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Parwan Gravity Dam is under construction stage in the Jhalawar district of Rajasthan, India. A thin sub-vertical surficial fracture trending N 75°W to S 75°E has been observed in the foundation area of the dam. Geophysical techniques such as electrical resistivity tomography (ERT), seismic refraction tomography (SRT), and multichannel analysis of surface waves (MASW) are utilized extensively in the field of civil engineering, exploration geophysics for the assessment and construction of large-scale infrastructures such as dams. These methods provide critical information about the subsurface conditions without the need of extensive drilling and excavation. The combination of electrical resistivity tomography (ERT), seismic refraction (SR), and multichannel analysis of surface waves (MASW) techniques with the different acquisition parameters have been used to image the extent of shallow subsurface geological structures. Various geophysical Surveys have been carried out along several profiles in the longitudinal direction and along the transverse direction to the fault axis. A total of 13 refraction and resistivity profiles were conducted of which 9 were transverse profiles and 4 were longitudinal profiles. A total of nine MASW profiles were conducted of which 8 are transverse profiles and 1 is a longitudinal profile. In this paper, the subsurface distribution of seismic wave velocity and electrical resistivity have been studied to identify any possible anomalous zone in bedrock and to detect the downward extension of surface fracture of brittle fault using the afore mentioned methods. The vertical and lateral extent of the surface fracture of the fault has been investigated by the analysis of these survey results. The analysis of the results indicates that a very tight and narrow fracture is present in the shallow subsurface. [ABSTRACT FROM AUTHOR]

Landslides are a rare but hazardous geological phenomenon in Egypt, with the El Mokattam plateau situated in the eastern part of Cairo covering approximately 64 km2 and ranging in elevation from 50 to 205 m. This study aims to identify and monitor landslides in the area using various geophysical methods. Twelve Electrical resistivity tomography (ERT) profiles,twenty-two P-wave Seismic Refraction profiles, twenty-two Refraction microtremors profiles, three ground penetrating radar (GPR) profiles and borehole data were utilized to analyze the occurrence of landslides in the El Mokattam Plateau. Additionally, we employed a relatively new geophysical method, studying high-frequency microtremor sounds emitted from landslide collapses at 22 stations. Our analysis identified steep slopes, jointed or fractured rocks, and irrigation water as primary factors contributing to landslides, with irrigation water acting as a lubricant for clays and promoting ground sliding. Examination of high-frequency microtremor sounds revealed a potential correlation between vertical high-frequency spectra at 100 Hz and landslide collapses, which aids in the identification of landslide-prone zones. Therefore, we conclude that seismological studies, particularly spectral analysis of high-frequency and low-amplitude sounds (microtremors) emitted from soil, offer a promising approach for investigating landslides.

Geophysical exploration of bauxite deposits has been carried out in the area of Posušje in Bosnia and Herzegovina, which were formed on an Upper Cretaceous carbonate substrate, whereas the hanging wall rocks can be Paleogene limestones and sedimentary clastic rocks. Karst terrains are demanding for geophysical exploration due to the relatively complex geological relationships and exceptional near-surface inhomogeneities that generate large noises and challenging conditions for taking field measurements. The fundamental question is whether geophysical research can detect exceptionally irregular karst bauxite deposits with relatively small dimensions. The basic idea is to combine several geophysical methods and a joint interpretation of several data sets to increase the efficiency of geophysical surveying in detecting complex bauxite deposits in karst terrains. Therefore, fundamental near-surface research methods, electrical tomography and seismic refraction are used. In addition, magnetometry was used to examine whether bauxite deposits yield potential magnetic anomalies that could help in detecting them. Research undertaken in the area of Posušje was carried out in the first step on already discovered and known bauxite deposits to determine whether geophysical responses correlate with the occurrence of bauxite deposits and to evaluate the effectiveness of each of the applied surface geophysical methods. Measurements were taken at several locations, and results for two micro-locations, Krstače and Mratnjača, are shown. Geophysical measurements were firstly performed on discovered bauxite deposits in order to reliably determine the possibility of identifying deposits in geophysical inverse models. Bauxite deposits were clearly recognised as characteristic geophysical responses in inversion models using both methods, electrical tomography and seismic refraction. Although the response of bauxite deposits is expressed in both models, resistivity and velocity, it is much more evident in resistivity models. The characteristic resistivity response was confirmed by the discovery of a new deposit. Therefore, the conclusion is that electrical resistivity tomography should be considered a basic method for exploring karst bauxite deposits. Seismic refraction provides a better characterisation of deposits and reduces the interpretation ambiguity. This solution can generally be applied to the problem of researching bauxite deposits in the Dinarides and similar geological models in the Mediterranean. Magnetometric measurements have shown that no magnetic anomalies could be associated with bauxite deposits, and only magnetometry was not successful in discovering bauxite deposits. [ABSTRACT FROM AUTHOR]

This study investigates the weathered layer parameters of the Gbaran (OML 28) field in the Niger Delta using uphole refraction. 57 boreholes were bored and logged to study stratum components and characteristics. Weathered layer thickness ranges from 15.1m to 4.3m, with an average unconsolidated layer thickness of 6.9105m. Most of the unconsolidated stratum is silt or clay. This stratum has seismic wave velocities from 299 to 997m/s, averaging 697.14m/s. Consolidated stratum velocities average 1742.58m/s, ranging from 1551 to 1925. Subsurface refraction surveys were conducted at numerous locations, drilling and logging 57 boreholes. The acquisition plan included flushing drilling, cut lithology sampling, and logging from 0 to 60 metres. The velocities and thicknesses measured for each uphole site distinguish worn and cemented layers. Weathered layer thickness shows geological formation-influenced variations. Weathered layer velocity is 299-997m/s lower than consolidated layer velocity. Consolidated layer velocity is 1551-1925 m/s. Weathered layer thickness, velocity, and consolidated layer velocity are examined, focusing on thickness-velocity relationships. The recommendations include foundation design, construction methods, water management, geotechnical research, seismic design, monitoring, and geotechnical specialist coordination. Seismic refraction surveys can characterize underlying material variations and aid engineering design and risk assessment in the Niger Delta's dynamic geology. [ABSTRACT FROM AUTHOR]

We combined datasets from multiple research projects and remote sensing technologies to evaluate conservation conditions at La Fortaleza de Kuelap, a pre-Hispanic site in Peru that suffered significant damage under heavy seasonal rains in April 2022. To identify the causes of the collapse and where the monument is at further risk, we modeled surface hydrology using a DTM derived from drone LiDAR data, reconstructed a history of collapses, and calculated the volume of the most recent by fusing terrestrial LiDAR and photogrammetric datasets. In addition, we examined subsurface water accumulation with electrical resistivity, reconstructed the stratification of the monument with seismic refraction, and analyzed vegetation loss and ground moisture accumulation using satellite imagery. Our results point to rainwater infiltration as the most significant source of risk for La Fortaleza's perimeter walls. Combined with other adverse natural conditions and contemporary conservation interventions, this led to the 2022 collapse. Specialists need to consider these factors when tasked with conserving monuments located in comparable high-altitude perhumid environments. This integration of analytical results demonstrates how multi-scalar and multi-instrumental approaches provide comprehensive and timely assessments of conservation needs. [ABSTRACT FROM AUTHOR]

