Geophysical Profiles Research Articles

Geophysical characterization of a potentially active fault in the Agua Fría micro-graben, Los Azufres, Mexico

In this study, three geophysical techniques were used to identify, localize, and characterize a partly blind fault in the Llano Grande basin within the Agua Fría Graben. This tectonic basin is located in the Los Azufres Volcanic Complex, one of the major silicic volcanic centers in the Trans-Mexican Volcanic Belt. The 1 km wide Agua Fría graben could be considered as an analogous of the larger graben structures bounded by the Morelia-Acambay Fault System. Since it is filled by recent sediments, it represents a challenge for the recognition and characterization of active faults that lack clear surface expression. Newly collected magnetic data led to the identification of lineaments interpreted as structural discontinuities. Ground penetrating radar and seismic refraction surveys were carried out across one of these magnetic lineaments crossing the basin to characterize the nature and geometry of the inferred discontinuity. The ground penetrating radar profiles allowed the identification of buried deformational structures interpreted as the northern segment of the Agua Fría fault. The subsurface reflectors displaced 1 to 1.5 m by the fault indicate that this structure is potentially active. The opening of trenches based on these results makes it possible to confirm the interpretation of the geophysical profiles, to discuss the precision of the data and to validate their use for such studies. On seismic refraction profiles, the deformation zones are related to low P-wave velocity zones. These geophysical studies demonstrate the potential of such techniques to locate faults in the subsurface, partially characterize the width of the fault zone and the associated displacement within the uppermost of the subsurface. Our results may be applied to define ideal sites for paleoseismic excavations which are essential for the identification and description of historical and prehistoric earthquakes, and thus, for the characterization of the local seismic hazard.

Increasing Resolution of Seismic Hazard Mapping on the Example of the North of Middle Russian Highland

The standard problem of engineering geophysics, solved for road and house building and other construction types, is in the localization of areas with increased mobility in the upper part of a geological cross-section and in the parameterization of this mobility in terms of seismic intensity. There is a standard approach, according to which researchers assess the elastic strength characteristics of the core to a depth of about 30 m, implement the accumulation of seismogram observations, simulate accelerograms for particular conditions and, taking into account the data of complex geophysical methods, calculate the increment of seismic intensity as one of the parameters of a seismic hazard. The final result of this approach has the form of a seismogenic hazard map and a set of recommendations including the consideration of identified areas with a significant increasing seismic intensity increment, due to the peculiarities of the geological structure of polygons. This result is reliable, but very expensive, and requires the development of primary estimations of the rock massif with reduced resistance to external loads, which would optimize the efforts in engineering drilling and in field geophysical measurements in order to densify their spatial grid in the vicinity of a priori known positions with an increased seismogenic hazard. In addition, relatively sparse grids of wells, as well as local geophysical profiles laid under conditions of a complicated landscape, do not accurately localize risky areas in order to focus the attention of builders on strengthening the specific part of raised constructions. Following the wishes of our customers and relying on long-term testing of our interpretational developments, we formed an approach to primary hazard forecasting based on remote sensing data and digital elevation models, which can be classified as data with relatively free access. This article presents the results of research which was based on these free-of-charge data and which was developed in the field of construction of ground engineering structures for agricultural purposes, where one of the factors of mobility in the upper part of a cross-section is intensive karstification. Basically, the construction area according to the general seismic zoning maps is seismologically passive, though the relatively fast dynamics of karst determines the relevance of the detailed seismic zoning. The results of our interpretations are verified by deep geological and structural reconstructions based on wave analogies. The representativeness of the final forecast was confirmed by subsequent seismic assessments, which is related to the scientific novelty of the presented article. The authors’ technology for the qualitative and quantitative interpretation of remote sensing data and digital elevation models with high resolution provides the opportunity to increase the spatial resolution of seismic microzonation forecasts, implemented by standard geophysical methods, and it determines the practical significance of completed research.

