Bataleva, Elena Anatolievna

Rybin A., Bataleva E., Nepeina K.

The identification of hidden areas of active faults in the Earth’s crust that can generate earthquakes is the most urgent problem in assessing the seismic hazard of various regions. The main goal of this study was a detailed study of the geophysical characteristics in the zone of individual segments of active faults in the Northern Tien Shan with electromagnetic geophysical methods. The structural line of the Issyk-Ata fault is clearly, but fragmentary, revealed on the surface by geological methods, since the tectonic disturbance is hidden by loose deposits of the Cenozoic age. The results of inversion of detailed magnetotelluric soundings in the fault impact zone of the fault made it possible to determine the position of the upper edge, width, depth, strike and inclination of the fault zone. At the stage of complex construction of 2D geoelectric models of the Issyk-Ata fault zone, the results of field profile soundings by the method of surface electrical resistivity tomography were used. To study the dynamics of the constructed block model of the fault zone, we considered variations in the following electromagnetic parameters that reflect the response of the geomedium to a change in its stress–strain state: impedance and tipper components, apparent resistivity and impedance phase, time–frequency series, and anisotropic properties. Based on this, estimates of the correlation between variations in electromagnetic parameters and lunar-solar tides and the spatiotemporal distribution of seismicity were made. This work was supported by the Russian Science Foundation under grant No. 22–27-00567.

Rybin A., Bataleva E., Zabinyakova O., Nepeina K.

In 2023, monitoring geophysical studies were carried out using the electrical resistivity tomography (ERT) method along three profiles that cross the strike zone of the Issyk-Ata fault in the transverse direction. A detailed study was carried out of the observed variations in apparent electrical resistivity, which characterize the change in the electrical properties of the upper part of the Earth's crust section with a 40-minute discretization in time. Using the analysis of difference pseudo-sections of apparent resistivity, constructed based on the results of ERT monitoring, the most informative pseudo-depth interval from the point of view of geoelectric activity was determined for all three monitoring profiles. Accordingly, for a pseudo-depth of 24 m on each monitoring profile, an assessment was made of the geodynamic activity of these sections of the Issyk-Ata fault based on an analysis of the magnitude of two parameters: the amplitude of apparent resistivity variations and the correlation coefficient of electrical resistivity variations with lunar-solar solid tides. High values of these parameters, in our opinion, determine the location of modern active fault zones.

Nepeina K., Bataleva E., Alexandrov P.

This study focuses on microscale anisotropy in rock structure and texture, exploring its influence on the macro anisotropic electromagnetic parameters of the geological media, specifically electric conductivity (σ), relative permittivity (ε), and magnetic permeability (μ). The novelty of this research lies in the advancement of geophysical monitoring methods for calculating cross properties through the estimation of effective parameters—a kind of integral macroscopic characteristic of media mostly used for composite materials with inclusions. To achieve this, we approximate real geological media with layered bianisotropic media, employing the effective media approximation (EMA) averaging technique to simplify the retrieval of the effective electromagnetic parameters (e.g., apparent resistivity–inversely proportional to electrical conductivity). Additionally, we investigate the correlation between effective electromagnetic parameters and geodynamic processes, which is supported by the experimental data obtained during monitoring studies in the Tien Shan region. The observed decrease and increase in apparent electrical resistivity values of ρk over time in orthogonal azimuths leads to further ρk deviations of up to 80%. We demonstrate that transitioning to another coordinate system is equivalent to considering gradient anisotropic media. Building upon the developed method, we derive the effective electric conductivity tensor for gradient anisotropic media by modeling the process of fracturing in a rock mass. Research findings validate the concept that continuous electromagnetic monitoring can aid in identifying natural geodynamic disasters based on variations in integral macroscopic parameters such as electrical conductivity. The geodynamic processes are closely related to seismicity and stress regimes with provided constraints. Therefore, disasters such as earthquakes are damaging and seismically hazardous.

РЫБИН А.К., ЗАБИНЯКОВА О.Б., БАТАЛЕВА Е.А., НЕПЕИНА К.С.

Представлены результаты исследования разломной структуры, полученные с использованием комплекса электромагнитных методов -электротомографии и магнитотеллурического зондирования. Работы выполнены с целью детального изучения положения пространственных гео-электрических неоднородностей и аномалий повышенной проводимости. Построены геоэлектрические модели верхней части разреза (осадочного чехла и фундамента) для двух профилей, секущих зону динамического влияния Иссык-Атинского разлома. Полученные в результате двумерной инверсии аномалии низкого сопротивления коррелируют с положением отдельных сегментов разломной структуры. Получены оценки электромагнитных параметров в разломной зоне и определены элементы ее залегания.

