal. The National Laboratory of Energy and Geology is also supporting the project. The aim is to do a first geological survey of the area, mapping already known structures and ore lenses and measuring their densities. In the end, newfound data will be added to the existing information to improve it, but the whole process is also serving to test the performance of the muon telescope and the muographic analysis tools. The muon telescope, developed by LIP, uses RPC detectors to observe the crossing muons in real time. Available geological and geophysical information and new measurements done with seismic refraction and ground penetrating radar are being used to create a 3D model, which provides a reference against which to compare the muography results. From the muography data, an equivalent 3D map of densities will be reconstructed, and the geological model will be used to cross-check and improve the muography results. This paper provides an overview of this ongoing project, focused on the muography work done so far. Its implementation is described, and the first image obtained with the telescope is presented, showing the local geology and in particular the Corona N–S direction strike-slip fault visible in the mine gallery. The planned work progression is shared as a final consideration.

Estimating soil infiltration rate is of utmost importance in agricultural applications. The infiltration rate determines the amount of water to enter the soil, which in turn controls the load of dissolved chemicals (nutrients or pollutants) that will interact with the soil. The soil infiltration rate is commonly measured using the cylinder infiltrometer method, which is tedious and time consuming. Geophysical methods on the other hand have proven to be a powerful tool in providing valuable information about water content in the soil, but rarely used to give a quantitative estimation of the infiltration rate. Ground-penetrating radar (GPR) in particular has the potential to offer a suitable, non-invasive, and cost-effective method for studying the wetting front at shallow depths. A time-lapse GPR experiment was conducted in order to study the feasibility of utilizing GPR method in estimating the soil infiltration rate. A GPR survey was conducted along a 20 m traverse before and immediately after pouring water at two specific locations over the traverse. The GPR measurements were repeated over the same traverse with 5 min time interval, to monitor the downward movement of the wetting front. The time-lapse GPR sections were successful in monitoring the changes of the location of the wetting front with time, which can be used to estimate the vertical soil infiltration rate. The preliminary results are quite encouraging and show that GPR can be efficiently used in monitoring the wetting front downwards movement.

Due to the presence of an excessive amount of noise in the data, archeological geophysics frequently produces results that cannot be used to evaluate the content that may exist in the subsurface. If it is impossible to differentiate between signal and noise, excessive noise will result. Its genesis, when it is attributable to heterogeneities in the ground (overthrows, corners) that produce as many reflections as structures that may exist, prevents a fair assessment of the subsoil composition. Low perceptibility circumstances happen when there is no contrast between buried structures and the surrounding environment. It could be due to elements that are harmful to the method (metals and ceramics in the magnetic method; clay and water in the electromagnetic method) or when the buried objects are formed of the same material as the surrounding medium. The problem of the identification and selection of useful signals in geophysical data is one of the research topics of effective methodologies of archeological geophysics, with the aim of producing more accurate models that allow a more precise interpretation of structures buried beneath the earth. In this paper, three approaches conceived by the team are described, which allow: to increase the sharpness of the GPR models by reducing the background noise through factoring techniques applied in the 2-D spectral domain; to increase the resolution of the models by increasing the density of the profiles with Fourier interpolation; and to increase model information by combining maps from the two geophysical methods, using data fusion techniques that combine mathematical transformations and statistical analysis.

‘Water in Istanbul: Rising to the Challenge?’ is the title of a new 24-month project which brings archaeologists, historians, engineers, and urban scientists together to explore the historical water management infrastructure and evolution of water technology in the city of Istanbul through history. One of the outcomes of this research will be producing a hydraulic model that will help us to understand how the past system functioned and was managed. This in-depth research also hopes to bring a new perspective for the contemporary water-related challenges. The archaeological field work geographically focuses on the I. Hill of the Byzantine city where Ottoman imperial palace called Topkapı gets located over. This is the most challenging topographical area regarding the historical water distribution which functioned according to the principle of gravity. Non-destructive survey methods are crucial in such fragile archaeological areas. Also, the bureaucratical difficulties related to the legal permissions make it a necessity to apply archaeogeophysical methods. In the first field work phase, we preferred ground-penetrating radar (GPR) in order to identify the remains, including supply lines providing freshwater to the Topkapı area. Our survey based on previous research by Hülya Tezcan and the archaeological survey results of Çiğdem Özkan Aygün in order to identify the areas for investigation with GPR. Thanks to GPR, the location, geometry, and depth of the buried historical structures would be possible to determine. GPR, which provides high-resolution information from shallow areas, is a geophysical method frequently used, especially in archaeogeophysical studies. The method is based on recording the travel times of reflected and scattered electromagnetic waves, which are sent to the subsurface with high-frequency antennas, with a receiver. In this study, results of the GPR study, which was carried out using a 350 MHz centre antenna frequency to detect the historical water channels beneath the area surrounding the Topkapı Palace are mentioned. After processing the data sensitively, GPR sections were interpreted and all possible water channels were detected. Depths of the detected channels are between 2 and 5 m below the surface.