Mid-to Late Holocene landscape reconstruction of the Maye Estuary (Picardy, Northern France) and its implications for human occupation

The town of Rue was one of the most important coastal harbours of Picardy, Northern France, from the beginning of the 12th century to the end of the 15th century CE. Document sources and ancient maps confirm the existence of this vibrant harbour. Until now, however, no palaeoenvironmental studies have attempted to reconstruct the configuration of the region's coastline during medieval times. Here we employ a geoarchaeological approach to reconstruct the Mid-to Late Holocene shoreline and landscape changes in the Rue area. Our approach includes a geophysical survey (Electric Resistivity Tomography method) and a series of eight sediment cores that reveal the region's chronostratigraphy. Document sources were also used to shed light on the landscape configuration during the Late Middle Ages (ca. 1300 CE). Our coring results, based on sedimentological analyses, are combined with 2D geophysical profiles down to 21.50 m. This reveals, firstly, that a calm marine environment prevailed at the beginning of the 4th millennium BCE, particularly in depressions bordered by Pleistocene coastal spits (foraines). Secondly, from ca. 3500 BCE to ca. 1000 BCE, coastal swamps predominated. Then, thirdly, at around 1000–1250 CE, an estuarine depositional environment prevailed, prior to a final period of land reclamation of the former Maye Estuary from the 13th century CE onwards. These results agree well with recent work on sea level changes along the Atlantic and English Channel coasts of France, where continuous post-glacial sea level rise has been observed. Our study also proposes a location of the medieval harbour of Rue to the west of the town at the upstream boundary of the upper part of the Maye Estuary, near ‘Le Moulin de Saint-Jean’, although archaeological evidence of the exact site of this tidal harbour is still lacking.

TO STUDY THE POSSIBILITIES OF USING THE SEISMOLOGICAL NETWORK OF THE ALTAI-SAYAN REGION FOR REGIME VIBRO-SEISMIC OBSERVATIONS

The results of deep seismic studies based on P - and S-wave data on the East-Stanov fragment of the reference 700-kilometer geophysical profile 8-DV are presented. Deep seismic sections of the upper crust (up to a depth of 20 km) with the distribution of the velocities of longitudinal and transverse waves are constructed. The P - wave velocities in the upper part of the section vary from 4-5 km / s within the Upper Zeya and Amur-Zeya depressions to 5.5-6.0 km/s within mountain ranges and plateaus; at depths of 10-20 km, lenses of high-velocity rocks up to 6.7-7.0 km/s are distinguished in the profile alignment. According to the S - waves in the upper part of the section, the velocity values are generally 3.0-3.2 km/s; reduced velocity values of 2.5-2.6 km / s are observed in the Upper Zey depression. At depths of 5-20 km within the section, according to the transverse wave data, a number of sections with reduced and increased velocity values are distinguished, respectively, up to 3.4-3.5 km/s and 3.75-3.8 km/s. The correlation of the selected anomalies according to the data of P-and S-waves is carried out.

Geomorphological and stratigraphic evolution of a fluvial incision in the coastal plain and inner continental shelf in southern Brazil

This paper describes the evolution of a sector of the southern coastal plain of the Pelotas Basin, southern Brazil, between the last Pleistocene sea-level lowstand and the Holocene highstand, based on geomorphology and high-resolution stratigraphy. A fluvial drainage system associated with an incised valley developed during the Last Glacial Maximum (LGM) was identified. Two high-resolution 2D and 2.5D geophysical profiles using Ground-Penetrating Radar (GPR) show a Pleistocene fluvial system's former path, starting close to its present mouth inside Mirim Lagoon crossing the coastal barriers and reaching the inner continental shelf, covering some 60 km across the coastal plain. During the LGM, with the sea-level at −120 to −130 m and the coastline positioned close to the shelf edge (distant 200 km from the present coastline), the fluvial system excavated a ~31.5-m deep channel. Two cores, 36 and 32 m long, show that the paleochannel was filled with sedimentary deposits after 19.4 ka BP, and the facies succession represents the transition from fluvial, to estuarine, to the coastal barrier, and finally to inner shelf depositional environments, generated by processes connected to LGM and the Postglacial Marine Transgression (PMT). The study region behaved as a sediment by-pass zone, connecting the adjacent coastal plain's inner portion with the inner continental shelf. The studied area presents an unusual record of the LGM at a coastal plain domain.