Poisson's ratio for earth materials is usually assumed to be positive (Vp/Vs > 1.4). However, this assumption may not be valid in the critical zone because near Earth's surface effective pressures are low (<1 MPa), porosity has a wide range (0%–60%), there are significant texture changes (e.g., unconsolidated vs. fractured media), and saturation ranges from 0% to 100%. We present P‐wave (Vp) and S‐wave (Vs) velocities from seismic refraction profiles collected in weathered crystalline environments in South Carolina and Wyoming. Our data show that ∼20% of the subsurface has negative Poisson's ratios (Vp/Vs values < 1.4), a conclusion supported by borehole sonic logs. The low Vp/Vs values are confined to the fractured bedrock and saprolite. Our data support the hypothesis that weathering‐generated microcracks can produce a negative Poisson's ratio and that Vp/Vs values can thus provide insight into important critical zone weathering processes. Plain Language Summary: When a material is squeezed, the ratio between the change in height and width is described by an elastic parameter called Poisson's ratio. Most earth materials have a positive Poisson ratio, meaning the material will expand when squeezed (e.g., Playdough or wet sand). Materials with a negative Poisson's ratio rarely occurs naturally and will shrink in all directions when squeezed. Cork is a common material with a Poisson's ratio of approximately zero. Cork is ideal for bottling wine because its width does not change when pushing it into the bottle's narrow neck. Here we use surface‐based measurements to quantify Poisson's ratio from P‐wave (Vp) and S‐wave (vs.) velocities in the top 50 m of Earth's surface. Our results show an unexpected result—material in the CZ has a negative Poisson's ratio. We believe this unexpected behavior is caused by the combination of low effective pressures and small and irregular cracks created during rocks' transformation into soil. The cracks have a greater impact on the material's ability to resist compression. At the same time, most of the rock is still coherent and thus only experiences a minimal loss of shear strength. Key Points: Vp/Vs values in the critical zone can be less than 1.4, suggesting a negative Poisson's ratioIn near‐surface environments, the assumption that materials have a positive Poisson ratio is not always justifiedLow Vp/Vs ratios may identify the onset of physical weathering in crystalline rock [ABSTRACT FROM AUTHOR]

Understanding the near-surface structure of the Earth requires accurate prediction of physical properties of the subsurface, such as velocity estimated from tomographic inversion of seismic refraction data. The predicted velocity values are often uncertain due to epistemic uncertainty in the inversion process (i.e., imperfectly known underlying physics) and aleatoric variability in the data (i.e., inherent noise in observations). Although seismic refraction is widely used in near-surface applications, the associated uncertainty is rarely quantified and presented alongside the inverted velocity tomograms. In this study, the effect of epistemic uncertainty due to local variability in the initial model and aleatoric variability due to first-arrival picking error on the velocity prediction uncertainty are investigated. A stochastic framework is implemented based on a statistical approach where multiple realizations of stochastically perturbed initial models and travel time picks are generated and the uncertainty in the predicted velocity models is quantified. The two sources of uncertainty are first studied independently and then the combined effect is investigated. The results show that both sources affect the posterior uncertainty, but the uncertainty in the initial model has a greater effect than picking error on the uncertainty of the posterior velocity model. In addition, joint analysis of both sources of uncertainty shows that the uncertainty in the inverted model depends on predicted velocity values, depths, velocity gradients and ray coverages. [ABSTRACT FROM AUTHOR]

Hydrologic modeling has been a useful approach for analyzing water partitioning in catchment systems. It will play an essential role in studying the responses of watersheds under projected climate changes. Numerous studies have shown it is critical to include subsurface heterogeneity in the hydrologic modeling to correctly simulate various water fluxes and processes in the hydrologic system. In this study, we test the idea of incorporating geophysics‐obtained subsurface critical zone (CZ) structures in the hydrologic modeling of a mountainous headwater catchment. The CZ structure is extracted from a three‐dimensional seismic velocity model developed from a series of two‐dimensional velocity sections inverted from seismic travel time measurements. Comparing different subsurface models shows that geophysics‐informed hydrologic modeling better fits the field observations, including streamflow discharge and soil moisture measurements. The results also show that this new hydrologic modeling approach could quantify many key hydrologic fluxes in the catchment, including streamflow, deep infiltration, and subsurface water storage. Estimations of these fluxes from numerical simulations generally have low uncertainties and are consistent with estimations from other methods. In particular, it is straightforward to calculate many hydraulic fluxes or states that may not be measured directly in the field or separated from field observations. Examples include quickflow/subsurface lateral flow, soil/rock moisture, and deep infiltration. Thus, this study provides a useful approach for studying the hydraulic fluxes and processes in the deep subsurface (e.g., weathered bedrock), which needs to be better represented in many earth system models. Plain Language Summary: The precipitation received in a watershed is usually partitioned into streamflow, plant water use, soil/rock moisture, and groundwater. While many of these components can be directly measured in the field or estimated from hydrometeorological measurements, the moisture stored in the subsurface (soil and rock layers) is difficult to quantify and measure. Using the computer to simulate the water flow and storage in a watershed provides a useful tool for quantifying water partitioning in a catchment. Previous research highlighted the importance of including both above‐ground and below‐ground variations in computational modeling. Compared to above‐ground heterogeneity, it is much more challenging to characterize below‐ground heterogeneity because we cannot see the variations in the subsurface. In this study, we propose to determine the subsurface heterogeneity/variations with geophysical imaging (more specifically, the seismic refraction method), and the geophysics‐obtained subsurface model is then incorporated into the computational simulation of a watershed or catchment. A small mountainous headwater catchment in Idaho is used to demonstrate this method, and the results show that the new modeling well reproduces the field‐measured streamflow of the catchment. This new modeling also gives reliable estimates for some properties that are difficult to determine using traditional methods. With the changing climate, the proposed new method will help better understand how a catchment will respond to the projected weather, such as extreme snowfalls or severe droughts. Key Points: The 3D velocity model of a mountain catchment was created based on the results of a series of 2D seismic refraction testsThe 3D subsurface critical zone structure was extracted from the velocity model and incorporated into hydrologic modelingGeophysics‐informed hydrologic modeling provides valuable additional information on the hydrological partitioning in the catchment [ABSTRACT FROM AUTHOR]

Abstract Lembang groundwater basin has an area of 209 km2. Increased tourism activities in the Lembang Groundwater Basin require sufficient groundwater resources to support the sustainability of these tourism activities. The purpose of this study was to analyze the hydrostratigraphy of the groundwater recharge zone of the Lembang groundwater basin in the Cikole-Lembang. Electrical Resistivity Tomography (ERT) with dipole–dipole electrode array and seismic refraction was used to analyze the hydrostratigraphy. The results of ERT and seismic refraction inversion show that Tangkubanparahu Pyroclastic Fall 2 can be characterized as aquifers. This layer consists of low (123–292 $$\Omega $$ Ω m) and intermediate (293–700 $$\Omega $$ Ω m) resistivity value and also has low (300–1350 m/s) to medium (2700–1350 m/s) velocity. Tangkubanparahu lava (Tl) layer has a high resistivity value (701–3875 $$\Omega $$ Ω m) and high (1350–2999 m/s) velocity. The Tangkubanparahu Pyroclastic Fall 1 has a resistivity of 300–700 ohms. Tangkubanparahu (Tl) lava deposits can be characterized as fracture aquifer and impermeable layers in the Tangkubanparahu volcanic hydrogeological system depend on the historical structural geology event.

