Geophysical Surveys Research Articles

Synergizing Geophysical Analysis and Geotechnical for Artificial Recharge Well and Aquifer Studies: A Comprehensive Review

The harvesting of surface runoff stands as a pivotal process in artificially recharging groundwater, playing a crucial role in augmenting groundwater within aquifers. Groundwater recharge via recharge wells is one of the successful direct sub-surface methods. To pinpoint the most suitable locations for recharge wells, a combination of geophysical surveys, including Electrical Resistivity, Magnetic, and Electrologging surveys, was used. These geophysical surveys serve as essential tools for comprehending the sub-surface lithology and played a pivotal role in identifying distinct aquifers and determining their respective dimensions, thereby aiding in the precision of recharge well placement. Our objective is to review the various methods to assess the underground water storage capacity of the aquifer based on tests viz. Sieve Analysis, Soil Water Retention Capacity, and Lateral Permeability tests. These combination of theoretical and practical evaluations aim to determine the aquifer's potential for storing groundwater. Geophysical surveys are invaluable for deriving various relationships through diverse analyses. Moreover, exploring the correlation between geophysical methods, such as electrical resistivity, and shear strength parameters is essential for comprehending the strength characteristics of subsurface layers.

An ethical framework for geophysical survey in historic Black cemeteries

AbstractHistoric Black cemeteries in the south‐eastern United States are actively threatened by development, neglect, environmental degradation and vandalism. Geophysical archaeological tools are often championed as a solution to document unmarked graves, determine cemetery boundaries and help preserve these spaces. This process can be problematic as geophysical instruments themselves do not find graves; rather, the data collected are reviewed by a skilled professional to interpret where graves might be present. Archaeological geophysical practitioners thus hold a great responsibility to conduct themselves in an ethical manner. Important considerations include archaeological ethics, professionalism and honest communication, as well as centring the needs of preservation within the communities of descendants and stakeholders, if possible, in the way we process, interpret and communicate results.

Diagnosis and Monitoring of Tunnel Lining Defects by Using Comprehensive Geophysical Prospecting and Fiber Bragg Grating Strain Sensor.

Tunnel excavation induces the stress redistribution of surrounding rock. In this excavation process, the elastic strain in the rock is quickly released. When the maximum stress on the tunnel lining exceeds the concrete's load-bearing capacity, it causes cracking of the lining. Comprehensive geophysical exploration methods, including seismic computerized tomography, the high-density electrical method, and the ultrasonic single-plane test, indicated the presence of incomplete distribution of broken rock along the tunnel axis. Based on the geophysical exploration results, a carbon-fiber-strengthened tunnel simulation model was established to analyze the mechanical characteristics of the structure and provide a theoretical basis for sensor deployment. Fiber Bragg grating (FBG) strain sensors were used to measure the stress and strain changes in the second lining concrete after carbon reinforcement. Meanwhile, one temperature sensor was installed in each section to enable temperature compensation. The monitoring results demonstrated that the stress-strain of the second lining fluctuated within a small range, and the lining did not show any crack expansion behavior, which indicated that carbon-fiber-reinforced polymer (CFRP) played an effective role in controlling the structural deformation. Therefore, the combined detection of physical exploration and FBG sensors for the structure provided an effective monitoring method for evaluating tunnel stability.

Circulation of hydraulically ponded turbidity currents and the filling of continental slope minibasins

Natural depressions on continental margins termed minibasins trap turbidity currents, a class of sediment-laden seafloor density driven flow. These currents are the primary downslope vectors for clastic sediment, particulate organic carbon, and microplastics. Here, we establish a method that facilitates long-distance self-suspension of dilute sediment-laden flows, enabling study of turbidity currents with appropriately scaled natural topography. We show that flow dynamics in three-dimensional minibasins are dominated by circulation cell structures. While fluid rotation is mainly along a horizontal plane, inwards spiraling flow results in strong upwelling jets that reduce the ability of minibasins to trap particulate organic carbon, microplastics, and fine-grained clastic sediment. Circulation cells are the prime mechanism for distributing particulates in minibasins and set the geometry of deposits, which are often intricate and below the resolution of geophysical surveys. Fluid and sediment are delivered to circulation cells by turbidity currents that runup the distal wall of minibasins. The magnitude of runup increases with the discharge rate of currents entering minibasins, which influences the amount of sediment that is either trapped in minibasins or spills to downslope environs and determines the height that deposits onlap against minibasin walls.