Hydrogeological estimation of brackish groundwater lens on a small Dinaric karst island: Case study of Ilovik, Croatia

Ilovik is one of the smallest inhabited islands (5.51 km2) in the Adriatic Sea. It is composed of karstified Cretaceous and Paleogene limestones. Despite its small size, the island was the subject of an extensive research program.The main objective was setting up a groundwater extraction site to extract brackish groundwater at a rate of least 1.0L/s with chloride concentrations below 5000 mg/L.The research was carried out in three phases using various methods: geological and hydrogeological mapping, geophysical profiling (electrical tomography and seismic refraction), investigatory core drilling, test-well design, pumping tests, groundwater level monitoring, and hydrogeochemical analyses (in situ and laboratory tests). The underground spread of electrical resistivity mapped the groundwater level and transition zone from fresh to brackish water, and seismic velocities indicated fractured zones. After the pumping tests, hydraulic parameters were calculated based on calculations for similar karstic aquifers, and hydraulic conductivity was within orders of magnitude of 10−4–10−6m/s. The results have great applicability, as the water quantity and quality were determined. Additionally, parametric estimation of the hydrogeological properties was useful even in heterogeneous Dinaric karst environments. Such karst environments have to be studied via several different methods, with common interpretation, to avoid ambiguous conclusions.

Deep Structure, Tectonics and Petroleum Potential of the Western Sector of the Russian Arctic

The evolutionary-genetic method, whereby modern sedimentary basins are interpreted as end-products of a long geological evolution of a system of conjugate palaeo-basins, enables the assessment of the petroleum potential of the Western sector of the Russian Arctic. Modern basins in this region contain relics of palaeo-basins of a certain tectonotype formed in varying geodynamic regimes. Petroleum potential estimates of the Western Arctic vary broadly—from 34.7 to more than 100 billion tons of oil equivalent with the share of liquid hydrocarbons from 5.3 to 13.4 billion tons of oil equivalent. At each stage of the development of palaeo-basins, favourable geological, geochemical and thermobaric conditions have emerged and determined the processes of oil and gas formation, migration, accumulation, and subsequent redistribution between different complexes. The most recent stage of basin formation is of crucial importance for the modern distribution of hydrocarbon accumulations. The primary evolutionary-genetic sequence associated with the oil and gas formation regime of a certain type is crucial for the assessment of petroleum potential. Tectonic schemes of individual crustal layers of the Western sector of the Russian Arctic have been compiled based on the interpretation of several seismic data sets. These schemes are accompanied by cross-sections of the Earth’s crust alongside reference geophysical profiles (geo-traverses). A tectonic scheme of the consolidated basement shows the location and nature of tectonic boundaries of cratons and platform plates with Grenvillian basement as well as Baikalian, Caledonian, Hercynian, and Early Cimmerian fold areas. Four groups of sedimentary basins are distinguished on the tectonic scheme of the platform cover according to the age of its formation: (1) Riphean-Mesozoic on the Early Precambrian basement; (2) Paleozoic-Cenozoic on the Baikalian and Grenvillian basements; (3) Late Paleozoic-Cenozoic on the Caledonian basement; (4) Mesozoic-Cenozoic, overlying a consolidated basement of different ages. Fragments of reference sections along geo-traverses illustrate features of the deep structure of the main geo-structures of the Arctic shelf and continental regions of polar Russia.

Historical pond systems as long-term composite archives of anthropogenic contamination in the Vrchlice River, Czechia

