Geophysical Surveys Research Articles

Structure of the Gonghe Sedimentary Basin in the northeastern Tibetan Plateau: evidence from teleseismicPwaves recorded by a dense seismic array

SUMMARYThe Gonghe Basin in the northeast Tibetan Plateau presents significant potential for hot dry rock (HDR) geothermal resources. A 1990 Mw 6.4 earthquake in the basin furthers the need for an improved understanding of its sedimentary structure. In this study, we utilize data from a dense seismic array of 88 short-period seismometers deployed at an interstation spacing of approximately 3 km to scrutinize the sedimentary structure of the Gonghe Basin. By analysing teleseismic P waveforms, we identify P-to-S converted waves (Ps wave) originating from the sedimentary basement. We then determine the delay time between the Ps waves and the direct P waves (P wave) through waveform cross-correlation. By integrating this delay time with empirical velocity structure models, HDR borehole data and results from teleseismic receiver function analysis, we derive a sediment thickness model of the Gonghe Basin for the Qabqa geothermal area. Our findings reveal a gradual increase in sediment thickness from around 500 m in the east to approximately 3000 m in the west, which is consistent with other geophysical surveys and borehole data. The thick sediments in the basin could potentially serve as an excellent thermal storage cover for HDR. The strong ground motion simulation using our sediment thickness model shows that thick sediments can amplify seismic waves, increasing the risk of seismic hazards. Moreover, our study indicates that the clear Ps waves can be effectively extracted to construct a dependable sediment thickness model using teleseismic P waves recorded by a short-period dense seismic array.

Reinterpretation of geophysical surveys of pre-Permian basement in SW Poland: structural evolution and its implications for prospecting Cu and other ores

Reinterpretation of geophysical surveys of pre-Permian basement in SW Poland: structural evolution and its implications for prospecting Cu and other ores

Analysis and Evaluation of Engineering Geological Conditions of Dong Tianshan Tunnel

Through the investigation of the topography, stratum lithology, geological structure, and rock and soil engineering geological characteristics of the tunnel site area of ​​the Dong Tianshan Extra-long Tunnel, combined with the survey results of geophysical prospecting, drilling, hydrogeological tests, and rock mass physical and mechanical tests, the engineering project was carried out. geological analysis. The geological conditions in the tunnel site area are complex and risky, and there is a risk of collapse on the slope of the tunnel entrance. The fault fracture zone is prone to instability of surrounding rock and water inrush. Rock bursts may occur in locally deeply buried hard surrounding rock sections. During construction, advance geological forecasts should be followed, tunnel advanced support should be done, and drainage prevention should be strengthened.

Glacier, permafrost and thermokarst interactions in Alpine terrain: Insights from seven decades of reconstructed dynamics of the Chauvet glacial and periglacial system (Southern French Alps)

AbstractThis study analyses the long‐term dynamics in the Chauvet glacial and periglacial system (southern French Alps) over seven decades (1948–2020), where several lake outburst floods have been documented since 1930. To accurately describe and explain the complex dynamics of this site, our multidisciplinary approach combines (1) photogrammetry of historical aerial photographs and modern high‐resolution satellite and UAV images, (2) geophysical surveys and (3) geomorphological mapping. We provide evidence for spatial and functional interactions between glacial and periglacial features, especially in the lower sector where different landforms with variable ice‐ and debris‐content and specific dynamics are interplayed. We found the highest thinning rates on ice‐rich terrain located in the central part of the valley bottom, which, together with bedrock morphology, most probably determine the location of the thermokarst. We also documented an overall acceleration of the creeping of the landforms after the 2000s, with a flow direction largely oriented towards the thermokarst depression. The outburst water flowed through a conduit whose successive opening and closure seem to mainly depend on the rate of lateral convergence of left‐ and right‐hand landforms and on the rate of ice melting (and roof collapse) along the conduit walls. Today, the site of Chauvet still represents a potential hazard for the region due to the large water storage capacity (up to 180 000 ± 450 m3) and the development of a predominantly bucket shape in the thermokarst sector.