Multi‐geophysical methods for characterizing fractures in an open pit mine, western Bushveld Complex, South Africa

AbstractIn the Bushveld Complex, South Africa, open pit mines are faced with a challenge of rock slope stability due to geological structures (fractures, faults and dykes) that compartmentalize the rock mass. Geophysical surveys (seismics, magnetics and electrical methods) were conducted in a 0.2 km2 area at Tharisa mine, with the goal to delineate fractures that may be potential conduits for water migration into the pit. Special processing techniques were applied to the dataset to obtain good quality seismic, magnetic and resistivity models. The P‐wave velocity models show distinct low velocities in the centre of the seismic profile, indicating the presence of weak zones associated with faulting or fracturing. Seismic reflection method was used to image the deeper discontinuities and mineralization contacts. Near surface reflections are observed throughout the profiles and are correlated with the contact between the chromitite and host rock. Ground magnetic surveys were conducted to delineate dykes and fractures. De‐trending and de‐culturing techniques were applied on the magnetic data for correcting regional and temporal variations. The low magnetic regions indicate the presence of fracture systems in the subsurface, whereas the high magnetic region is correlated with the dolerite dyke that crosscuts the pit. The electrical resistivity tomography exhibits linear low resistivity contrast zones that differentiate between the fractured and undisturbed hard rock at an estimated depth of 4–10 m. Resistivity shows discontinuities that suggests the presence of fracturing and dyke‐host rock contacts. Correlation among magnetics, P‐wave velocity models, resistivity section and seismic data is evident when overlaying the different datasets, implying that the low magnetic regions are highly weathered and prone to fracturing. The integration of geophysical data is encouraging, because it was able to image the depth to the bedrock, fractures within the host rock and dyke in a complex mining environment.

A Case History of Graphite Exploration in North Norway Integrating Various Geophysical Surveys

Graphite is considered to be one of Europe’s most critical minerals. It is necessary for the transition from hydrocarbon fuel to electricity due to its use in batteries that power electronic devices and electric transport. In the past, high-quality exposed graphite was found in Norway without today’s advanced geophysical and geological methods. Norway is a key destination in Europe for graphite production. With an increasing demand for graphite, there have been efforts to systematically survey the country using modern geophysical and geological methods to find hidden graphite deposits. Among the various geophysical survey methods, electrical and electromagnetic (EM) methods are the first choice for the exploration of graphite due to the material’s high electrical conductivity. Airborne surveys are often used to cover a large area for a regional reconnaissance survey to locate the sites with potential mineral deposits before performing ground geophysical and geological surveys. Therefore, frequency-domain helicopter EM (HEM) and airborne magnetic surveys were performed in Northern Norway to locate interesting anomalies which were followed by ground surveys such as electrical resistivity tomography (ERT), charged-potential (CP), self-potential (SP), ground EM, and geological surveys. Some locations were also investigated with drilling and petrophysical core-sample analysis. In this paper, we present helicopter EM and magnetic data, 3D inversion of HEM data, and a successful ground follow-up survey result from the Vesterålen district in Northern Norway. The HEM survey identified previously known and new graphite occurrences, both partially exposed or buried, which were confirmed using ground surveys, drilling, and laboratory analysis of the samples.