Conventional geophysical methods are suitable for estimating the thicknesses of subsoil layers. By combining several geophysical methods, the uncertainties can be assessed. Hence, the reliability of the results increases with a more accurate engineering solution. To estimate the base of an abandoned landfill, we collected data using classical approaches: high-resolution seismic reflection and refraction, with more modern methods including passive surface wave analysis and horizontal-to-vertical spectral ratio (HVSR) measurements. To evaluate the thickness of the landfill, three different datasets were acquired along each of the two seismic lines, and five different processing methods were applied for each of the two arrays. The results of all the classical methods indicate very consistent correlations and mostly converge to clear outcomes. However, since the shear wave velocity of the landfill is relatively low (

This paper presents the integration of seismic refraction and multichannel analysis of surface wave (MASW) measurements to investigate the anisotropy of P- and S-wave velocities. Additionally, synthetic forward modelling is presented as a tool for supporting seismic anisotropy studies. The geophysical measurements of cracks allowed to recognise the fracturing of a granite rock mass in a Paleozoic granite quarry (Strzegom, Poland) and a dolomite rock mass in a Triassic dolomite quarry (Podleśna, Poland). Application of the forward modelling supports the interpretation of seismic methods, simplifying data processing and verifying the final results based on data from difficult seismic conditions. As a result of direct measurements, two crack systems were determined in granite rock mass: NNE-SSW and NNW-SSE, and two in dolomite rock mass: NNE-SSW and NW-SE. Furthermore, the numerical results show the relationship between the highest values of P- and S-wave velocities and separated crack systems which allowed an unequivocal interpretation of the direction of stress, resulting in the deformations. The obtained information is promising to be helpful in mining exploration for optimising excavation works.

Abstract Poisson's ratio for earth materials is usually assumed to be positive (Vp/Vs > 1.4). However, this assumption may not be valid in the critical zone because near Earth's surface effective pressures are low (

Failure events in dams can be associated with processes in the dam body and in the foundation of the structure. If they are properly identified in early stages, corrective actions can take place, leading to a reduction in the risk of collapse and/or rupture of the dam. Most studies on dams are carried out on the body of the dam; however, problems associated with the foundation of the structure can also lead to loss of stability and subsequent ruptures. This study presents an analysis of the advantages and limitations of the use of seismic refraction in hydrogeological studies of fractured aquifers under pressure from large loads, specifically a dam in this case. Seismic refraction data were collected on an outcrop of fractured rock near a uranium storage dam foundation in southeastern Brazil. The results and interpretations were supported by a structural analysis performed through manual strike measurements collected with a Clark compass and an uncrewed aerial vehicle digital photogrammetry survey in an outcrop. The digital photogrammetric survey mapped the spatial distribution and orientation of the geological structures of the rock mass. Although the structural measurements performed through digital photogrammetry presented greater variability than the measurements collected from the compass, the maximum density of the fracture measurements obtained from both methods were similar and were corroborated by the regional and local fracture patterning. The integration of seismic refraction data with geotechnical and geological investigations allowed us to identify the positioning of structural lineaments in the rock mass and zones with a higher degree of rock alteration. The identification of highly fractured zones in the rock mass from such non-invasive investigations could be used to assist in decision making for structural reinforcements in the foundation of the dam to avoid the loss of stability at the foot of the dam from possible leaks or water flows from the reservoir.

Cam Mountain in An Giang Province, Vietnam, is a granite peak that is severely fractured and eroded on its slopes and summit. Trees cover the top of the mountain and around the side of the mountain. The roads are the primary means of transportation for indigenous people and tourists daily. Recently, there has been a phenomenon of large-sized boulders rolling down from the top of the mountain, causing an accident and killing tourists. To investigate the internal causes of landslides on a 2.3 km road stretch, geophysical profiles using GPR and seismic refraction methods were conducted to clarify the current status of geological structures beneath the road surface. The refractive seismic data analysis revealed four distinct layers based on elastic wave propagation velocity. Velocity values range from 1000 to 3000 m/s for the 2 upper layers corresponding to the weathered, broken, and highly fractured rock layers and in the lower 2 layers from 3000 to more than 4500 m/s, respectively corresponding to less fractured rock on the depth of more than 50 m. According to GPR data, the structural cross-section to an average depth of 30 m is a more complex picture. Detected 6 layers with different degrees of fracture cracking and showing different structural zones. In a few places are the drainage creeks from the mountain. These places need to be monitored regularly to have a basis for predicting landslides and rockfalls in the area of Cam Mountain. Landslides occur in geological rocks which are of different ages: claystone, mudstone, siltstone, shale, or marlstone. The rock-falls occur in more compact rocks: metamorphic or igneous rocks. [ABSTRACT FROM AUTHOR]

Landslides are often regarded as secondary hazards, typically triggered by major catastrophic events like storms, floods, volcanic eruptions, and earthquakes. In tropical regions such as Malaysia, the prevalent geohazard phenomenon involves landslides induced by moisture or rainfall. These incidents predominantly occur due to the unique composition of residual soils in the area, resulting from the weathering of bedrock in situ. Major landslides and local slope failures occur when water saturation exceeds a critical limit in certain parts of the slope. The foundation of a dependable stability analysis lies in the geological model of the landslide, which should accurately reflect the actual conditions. To achieve this, a thorough understanding of the landslide phenomenon and access to high-quality datasets are essential. In this study, 2D electrical resistivity imaging and seismic refraction tomography were utilized to identify subsurface characteristics, along with geotechnical data for data corroboration. The study shows a highly weathered zone (?< 1200 Om; Vp< 1200 m/s) was identified at a depth of less than 5 m. The number of blows (N-values) for standard penetration test (SPT) indicate a low range of 1-15, representing the low stiffness of the soil condition. The N-values show variation in the number of blows with depth, suggesting that the layer may not be competent due to the present heterogeneous material caused by the highly weathered process. The results emphasize the benefits of incorporating both geophysical and geotechnical parameters to define subsurface properties. The study offers insights into how spatial distributions of these parameters can be utilized to minimize uncertainty in ground models. [ABSTRACT FROM AUTHOR]

Lembang groundwater basin has an area of 209 km2. Increased tourism activities in the Lembang Groundwater Basin require sufficient groundwater resources to support the sustainability of these tourism activities. The purpose of this study was to analyze the hydrostratigraphy of the groundwater recharge zone of the Lembang groundwater basin in the Cikole-Lembang. Electrical Resistivity Tomography (ERT) with dipole–dipole electrode array and seismic refraction was used to analyze the hydrostratigraphy. The results of ERT and seismic refraction inversion show that Tangkubanparahu Pyroclastic Fall 2 can be characterized as aquifers. This layer consists of low (123–292 Ω m) and intermediate (293–700 Ω m) resistivity value and also has low (300–1350 m/s) to medium (2700–1350 m/s) velocity. Tangkubanparahu lava (Tl) layer has a high resistivity value (701–3875 Ω m) and high (1350–2999 m/s) velocity. The Tangkubanparahu Pyroclastic Fall 1 has a resistivity of 300–700 ohms. Tangkubanparahu (Tl) lava deposits can be characterized as fracture aquifer and impermeable layers in the Tangkubanparahu volcanic hydrogeological system depend on the historical structural geology event. [ABSTRACT FROM AUTHOR]