Geophysical Prospecting of Aquifer Hydrogeological Properties: Implications for Groundwater Resource Management in Parts of Indus Plain, Pakistan

Geophysical Prospecting of Aquifer Hydrogeological Properties: Implications for Groundwater Resource Management in Parts of Indus Plain, Pakistan

Unraveling the uncertainty of geological interfaces through data-knowledge-driven trend surface analysis

Modeling complex geological interfaces is a common task in geosciences. Many data sources are available for geological interface modeling, including borehole data and geophysical surveys. Geological knowledge, such as the delineation from geologists, is difficult to quantify but likely adds value to geological interface modeling. To integrate all information, we present a data-knowledge-driven trend surface analysis method to construct stochastic geological interfaces. We design a Metropolis–Hastings sampling framework to sample stochastic trend interfaces and quantify the uncertainty of geological interfaces given all information sources. This method is suitable for both explicit and implicit representations of geological interfaces. We demonstrate our method in three different test cases: modeling stochastic interfaces of Greenland subglacial topography, magmatic intrusion, and buried river valleys in Australia.

The development of a hydrogeological conceptual model of groundwater and surface water flows in the Silala River Basin

AbstractFrom 1999 a dispute between Bolivia and Chile concerning the status and use of the Silala River developed. In 2016 it was taken before the International Court of Justice. Over time, a key disagreement between the parties emerged, concerning artificial channels in the headwater wetlands of the Silala River in Bolivia and their impact on the river and groundwater discharge from Bolivia to Chile. To quantify this, a numerical groundwater model was developed by Chile, requiring a hydrogeological conceptual model of the Silala River Basin, reviewed here. This focussed on understanding the groundwater system and its interactions with the Silala River. The data and information used to gain this understanding included geological mapping, drilling, satellite imagery interpretation, geophysical surveys, hydrogeochemical analyses, groundwater level monitoring, surface flow monitoring, and groundwater pumping tests. These were focussed along the course of the river and wetlands. A three‐dimensional geological model of the Silala Basin was based on these investigations. The groundwater model area covers the topographic catchment, plus three adjacent closed (endorheic) topographical catchments to the northeast, which together form the groundwater catchment of the Silala River. The main deep regional aquifer is found in ignimbrite pyroclastic rocks and an interbedded alluvial deposit, but secondary perched aquifers on the flanks of the Silala River ravine contribute to the complexity. Although uncertainty remains, the hydrogeological conceptual model describes the main observed features of the system in a scientifically sound and coherent manner, with appropriate detail to support a credible numerical model.This article is categorized under: Science of Water > Hydrological Processes Engineering Water > Sustainable Engineering of Water

Geophysical Prospecting of the Coptic Monastery of Apa Moses Using GPR and Magnetic Techniques: A Case Study, Abydos, Sohag, Egypt

As a result of new discoveries, there is a greater opportunity for development and investment in the Al-Arraba EL-Madfuna region of Abydos, Sohag Governorate, Egypt, which benefits tourism and increases the national economy. The Coptic monastery, which was originally established by Apa Moses, the patriarch of the Coptic Church during the ancient Roman Empire, has vanished inside the current market on this site, along with numerous tombs. As a result, the primary goal of this work is to prospect on this site for these potential archaeological features. Ground magnetic and ground-penetration radar (GPR) surveys were employed for discovering these archaeological issues. This work was done in coordination with the Supreme Council of Antiquities. Ground magnetic and GPR surveys were implemented using the G-857 proton-precession magnetometer and GSSI SIR 4000 with a 200 MHz antenna. The data were processed and interpreted using Geosoft Oasis Montaj and REFLEXW v.5.8 software packages. The magnetic data were filtered to separate the shallower anomalies representing the archaeological remains from those of the deeper ones. Butterworth high pass filter, first vertical derivatives, analytical signal, and tilt derivative were employed to carry out the processing stages. The results were analyzed qualitatively and quantitatively to describe these anomalies and determine their locations, geometrical shapes, and depths. The source parameter imaging technique and 3D Euler deconvolution were used to calculate the depths. The analysis of magnetic maps shows that the study site is characterized by a number of anomalies that occur and have geometric squares and rectangle shapes with depths ranging from 0.7 m to ≈4 m. Some of these anomalies are related to potential archaeological objects. GPR findings reveal considerably scattered hyperbolas along several profiles, which may indicate the presence of potential buried objects. The integration of magnetic and GPR results showed that there is some consistency in the identification of the locations of the likely buried archaeological objects and their depths (0.7 to 3 m) for the majority of the discovered targets. The findings of this study suggest excavating at this location and relocating the market in order to protect the buried antiquities from being lost to be safeguarded as a tourist destination target.