Integrating near-surface geophysical methods and remote sensing techniques for reconstructing fault-bounded valleys (Mellieha valley, Malta)

The island of Malta (central Mediterranean) is dissected by several WSW-trending fault-line valleys related to Miocene-Pliocene extensional tectonics. Some valleys host remnants of alluvial deposits that could provide information on possible Quaternary faulting, but the thickness of these deposits and their subsurface extent is poorly constrained. Our study aimed to investigate the structural configuration of the southern sector of the Mellieha valley, which is located in the north-west part of the island and is limited by the ENE-WSW general trending Mellieha and Ghadira faults, and their relation with a thin layer of infill sediments. We employed different near-surface geophysical techniques (electrical resistivity tomography, active and passive seismic methods, ground-penetrating radar), as well as remote sensing techniques (unmanned aerial vehicle digital photogrammetry and ground-based Light Detection and Ranging) to complement classic structural surveys. The valley structure has an asymmetric graben configuration, being bounded by a normal fault to the southeast (Mellieha Fault) and other to the north-west (Ghadira Fault). Our study provides insights of possible Quaternary fault displacements and revealed the presence of an additional fault splay, the previously unmapped NNW-dipping Mellieha Fault 2 at the south-eastern edge of the valley. Additionally, by integrating results from geophysical surveys, we estimated the thickness of the valley's recent deposits, being thicker towards the Mellieha Bay sector, with maximum values of 8–10 m. Our study aligns with the general model of horst and graben structuring with associated regional tilting since the late Miocene, and supports the hypothesis that some segments of NW-trending normal faults within the North Malta Graben exhibit Quaternary activity, although with minimal throw rates (<< 0.1 mm/yr).

Экспедиция «Итуруп 2022–2023»: основные направления работ и предварительные результаты

The paper provides information on the objectives, methods, targets and some preliminary results of the expeditionary work carried out within the framework of the RSF project No.21-17-00049 by the employees of the Institute of Volcanology and Seismology of the FEB RAS, Institute of Marine Geology and Geophysics of the FEB RAS, Pacific Geographical Institute of the FEB RAS and Trofimuk Institute of Petroleum-Gas Geology and Geophysics of the SB RAS in 2022 and 2023. The main objectives of the expedition were geological-volcanological, hydrogeological, geophysical, tephrochronological, and paleoseismological studies. In accordance with the set objectives, field teams were formed, which began work in February 2022. On the basis of the data obtained during the expedition, previously unknown hydrothermal manifestations and seismic events on Iturup Island were identified. A number of geophysical and paleomagnetic surveys were carried out.

Geophysical electrical survey for aquifer detection, and carbon footprinting for groundwater abstraction in India

Geophysical electrical survey for aquifer detection, and carbon footprinting for groundwater abstraction in India

A Comprehensive Assessment of Submarine Landslides and Mass Wasting Processes Offshore Southern California

AbstractIt is critical to characterize submarine landslide hazards near dense coastal populations, especially in areas with active faults, which can trigger slope failure, subsequent tsunamis, and damage seabed infrastructure during earthquake shaking. Offshore southern California, numerous marine geophysical surveys have been conducted over the past decade, and high‐resolution bathymetric and subsurface data now cover about 60 percent of the total region between Point Conception and the United States‐Mexico border from the California coast out to the base of Patton Escarpment ∼200 km offshore. In a comprehensive compilation and interpretive mapping effort, we find evidence of seafloor failure throughout offshore southern California with nearly 1,500 submarine landslide‐related features, including 63 discrete slide deposits with debris and &gt;1,400 slide‐related scarps. In our analysis, we highlight new mapping of submarine landslides in Catalina Basin, the Del Mar slide, the San Gabriel slide complex, and the 232 km2 San Nicolas slide, the largest area of any known submarine landslide mass offshore southern California. Analysis of the spatial distribution of submarine landslide features suggests that most mapped slide features are located relatively near coastal sediment sources, particularly during sea‐level lowstand conditions, which underscores the importance of sediment supply and sediment accumulation on low‐gradient slopes as failure preconditioning processes. Tectonically driven uplift at shelf edges and along basin flanks is another key preconditioning factor, and our results also suggest that earthquakes along active faults trigger mass wasting, especially for repeated, small‐scale failures on tectonically steepened slopes.