The region of Majel Bel Abbes, west-central Tunisia, is characterized by a semi-arid to arid climate. Groundwater is the main source of water for domestic, agricultural and industrial purposes in the region. In order to better recognize the architecture and the lithology of the aquifer system of Majel Bel Abbes and evaluate its hydrogeological potentialities, a geophysical study based on electrical prospection was carried out. The latter allowed the delimitation of two potential aquifers including (i) a Plio-Quaternary hydrogeological unit exhibiting 30 to 50 Ω.m resistivity values and variable lithologies that thicken toward the central part of Majel Bel Abbes basin and (ii) a Miocene sandy hydrogeological unit exhibiting ~20 Ω.m resistivity values and acknowledged as Beglia Formation. This unit rests on the Campanian–Maastrichtian limestones of the Abiod Formation that overlays the Cenomanian limestones to the east of the basin and disappears toward their borders. The new results concerning the Majel Bel Abbes basin architecture and their hydrogeological unit lithologies, thickness and potentialities should be considered by the local authorities in the planning and design of new drilling hydraulics wells to ensure safe management of water supplies.

This work aims at describing from a fluid dynamic point of view the occurrence and the origin of sand injectites outcrops observed in two sites within the Bahrah coastal plain area, northern Kuwait Bay, through analogies with the knowledge on spouted beds. For non-cohesive systems, the channel formation can be easily reproduced through Eulerian–Eulerian computational fluid dynamics (CFD) simulations. When a certain fluid inlet velocity is set, the fluid breaks through the bed of particles creating the central channel. Cohesiveness, most likely present and relevant in the field of interest, was introduced by simulating the fluid–sand multiphase system with the CFD software adapted to satisfactorily describe previously reported field observation. To simulate such systems, the volume-of-fluid (VOF) method yielded the best results. In fact, cohesiveness can be taken into account through the Bingham model, which introduces additional parameters to estimate, and these parameters determine whether the fluid can create a central vertical channel or diagonal cracks. The CFD simulations proved to be a valid tool to reproduce laboratory-scale observations and may further explain the mechanisms behind these enigmatic formations, confirming the role of fluid–solid drag in the creation of the injectites. Future works will address further development of this approach and the application on larger scales.

Carbonate stringers are self-charging reservoirs residing inside salt structures and known for their challenging characterization and fluid identification. We build a geological model that conceptualizes stringers in some fields from south Oman Salt Basin. We use the model to produce P-wave and S-wave velocity, and density models. The models are used to create pre-stack gathers from which AVO attributes are extracted. The gathers are inverted back to impedances and density models using pseudo-well logs that are created from the input models. The AVO analysis demonstrated that AVO attributes may not be able to detect the carbonate reservoirs because of the increase of Vp/Vs from the Ara salt to the reservoir rock. However, the post-stack and pre-stack inversion results suggested that the reservoirs can be detected using different elastic products, namely Vp/Vs, Poisson ratio, bulk modulus, and Lambda Rho among other impedance-based fluid indicator. The result from the study will be used for the interpretation of a new seismic data which is acquired in the area.

Located in the central-western part of Morocco, where the climate is arid and semi-arid, the Essaouira basin is an area at high risk of water shortage due to the decrease in precipitation as a consequence of climate change on the one hand, and on the other hand to the incessant increase in the demand for this resource necessary for life. That is why, more and more underground water resources are used to meet the needs of the population, whether for domestic use or for irrigation. However, the mobilization of these resources requires a good knowledge of the aquifers of the Essaouira basin. The present study was undertaken with this perspective. Its main purpose is to achieve a better understanding of the deep structure of this basin. This study is based on the analysis of gravity data. The methodological approach involves, in addition to the qualitative interpretation of these data, the use of various filtering processes that help map hidden geological structures. The obtained results reveal the existence of a network of faults that complement the structural map of the study area. Some negative anomalies are clearly associated with evaporate deposits. However, most of them are in all probability related to structural lows and subsided depressions that represent favorable areas for groundwater accumulation and, consequently, favorable zones for drilling water exploitation boreholes.

The western part of Mali belongs to the West African Craton (WAC) which abounds in significant potential for gold resources hosted in the Birimian Paleoproterozoic formations. These formations and associated structures are most often masked by the thickness sedimentary and lateritic covers. It is why need to use of geophysical methods. The geophysical signatures of these geological formations are little studied specially in the Inlier of Kedougou Kenieba. Previous studies have proposed a magnetic signature model of geological structures in western Mali, allowing to characterize some gold-bearing structures. However, many auriferous structures have a low magnetic response requiring the use of other geophysical methods such as electromagnetism. This allows understanding the resistant or conductor character of structures. The electromagnetic and magnetic data will be analyzed out in order to characterize the geophysical signatures of the structures related to gold mineralization. These results will be calibrated to geological field data in order to consolidate the geophysical interpretation. This study helped to assess the degrees of magnetization and conductivity of rocks and linear structures within western Mali. Structures related to gold mineralization have low-to-moderate magnetism with a high conductivity. This geophysical signature model is well known in volcano-sedimentary rocks along the main shear zone as well as NE–SW trend faults. These results support previous work in western Mali and are also corroborated by surface geological data. The geology shows the presence of gold in quartz veins and facies bearing sulfide minerals. Generally, the massif sulfide minerals are known by their high influence on the conductivity of rocks.