One of the most important parameters used to determine the dynamic properties of soil layers is the shear wave velocity. In geotechnical earthquake engineering, the shear wave velocity is used to determine the shear modulus, which provides the input parameters for the design of earthquake-resistant structures. Although there are measurement methods used in field studies to determine the shear wave velocity, they may not be economical in some cases. In this study, the empirical correlations between the shear wave velocity and penetration resistance in sandy soils were investigated with the use of geotechnical and geoseismic data obtained within the scope of microzonation studies performed in the Canakkale residential area. The results of the study were compared with correlations obtained from previous studies, and the equation we produced showed a good ability to predict the shear wave velocity. In addition, it was determined that standard penetration resistance, without energy correction, provided a better correlation coefficient. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Conventional geophysical methods are suitable for estimating the thicknesses of subsoil layers. By combining several geophysical methods, the uncertainties can be assessed. Hence, the reliability of the results increases with a more accurate engineering solution. To estimate the base of an abandoned landfill, we collected data using classical approaches: high-resolution seismic reflection and refraction, with more modern methods including passive surface wave analysis and horizontal-to-vertical spectral ratio (HVSR) measurements. To evaluate the thickness of the landfill, three different datasets were acquired along each of the two seismic lines, and five different processing methods were applied for each of the two arrays. The results of all the classical methods indicate very consistent correlations and mostly converge to clear outcomes. However, since the shear wave velocity of the landfill is relatively low (<150 (m/s)), the uncertainty of the HVSR results is significant. All these methods are engineering-oriented, environmentally friendly, and relatively low-cost. They may be jointly interpreted to better assess uncertainties and therefore enable an efficient solution for environmental or engineering purposes. [ABSTRACT FROM AUTHOR]

Detailed models of crustal structure at volcanic passive margins offer insight into the role of magmatism and the distribution of igneous addition during continental rifting. The Eastern North American Margin (ENAM) is a volcanic passive margin that formed during the breakup of Pangea ∼200 Myr ago. The offshore, margin‐parallel East Coast Magnetic Anomaly (ECMA) is thought to mark the locus of syn‐rift magmatism. Previous widely spaced margin‐perpendicular studies seismically imaged igneous addition as seaward dipping reflectors (SDRs) and high velocity lower crust (HVLC; >7.2 km/s) beneath the ECMA. Along‐strike imaging is necessary to more accurately determine the distribution and volume of igneous addition during continental breakup. We use wide‐angle, marine active‐source seismic data from the 2014–2015 ENAM Community Seismic Experiment to determine crustal structure beneath a ∼370‐km‐long section of the ECMA. P‐wave velocity models based on data from short‐period ocean bottom seismometers reveal a ∼21‐km‐thick crust with laterally variable lower crust velocities ranging from 6.9 to 7.5 km/s. Sections with HVLC (>7.2 km/s) alternate with two ∼30‐km‐wide areas where the average velocities are less than 7.0 km/s. This variable structure indicates that HVLC is discontinuous along the margin, reflecting variable amounts of intrusion along‐strike. Our results suggest that magmatism during rifting was segmented. The HVLC discontinuities roughly align with locations of Mid‐Atlantic Ridge fracture zones, which may suggest that rift segmentation influenced later segmentation of the Mid‐Atlantic Ridge. Plain Language Summary: The East Coast of the United States is a passive margin that formed during continental breakup of Pangea, the most recent supercontinent. Although passive margins are generally not locales of active faulting and magmatism, by investigating their current structure, we gain insight into processes during past rifting. We know that extensive volcanism and magmatic addition to the Earth's crust occurred during the breakup of Pangea, but we do not fully understand how the distribution changes from north to south along the margin. To study these rocks, which are buried 10–20 km beneath the seafloor, we use ocean bottom seismometers to determine the sound speed of rocks beneath the surface, which can tell us about composition and rock type. We found that the thickness and extent of magma‐derived rocks are variable along the margin, with gaps up to 30 km wide. This variability is likely related to processes happening in the continental rift which may have influenced the structure of the Mid‐Atlantic Ridge that formed after rifting ended. Key Points: High velocity lower crust beneath the East Coast Magnetic Anomaly is variable along‐strike and discontinuous in some placesThe lower crust variability reflects variable intrusion into lower continental crust and represents magmatic segmentation during riftingThe high velocity lower crust discontinuities are coincident to Mid‐Atlantic Ridge fracture zones, suggesting a rift‐to‐ridge connection [ABSTRACT FROM AUTHOR]

New geophysical profiles across the central Dead Sea Transform (DST) near the Sea of Galilee, Israel, and surrounding highlands, augmented by static stress modeling, allow us to study continental transform plate deformation. The DST separates a ∼10 km thick sedimentary column above a thinned (16–23 km) crust to the west from a ∼7 km column above a ∼30‐km thick crust to the east. Crustal thinning starts under the DST, as observed also farther south, indicating that the DST is indeed located along the boundary between the Arabian plate and its continental margin. Moho step here is gradual. The DST's eastern shoulder dips westward toward the DST unlike the upward flexed shoulder observed farther south, perhaps delineating the northern limit of a thinner and hotter lithosphere. The shape of the Sea of Galilee is modeled as an asymmetric pull‐apart basin formed by a left‐lateral stepover of 2.6 km between slightly divergent and underlapping strike‐slip fault strands dipping 70° to the west. Reflection data indicate that these strands are not connected. Several fault traces within the Sea of Galilee have previously been suggested to carry part of the relative plate motion. However, given slip along the main DST faults, Coulomb stress will increase only on fault portions in the northern part of the lake, in accord with the geographical distribution of seismicity, suggesting that these faults are likely secondary. Mismatch between the DST strand locations in the geophysical profiles and the subsidence model, may reflect temporal changes in fault geometry. Plain Language Summary: The Dead Sea fault system is a vertical discontinuity in the Earth upper layers, where two tectonic plates move laterally relative to each other. Their relative motion produce earthquakes and control the surface topography and sub‐surface structure. We imaged by geophysical methods the subsurface structure of this fault system and its surrounding region at the northern end of the Sea of Galilee, Israel, and we modeled the shape of the lake and the seismic rupture potential of faults there. The two plates, separated by the Dead Sea fault system, are the interior Arabian plate and its former margin, created during the formation of the Eastern Mediterranean Sea. As expected, the geological structure is different on either side of the fault system. The shape of the lake and recent seismicity in the area can be explained by lateral plate motion centered on two major faults with an intervening gap between them along the NE side of the lake. The fault geometry may have changed through geologic time. The geologic layers on the eastern side of the fault system plunge toward the fault system whereas farther south along the Dead Sea fault system, they curve up, possibly reflecting deep‐seated properties or processes. Key Points: The Central Dead Sea Transform separates a sediment and crustal structures of a passive continental margin from the Arabian plate interiorSeismic and gravity data show that unlike farther south, shoulder uplift here is absent and Moho step is more gradualThe shape of the Sea of Galilee and recent seismicity is explained by underlapping strike‐slip fault stepover activating secondary faults [ABSTRACT FROM AUTHOR]