Application of Multi-Near-Surface Geophysical Surveys for Geothermal Spring: A Case Study in Kon Tum Province, Vietnam

The occurrence of geothermal spring not only enhances human health, but also plays a crucial role in generating community’s revenue that boosts up the standard living of locals. An endeavor has been made to delineate the prospective areas of geothermal spring in Kon Tum province, Vietnam by the utilization of joint-geophysical techniques. The blended mode as mentioned is opted for its superiority in providing the rapidassesments of temperature in shallow temperature survey, comprehensive understanding the subsurface structure in electrical resistivity tomography in copporating with the validation in well log interpretation. The results found that the overlapping region of high temperature (35°C) region and low resistivity (200 Ωm) is observed in the east in the vicinity of Dlak Bla river, and it probably broadens to the west of the study area. The outcome of geophysical approaches strongly concur with the well log interpretation, revealing the presence of water-bearing zone encountered in fractured granite. The results also corroborated the existence of concealing fault F5 as a branch of the NE-SW fault F2 which is favorable for creating a route to form the geothermal spring. The output of this research could be considered as an intentive consultation for Kon Tum’s planners and makers on expanding the investigation and exploitation.

Geological exploration of coal mine burnt rock and waterlogged area boundary based on transient electromagnetic and high-density electrical resistivity

The water-rich burnt rock may threaten the safe production of coal mines. Identifying the boundaries of burnt rock and the water-rich area is of great practical significance for the ensuring the safety of mining operations. Transient electromagnetic and high-density resistivity methods are commonly employed in geophysical exploration, such as for investigating the presence of groundwater or delineating boundaries of altered rocks. These methods are non-invasive and provide detailed information about subsurface conditions without the need for drilling or excavation. The Jiangjun Gobi No. 1 open-pit coal mine is situated in the Kalamaili fault zone and is characterized by a high groundwater content. In certain mining sites within the study area, the inflow of water reaches tens of thousands of cubic meters per day, which significantly impacts production and presents major risks. To accurately determine the boundaries of burnt rock and water accumulation areas in the Jiangjun Gobi No. 1 open-pit coal mine, this paper uses different geophysical prospecting methods based on the depth of the strata. The middle and deep parts are investigated using the high-resolution transient electromagnetic method, while the shallow parts are examined using the high-accuracy high-density electric method. Through analyzing the electrical characteristics of the study area, it is inferred that the low-resistivity area in the northwest represents a shallow surface water-rich region. This area extends continuously towards the northwest, is not trapped, and is supplied by surface water. The deep low-resistivity zone primarily consists of sandstone and coarse sandstone. It is inferred that the low-resistance area in the southern part of the study area is also a shallow surface water-rich region, extending towards the east and west sides, not trapped, and supplied by surface water. The deep low-resistivity zone mainly comprises a combination of sandstone, coarse sandstone, and burnt rock, with intermittent layers of mudstone and argillaceous sandstone. The boundary line of burnt rock (coal-bearing strata) is located in the south of the study area. The resistivity of burnt rock (coal-bearing strata) is higher than that of the surrounding rocks, and the resistivity of coal seams is slightly higher than that of sandstone with larger porosity. Estimating the boundaries of groundwater and altered rocks serves to prevent geological disasters and provides valuable information for mineral development and ecological protection.

Verification of Geophysical Surveys by New Archaeological Excavations on the Grounds of the Middle La Tène Site of Němčice in 2021–2022

The Němčice site located in a strategic area of an agricultural plateau represents one of the most important archaeological sites in Moravia. Non-destructive archaeological surveys including a largescale magnetometer survey, field artefact collections, and metal detector surveys have been carried out there repeatedly over the past two decades. New archaeological excavations during a new project were focused on selected areas and situations identified during magnetometer prospection. The results of an archaeological investigation of the site using test pits confirmed settlement, glass-making and ritual activity under magnetic anomalies at the site. The new possibility of comparing uncovered sunken features and distributions of magnetic anomalies provided new feedback for a more precise interpretation of similar anomalies from magnetograms. An additional detailed apparent magnetic susceptibility measurement in situ showed another possibility for the application of the geophysical method during archaeological excavations. We were able to obtain additional information about the fills or possible post-depositional processes of various sunken features in the case of vertical profiles monitored by magnetic susceptibility meter measurements. The use and combination of various geophysical data has been beneficial in the case of an archaeological site as important as Němčice, and will continue to be so in future archaeological research of the site.

Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era

Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier's history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability.

Geophysical prospecting of ground water in crystalline rocks in an arid Region of Northeast Brazil

Perfis de resistividade horizontal foram conduzidos em área de rochas Precambrianas ígneas e metamórficas na região semi-árida do Estado de Pernambuco, nordeste do Brasil, com a finalidade de contribuir para a analise dos fatores que controlam a grande variação na vazão em poços localizados a pequena distancia entre si. Dezesseis linhas de resistividade paralelas e com direção 345 Az e espaçamento de 15 metros foram conduzidas, com separação de 15 metros entre estações de medidas ao longo das linhas. Os resultados mostraram que as zonas de condutividade podem não estar diretamente relacionadas a zonas de maior densidade de fraturas e, consequentemente, maior saturação de água. As feições litológicas e estruturais, que não foram observadas diretamente em função da cobertura de solo possuem grande importância. Os perfis geofísicos associados a trabalho de campo de detalhe, através de observações em cacimbas escavadas para suprimento de água mostrou que para este caso a elevada capacidade de armazenamento de água subterrânea esta relacionada a dobramentos e ao sistema de fraturas em gnaisses intercalados com sheets de rochas graníticas.

Structural control on carbon emissions at the Nirano mud volcanoes – Italy

The Nirano Salse in Italy is a well-studied site where natural gas seepage (NGS) and other hydrocarbon fluids and gases are emitted at the earth's surface. A novel integrated approach is applied to define a comprehensive structural interpretation of the gas seepage and flow dynamic in the mud volcano system of the Nirano Salse Regional Nature Reserve (Modena, Northern Apennines). The paper investigates the relationship between gas emissions and local structures, particularly faults and fractures, in the shallow subsurface (down to 500–600 m depth) to understand the control that structures have on fluid ascent from deep leaky hydrocarbon traps. We performed continuous monitoring of mud levels within vents; carried out geological surveys to characterize the main stratigraphic and structural discontinuities; measured the carbon emissions (CH4 and CO2) seepage both from volcanoes and the surrounding soil by a portable gas fluxmeter; and integrated the results with available geophysical surveys. The authors argue that the transgressive Pleistocene-Pliocene Argille Azzurre Formation hides the complex and highly structured pre-Pliocene geology of the area, in which faults and fractures act as pathways for deep fluid ascent. The emissions are aligned along a NE-SW trend at the intersection of a NE-SW fracture system and NW-SE-oriented normal faults, which are both associated to the local tensional stress field of a likely left-lateral strike-slip transfer structure or in the extrados of a fold. By examining both natural gas macroseepage and diffuse flux, it is shown that local structures control the fluid ascent and contribute to the emission of hydrocarbon gases and fluids at the Earth's surface. Understanding the structural control of carbon emissions at the Nirano Salse is also important for evaluating the carbon budget at the site, particularly in areas where there are detectable surface emissions. The study has implications for geologic, environmental, and economic issues, including hydrocarbon exploration, hazard assessment, and impact on the atmospheric carbon budget. Furthermore, the outcomes have an important implication to evaluate the potential for dangerous abrupt mud eruptions, and the site safety in proximity to the mud volcanoes.

Exploring the chronostratigraphy of a Bronze Age settlement through core drilling

Abstract Core drilling has been used successfully in archaeology for a variety of applications, including mapping stratigraphy across large areas, estimating feature depth and content, understanding site formation processes, as well as complementing information obtained through surface collection and geophysical survey. In this paper, we provide an overview of the first core drilling campaign carried out in 2021 on the outer settlement of the Bronze Age tell from Toboliu in western Romania. The overall aim of this coring program was to gather information regarding the nature of various features within the settlement, with a focus on the anomalies visible in the geomagnetic site plan. Based on 165 drilled cores, a reconstruction of the site’s stratigraphy is presented in this paper. This reconstruction was controlled and confirmed by excavations in one of the coring transects where the stratigraphic interpretation of the cores could be linked with the excavated stratigraphy. Additionally, samples for radiocarbon dating were collected from several cores. Based on this data, we discuss preliminary insights into possible house locations and preservation issues, as well as the chronological development and occupation sequence of this complex site.