Geophysical methods and geological investigations are efficient techniques for studying the geological structures of the sedimentary basins (Jaffal et al. Journal of African Earth Sciences 193, 2022). By integrating subsurface and surface geological information, we can improve geological modeling and resource exploration. To gather this information, we use an indirect approach that relies on geophysical methods and direct observation through boreholes and surface geological investigations. These investigations help acquire a variety of geoscientific data that can be used in resources exploration. This study focuses on the Bahira basin that hosts, with the Gantour plateau, an important part of Morocco’s phosphate reserves. The main objective is to provide a better understanding of the deep structure of the study area. The methodological approach adopted in this study concerned (i) the combined analysis and reinterpretation of existing geophysical and borehole data and (ii) the implementation of new electrical resistivity tomography surveys. The processing and interpretation of gravity data highlight the major geological structures such as faults and geological contacts that are totally or partially covered by plio-quaternary deposits. Additionally, the gravity anomalies perfectly delineated the structural highs in the basement and sedimentary thickening in depressions and grabens. Furthermore, the combined analysis of geoelectrical and borehole data provides more precisions about the deep geological structure of the phosphatic series of the Bahira basin, in terms of depth and lateral changes in thickness.

Surveyors, explorers and managers investigate for improvements in geophysical operations in hassle-free environments, including planning, survey designs and budgetary regulations. The critical tasks are field crew induction, wildlife and domestic animal protection, oil spill prevention, land management, built-up areas and shot hole drilling. Geophysical field-data acquisition tasks include survey planning, landowner and community consultations, ecological awareness, operations, road and truck movements and campsite establishment. Besides, field and cable layouts, survey type, arrays, machinery and source usage and latitude and longitude of survey areas need attention while scrutinizing survey operations, including a detailed examination of geological features. Waste management, explosive ordinance areas, abandoning survey areas and campsites are added challenges while managing geophysical field operations. Under survey operations, careful handling of chemicals and hazardous material management, emergency responses, geophysical survey completions and environmental audits need attention in project executions. Manageable crop compensations in the fields can ease settlements with farmers and landowners whose lands are damaged by geophysical surveys. Finally, rehabilitation of field areas is focused on abandoning seismic lines and tracks, including campsites. The research aims to examine the challenges of the geophysical surveys in a diverse range of environments, including land use. We interpret various entities and dimensions of the geophysical survey designs, plans to articulate, and model field operations and the environments for which databases are operationalized. We construe the entities and dimensions for articulating Information Systems (IS) artefacts in geophysical engineering. Several schemas are prepared pertinent to geophysical operations, environment awareness, men, machinery and materials movement and management, including hazards, time and budgetary constraints to integrate data-driven structures in repository systems. We propose a shared common ontology approach with knowledge-based connectivity between attribute dimensions. Multidimensional structures are designed to unify metadata and its management. The IS artefacts are reusable by changing key attributes such as period and geography attribute dimensions. The approach facilitates easy handling of geophysical operations and environmental challenges by explorers, surveyors and managers involved in geophysical surveys, including land procurement and disaster management, to acquire quality geophysical data.

The magnetic resonance sounding (MRS) method is one of the most used techniques in hydrogeophysics that directly quantifies the water content distribution from surface measurements. Direct MRS modeling is usually performed as a part of the planning phase of an MRS field survey, with the aim of determining the feasibility and usefulness of this method in a given hydrogeological context, by evaluating the MRS signal amplitude of one or more aquifer layers, using their lithological and piezometric characteristics derived from actual field data. The direct modeling of the MRS signal, of Youssoufia and Khouribga phosphate deposits, was calculated using the lithological and piezometric characteristics derived from boreholes data. The MRS signal was then calculated considering the maximum, average and minimum values of the water content (WMRS) and the relaxation time (T2*) for different electromagnetic noise levels. MRS modeling results show that the Youssoufia mining sites are highly adapted to the use of the MRS method even with significant magnetic noise levels. However, the application of the MRS method in the hydrogeological context of Khouribga mining sites depends strongly on the electromagnetic noise level in the investigated area, but also on the characteristics of the aquifer.

Argamum-(Orgame) is one of the four oldest Greek settlements established on the shore of the Black Sea alongside Callatis, Tomis, and Histria. Founded around the middle of the seventh century BC, on the northern coast of Dobrudja-Romania, the ancient city occupies the entire area of Cape Dolojman, which dominates an important lagoon complex located south of the Danube delta. The main purpose of the geophysical surveys, which were made in the spring of 2022 by using the cesium vapor magnetometer (G-864), was to identify the fortification elements and adjacent buried structures in the main gate zone specific to this type of settlement and to establish a new archeological research strategy. The delimitation area for the magnetic survey was chosen in accordance with the presence of ceramic material on the surface. By subsequently using a Trimble R4 GPS system, two grids, aligned in a north–south direction inside the fortress near the main gate, were assigned and traced with respect to the geomorphological configuration and vegetation present on the site. The data were bidirectionally collected by surveying a grid characterized by a line spacing of 1 m and a sample rate of 25 readings per meter. This paper presents the interpretation of the large magnetic anomalies observed on the two investigated grids. Archeological research carried out in 2022 confirmed the results obtained by using the geomagnetic survey method and by revealing the existence of fortification walls and adjacent buildings in the main gate zone. In the second phase, we used the Potent Q software to model the dimensions, positions, shapes, and tilt of the buried artifacts. Finally, the geophysical study performed at the ancient city’s main gate area demonstrated that magnetometry is capable of providing a rapid overview of the distribution of buried artifacts, which may prove useful for future excavation planning.