Seismic velocity structure and tectonic evolution of the Continent-ocean transition in the mid-northern South China Sea

Continent-ocean transition (COT) is a key area for studying the lithospheric replacement from the thinned continental to oceanic crust. The extent and nature of the COT in the mid-northern margin of the South China Sea (SCS) have been reported recently after multiple geological and geophysical surveys, including IODP Expeditions 367/368/368X. However, the debate still remains due to limited constraints on the deep crustal structure and lateral variations. A 172 km long wide-angle reflection/refraction profile was conducted. The detailed crustal structure of the COT was mapped based on the forward and inverse modeling. The crust thickness decreased from ∼12 km in the thinned continental domain to ∼7 km in the COT, and then transitioned to ∼5 km in the oceanic domain. A ∼ 3 km thick layer with high velocity of 7.0–7.5 km/s at the bottom of the crust occurred continuously from the thinned continental to COT domains, which is interpreted as syn-rift underplating. Based on the features of crustal structure, sedimentary sequence and gravity anomaly, the landward and oceanward boundaries of the COT were determined which delimit a ∼ 20 km wide COT. The COT documents prominent tectono-magmatic interaction and rapid transition from final rifting to seafloor spreading. Eventually a model was proposed to explain the breakup processes characterized by brittle faulting in the upper crust coevally with ductile flow in the lower crust.

Assessment of the technical condition of the Sukhumi Lighthouse, Abkhazia using passive seismic standing waves method

The results of a geophysical survey of the technical condition of the lighthouse are presented. The stress–strain state, the residual resource, the tension of the fastening cables, the fixation of piles in the ground (rigid/non-rigid), and the immersion depth of the historical study object, the Sukhumi Lighthouse built in 1861 were determined. The passive seismic standing method based on the extraction of the natural vibrations of the object from noise records, as well as the tapping method, based on the recording of a reflected seismic wave passing along the structure were used to solve the above problems.

Paleohydrogeology of the Horonobe area, Northern Hokkaido, Japan: Groundwater flow conditions during glacial and postglacial periods estimated from chemical and isotopic data for fracture and pore water

Understanding the difference in groundwater flow between glacial and interglacial periods is crucial for predicting the impact of future climate changes on groundwater movement. This study assesses the difference in groundwater flow between the last glacial period (LGP) and the postglacial period (PGP) in fractured mudstones of the Horonobe area, Japan, by combining the data for stable isotopes (δD and δ18O) and Cl− concentration of fracture and pore waters with radiocarbon (14C) age. The isotopic compositions of fractures and pore waters indicate that groundwater at 28–250 m deep in a borehole closest to the recharge area comprises meteoric water, recharged under the same climates as the present. The fracture water has isotopic compositions more similar to meteoric water than the matrix pore water near the fracture. The 14C age of fracture water suggests meteoric water recharge during the PGP. At greater depths in the borehole and sampling points in other boreholes, the isotopic compositions indicate the mixing of glacial meteoric and altered connate water, with the fracture water having comparable isotopic compositions with the matrix pore water. The recharge timing of meteoric water is inferred to be the LGP or before based on 14C dating. These results suggest that the meteoric water recharged during the PGP flows at a shallow depth, whereas the meteoric water recharged during the LGP intruded to greater depths. This result is consistent with previous inferences from surface geophysical and geological surveys that the depths of local valleys during the LGP were greater by < 50 m than the present ones and enhanced the downward hydraulic gradient. Combining the chemical and isotopic compositions of groundwater with 14C age helps assess the groundwater flow during the LGP and PGP in fractured rocks.

Overview of Flowslide in Petobo during liquefaction of the 2018 Palu Earthquake

Massive flowsides inducing deformation of about 1 km on gentle slope occurred in Petobo during liquefaction of the 2018 Palu Earthquake. The liquefaction mechanism attributed to this enormous lateral deformation is not fully understood yet. In fact, a comprehensive understanding of this phenomenon mechanism is crucial to mitigate similar disasters in the future. This manuscript describes the flowslide observations in Petobo based on geotechnical investigations, including trench, geophysical survey, CPT, boreholes, and laboratory testing. The investigation showed that the flowslide location consisted of a liquefaction layer with a cap layer on it. The liquefaction layer consists of two successive liquefied layers, the upper layer is finer and less permeable than that of the one below. With the upper layer less permeable, this may result in an increase in the void ratio due to void redistribution distributed in the liquefied upper layer. This study demonstrates that variations in liquefied layer conditions have a major effect on whether flowslide due to liquefaction occurs or not. The results of this study are expected to enrich our knowledge related to liquefaction-induced flowslide and can be used as a basis to evaluate flowslide potential in other locations.