Nigmatullin R.R., Bataleva E.A., Nepeina K.S., Matiukov V.E.

The research is based on the typical measurement calibration procedure of magnetotelluric soundings (MTS) prior to deep Earth exploration. We suggest the testing and new possibilities of the using MTS equipment calibration. We used two Phoenix MTS station boxes with different magnetic coil sets and mixed sets of coils for verification (check-up) stations calibration and the identity sessions. As a result of the experiments carried out and careful running over sorting of standard functions (exponential, power-law, polynomial), the verification of the proposed method was performed. Eventually this study proposes a “universal” fitting curve after one-station calibration curves to be normalized and are compared to another (etalon) station calibration curves (written in the form of two polynomials ratio). This procedure can be generalized for the case x → f(x), where f(x) is known function. It enables to fit all these 4 typical normalized curves (two for amplitudes (mV) and two for phases (degrees)) by the ratio of fourth degree function containing 9 fitting parameters C0-7 and B0, simply calculated as numeric constants through linear least squares method (LLSM).

Zabinyakova O., Bataleva E., Medved I.

The paper is dedicated to consider the approach of longitudinal electrical conductivity maps construction for Central Tien Shan region and to complete the comparison analysis of these maps with related seismic tomography data. The results of joint analysis of longitudinal electrical conductivity distribution and seismic tomography velocity models with respect to geological and geophysical senses allow to confirm the already known and to establish the new patterns of structure and geodynamics of the Tien Shan segment of Central Asia such as the manifestation of characteristic structural ensembles, reflection of the longitudinal and transverse segmentation of the Tien Shan, the existence within the framework of a “single” orogen of segments with different near-surface and deep structure and morphological expression. As well, the correlation between the velocity characteristics and geoelectric properties was found. This correlation allows to identify signs of reflection of fault structures in geophysical fields and to clarify the territorial and structural position of both visible and hidden faults. Additionally, in the paper, the geological interpretation of geophysical anomalies is considered.

Rybin A.K., Bataleva E.A., Aleksandrov P.N., Nepeina K.S.

Abstract—Electromagnetic investigation of stress-strain state dynamics in the geological medium is based on the analysis of two groups of physical phenomena. The first group includes phenomena associated with the dynamics of electrical properties of rocks caused by a change in their fracturing, porosity, fluid content, structure and texture, temperature and pressure, etc. The second group covers the effects of generation of endogenous (geodynamic) sources of electromagnetic field under irreversible deformations of the geological medium. In this paper, we present the practical results of the studies of the Earth’s natural electromagnetic field that have been carried out at the Research Station of the Russian Academy of Sciences in Bishkek over 40 years of operation of the Bishkek Geodynamical Test Site of the Research Station and aimed at gaining new insights into the present-day geodynamics of the Tien Shan lithosphere. The results of the experimental study of the first group of phenomena are based on the analysis of temporal changes in the magnetotelluric transfer functions. In this analysis it is assumed that the present-day geodynamic processes including catastrophic ones, e.g., earthquakes, trigger the crack formation processes which, in turn, changes the pore-fracture space of the rocks and causes fluid redistribution in them, thus resulting in the changes in the electrical conductivity of the geological medium. The practical results of the studies of the second group of phenomena are based on the notion that the geodynamic processes induced in the Tien Shan crust by irreversible deformations of rocks create sources of electromagnetic radiation leading to the variations in the endogenous electromagnetic field which can be observed on the ground.

Bataleva E.A.

The results of monitoring studies of the fault structures of the Northern Tien Shan are presented, where regime (regular) observations by the magnetotelluric sounding method are carried out over the state of the geological environment under the influence of geodynamic processes. Fault zones identified from geological and electromagnetic data appear in the upper part of the section as subvertical objects with high electrical conductivity due to increased fracturing and have a good correlation with lunisolar tidal effects. The relationship between the behavior of geophysical fields variations and the stress-strain state of the Earth's crust in the seismically active regions of the Tien Shan is considered based on the analysis of correlations between the components of lunar-solar tidal influences, variations in electromagnetic parameters, and the distribution of seismic events.

Пржиялговский Е.С., Рыбин А.К., Морозов Ю.А., Лаврушина Е.В., Леонов М.Г., Баталева Е.А.