The success of full-waveform inversion (FWI) modeling depends on many factors, i.e., initial model, source wavelet, and low-content. Low-frequency seismic data is extremely important for FWI as it allows for accurate sub-surface imaging and increasing the resolution of sub-surface features, while also providing information on overall sub-surface geological features. However, the lack of low-frequency data can lead to cycle-skipping which could negatively affect the results of the inversion process. To resolve this issue, low-frequency data can be reconstructed using artificial intelligence or deep learning algorithms. In this study, we utilized a convolutional neural network (CNN) algorithm to automatically extrapolate the low-frequency data from band-limited Common Shot Gather (CSG) seismic data in time domain without any preliminary processing steps. The CNN model was tested and validated with synthetic seismic data to select the best model. The best model was then applied to marine seismic data in the Kutei Basin, East Kalimantan, Indonesia. The results demonstrate that deep learning has been accurately applied to extrapolate low frequencies in marine seismic data with an RMS error below 1% and that it produces results that are in line with the broadly established in conventional seismic processing methods (i.e., deghosting). Therefore, our study can be a powerful and effective alternative method to estimate the low-frequency content in the seismic reflection data of other areas.

The reflection seismic is technique to image subsurface structures to depth of thousand meters. In addition, the method is also applied to shallow targets with depths from 10 to 1000 m, for engineering problems and site investigations. Even though shallow seismic method is only scaling of reflection seismic method, problems encountered in the survey operation are not simple. Problems are cost and environmental issues, particularly related to sources used. The use of explosive seismic sources has implications for costs and environmental issues. One promising source option is an accelerated weight drop (AWD). The use of AWD as seismic source is highly dependent on surface conditions of survey area. Therefore, an AWD design that is suitable for various types of survey areas is needed. A new prototype has been developed as an improvement over previous prototype. The design modification is intended to increase penetration depth and widen frequency band of the source signal. Important criteria have been considered in AWD’s design, such as impact energy (penetration and bandwidth), repeatability, portability, economical and environmentally friendly. This paper reports performances test of prototype AWD for generating seismic sources to obtain high-quality data. The survey was conducted to test performances. There is no specific target of geological structure in areas. The survey located in a densely populated area was conducted using 100 units of wireless seismometer (5 m interval) and shot point interval of 15 m. The recorded data has been processed using a standard seismic data processing workflow. The results show that the reflected signal is visible at a depth of 50 ms to 800 ms or about 50–700 m, with a signal frequency of up to 100 Hz with good image quality. The criteria of penetration depth and frequency band have been achieved. Survey cost to obtain 0.5 km is less than 500 USD. This AWD has met other expected design criteria, economical and low environmental impact. Results are better than the old prototype and product in the market.

Wellbore instability is caused by formation break-out or drilling-induced fracture. Formation break-out and drilling-induced fracture depend on the formation strength and in situ stresses near the borehole. The main objective of this study is to use the concept of milling machine theory to predict the break–out depth of the formation. A new approach is proposed for the prediction of formation break-out dimensions for maximum wellbore stability. The formation break-out is due to the stress concentration around the borehole. This stress concentration acts as an additional shear cutting force to break a formation. The shear cutting force is similar to the milling cutting tool force for the same formation to produce an equal dimension chip. The formation cutting force causes break-out by an imaginary milling tool. This additional shear cutting force plays an important role in the calculation of the break-out dimension. The concept of milling machine theory is applied to develop the mathematical model for the prediction of break-out dimension. Through this study, it has been observed that the depth of the break-out is the function of the break-out angle and yield strength of the formation. Shear cutting force around the wellbore is the maximum at a point near the minimum horizontal stress direction that produces break-out. Break-out angles can be calculated theoretically, empirically (using failure criterion) and actual (using image log). It has been shown that the radial stress acting on the boundary of the wellbore is not responsible for the shear failure of the formation. In this study, a relationship between break-out and stresses around the borehole has been established. The new relation established through this study may help to predict break-out dimension from the shear strength of the formation and stress profile. Till date, no such literature is available for the prediction of break-out dimensions for the wellbore stability in geomechanics. The proposed mathematical model helps us to design a cost-effective and safe well in the geologically complex reservoir for exploitation and exploration of hydrocarbon.