Geophysical exploration of bauxite deposits has been carried out in the area of Posušje in Bosnia and Herzegovina, which were formed on an Upper Cretaceous carbonate substrate, whereas the hanging wall rocks can be Paleogene limestones and sedimentary clastic rocks. Karst terrains are demanding for geophysical exploration due to the relatively complex geological relationships and exceptional near-surface inhomogeneities that generate large noises and challenging conditions for taking field measurements. The fundamental question is whether geophysical research can detect exceptionally irregular karst bauxite deposits with relatively small dimensions. The basic idea is to combine several geophysical methods and a joint interpretation of several data sets to increase the efficiency of geophysical surveying in detecting complex bauxite deposits in karst terrains. Therefore, fundamental near-surface research methods, electrical tomography and seismic refraction are used. In addition, magnetometry was used to examine whether bauxite deposits yield potential magnetic anomalies that could help in detecting them. Research undertaken in the area of Posušje was carried out in the first step on already discovered and known bauxite deposits to determine whether geophysical responses correlate with the occurrence of bauxite deposits and to evaluate the effectiveness of each of the applied surface geophysical methods. Measurements were taken at several locations, and results for two micro-locations, Krstače and Mratnjača, are shown. Geophysical measurements were firstly performed on discovered bauxite deposits in order to reliably determine the possibility of identifying deposits in geophysical inverse models. Bauxite deposits were clearly recognised as characteristic geophysical responses in inversion models using both methods, electrical tomography and seismic refraction. Although the response of bauxite deposits is expressed in both models, resistivity and velocity, it is much more evident in resistivity models. The characteristic resistivity response was confirmed by the discovery of a new deposit. Therefore, the conclusion is that electrical resistivity tomography should be considered a basic method for exploring karst bauxite deposits. Seismic refraction provides a better characterisation of deposits and reduces the interpretation ambiguity. This solution can generally be applied to the problem of researching bauxite deposits in the Dinarides and similar geological models in the Mediterranean. Magnetometric measurements have shown that no magnetic anomalies could be associated with bauxite deposits, and only magnetometry was not successful in discovering bauxite deposits.

We combined datasets from multiple research projects and remote sensing technologies to evaluate conservation conditions at La Fortaleza de Kuelap, a pre-Hispanic site in Peru that suffered significant damage under heavy seasonal rains in April 2022. To identify the causes of the collapse and where the monument is at further risk, we modeled surface hydrology using a DTM derived from drone LiDAR data, reconstructed a history of collapses, and calculated the volume of the most recent by fusing terrestrial LiDAR and photogrammetric datasets. In addition, we examined subsurface water accumulation with electrical resistivity, reconstructed the stratification of the monument with seismic refraction, and analyzed vegetation loss and ground moisture accumulation using satellite imagery. Our results point to rainwater infiltration as the most significant source of risk for La Fortaleza’s perimeter walls. Combined with other adverse natural conditions and contemporary conservation interventions, this led to the 2022 collapse. Specialists need to consider these factors when tasked with conserving monuments located in comparable high-altitude perhumid environments. This integration of analytical results demonstrates how multi-scalar and multi-instrumental approaches provide comprehensive and timely assessments of conservation needs.

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Understanding how soil thickness and bedrock weathering vary across ridge and valley topography is needed to constrain the flowpaths of water and sediment production within a landscape. Here, we investigate saprolite and weathered bedrock properties across a ridge‐valley system in the Northern California Coast Ranges, USA, where topography varies with slope aspect such that north‐facing slopes have thicker soils and are more densely vegetated than south‐facing slopes. We use active source seismic refraction surveys to extend observations made in boreholes to the hillslope scale. Seismic velocity models across several ridges capture a high velocity gradient zone (from 1,000 to 2,500 m/s) located ∼4–13 m below ridgetops that coincides with transitions in material strength and chemical depletion observed in boreholes. Comparing this transition depth across multiple north‐ and south‐facing slopes, we find that the thickness of saprolite does not vary with slope aspects. Additionally, seismic survey lines perpendicular and parallel to bedding planes reveal weathering profiles that thicken upslope and taper downslope to channels. Using a rock physics model incorporating seismic velocity, we estimate the total porosity of the saprolite and find that inherited fractures contribute a substantial amount of pore space in the upper 6 m, and the lateral porosity structure varies strongly with hillslope position. The aspect‐independent weathering structure suggests that the contemporary critical zone structure at Rancho Venada is a legacy of past climate and vegetation conditions. Plain Language Summary: Below Earth's ground surface, porous space within weathered bedrock can store a significant amount of water, which is essential for ecosystems, particularly during the growing seasons. Collecting hydrologic data and core samplings from boreholes provides direct measurements about how bedrock is weathered and broken down toward the earth surface. Our study site is located in a series of ridges and valleys in Northern California, USA, where the local Mediterranean climate has distinctive dry summers and wet winters. This site represents a common topography along the east side of the Coast Ranges. In addition to synthesizing borehole and hydrologic data, we conduct complementary seismic refraction surveys to image material strength in the subsurface in 2D. These images can better capture the lateral variation of weathering zone thickness from channels to ridgetops. Seismic velocity derived from seismic refraction data shows an increase of material strength at the transition zone between saprolite and bedrock that agrees with borehole observations. Although vegetation density is much higher in the north‐ than the south‐facing hills, the depth to fresh bedrock is roughly the same. Our results also indicate that porous spaces in the weathered bedrock have the potential to store more water than annual precipitation. Key Points: A combination of geophysics and borehole measurements allows us to characterize lateral critical zone structure in a ridge‐channel systemDespite a strong aspect‐dependent contrast in soil thickness, saprolite thickness does not vary with slope aspectRock physics modeling using seismic velocity suggests that inherited bedrock fractures substantially contribute to saprolite total porosity [ABSTRACT FROM AUTHOR]

Global optimization methods have recently become an essential option in the processing and interpretation of geophysical data sets. In this study, we compared the optimization capability of five global optimization techniques in terms of their ability to localize a global solution and computation cost using objective functions for direct current resistivity (DCR), and seismic refraction (SR) data processing and interpretation. The genetic algorithm (GA), particle swarm optimization (PSO), simulated annealing (SA), surrogate optimization (SO), and pattern search (PS) optimization techniques were tested. The recently developed combined (global and local) optimization algorithm that uses the local optimization's output to minimize the search space for the global search method and achieve faster convergence is applied to solve the optimization problem for comparison. Because all the optimization algorithms try to minimize the same objective function, we benchmarked the comparison with the result of the local optimization algorithm using the Gauss–Newton (GN) method. The combined optimization algorithms run for 500 iterations for both synthetic and real data. All the optimization algorithms satisfactorily reconstructed the positive anomalies (synthetic data) and defined a suspected fault (real data). However, considering the result of the local optimization as a benchmark (in terms of misfit and run time), only the GA and PSO satisfactorily reduce the misfit obtained from both DCR and SR inversion using the GN method. Therefore, the GA and PSO should be considered as the proper techniques for inverting the real DCR and SR data sets, with sequential use of local and global optimization methods. [ABSTRACT FROM AUTHOR]