The article presents the results of integrated geological and geophysical research works dealt with detailed magnetotelluric (MT) sounding and the study of the morphology and spatial position of the sedimentary cover and basement structures along the key transect of the Middle Tien Shan crossing the Naryn and Atbashi depressions. The data on the distribution of deep electrical conductivity of the crust and upper mantle were compared with the seismic profiling data. The compilation of the results of structural-geological and geophysical studies provided the opportunity to draw 2D upper-crust geological structure, consistent with the structure of electrical conductivity of the crust to depths of about 10 km. The detailed geological cross-sections and the structural and geological data allow us to characterize the deformations of the Cenozoic sedimentary complex and Paleozoic basement surface associated with the alpine activation of the key segment of the Tien Shan. It is shown that the Cenozoic structural parageneses emerged during a relatively short-term phase of deformation and orogeny under conditions of horizontal compression and transpression, which did not manifest themselves during sagging that occurred previously.

Nepeina K., Bataleva E.

This work is aimed to develop a new approach to study the relationships between the spatial distribution of the electrical conductivity and earthquake hypocenters in seismically active regions such as the Tien Shan. The basis of a complex deep complex model (up to 30 km depth) of the Tien Shan lithosphere is a fault-block model. The joint analysis of the geoelectric model and seismicity provides important information for understanding the distribution of deep electrical conductivity, which is an indicator of active geodynamic processes and provides indirect estimates of the stress-strain state of the geological media. The purpose of our investigation is to extend the study of the relationship between hypocenter depth distribution and geoelectric boundaries on a 2D cross-sections in the Central Tien Shan. This paper shows complex models, built for several meridional magnetotelluric soundings (MTS) profiles located (74.3° E and 75.2° E). We use seismic bulletins for 5 years (2015–2019) and select earthquakes nearest to the MTS profile lines. Based on our previous studies, we are interested in the behavior of seismicity with energy classes K  8 separately. We calculate relative coordinates (latitudes) to the kilometers from the starting point of the profile. As a result, the graphs present colored 2D cross-section with profile distance (R) and earthquake hypocenters into the depth marked by dots. The analysis of this study indicates the presence of a certain relationship: the earthquakes hypocenters clustering attach to the boundaries of objects and outline geological bodies, or are located inside certain zones.

Bataleva E.A., Matiukov V.E.

The paper presents the results of a comprehensive analysis of geological studies with data on the deep structure obtained by various geophysical methods for the Tien Shan territory. The areas of junction of different tectonic segments are characterized by anomalies of increased electrical conductivity, are clearly manifested in the magnetic and gravity fields and correspond to the zones of deep faults. Studying of these objects having high permeability and providing heat and mass flow as well as transport of fluids, is the main object of this work. In order to identify the boundaries of the largest tectonic fragments of the Tien Shan the geoelectric and velocity sections along the profiles intersecting the main tectonic elements of the Tien Shan were analyzed. Comparison of velocity anomalies in seismotomographic sections and objects of abnormally low electrical resistivity in geoelectric sections of the Earth’s crust indicates the existence of zones of increased fracturing or plasticity in the indicated intervals of the Earth’s crust, as well as the coincidence of waveguides and zones of increased conductivity. The distribution of seismic events clearly shows the zones of the Northern, Middle and Southern Tien Shan and the segmentation of the Western and Central Tien Shan.

Matiukov V.E., Bataleva E.A.

Abstract The paper discusses various approaches for processing and analysis of synchronous magnetotelluric and magnetovariational data obtained at the Kentor mini test polygon, which is located in the Baytic basin of the Chui region of Kyrgyzstan. The versions of noise reduction of received electromagnetic signals at the stage of robust processing are considered. The materials were processed using a remote reference technique for possible noise detection and calculate the additional components, such as a horizontal magnetic tensor for further interpretation of the obtained data. The dynamics of changes in the geoelectric cross-section for 2 sessions of researches by the tested profiles is considered.

Polyak B.G., Bataleva E.A., Rybin A.K.

Abstract The research shows new results of isotope-helium studies carried out in the Tien Shan - Naryn and Atbashi basins. Sampling of thermal mineral springs in the Eastern Tien Shan was carried out in order to identify traces of mantle emanations in fluids and to assess the degree of permeability of the Earth’s crust for the introduction of deep masses, which would make it possible to clarify the nature of the interaction of the crust and mantle in the zone of recent orogeny. Concentrations of helium isotopes were measured in gas and water samples from 6 thermal mineral springs in the Central Tien Shan. It was found that fluids from three sources contain an abnormally high amount of mantle helium. In the gases of the Narzan source, the ratio 3He/4He in the gas phase (597÷600) × 10−8 reaches the Central Asian maximum found earlier on the Fergana ridge in the Kyzyl-Beles source (510÷630) × 10−8. The obtained results support the ideas on the existence of two sublatitudinal positive helium isotope anomalies on the northern and southern flanks of the Eastern Tien Shan - in the zones of junction of the epiplatform neoorogene with more ancient tectonically stable structures.