Drilling mud weight and wellbore orientation are convenient factors to manage wellbore stability. Improper selection of these convenient parameters causes the formation break-out or drilling-induced fracture. The main objective of this study is, to predict the optimum drilling mud weight with the concept of a new 3D failure criterion and drilling-exponent (D-exponent) factor for the proper maintenance of wellbore stability in challenging environments. The new failure criterion is derived as the function of principal stresses acting on the in situ rock. To prevent the formation break-out, optimum mud weight is calculated by the proposed criterion. Stresses around the wellbore acted in the cylindrical coordinate, so the kirsch equation converted all orthogonal stress into the cylindrical coordinate. A theoretical model calculates optimum mud weight by the proposed failure criterion and existing criteria like the Mohr-Coulomb criterion and the Mogi-Coulomb criterion. The D-exponent factor further corrects this suggested mud weight by real-time monitoring the drilling event. Mohr-Coulomb failure criterion overestimates the formation's strength as the criterion neglects the intermediated principal stress. Mogi-Coulomb criterion gave a dual result for optimum mud weight due to the quadratic equation of octahedral shear stress. Optimum mud weight prediction by the above methods is comparatively less accurate than our proposed model. The proposed criterion considers the effect of intermediate principal stress as a linear function of all stresses that make the mathematical model more effective and reliable for real problems. The predicted mud weight is updated in real-time monitoring by the D-exponent factor considering the drilling parameters like penetration rate (ROP) and tool cutting speed (RPM), weight on bit, and borehole diameter. This proposed model is also recommended for exploratory wells to predict and implement drilling parameters to maintain wellbore stability. The proposed new 3D failure criterion is an extended form of the Mohr-Coulomb criterion, where the roles of intermediate stress are also considered to predict optimum mud weight to keep the wellbore stable in a challenging environment. The proposed model is further helpful for maintaining wellbore stability in the exploratory well in high-pressure and high-temperature well, and environmentally challenged well by real-time monitoring.

For several years, geoscientists studied the seismicity of Arraiolos (central Portugal) which shows persistent but diffuse activity. Due to the slow Iberian intraplate deformation, it is difficult to observe a correlation between earthquakes and outcropping faults which induce a complexity in the interpretation of tectonic processes hidden behind the occurrence of the observed seismic activity. To overcome this issue, the study of the variation of velocity structures within depth in three-dimensions is obtained through seismic tomography. The crustal image will help to better constrain the seismicity. As it is generally unlikely to obtain a uniform distribution of rays sampling a medium, several approaches can be followed to enhance the tomographic imaging. In order to improve the ray coverage, we add reflected PmP and SmS phases. Following the Mw4.9 magnitude earthquake (January 15th, 2018), a temporary network of 34 seismic stations [21 short-period stations (Institute Dom Luiz, IDL) and 13 broadband stations (Institute of Earth Science, ICT)] were deployed recording a number of 437 earthquakes during a period of 6 months. The additional local and teleseismic events were detected on seismograms and relocated from a set of 12 broadband stations (DOCTAR network—Deep Ocean Test Array) operating between May 2011 and September 2012. In this study, a first inversion was performed from the Arraiolos aftershock sequence, generating crustal images that covered only a small part of the area and showing a poor ray density, mainly due to the narrow distribution of hypocenters. To significantly improve the resolution of the model, additional events and seismic phases are integrated in the process with the purpose of detecting the eventual presence of blind faults, correlating velocity layers with geological units and relocating the seismic events within the crustal model. This broader approach can be applied to any region of the world.

This paper uses high-resolution seismic profiles of the complex active zone of Al Hoceima (Morocco) to illuminate the active fault system, acquired along a main, 10 km long transect cutting across the strands of an active fault system in Al Hoceima bay area. The investigation approached was to tackle and follow faults vertical offset. The final seismic sections led to identify faults on the profiles and to distinguish the likely-active ones, with visible wide deformation features, where normal strike-slip faults trend N–S and NW–SE, principally related to the major Al Idrissi strike-slip fault system. To aid interpretation of this complex setting, we complemented seismic images with seismicity catalogs and focal mechanism solutions to investigate the active tectonics. These faults are accommodating an important part of the complex seismotectonic movements. Seismicity catalog in the Al Hoceima area exhibits a moderate seismic release (Mw < 6), with shallow depths mostly ≤ 20 km, focal mechanisms suggest mainly a strike-slip regime with a subvertical σ3 and subhorizontal σ1 implying a transtensional regime in the area. The seismicity seems to be confined between two major faults: Trougout in the east and Rouadi in the west. However, this trend is no longer respected in the last 2 years as seismic activity is shifting toward the eastern side of the Trougout fault. Moreover, a seismic gap zone around this fault is evident considering the instrumental seismicity catalog of last 100 years. This fault system and related seismicity could represent a potential hazard for neighbor cities.