River damming has numerous benefits and adverse consequences. Unlike large dam reservoirs whose construction peaked in the twentieth century, historical ponds and their accumulated legacy sediments span much longer time periods. Small ponds in many areas worldwide are sinks for anthropogenic pollutants and affect sediment delivery to downstream river reaches. Thousands of ponds cover an area of >0.2 % of the territory of Czechia, equal to the area of its ten largest dam reservoirs. This paper reports a sequence of constructed and removed pond dams along the Vrchlice River, Czechia, and their use as sedimentary archives, in order to reconstruct the long-term (>200 yr) history of contamination. Historical maps, geophysical profiles, activities of caesium-137 isotope, grain size, and sediment geochemistry in 16 sediment cores enabled the reconstruction of contamination in the pond, dam reservoir, and floodplain sediments since ∼1780. Contamination by lead, copper, zinc, arsenic, and cadmium from atmospheric, geogenic and agricultural sources increased since ∼1850 peaked in the 1970s and 1980s, and then decreased slightly. Polycyclic aromatic hydrocarbons and pesticides polluted post-1970 sediments, reflecting their use in agriculture. The removal of dams resulted in the rapid incision of newly formed river channels into the old pond deposits. Following the reinstatement of dams, channels filled rapidly (up to 5.2 cm/yr) with new lacustrine sediment, whereas sediment accumulated slowly (<0.4 cm/yr) outside the channels. Upon dam removal, contaminated channel-fill sediment likely redistributed into the water course. As ponds are complex depositional systems with the heterogeneous distribution of sediment and associated contaminants, active and extinct ponds are promising long-term sedimentary archives that can extend understanding of human interactions with Earth systems.

UWB locating system in semi-open space

Simulation of the processing of navigation signals and estimation of the noise immunity of the receiver of an ultra-wideband positioning system in difficult conditions for receiving GNSS signals with dense taiga vegetation was performed. Experimental data were obtained on microwave interference and the conditions for the propagation of radio waves at real production facilities, including operating mountain taiga geophysical profiles.

Development of an electrical exploration data post-processor

In modern times, the development of geology and geophysics is associated with complex experiments. The results of these experiments are large arrays of numerical data, which require processing and further analysis. If to process these data manually, it can be a very difficult and routine task. For such studies, specialized tools are important, which are necessary to significantly speed up the processing process and to render visualization of geophysical data in real time. The software is worked out to automate the geophysical data processing obtained after electrical exploration procedure. The designed postprocessor performs functions of data correction and geological and geophysical profile visualization. The user interface of the program provides researchers with the ability to interactively process the initial geophysical data.

STRUCTURAL FEATURES OF THE DEEP STRUCTURE OF THE SOUTHEASTERN YANA-KOLYMA FOLD SYSTEM FROM COMPLEX GEOPHYSICAL DATA

Ore deposits of the Magadan region are now in the focus of comprehensive studies as information on their deep structure is needed for both subsoil prospecting and regional development planning. This article presents the research results for the southeastern flank of the Yana-Kolyma orogenic belt. This area located at the junction with the Okhotsk-Koryak orogenic belt was investigated using the northeastern segment of the regional geophysical profile 3-DV. We analyzed the frequency-energy sections of the crust along the profile, 3D crustal density model of the entire study area, and magnetic, geoelectric and gravimagnetic characteristics of the crust. Complex data interpretation allowed tracing the crustal fault zones, areas wherein the crust material was strongly reworked, and zones of quasi-horizontal stratification. Considering the revealed features of the physical parameters of the crust material, we conclude that the currently accepted boundaries of individual tectonic blocks in the study area need to be adjusted. The northern boundary of the Balygychan uplift should be mapped along the Pautov fault. The Srednekansky branch of the Inyali-Debinsky synclinorium should be considered a transitional block that belongs to the Sugoi synclinorium, and its name should be changed to the Orotukan block.

Geological, Geotechnical and Geophysical Aspects of Zafarana Wind Farms Sites and Their Expansion at Gabel El Zeit Sites Egypt