Bataleva E.A., Nepeina K.S.

Abstract Based on the analysis of deep geophysical (geoelectric and seismic) models of the Central Tien Shan, structures with the morphology resembling the crown of palm trees or the shape of a flower were identified. Geoelectric models are considered along a series of regional profiles (75º, 76º, 76º 30’). The length of the profiles intersecting all the main tectonic structures of the Tien Shan ranges from 75 to 250 km. Particular attention was paid to those zones of concentrated deformation, where the tectonic regime combines the conditions of shear and lateral compression (transpression zones). The structure of the collisional - accretionary wedge of the Atbashi zone in the distribution of electrical and velocity characteristics of the geological section is considered. Geoelectric models plotted along a series of regional profiles identify areas of increased electrical conductivity and show “flower structures”. The integral picture of the distribution and morphology of zones of increased electrical conductivity in the segments of the Earth’s crust of the Central Tien Shan may reflect a discretely localized manifestation of palm tree structures due to the evolution of transpressive suture zones during the Hercynian and Alpine tectogenesis.

Przhiyalgovskii E.S., Rybin A.K., Morozov Y.A., Lavrushina E.V., Leonov M.G., Bataleva E.A.

Abstract The article presents the results of complex geological and geophysical studies in the Naryn depression and Atbashi depression in the Middle Tien Shan. They included the geological interpretation of new magnetotelluric data along the detailed profile crossing the key segment of the Tien Shan, and the study of the morphology and spatial position of the sedimentary cover and basement structures. The compilation of the results of structural-geological and geophysical studies makes it possible to create a 2D model of the upper-crust geological structure, consistent with the structure of the electrical conductivity to depths of about 10 km and to analyze the structural features of deeper horizons. Two types of structural patterns of the electric conductivity, corresponding to the sedimentary complexes of the cover and the folded-metamorphic complexes of the basement, have been identified. Sedimentary rock complexes in depressions have a high electrical conductivity and subhorizontal structure. The upper crust above the K2 density layer is characterized by an alternation of rocks volumes with contrasting conductivity, elongated vertically. The recorded structure of the field confirms the presence of steep zones of fluid permeability and fragmentation, noted earlier in seismic profiles and probably corresponding to the Paleozoic structures of fragmentation of the Earth’s crust, activated during Alpine orogeny. Comprehensive research allow to characterize the deformations of the Cenozoic sedimentary complex and the surface of the Paleozoic basement associated with the Alpine activation of the key segment of the Tien Shan.

Spichak V.V., Goidina A.G.

Ma X., Huang Z.

Pospeev A.V., Buddo I.V., Absalyamova D.F.

The article considers the possibilities of reducing the starting depth of studies using the near-field transient electromagnetic method by determining the effective transmitter-receiver offset. The solution of this problem is relevant due to the need to apply inductive electromagnetic exploration using ungrounded multi-offset templates in the climatic conditions of the Arctic. Optimization of the transient electromagnetic method technology in the far and near-field zones will expand the range of explored depths, which is extremely important for studying the accumulations of difficult to recover hydrocarbons located at depths from the first tens of meters to 3–4 km. To solve this problem for a half-space model, mathematical modeling of the transient electromagnetic signals was carried out taking into account the geometric spacing of soundings, which allowed to determine the effective signal offset by solving the inverse problem. On the basis of the mathematical modeling performed, a nomogram of the effective offset dependence on the transmitter loop size and template geometric spacing has been built. The use of the results obtained makes it possible to provide the actual starting depth of electromagnetic soundings from 7–10 m, which significantly increases the range of the studied depths due to the interpretation of the far-field sounding zone.

Talebi A., Medved I., Koulakov I.

This study presents a 3D seismic velocity model of the crust beneath northwestern Iran. The data include arrival times of 76,589 P-waves and 10,796 S-waves from 7245 events recorded by 233 stations. The seismic velocity model presented in this research provides a detailed understanding of the crustal structure and tectonic processes shaping northwestern Iran. The interplay between volcanism, fault activity and mantle dynamics has produced a complex velocity structure. The findings in the region offer new insights into the geodynamic evolution of this tectonically active area. Understanding these features is crucial for assessing the region’s seismic hazard and geothermal potential, particularly in light of its active tectonic faults and volcanic systems. Moreover, the crust of northwestern Iran represents a two-layered structure: a high P-velocity upper crust and low-velocity lower crust. The authors documented a similar structure on the basis of tomographic data of different collision regions, such as Eastern Anatolia, Tien Shan and Pamir–Hindu Kush. The structure concerned is supposed to be due to delamination processes in the upper mantle.

