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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]

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 (

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.

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.

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 km 2 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., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Two wide-angle seismic reflection/refraction profiles were acquired to determine the velocity characteristics of the Meguma terrane and adjacent Avalonia northeast of the Cobequid-Chedabucto Fault Zone (CCFZ) in eastern Canada. Line 99–1 is located along the Scotian margin whereas line 99–2 crosses the Scotian margin and onshore Nova Scotia and extends into the Gulf of St. Lawrence. Velocity models were derived by forward modelling of travel times. P-wave velocities of 5.5–6.0 km/s and 6.0–6.4 km/s are interpreted to be metasedimentary rocks of the Goldenville and Halifax groups and granitic rocks, respectively. This inference is based on comparison with laboratory velocities of a suite of rock samples, offshore sampling, links to onshore geology with multibeam bathymetry, and gravity modelling. On both lines a low velocity zone (LVZ) >350 km wide and up to 15 km thick is present at mid-crustal levels. The LVZ is not observed beneath onshore Nova Scotia or northeast of Orpheus Graben, the offshore extension of the CCFZ. The crustal thickness of the Meguma terrane varies between 31 and 38 km; in contrast, the Moho is at a depth of 41 km beneath Avalonia. The velocity of the lower crust on line 99–2 is 6.8–7.1 km/s beneath the LVZ and Avalonia, and 6.6 km/s beneath onshore Meguma terrane. Poisson's ratios calculated from P- and S-wave velocities are 0.19–0.23 in the Meguma terrane crust; in contrast, Poisson's ratios of 0.24–0.25 are indicated for Avalonian crust. • Seismic reflection/refraction, gravity, and rock density/velocity data were obtained. • Two velocity/depth models were generated onshore and offshore of Nova Scotia, Canada. • Both models show an extensive low-velocity zone in the offshore Meguma terrane. • Meguma terrane has crustal structure different from that of adjacent Avalonia. • Avalonia extends only 30 km under Meguma terrane in faulted contact. [ABSTRACT FROM AUTHOR]