The growing need for sustainable power generation has led to increasing number of power plants, of fossil-fuel type and of non-conventional type. The foundation types of wind turbine towers in power plant structures are mainly depend on the geotechnical and structural considerations and other geological and geophysical considerations. The safety and economic conditions also play a vital role in the design of foundations. Such foundations must effectively be designed taken into consideration large overturning moments and dynamic loading due to extreme wind and earthquakes. The present research is focused on studying the geotechnical, geological and geophysical aspects and characterizes of soils in Zafarana Wind Farms sites and their expansion at Gabel El Zeit sites on the Suez Gulf of Egypt. The study first address and study the geological aspects of both sites Zafarana Wind Farms sites and Gabel El Zeit sites. Secondly, the geotechnical and geophysical characteristics are studied based on establishing data base from 698 borings and 8 seismic refraction profiles across Zafarana wind Farm sites and 10 borings and 2 seismic refraction profiles at Gabel El Zeit site. The geotechnical testing and geophysical profiles were compiled to determine the variation of the soil profile as well as the characteristics of the soil layers within the study sites. The results showed construction of 8 representative boring logs at Zafarana Wind Farm sites and 2 representative boring logs Gabel El Zeit sites to represent the characteristics of the soil layers and site statgerphy. Also, the study shows the result of compression wave velocity and shear wave velocity across both sites and within the studied soil layers up to 30 m. All these results from this research will help to study the foundation and the structure of wind turbine tower, where these types of tall structures are similar to chimney structures in design and other engineering considerations.

Improvement of Shallow Seismic Characterization Using the Singular Value Decomposition (SVD) Method in Seismic Data Inversion: A Case Study of a Site in Northeast Mexico

Several approaches can be taken to conduct seismic data inversion. However, usually, these approaches are unable to distinguish vertical and horizontal heterogeneities. Seismic inversion through the singular value decomposition (SVD) method offers an adequate and simple way to improve these traditional inversion models. For this study P and S wave data were acquired at a site located in northeastern Mexico, obtaining their travel times. An inversion algorithm involving the SVD analysis was then developed to establish the seismic velocities of the lithological units. Further, images of compressional and shear-wave velocities ( Vpand Vs, respectively), Vp/ Vsratio, and elastic moduli (bulk, shear and Young's moduli, Lamé's constant, and Poisson's ratio) were obtained. These were compared with two geotechnical soundings positioned over a geophysical profile line. The geological features of the exposed units were recognized on some trenches. Further, seismic images demonstrated correlations with the thickness and distribution of the geological units. Unconsolidated sediments and fine-grain clastic rocks (in the Méndez formation) were clearly distinguished by the high velocity contrast. SVD seismic inversion has shown the ability to distinguish small physical heterogeneities of shallow geological units. Its application in civil engineering, hydrogeology, and to solve soil pollution problems can be relevant.

Sediment Deposition Following Construction of a Breakwater Harbor: Point Judith Harbor of Refuge, Rhode Island, USA

Breakwaters are a common shoreline protection structure, often trapping sediment as the incoming wave energy is reduced. Quantifying the dynamics and volume of these sediment sinks within a coastal system is an important step toward understanding the sediment budget for a particular coastal area. This study examines the volume of sediment deposited within the breakwater enclosed Point Judith Harbor of Refuge (Rhode Island, United States of America (USA)) in the late 19th century using seismic reflection profiles, bathymetric mapping, and isotopic analysis of core sediment. Geophysical profiles show a district seismic facies up to 4 m thick above the ravinement surface, particularly in the western and central portion of the harbor. Century-scale bathymetric changes revealed shoaling of a similar magnitude, and isotopic data support the deposition of this sediment package within the 20th century. The total volume of sediment within the harbor exceeds 5.0 × 106 m3, with an estimated sand volume of 3.6 × 106 m3. The results show that the harbor is a substantial sediment sink for the Rhode Island South Shore and provide the basis for future studies of the sediment budget for this shoreline.

Correction of water column height variation on 2D grid high-resolution seismic data using dGPS based methodology

Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments. Changes in water column properties can be attributed to variation in tides and currents, wind-generated swells, long and short amplitude wave-fronts, or variation in salinity and water temperature. Likewise, the proper motion of the vessel complicates the determinability of the water column height. This study provides a less time-consuming and precise differential Global Positioning System based methodology that can be applied to most types of high-resolution seismic data in order to significantly improve the tracking and quality of deduced geological interpretations on smaller depth scales. The methodology was tested on geophysical profiles obtained from the German sector of the North Sea. The focus here was to identify, distinguish and classify various sub-surface sedimentary structures in a stratigraphically highly complex shallow marine environment on decimeter small-scale. After applying the correction to the profiles, the sea floor, in general, occurs 1.1 to 3.4 m (mean of 2.2 m) deeper than the uncorrected profiles and is consistent with the sea floor from published tide corrected bathymetry data. The corrected seismic profiles were used in plotting the depth of the base of Holocene channel structures and to define their gradients. The applied correction methodology was also crucial in glacial and post-glacial valley features distinction, across profile correlation and establishing structural and stratigraphic framework of the study area.