On 25th April 2012, a moderate Mw4.9 earthquake, followed by an aftershock sequence (0.6 ≤ ML ≤ 4.3), occurred in Beni Haoua, northern Algeria. To reveal the fault responsible for this earthquake and the likely associated subsurface deformation, a detailed study of the weak seismicity based on spectral modelling of source parameters has been performed. The earthquake affected the area located in the north-eastern extend of the El Asnam seismic zone and it appears likely related to the reactivation of a segment of the fault zone that caused the El Asnam Mw7.1 earthquake on 10th October 1980, one of the most destructive earthquakes recorded in northern Africa and western Mediterranean. The determination of the source parameters of these earthquakes is important because they are too small to be reported in a global catalogue. In this study, source parameters are determined for 35 associated aftershocks using spectral modelling of three components P and S waves, assuming the Madariaga 1976 model. This model is one of the most widely used for a singular crack, radially expanding at a constant rupture speed. In this study, we estimated the source parameters (seismic moment, size of the seismic source, source dislocation and stress drop) from data in the frequency domain and we show how the results depend on the model assumptions. The Q attenuation factors for P and S waves are estimated to be 97 (50–170) and 153 (73–242), respectively, with a ratio of Qs/Qp = 1.62. We analysed source spectra and stress drops of 35 micro-earthquakes and resolved significant variations in earthquake stress drop and apparent average source dimension Rp and Rs of about 17 and 75 m, respectively. From the local magnitude calculated for the studied aftershock sequence, we highlighted similar relationship between the moment magnitude and the local magnitude, Mwp = 0.62 ML + 0.86 and Mws = 0.63 ML + 0.81, for P and S waves, respectively. This type of study is very important since we have exploited low magnitude earthquakes to obtain information that can contribute to the seismotectonic analysis of active seismic zone.

The Wadam As Sahil port and facility (study area) is part of al Batinah region of northern Oman coast. This important coastal segment may be subjected to tsunami from two subduction zones in the Indian Ocean, namely Makran Subduction Zone (MSZ) and Sumatra Subduction Zone (SSZ) in the Indian Ocean. The MSZ is divided into the East Makran Subduction Zone (EMSZ) and the West Makran Subduction Zone (WMSZ) segments. The deterministic approach for tsunami hazard assessment is estimated using the scenarios of the historic events of 1945 (HMSZ), along with two scenarios featuring Mw 8.8 event in EMSZ and Mw 7.2 in WMSZ. Sumatra Subduction Zone (SSZ) poses a very low hazard to the coast of the study area due to shielding of the Indian subcontinent, therefore, it is not considered in this study. Tsunami numerical simulations are performed utilizing validated shallow water model over a high-resolution digital elevation model of the study area. A compilation of multisource elevation data from several sources was utilized to generate the digital elevation model (DEM) for the study area. The simulated maximum probable earthquake with 7.2 magnitude from the WMSZ resulted in tsunami hazard of more than 3 m wave height, about 2.8 m run up, and nearly 800 m inundation at the study area coast. The simulated maximum probable earthquake with 8.8 magnitude from the EMSZ resulted in tsunami hazard of less than 1.5 m wave height, about 2.0 m run up, and nearly 680 m inundation at the study area coast. The WMSZ Tsunamigenic source dominates the tsunami hazard due to its close proximity to the study area coast. The EMSZ poses less hazard to the study area due to orientation of the fault and it is distant from the study area coast. The last tsunami hazard is due to Makran 1945 earthquake due to its distance, strike orientation, and relative magnitude.

Ionospheric anomalies associated with the Mw 6.0 and Mw 6.4 south Iran twin earthquakes were investigated through GPS and ground Ionosonde observations. The pre-seismic and the co-seismic ionospheric disturbances (CIDs) were observed in the GPS measured Total Electron Content (TEC) and the Ionosonde measured NmF2 and hmF2. The results show positive enhancement of TEC at near field stations ~2–6 days prior to the twin earthquakes. The estimated NmF2 and hmF2 values also show positive values in the pre-seismic phase compared to their mean values. These anomalies are attributed to seismic activity as the Planetary K index (Kp) and Disturbance Storm-time index (Dst) were quiescent during the entire observation period. Observation of sudden CIDs at near field stations immediately after the earthquakes explains the co-seismic energy propagation mechanism through the Lithosphere Atmosphere Ionosphere (LAI) coupling. Our observation on the differential NmF2 marks a dip in the peak electron density by -2.84 × 1011 e/m3 during the time of earthquakes. The estimated TEC, NmF2, and hmF2 results show a consistent reduction in their values on the day of earthquakes. Moreover, their changes were similar in both pre- and co-seismic phases and hence they are qualified as potential parameters for earthquake precursors. Thus the pre- and co-seismic ionospheric anomalies detected in this study reveal the characteristic signatures of twin earthquake preparation processes and the co-seismic energy propagation.

In this study, we present the outcome of a trial of the Radio Direction Finding detection system, aimed at verifying the link between electromagnetic signals detected in Italian monitoring centers from those emitted in tectonically stressed areas. The area studied is in the Po Valley, in Northern Italy, in an area historically affected by seismicity with earthquakes rarely exceeding magnitude 6. The Radio Direction Finding system, designed to detect the direction of electromagnetic signals, confirmed the applicability of this method for areas subjected to crustal stresses that can evolve into seismic shocks. In the case of this experiment, the signals preceded the seismic events by about 24 h, and the intersection of the colorimetric lines, which appeared in the dynamic spectrograms, coincided with the future epicenter zone of the earthquakes. The seismic occurrence fell within a time window of three days, confirming a well-established trend, that overlapping with previously studied cases.