Seismic refraction tomography provides images of the elastic properties of subsurface materials in landslide settings. Seismic velocities are sensitive to changes in moisture content, which is a triggering factor in the initiation of many landslides. However, the application of the method to long-term monitoring of landslides is rarely used, given the challenges in undertaking repeat surveys and in handling and minimizing the errors arising from processing time-lapse surveys. This work presents a simple method and workflow for producing a reliable time-series of inverted seismic velocity models. This method is tested using data acquired during a recent, novel, long-term seismic refraction monitoring campaign at an active landslide in the UK. Potential sources of error include those arising from inaccurate and inconsistent determination of first-arrival times, inaccurate receiver positioning, and selection of inappropriate inversion starting models. At our site, a comparative analysis of variations in seismic velocity to real-world variations in topography over time shows that topographic error alone can account for changes in seismic velocity of greater than ±10% in a significant proportion (23%) of the data acquired. The seismic velocity variations arising from real material property changes at the near-surface of the landslide, linked to other sources of environmental data, are demonstrated to be of a similar magnitude. Over the monitoring period we observe subtle variations in the bulk seismic velocity of the sliding layer that are demonstrably related to variations in moisture content. This highlights the need to incorporate accurate topographic information for each time-step in the monitoring time-series. The goal of the proposed workflow is to minimize the sources of potential errors, and to preserve the changes observed by real variations in the subsurface. Following the workflow produces spatially comparable, time-lapse velocity cross-sections formulated from disparate, discretely-acquired datasets. These practical steps aim to aid the use of the seismic refraction tomography method for the long-term monitoring of landslides prone to hydrological destabilization.

Buried bedrock valleys are common erosional features in northern mid-latitude environments that form through glaciofluvial or paleoalluvial processes and are typically infilled by Quaternary-aged sediments. The erosional extent and geometry of the valley including a weathered interface, along with sediment infill that can contain complex sequences of unconsolidated aquifer and aquitard sediments, mean these features may act as preferential pathways to deeper bedrock aquifers. Noninvasive geophysical tools can provide rapid, high-resolution subsurface characterization of these features. This study evaluates the application of electrical resistivity and seismic refraction tomography along two transects centred over a buried bedrock valley in Elora, Ontario, Canada. Geophysical measurements were combined with existing continuous core records and an electrofacies model based on downhole geophysical logs to constrain the morphology and infilled lithostratigraphic architecture of the valley. Bedrock competency associated with lithology may act as a control on depth and width of valley incision during erosion, with resistivity measurements of the bedrock revealing a potential association between interpreted mechanical properties and variations in the resolved valley morphology. Seismic velocity corroborated these contrasting valley widths but could not assess bedrock competency variability below the bedrock interface. This study reveals the sequence of events depositing sediments in the valley, yielding a revised architectural mapping that improves on previous regional scale lithostratigraphic interpretations. Results will be of use to groundwater practitioners requiring detailed conceptualization of this buried bedrock valley and its role on preferential zones of groundwater flow. Similar approaches can be used for delineation of these common and hydrogeologically significant features. [ABSTRACT FROM AUTHOR]

Yellowstone National Park (YNP) is home to roughly 500 geysers, making it the most concentrated geyser field in the world. Recent studies exploring the mechanics of geyser eruptions utilizing laboratory models were limited by a lack of knowledge of the subsurface geometry of the geyser features. This study presents results from active hydrogeophysical surveys, including ground penetrating radar, nuclear magnetic resonance (NMR), seismic refraction, electrical resistivity tomography, and transient electromagnetics to image subsurface geyser structure and constrain the geophysical response of the reservoir structure of Spouter Geyser, Yellowstone National Park. Previous geophysical studies on similar geyser systems in Yellowstone characterize the hydrothermal reservoir that supplies the geyser with hydrothermal fluids and vapors as high porosity, low density structures. Whereas our imaging highlights the hydrothermal conduits and reservoir as high resistivity and high velocity structures, interpreted as silica precipitate decreasing the porosity and increasing the bulk modulus (i.e., from unconsolidated media to semi/fully consolidated). Ground penetrating radar identifies sinter thickness around the geyser, NMR provides porosity measurements of the geyser reservoir, and transient electromagnetics maps the depth to the Biscuit Basin Rhyolite bedrock throughout the field site. Electrical resistivity tomography and seismic refraction image the shallow geyser conduit structures to ∼15 m depth and establish the extent of the geyser hydrothermal reservoir structure. Furthermore, a spatial correlation of the electrical resistivity and seismic velocity results establishes the interpreted hydrothermal geyser reservoir as a high resistivity, high velocity structure located to the northeast of Spouter Geyser at depths greater than 15 m. Plain Language Summary: The dynamics of geyser eruptions are uncertain. Much of this uncertainty stems from a lack of knowledge of their subsurface structure. Therefore, to better understand geyser eruption dynamics, we must first establish the subsurface structure of geysers and their associated hydrothermal geyser reservoirs that supply the erupted hydrothermal fluids and vapors. Geophysical imaging provides an opportunity to image these structures, but active geophysical methods have not been extensively explored for this application. In this study, we use various active geophysical methods to (a) constrain the characteristics of the structure and (b) better understand the subsurface geometry of Spouter Geyser (YNP) and its hydrothermal reservoir. We find that Spouter Geyser's structure and its reservoir have high electrical resistivity and seismic velocity responses, indicative of low porosity and highly cohesive characteristics due to silica precipitate from hydrothermal fluids. We also find that Spouter Geyser's subsurface geometry consists of silica‐lined conduits that extend 15 m to a broad, laterally offset geyser hydrothermal reservoir structure. With the knowledge of the characteristics and geometry of Spouter Geyser and its hydrothermal reservoir, an additional study (Geyser Dynamics II) is better positioned to explore the dynamics of geyser eruptions with active geophysical methods. Key Points: Geophysical results reveal a laterally offset, low porosity and highly consolidated geyser reservoir structure at Spouter GeyserDistinct vertical conduit structures extending to the hydrothermal geyser reservoir at 15 m depth are interpreted at Spouter GeyserVelocity and resistivity distribution characterize Spouter Geyser's reservoir structure as high velocity‐high resistivity [ABSTRACT FROM AUTHOR]

Physical, chemical, and biological processes create and maintain the critical zone (CZ). In weathered and crystalline rocks, these processes occur over 10–100 s of meters and transform bedrock into soil. The CZ provides pore space and flow paths for groundwater, supplies nutrients for ecosystems, and provides the foundation for life. Vegetation in the aboveground CZ depends on these components and actively mediates Earth system processes like evapotranspiration, nutrient and water cycling, and hill slope erosion. Therefore, the vertical and lateral extent of the CZ can provide insight into the important chemical and physical processes that link life on the surface with geology 10–100 s meters below. In this study, we present 3.9 km of seismic refraction data in a weathered and crystalline granite in the Laramie Range, Wyoming. The refraction data were collected to investigate two ridges with clear contrasts in vegetation and slope. Given the large contrasts in slope, aspect, and vegetation cover, we expected large differences in CZ structure. However, our results suggest no significant differences in large-scale (>10 s of m) CZ structure as a function of slope or aspect. Our data appears to suggest a relationship between LiDAR-derived canopy height and depth to fractured bedrock where the tallest trees are located over regions with the shallowest depth to fractured bedrock. After separating our data by the presence or lack of vegetation, higher P-wave velocities under vegetation is likely a result of higher saturation.