Discrete fracture network characterization using multiple, high-resolution borehole methods in a crystalline rock aquifer in tropical Sao Paulo city, Brazil

The geological scenario of thick weathering materials over a fresh bedrock is characteristic of tropical climate regions. The application of the Discrete Fracture Network (DFN) methodology relying on multiple, high resolution measurements methods on continuous cores and/or boreholes in such geological conditions, particularly in a contaminated area, is unprecedent. A total of 977 structures were described, between rock cores, geophysical profiling and outcrops, with emphasis on brittle structures due to their importance for groundwater flow. Five fracture sets were characterized, related to lithology. The correlation of these fracture sets with large structures from regional studies indicated the representativeness of this detailed survey. Finally, it is expected that the model presented here can be applied in the management of other contaminated areas of similar geological contexts, particularly in Brazil, where the discussions regarding contaminated fractured aquifers are still quite recent.

The Features of the Deep Velocity Structure of the Trans-Baikal Section of the Central Asian Fold Belt from the Seismological and DSS Data (Alignment of the 1-SB Reference Profile)

The materials of deep seismic studies carried out on the 1-SB reference geophysical profile and the areal interpretation of the seismological data obtained in the Trans-Baikal part of the Central Asian Fold Belt are presented. It is shown that longitudinal and transverse waves were recorded from the reference boundaries within the crust and the Moho surface in the Trans-Baikal region using explosions and powerful vibration sources on the 1200-km long 1-SB geophysical profile. The inhomogeneous upper crust velocity structure down to 15–20-km depths and the Moho surface was revealed from P- and S-waves. The anomalous mantle, which exhibited decreased boundary velocity values of P- and S-waves at 7.8–7.95 km/s and 4.3–4.5 km/s, respectively, was reliably traced within the Baikal Rift Zone from the DSS and seismological data. In the southeastern part of the area (the central Mongol-Okhotsk Orogenic Belt and adjacent folded structures of the Trans-Baikal region) a layer of increased P-and S-wave velocity values of 8.4 ± 0.15 km/s and 4.9 ± 0.05 km/s, accordingly, was detected at the mantle surface. A comparison was made with the materials of other studies.

Characteristics of Deep Groundwater Flow and Temperature in the Tertiary Pohang Area, South Korea

The geothermal characteristics of specific areas on Earth can be identified using geophysical and lithological logs based on deep boreholes, such as those more than 1000 m in depth. Based on the combined analyses of geophysical logs (temperature, caliper, electrical conductivity (EC), and natural gamma-ray logs) and lithological logs, as well as 1D steady-state heat transfer model, the deep groundwater flow and temperature were characterized in four deep boreholes (BH-1–BH-4) roughly 2000 m deep in the area of Heunghae-eup, Pohang, South Korea. The estimated thermal gradients from the temperature profiles are as follows: 22.37–30.77 °C/km for BH-1, 35.67–64.52 °C/km for BH-2, 40.85–46.44 °C/km for BH-3, and 33.33–35.71 °C/km for BH-4. According to the geophysical logs and lithology profiles, the groundwater mainly flows into and out of the boreholes through the basic dyke, rhyolite, and sandstone/mudstone. Evidently, the groundwater flows moving through the fractures and faults induce nonlinear temperature changes. The upward and downward groundwater flows passing through fractures and faults can be estimated using a 1D steady-state heat-transfer equation, by considering a fracture angle based on the lithological and geophysical profiles. To determine the direction (up/down) and rate of groundwater flow, the values for the parameter β were estimated as follows: −1.95 to 5.40 for BH-1, −13.48 to 4.87 for BH-2, −1.76 for BH-3, and −3.39 to 14.15 for BH-4.