Thermal pattern at kueishantao (KST) volcano of Taiwan from satellite-observed temperatures and its implication

Abstract Kueishantao (KST) is an active volcanic island off the northeastern coast of Taiwan. Tectonically, it lies in the south of the Okinawa Trough and opposite to the Ilan plain, in which is the southwestern end of the trough. KST provides a convenient observation site for the subsurface geological and geothermal activity and mechanism at its proximity. Land surface temperature (LST) of volcanoes detected from satellite sensors reflects the thermal status of heat sources in the subsurface. LST thus is a key parameter to the understanding of the volcanic process and geothermal resources. This research utilizes the satellite-observed multi-temporal land surface temperature imagery in 1999–2022 on the Kueishantao volcano of Taiwan to explore its geothermal state. The U.S. NASA Earth-observing satellites onboard three thermal sensors (i.e., Landsat ETM+, Terra ASTER, and Aqua/Terra MODIS) derived time series of land surface temperature from 1999 are employed to define the past and current pattern of geothermal activity plus the future trend of the KST. The spatiotemporal LST distribution of KST volcano is explored and analyzed. The spatial LST distribution of the KST volcano indicates that LST anomaly areas are mainly located on the southeast island, which is well correlated with the possible magma reservoir location from previous geophysical and geological surveys. An increasing trend of two-decade LST time series is revealed from all three thermal sensors. The retrieved surface thermal pattern shows non-linear temperature variations that imply the non-steady-state nature of the subsurface thermal sources at this volcano. In summary, satellite LST observations facilitate the understanding on the subsurface magmatic processes of active volcanoes for further management of geothermal resources.

Development of the renewable geothermal energy in Uzbekistan (as an example – the Muruntau area)

This paper presents a Multidisciplinary geophysical study of the geothermal areas in Uzbekistan. Based on the developed new geothermal map, data on anomalous geothermal areas were analyzed. Based on the study of the Muruntau area, a comprehensive methodology has been developed for detailing geothermal anomalies. New data of integrated geophysical surveys (gravity survey, seismic survey, magnetotelluric survey) and their interpretation at the stage of geophysical exploration are presented.

A POSSIBLE IMPACT OF SCENARIO EARTHQUAKES IN THE CAUCASIAN MINERAL WATERS ZONE

This paper analyzes a possible impact of scenario earthquakes in the zones of high seismic hazard in order to justify measures for ensuring population safety by the example of the southern Stavropol krai area. Over the past twenty years, the Central CisCaucasus region shows elevated seismicity based on the data recorded by the Geophysical Survey RAS network, reporting the occurrence of seismic events within a wide range of magnitudes, М≥1. One of the last felt events with mb = 4.4 occurred in the studied area on April 1, 2023, producing shaking intensity of 3 to 4 grades on the MSK-64 scale in large resort cities of the region. The parameters for the scenario events are based on the results of detailed seismic zoning (DSZ) and review seismic zoning (RSZ-2016) obtained by the Schmidt Institute of Physics of the Earth RAS. The Extremum system was used to assess felt effects in resort centers located in the southern Stavropol krai. We analyzed the influence of seismic intensity propagation and the parameters of macroseismic field equation on the assessed impact of the scenario earthquakes. Special attention was paid to the depths of strong and moderate events in the considered area of the Northern Caucasus and to the orientation of macroseismic isoseismals. Pre-calibration of the Extremum system loss models is recommended. Estimates of possible simulated damage due to scenario earthquakes with M=6.0 and M = 5.0 for individual large resort cities of the Kavminvody zone are given. The results can be used in the development of both preventive measures and response plans in case of possible events in the region.

About the application of modern geophysical research methods and the problems solved Summary

The vast majority of oil and gas fields in Azerbaijan are at the final (late) stage of development, and therefore a natural decline in production is expected. Despite the long-term development of fields, their reserves are of great industrial importance for ensuring the stability of the energy balance of our country. Therefore, it became necessary to introduce new technologies in order to maintain or partially increase production at fields that are in long-term development. Before carrying out geological activities, it is necessary to apply a new type of more modern borehole geophysical research in order to involve in the processing of zones with residual resources of these depleted fields. From this point of view, the article considers the application and results of modern borehole geophysical surveys, and analyzes the possibilities for expansion. Keywords: Logging; Geophysical research; Reservoir; Formation; QUAD; Logging tool.