Geothermal power generation and positive impact in the greater bay area: a case study of Huizhou City, Guangdong Province.

Geothermal resources, as abundant renewable and clean natural resources on Earth, have been utilized for geothermal power generation in 29 countries. Guangdong Province, as one of the most developed, economically vibrant, and attractive investment regions in China, has experienced rapid economic growth. However, further development is constrained by resource limitations and severe ecological environmental pressures. The issue of energy consumption and economic growth imbalance needs to be urgently addressed. Geothermal energy, as a clean and stable form of energy, can reduce reliance on fossil fuels, decrease dependence on imported energy, and enhance national energy security. In this study, geological survey, geophysical survey, geochemical survey, remote sensing detection and drilling were carried out in the Shiba-Huangshadong area of Huizhou, and by analyzing the data on geothermal energy reserves in the study area, the available geothermal energy and its potentials in the study area were identified and its impact on the current energy consumption in Huizhou City was assessed, to validate the feasibility of the detailed application of the geothermal energy in the Greater Bay Area, which will enable the energy structure of Huizhou City optimize the energy structure.

PERSPECTIVES OF SEARCH FOR RAW HYDROCARBON AND SOLID MINERALS DEPOSITS IN THE EASTERN HALF OF PRECASPIAN DEPRESSION (AKSAI – NORTH MAKAT AREA)

The possibility of identifying deep and ultra-deep raw hydrocarbon deposits and also the deposits of solid minerals in eastern part of Precaspian basin within Aksai-Northern Makat section totaling 70,000 sq.km. has been studied on the basis of the analysis of isodata, geological, tectonic, geophysical maps, mineral resources maps, specialized mineragenic studies, as well as new ideas on geodynamic development of Kazakhstan and, most crucial, taking into account theoretical and practical ideas about origin of abiogenic raw hydrocarbon deposits associated with formation of volcanic hydrogen, referring to the deliverables of gravity study and prospecting work, primarily magnetic prospecting. At the same time, a keen attention has been paid to the deep structure and morphology of Precaspian rift, providing significant impact on the deposits` formation. The analysis resulted with identification of, for the first time ever, several highly promising magnetic anomalies where new shallow, medium and deep petroleum and gas deposits may concentrate, including potential deposits of ferrous, non-ferrous, rare, rare earth and radioactive metals. A considerable effort has also been made to the perspectives of search for oil shale and light tight oil which are potential sources for multiple augmentation of the reserves of natural raw hydrocarbons.

Coda Q in the geophysical medium of the Northeast Caucasus

For the eastern zone of the North Caucasus, including the Tersko-Caspian trough, the Dagestan wedge and adjacent structures, with the maximum coverage of the data from the Federal network of seismological observations of the Geophysical Survey of the Russian Academy of Sciences (GS RAS), the regional frequency-dependent relations for estimating the seismic Q-factor of the Earth’s crust and upper mantle are determined by the coda-wave envelope method. In total, waveforms of 394 crustal earthquakes with source depths from 1 to 42 km and magnitudes from 2.2 to 5.5 are analyzed using the Coda Q module of the SEISAN software package (Havskov et al., 2020). The seismic-Q estimation technique using the single-scattering model is described in detail. Recommendations are given how to practically use the obtained estimates characterizing the wave properties of different-scale volumes of the fault-block geological environment to make attenuation corrections when calculating the source spectral parameters in the eastern zone of the North Caucasus. The results of the study will help to improve the information content of earthquake catalogs, in particular, to fill them with data on the energy characteristics of seismic events (universal values of moment magnitudes, Mw) in the most seismically active regions of the Russian Federation.