Regime geocryological observations of the high altitude mountain passes of Tien Shan

This article examines the questions of assessment of the state and dynamics of frozen rocks in the conditions of changing climate on the territory of Tien Shan. The consists in evaluation of geocryological conditions of frozen rocks in Northern and South-Western Tien Shan regions in accordance with the data of regime observations conducted by authors on the equipped stationary sites of high altitude mountain passes. The article provides the results of a set of methods of geocryological and geophysical research, including drilling of engineering-geocryological wells with sampling and determination of the structure and composition of soils, thermometry in wells, geophysical profiling with construction of geoelectric sections. The proposed set of geophysical methods allows stratifying the section, obtain the boundaries of thawed and frozen rocks, as well as follow the dynamics of dangerous cryogenic processes. The geophysical TEM method for work in the mountains features a number of advantages &amp;ndash; &amp;nbsp;the absence of galvanic grounding, mobility of installation, determination in addition to the characteristics of the rock resistance, polarization, the high values of which (according to laboratory data) indicate the presence of ice. The importance of direct observations and geocryological monitoring is emphasized, since in the zones of proliferation of high altitude permafrost, climate warming can lead to the activation of catastrophic processes such as mudflows, outbursts of glacial mountain lakes, landslides, thermal erosion, and thermokarst. Therefore, constant monitoring of the glacial zone is necessary for determination of the new and assessment of the state of the existing foci of hazardous exogenous geological processes.&amp;nbsp;

Diagnosing the landslide areas of Angren open pit marginal mass according to the data of seismo- and electrical prospecting

Introduction. Sloping structures (quarry sides, dumps, banks, cuts, dams, etc) stability forecasting accuracy improvement requires detailed elaboration of physical-mechanical properties of the rock mass under consideration. Traditional methods of well engineering-geological exploration and hydrogeological monitoring are therefore supplemented by geophysical study. Research aim is to diagnose unstable deconsolidated and wetted zones in marginal masses for the purpose of further forecast of quarry sides stability. Methodology. Databases of geophysical studies obtained by the expeditions of the services of the Republic of Uzbekistan at Angren open pit. Results. For the test area represented by 11 seismic stations at the southern side of the quarry, the criterion assessing the state of the site as potentially landslide hazardous according to the results of circular seismic sounding has been experimentally obtained. With the use of this criterion, in the plan of the landslide zone the borders have been established. For the test area represented by 16 geophysical profiles at the northers side, by electrical profiling graphs and geological sections for the corresponding profiles, 58 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 1. 2020 ISSN 0536-1028 the following regularities have been found: at profile areas adjacent to the runs (rivers), local negative anomalies of effective resistivity up to 20–50 Ohm ∙ m are observed connected with soils wetting; between the anomalous areas the alternation of effective resistivity qualitatively coincides with the alternation of the thickness of a layer of loose deposits. By the arrangement of the negative anomalies borders at the graphs pf effective resistivity dependence on the spread of the profile along all profiles (PR1–PR16), the borders of the wetted zones were established in the plan of the test area. Summary. For geomechanical processes monitoring in the landslide zones it is advisable to apply the method of circular seismic sounding determining the value and the anisotropy coefficient according to the extreme values of compressional arrival time. For the conditions of the Angren open pit, the criterion of potential hazard of landslide development is the value of the anisotropy coefficient higher than 1.6. When elaborating the detailes of the physical properties of landslide zones in quarry sides which are weakened by sand-clay Quaternary sediments, by the method of electrical profiling it is advisable to use: the linear dependence on the thickness of Quaternary sediments on the value of the effective resistivity; hyperbolic dependence of soils relative wetness within the water saturation zones on the value of the effective resistivity ascribed to the reference value defined in the site of soil samples collection, and the borders of wetting zones are to be established by the negative anomalies at electrical profiling graphs. In order to construct the solid geologicalgeophysical models of the landslide zones of the sides, in addition to the geological sections data, the following results of geophysical sounding should be used: the boundaries of landslide zones in the plan, detailed contact geometry of loose Quaternary sediments with bedrock; soil properties modified by wetting