Metal hoards in a ritual space? The Atlantic Middle Bronze Age site of Kerouarn, Prat (Côtes-d'Armor, France)

Geophysical prospection and archaeological excavation are helping to contextualise a group of Middle Bronze Age metalwork hoards in Brittany. At Kerouarn, three hoards with a total of 89 bracelets were found buried in a semi-circular enclosure with a monumental entrance, bounded by two deep ditches and their associated embankments. No domestic or funerary remains were discovered.

Inner structure of monogenetic Pilot Knob submarine volcano (Austin, Texas) revealed by electrical resistivity tomography and magnetic surveys

Pilot Knob is the eroded and exposed core of an extinct subaqueous to emergent volcano that formed in a shallow Late Cretaceous epicontinental sea in the ancient Gulf of Mexico during the deposition of Austin Chalk Limestone. With the aim of understanding the inner structure of this volcano, we have conducted geophysical surveys (resistivity and magnetometry) to provide an insight into the past eruptive history. High-resolution electrical resistivity and magnetic data reveal, for the first time, a buried tuff mound, an explosion crater, several dikes and vents, basaltic flows, and limestone blocks within the volcano. A combination of geologic and geophysical data suggests that Pilot Knob volcano started with an explosion as a maar-type volcano beneath a shallow sea floor. Then, it likely has evolved into a tuff mound-type volcano with “Surtseyan” eruptions, before finally evolving into an emergent volcanic center. Major resistivity and magnetic anomalies align approximately in the east–west and north–south directions, respectively. Such alignments suggest that Pilot Knob is situated on east–west and north–south fractures, along which its most significant volcanic activity occurred. Results also provide valuable information in delineating tuff mounds and their structural characteristics.

Symmetry in Hillslope Steepness and Saprolite Thickness Between Hillslopes With Opposing Aspects

AbstractThe structure of the critical zone (CZ) is a product of feedbacks among hydrologic, climatic, biotic, and chemical processes. Past research within snow‐dominated systems has shown that aspect‐dependent solar radiation inputs can produce striking differences in vegetation composition, topography, and soil depth between opposing hillslopes. However, far fewer studies have evaluated the role of microclimates on CZ development within rain‐dominated systems, especially below the soil and into weathered bedrock. To address this need, we characterized the CZ of a north‐facing and south‐facing slope within a first‐order headwater catchment located in central coast California. We combined terrain analysis of vegetation distribution and topography with soil pit characterization, geophysical surveys and hydrologic measurements between slope‐aspects. We documented denser vegetation and higher shallow soil moisture on north facing slopes, which matched previously documented observations in snow‐dominated sites. However, average topographic gradients were 24° and saprolite thickness was approximately 6 m across both hillslopes, which did not match common observations from the literature that showed widespread asymmetry in snow‐dominated systems. These results suggest that dominant processes for CZ evolution are not necessarily transferable across regions. Thus, there is a continued need to expand CZ research, especially in rain‐dominated and water‐limited systems. Here, we present two non‐exclusive mechanistic hypotheses that may explain these unexpected similarities in slope and saprolite thickness between hillslopes with opposing aspects.

Penentuan Kedalaman dan Sudut Kemiringan Sesar Grindulu di Pacitan Menggunakan Metode Crow Search Algorithm (CSA) pada Data Self-Potential (SP)

Self-Potential (SP) is a geophysical survey method that is relatively easy and inexpensive. Interpretation of SP data can be used for various purposes such as the detection of landslide-prone areas, exploration of various types of minerals, and identification of the parameters of a fault or crack. In this study, SP data acquisition was carried out in Tambakrejo Village, Pacitan District with a total of 102 measurement data which aims to determine the depth and dip of the Grindulu Fault. SP data acquired in the field needs to be corrected for reference, namely corrections caused by a displacement of the starting point of measurement. This data is then filtered to increase the signal-to-noise ratio (SNR) and sharpen the resulting anomalies. This filtering process is carried out using the ICEEMD (Improved Complete Ensemble Empirical Mode Decomposition) method which is a development of the EMD method. Furthermore, the SP data inversion process to obtain model parameters is carried out by utilizing the CSA (Crow Search Algorithm) method. Based on the anomaly model generated from the SP data inversion process, it can be concluded that the Grindulu Fault was identified at a distance of 803,8 meters from the starting point of measurement with depths ranging from 11,06 to 102,74 meters. Furthermore, based on distance, depth, and anomaly shape data, the dip value can be calculated. The calculation results show that the dip of the Grindulu Fault in the study area is 75.58o. Identification of the Grindulu Fault in the form of depth and dip is very important in efforts to model the fault comprehensively.