Some regions of Morocco are characterized by relatively moderate active seismicity and mining. The seismic activity in Morocco is related to the African and Eurasian plate’s convergence. In this work, we examined several diagnostic techniques to identify and distinguish between earthquakes as natural events and explosions as artificial events in the northern part of Morocco. The methods used are based on seismic spectral amplitude ratio, moment magnitudes (Mw), the time duration of signals, and focal mechanisms. The discrimination has been checked regarding monitoring of local seismicity and chemical explosion using the data recorded from more than 80 seismic stations in the framework of several projects; PICASSO, Topo Iberia, Morocco-Array, SIMA, RIFSIS for the period from 2010 to 2012. It comes out that using the distribution of Amplitude/Frequency methods between 0.1 and 25 Hz frequency band, the separation appears clearly for the earthquakes in the range 1–3 Hz and explosions in the range 9–12 Hz. Therefore, the moment magnitude of natural earthquakes is greater than that of artificial explosions. The detectability of the local earthquake and chemical explosion is estimated by the near station to the mine. The magnitude of explosions and earthquakes is between 2 and 4. Our approach is to apply these methods to better separate the populations of earthquakes and explosions to help calibrate local discriminants, especially in the phosphate areas where explosions rich database is available. This may shed light on the seismicity pattern of the region.

Bright bolides entering the atmosphere announce the entrance of meter-sized meteoroids often surviving as meteorites reaching the ground. To be able to find them, it is necessary to locate quickly the position of the final explosion. This is usually done using optical sensors, but the bolides produce shock waves that can be detected by infrasound stations and, after coupling to the ground, also by seismic stations. The increasing availability of temporal seismic station deployments and the gathering of the records on permanent seismic networks can become a powerful tool to complement optical data, in particular for diurnal events or explosions located far from optical stations. We present here two examples of bolides exploding over NE Iberia that were reported in the Spanish Fireball and Meteorite Network (SPMN) catalog with magnitudes − 12 and − 17 and recorded by temporary seismic arrays deployed near their entry trajectory. The location of the final explosions has been derived from the seismic data using a simplistic hypothesis and the codes used systematically for earthquake location. Although locating accurately the origin point of sonic waves is a complex task, our approach allows getting a quick location of the explosion location, with errors estimated in few kilometers that appears as a useful tool to better define the search zone for eventual meteorites.

During 2020, people around the world lived a lockdown of different stages consequence of COVID-19 pandemic, switching almost every daily life activity to a remote version. As evidenced by previous studies, the human activity reduction resulted in lower levels of background seismic vibrations mostly for frequencies ranging between 2 and 20 Hz. As this is also the characteristic frequency band for the body-wave arrivals of local events, we could expect an increase on the signal-to-noise ratio during lockdown, resulting in a better detection of such phases, for seismic stations located in urban environments. The deployment in the city of Barcelona of a large seismic network during the lockdown period provides a unique opportunity to check this hypothesis. A manual picking of the local earthquake arrivals reported in the Institut Cartogràfic i Geològic de Catalunya ICGC catalog has been carried out on the waveforms recorded by the permanent and temporary seismic stations located within the city. We have reviewed the seismic events occurring between December 2019 and September 2020, to compare the detection level in the pre-lockdown, lockdown, and post-lockdown time periods. By quantifying the number of picked P-waves on each station and classifying this information according to the hour of day, it has been possible to analyze the correlation between the human common activity and the capacity of seismic stations to record seismic events. First results indicate that the reduction of seismic noise during lockdown resulted in a higher number of pickings at labor hours. However, the limited number of local events and the occurrence of a small seismicity cluster close to Barcelona during the lockdown, makes it difficult to be conclusive on the influence of the seismic noise reduction on the detection capability.

Seismic hazard assessment in stable continental regions (“intraplate domain”) involves specific difficulties, due to the lower recurrence of events compared to active zones, and to the fact that the triggering processes are particularly complex and still poorly understood. Several recent studies emphasize the role of local processes such as erosion, deglaciation, fluid circulation, etc. The concept of “hydro-seismicity” (Costain, Geol Soc Lond Spec Publ 432:91, 2017) explains a possible mechanism, the triggering of intraplate seismicity by the pressure increase in the interstitial fluid, decreasing the effective stress within the fault plane. Although climate change may not be perceptible at the level of the annual volumes of precipitation, the alternation of drought periods with intense rainy episodes may constitute a significant transient water supply, reaching shallow faults by infiltration into the subsoil and inducing the phenomenon of hydro-seismicity. In this context, we have shown that the local magnitude 5.4 earthquake of November 11, 2019, in Le Teil (France) could have been triggered by the transient increase in hydraulic pressure following heavy rainfall in the days preceding the event, while the trigger of the event was initially attributed to the activities of a quarry located near the earthquake zone. Using soil moisture data acquired by the SMOS satellite and modeling the height variations of the unsaturated zone by the ComPass code developed by the Bureau de Recherches Géologiques et Minières (BRGM), we show that water infiltration has induced hydraulic overpressures. The maximum value is located at the intersection of a system of faults at 1200 m depth; the hypocenter of the earthquake. The impact of this overpressure has been estimated to be several times greater than the cumulative effect of mechanical stress release due to the exploitation of the quarry over the two past centuries.