This study investigates the ground characteristics of the high altitude (3410 m a.s.l.) permafrost site Stockhorn in the Swiss Alps using a combination of surface and subsurface temperature, soil moisture, electrical resistivity and P-wave velocity time series data including a novel approach to explicitly quantify changes in ground ice content. This study was motivated by the clear signal of permafrost degradation visible in the full dataset at this long-term monitoring site within the PERMOS (Permafrost Monitoring Switzerland) network. Firstly, we assess the spatio-temporal evolution of the ground ice and water content by a combined analysis of all available in situ thermal (borehole and ground surface temperature), hydrological (soil moisture) and geophysical (geoelectric and seismic refraction) data over two decades (2002–2022) regarding the driving factors for the spatially different warming. Secondly, we explicitly quantify the volumetric water and ice content and their changes in the subsurface from 2015 to 2022 using a time-consistent petrophysical joint inversion scheme within the open-source library pyGIMLi. The petrophysical joint inversion scheme has been improved by constraining the rock content to be constant in time for six subsequent inversions to obtain consistent changes in ice and water content over the monitoring period based on jointly inverted resistivity and traveltime data. All different data show a warming trend of the permafrost. The ice content modeled from the petrophysical joint inversion has decreased by about 15 vol.% between 2015 and 2022. Changes in ice content are first observed in the lower, south-facing part of the profile. As a result, resistivity and P-wave velocity have been decreasing significantly. Permafrost temperatures measured in the boreholes have increased between 0.5 °C and 1 °C in 20 years. Our study shows the high value of joint and quantitative analysis of datasets comprising complementary subsurface variables for long-term permafrost monitoring.

The monumental complex of Maredolce (Palermo) includes an Arab‐Norman castle that stands on the banks of an artificial lake carved out of the calcarenitic rock that rests on impermeable clays. The lake was originally filled with water, thanks to the channelling of a spring. Over time, the lowering of the water table and the high hydraulic permeability of the calcarenites have caused the lake to dry up. A project to renovate the monumental complex has recently been launched. It also provides the study of a possible restoration of the original conditions of the lake. To this end, a multidisciplinary geophysical study was carried out to investigate the geotechnical conditions of permeability of the land outcropping and provides valid technical solutions for waterproofing the bottom of the lake. For this purpose, a joint interpretation was performed using data acquired with different geophysical techniques, such as seismic refraction tomography, electrical resistivity and induced polarization tomography, multichannel analysis of surface waves and horizontal‐to‐vertical spectral ratio of environmental vibration recording. Joint interpretation, supported by cluster analysis techniques, allowed the reconstruction of the geophysical and geotechnical model of the subsoil of the ancient lake, helpful to suggest appropriate techniques for waterproofing the bottom of the lake. [ABSTRACT FROM AUTHOR]

Near-surface geophysical methods are the methods used to investigate the potential features or nature of materials in the subsurface/subsurface areas. Near-surface geophysical methods help to increase awareness of safety, efficiency, and comprehensiveness in the evaluation of surface/subsurface materials. The main aim of this study is to determine the surface/subsurface conditions along the pipeline route by conducting soil tests to determine soil resistivity, thermal conductivity, thermal resistivity, moisture content, and layer thickness in order to provide sufficient sub-surface geotechnical parameters for the design and construction of the proposed pipeline. The study employed three geophysical techniques which include electrical resistivity, thermal resistivity, and seismic refraction. The results have shown that the average resistivity values are high with a minimum resistivity value is more than 5 Ω m, which means that the soil is progressive corrosive to soil and steel. However, the seismic refraction method results showed two layers; the first layer is superficial deposits, and the second layer is basement rocks. Furthermore, the thermal resistivity results showed high thermal conductivity at stations from 120 to 147, located in the southwest part of the study area, and low conductivity in the northeast part. Therefore, the study suggests more geotechnical investigation methods should be applied such as boreholes or excavation operations that can provide a detailed understanding of the subsurface layer, especially at a depth of 15 m. [ABSTRACT FROM AUTHOR]

The main geological structures in the Dammam Dome are defined by integrating geophysical measurements and applying new methodological approaches. Dammam Dome is characterized by a well-developed fracture/joints system; thus, high complexity of the subsurface is expected. Direct Current Resistivity (DCR) and Seismic Refraction (SR) geophysical survey aimed to map the Dammam Dome's near-surface features. The geophysical data were acquired along two profiles in the northern part of Dammam Dome. To maximize the results from conducting DCR and SR measurements over a complex area, a combined local and global optimization algorithm was used to obtain high-resolution near-surface images in resistivity and velocity models. The local optimization technique involves individual and joint inversion of the DCR and SR data incorporating appropriate regularization parameters, while the global optimization uses single and multi-objective genetic algorithms in model parameter estimation. The combined algorithm uses the output from the local optimization method to define a search space for the global optimization algorithm. The results show that the local optimization produces satisfactory inverted models, and that the global optimization algorithm improves the local optimization results. The joint inversion and processing of the acquired data identified two major faults and a deformed zone with an almost N–S direction that corresponds with an outcrop were mapped in profile one, while profile two shows similar anomalies in both the resistivity and velocity models with the main E–W direction. This study not only demonstrates the capability of using the combined local and global optimization multi-objectives techniques to estimate model parameters of large datasets (i.e., 2D DCR and SR data), but also provides high-resolution subsurface images that can be used to study structural features of the Dammam Dome. [ABSTRACT FROM AUTHOR]

A good strength level of the ground surface is the main concern in an area with rapid housing infrastructure development, such as Baitussalam district-Aceh Besar, Indonesia. A seismic refraction method was applied with three similar profile lines using PASI 16S - 24P equipment and 10 Hz vertical geophones to identify the sub-surface layer. The result was processed using Winsism software and Surfer 8. The results of seismic refraction were deduced and correlated with conventional geotechnical investigation obtained by a previous study. The results of 3 survey lines show that the area has two main layers. The first layer was interpreted as overburden (soil and clayey sand) with a compressional wave velocity (Vp) value of fewer than 1.8 km/s. The second layer produces a high velocity of more than 2 km/s. This second layer is interpreted as highly to moderately weathered rock. The results of seismic refraction surveys of the present study suggest a reasonably good correlation with the standard penetration test (SPT) and rock quality designation (RQD) obtained in the previous investigation. The strength level of the second layer showed N-SPT of 65 and RQD of at least 50%. [ABSTRACT FROM AUTHOR]