Structural pounding among insufficiently separated buildings constitutes one of the main reasons for damage and the possible collapse of structures during severe earthquakes. Building pounding is still not properly understood, as it involves several complex phenomena, leading to unclear patterns for the dynamic behaviour of the colliding structures. Hence, this study considers floor-to-floor collisions between fixed-base reinforced concrete buildings under earthquake excitations. The different number of stories and separation distances are considered to analyze the results in terms of story shear forces and interstory drifts. Finite element models are constructed, considering a fibre-based approach to model the inelasticity at the ends of structural members. Structural pounding was simulated through the use of a viscoelastic impact model, the Kelvin-Voight model. Results showed that the stories above the points of impact experienced 50% to almost 100% increases in interstory drifts and shear force demands, which may lead to brittle failures of the columns. The number and magnitude of pounding forces were higher for upper stories. The case with no gap size did not always lead to the worst scenario, and a separation distance close to the no-pounding case still presented pounding forces of significant magnitude, emphasizing the importance of proper separation of building structures. In conclusion, the buildings in the scenarios with an unequal number of stories were more vulnerable to pounding forces, experiencing higher increases in story shear and interstory drift.

On May 26, 2019, at 02:41 h (Peruvian time), the Mw 8.0 Sismo Lagunas 2019 earthquake occurred. It had its epicenter at the coordinates: − 05.74°, − 75.55°, 60 km south of the town of Lagunas (Loreto), at a depth of 135 km with Mw 8.0. It caused a lot of damage, including the liquefaction phenomenon reported in the woody village of Tamarate. The maximum horizontal acceleration recorded was at the UNTRM Station (0.098 g) in Chachapoyas with an epicentral distance of 292.21 km. In December 2019, geophysical tests were conducted in the woody village center of Tamarate, the area where the soil liquefaction event was evidenced. The reasons for choosing to use multi-channel surface wave and ambient vibration tests are based on (i) the fact that the area is only accessible by river. And (ii) the used geophysical equipments are practical and easy to handle and transport compared to the usual equipment such as the Standard Penetration Test and Cone Penetration Test for liquefaction potential evaluation. Multi-channel surface wave and ambient vibration analysis tests were performed to determine the shear wave velocity profile and the fundamental period of the ground. Seismic profiles and average wave velocities were Vs30 (163–168 m/s). The predominant period values obtained in the study area were 0.5 and 0.7 s. The occurrence of soil liquefaction (FSL) was evaluated using the deterministic method as the ratio of the minimum strength normalized cyclic shear stress producing liquefaction or “Cyclic Resistance Ratio” (CRR) divided by the normalized cyclic shear stress induced by the earthquake or “Cyclic Stress Ratio” (CSR). The CRR parameter was determined at each depth up to 30 m. With this evaluation, the actual minimum acceleration value that occurred in Tamarate was found between 0.1 and 0.12 g. A soil liquefaction was generated up to a depth of 13.2 m.

The high seismicity of the territory imposes special requirements on the construction industry of the Kyrgyz Republic; it is necessary to develop and implement a long-term and targeted state policy in order to increase the level of seismic resistance of existing and newly constructed buildings and structures. This research presents the classification of low-rise buildings from local materials and the analysis of a series of experiments on models of low-rise buildings from local materials. The local material is clay. As a local type of clay used earthenware clay. Owing to their excellent insulation properties and their heat storage capacity, clay building materials help to reduce the energy consumption of buildings. A series of experiments were carried out to analyze seismic resistance and to increase insulation properties. Their intensity can reach 8–9 balls by the MSK64 scale or even more. The Medvedev–Sponheuer–Karnik (MSK) scale of seismic intensity was widely used in former Soviet Union countries starting in 1964 and it is based on typical masonry structures. The last series of experiments showed that the model of a house built from local materials and reinforced with a wooden frame of the “Synch” type has the following properties: does not collapse at different weights of coatings, even with intensity 9 by MSK64 scale (in terms of acceleration) earthquakes; of all the options, the most acceptable in terms of efficiency and seismic resistance were houses with a wooden frame “Synch” filled with clay materials. Wooden-framed houses filled with clay materials are called «synch» houses. The Synch is a timber frame structure filled up with earthenware clay.

Using seawater seismic reflection images has certain advantages for studying small and mesoscale physical ocean features. In addition to various physical phenomena such as internal waves and vortices, there may also be various interference factors in seawater seismic reflection images, which have different characteristics in seismic reflection images. Analyzing and extracting these different features is of great significance for image-denoising interpretation, analysis, and recognition. The wavelet analysis method is widely used in image processing, which can effectively separate different frequency/wavenumber components in the image to achieve image-denoising and specific frequency/wavenumber feature extraction. The effect of wavelet processing is greatly affected by the wavelet base function. Only selecting the appropriate wavelet base can have ideal results for different types of images. Here, three bases, Haar, db4, and bior4.4 are selected to process the seawater seismic wave images. Comparing the decomposition results of three different wavelet bases, the decomposition results of the Haar wavelet can clearly show the horizontal characteristics of the water layer in the image. In contrast, the decomposition results of DB4 and bior4.4 are relatively weak. The specific final decomposition order should be determined according to the purpose and demand of actual image interpretation.