Most geophysical inversions face the problem of non-uniqueness, which poses a challenge in the mapping and delineation of the subsurface anomalies. To tackle this challenge, a combined local and global optimization approach is considered for jointly inverting two-dimensional direct current resistivity (DCR) and seismic refraction (SR) data that aim to estimate the corresponding physical model parameters. In this combined approach, the output of the local optimization method is used to determine the search space and tuning parameters for the global optimization algorithm. The multi-objective genetic algorithm (non-dominated sorting genetic algorithm) was utilized to jointly optimize the objective functions of two different methods. Because the genetic algorithm is a population-based optimization method, it requires numerous forward calculations. To deal with the expected high computational cost associated with this approach, parallel computing was utilized for the forward function evaluations to reduce the run time of the entire process. The proposed approach was tested using synthetic two-dimensional resistivity and velocity models that had three different types of anomalies (dyke, positive, and combined positive and negative). The results showed an improvement in the anomaly delineation in the output of the combined local and global optimization method compared with the local optimization method. Additionally, similar synthetic models were tested using only the single objective global optimization algorithm (conventional global optimization), which showed promising anomaly delineation. [ABSTRACT FROM AUTHOR]

One of the most important parameters used to determine the dynamic properties of soil layers is the shear wave velocity. In geotechnical earthquake engineering, the shear wave velocity is used to determine the shear modulus, which provides the input parameters for the design of earthquake-resistant structures. Although there are measurement methods used in field studies to determine the shear wave velocity, they may not be economical in some cases. In this study, the empirical correlations between the shear wave velocity and penetration resistance in sandy soils were investigated with the use of geotechnical and geoseismic data obtained within the scope of microzonation studies performed in the Canakkale residential area. The results of the study were compared with correlations obtained from previous studies, and the equation we produced showed a good ability to predict the shear wave velocity. In addition, it was determined that standard penetration resistance, without energy correction, provided a better correlation coefficient.

We applied active-source seismic method for the interpretation of elastic parameters in tailings facilities which is essential for evaluating stability and seismic response. The methodology uses different analysis methods on the same dataset, i.e., conventional seismic refraction (SR) to determine compressional-wave velocity (Vp) and multichannel analysis of surface wave (MASW) to estimate shear-wave velocity (Vs). Seismic velocities in conjunction with tailings physics approach revealed interpretable data in terms of elastic parameters and hydrogeological conditions. The results determined the empirical linear relationships between Vp and Vs that are particular to an unconsolidated media such as tailings and showed that variability of hydrogeological conditions influences the elastic seismic response (Vp and Vs) and the elastic parameters. The analysis of the elastic parameters identified the state condition of the tailings at the time of the survey. The Bulk modulus K that relates the change in hydrostatic stress to the volumetric strain was predominant between 1.0−2.0 GPa. The Young’s modulus E in the tailings media was in the low range of 0.15−0.23 GPa. Poisson’s ratio values in all sections were in the upper limit in the range of 0.37−0.49, meaning that the tailings media is highly susceptible to transverse deformation under axial compression.

Meskiana Area is characterized by a semi-arid climate, where water supply for irrigation and industry is not sufficient as the priority goes for domestic use. To meet the increasing population growth and development, the authorities have considered building a new water retaining structure on some major temporary water streams. For this purpose, Chebabta Site on Meskiana Wadi was chosen as the future dam site. It is large enough to store the desired volume of water. This study investigates the conditions of the site and the adequacy of the ground as a foundation for the projected dam. The conditions of the site include the geological structure and mainly the presence of discontinuities in the formation on which the dam will be built, the nature of the lithologies under the foundation and the future lake, and the presence of any hazard. This site characterization is usually carried out using different methods in order to highlight any underground buried problematic structure. In this context, the different geophysical techniques remain the most used ones. Four geophysical methods were used in the case of Chebabta dam site, namely seismic refraction, constant separation traversing (CST), vertical electric sounding (VES) and electric resistivity tomography (ERT). The choice of the techniques and the location of the survey lines was made on the basis of the available geological data. In this sense, profiles were established on both banks of Meskiana Wadi. The obtained results allowed a better characterization of the geological structure, defining the limit between the surface cover and the bedrock, which is, in other words, the limit between the weathered zone and the bedrock. Their respective thicknesses were also determined by seismic refraction and VES. However, ERT succeeded in estimating the thickness of alluvial deposits in the left bank of the Wadi and positioning a fault structure passing at the east of the study area. [ABSTRACT FROM AUTHOR]

Purpose. The research purpose is to apply an original combined approach to the study of landslide occurrence in the Tarzoust region, based on geophysical approaches. This is extremely important because landslides damage roads and buildings in many parts of North Africa, especially in the city of Tarzoust, NE Algeria. Significant slope failures have resulted in serious disasters in the region. Methods. In this study we use Vertical Electric Soundings (VES) and Seismic Refraction Method (SRM) for underground exploration, as well as Electrical Resistivity Tomography (ERT) to support the latter two methods. Findings. The clayey nature of the terrain is confirmed, very often covered by a mantle of superficial colluvium formations. The depth of the bedrock and shear surface has been precisely determined. The ERT reveals that the terrain has already experienced instability in the past. Originality. The originality of this study is in the combination of data from various sources and different approaches for the purpose of planning the deployment and use of land. Practical implications. Our approach has proven that the combination of geological and geotechnical data with geophysical deterministic methods can help engineers and decision-makers in land management. Our recommendations consist of topographic, inclinometric and piezometric monitoring for slip development and the effectiveness of reinforcement measures for new housing, and equipment programs for regional planning. [ABSTRACT FROM AUTHOR]

Characterizing the structure of the critical zone (CZ), which is often tens of metres deep, is challenging and crucial to understand earth surface processes. Existing findings on the effect of topography on CZ thickness focused exclusively on mountainous regions with steep slopes, not considering low hilly regions with gentle slopes. Seismic refraction and borehole surveys were conducted to characterize the effects of topography on a red soil CZ structure in the low hilly region of Jiangxi Province, subtropical China. This CZ is derived from Quaternary red clay (QRC) overlying Cretaceous sandstone bedrock. Regolith with a thickness of 8.2–9.5 m consisted of an upper layer of QRC (4.8–6.2 m thick) and a lower layer of weathered sandstone (2.6–4.0 m thick). The boundary between weathered and unweathered sandstone was identified by a Ca depletion profile and calcite weathering front. The boundary between the QRC and weathered sandstone was identified by morphological and textural features and a feldspar weathering front. The QRC had seismic refraction velocities <1.3 km s−1, the weathered sandstone had velocities of 1.3–1.7 km s−1, while the sandstone bedrock had velocities >1.7 km s−1. Following the profile sequence downslope, regolith thickness decreased linearly with decreasing ground elevation. The linear fitted regression slope was <1. This was predominantly determined by QRC thickness, which in turn was mainly controlled by the difference between slopes of ground and bedrock surface and by surface erosion. Following the profile sequence across the slope, regolith thickness decreased linearly with decreasing ground elevation, with a slope of ~1. This was controlled by QRC thickness, which in turn was mainly controlled by surface erosion only, since the bedrock surface was nearly level. These results suggest that topography can control CZ structure in hilly regions with gentle slopes. [ABSTRACT FROM AUTHOR]