Jubaedah N.E., Parnadi W.W.

Abstract Electrical Resistivity Tomography (ERT) is a well-known standard geophysics technique for identification of geological phenomena such as faulting. The resolving power of this method is constrained by electrode spacing, device used, electrode configuration, resistivity contrast, and so on. On faulting, fault types are assumed to influence greater than the other parameter. In this research, we carried out a simulation study to detect the resolving power of ERT system using available software in public domain. Three different electrode configurations were used, namely Wenner, Schlumberger, and Dipole-dipole. We varied electrode spacing and resistivity contrast and fault types to yield optimal result. The results of this research are the most optimal model for identifying fault zones was a model that used a Dipole-dipole array with an electrode spacing of 1 m. The smaller the electrode spacing and the greater the number of cells in modelling, it produces a higher resolution modelling cross-section, so that the inversion results are more accurate to the models.

Cholponbek O., Ha S., Seong Y.B., Sultan B., Erkin R., Mirlan D., Sanzhar S.

Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt, characterized by a meridional shortening rate of up to 20 mm/a. The region has experienced significant seismic events, particularly along its northern boundary, highlighting the recurrent seismic activity in the Kyrgyz Republic. The Issyk-Ata fault, stretching 120 km from west to east in the northern Tien Shan, bounds from the north a young, growing anticline demarcating the foothills of the Kyrgyz Range and the Chui depression. This region is susceptible to strong earthquakes, posing a significant threat to the Chui region and Bishkek, the capital city with over a million residents. The youngest fault in the area is the Issyk-Ata fault, traversing the southern part of Bishkek, where modern construction has obscured its features. This study integrates remote sensing, detailed fieldwork, and paleoseismological investigations to map and analyze surface ruptures, quantify vertical displacements, and assess seismic hazards along the Issyk-Ata fault. Using optically stimulated luminescence and radiocarbon dating, we determined ages for documented paleoseismic events, placing two ancient earthquakes in the Holocene. Magnitude estimates suggest seismic events with magnitudes ranging from 6.6 to 7.1. In the Dzhal area, geological and geomorphological analysis yielded a long-term fault-slip rate of 1.15 mm/a. The Issyk-Ata fault shows variable rupture behavior, with distinct segments demonstrating different seismic characteristics and histories of activity. This variability necessitates comprehensive seismic hazard modeling to better understand and mitigate potential risks in the region.

Takele T., Husein M., Diriba D., Assefa G.

Timoshkina E.P., Konvisar A.M., Mikhailov V.O., Ponomarev A.V., Smirnov V.B.

In this study we present the model of the rupture surface of the MW = 7.0 Aykol earthquake, which occurred on the border of PRC and Kyrgyzstan on January 22, 2024, as well as the model of the rupture surface of its strongest aftershock on January 29, 2024, with magnitude MW = 5.7 based on satellite radar interferometry data. We derived displacement fields of the Earth’s surface in the satellite line of sight for these events using Sentinel-1A imagery and resolved the inverse problem of estimating displacement fields on the rupture surfaces. The resulting rupture surface models reveal the presence of fault systems dipping towards one another. The fault plane of the main event is a thrust with left-lateral shear component dipping to the northwest. During the development of the aftershock process, a backthrust dipping to the southeast developed in the frontal region, displacing the western portion of the frontal thrust formed during the main shock. Such fault dynamics is a result of the complex structure of the fault zones in the studied region. Backthrusts in this area had been mapped during previous field works.

Li S., Yuan W., Zhao Z., Zhang A., Dong G., Li X., Sun W.

This study presents new fission track data from 40 apatite and 40 zircon samples in the Southern Altai Mountains (SAMs), revealing apatite fission track (AFT) ages of 110 ± 8 Ma to 54 ± 4 Ma and zircon fission track (ZFT) ages of 234 ± 24 Ma to 86 ± 7 Ma. The exhumation rates derived from three thermochronological methods range from 0.01 to 0.1 km/Ma (Age-Elevation method), 0.01 to 0.14 km/Ma (Half-Space thermal model), and 0.027 to 0.075 km/Ma (Age2exhume model). Thermal history modeling using HeFTy software reveals similar thermal histories on both sides of the Kangbutiebao Fault, with a notable cooling event and higher exhumation rates to the northeast. The Late Cretaceous (100–75 Ma) rapid cooling is associated with tectonic reactivation, likely linked to the collapse of the Mongol–Okhotsk Orogen and slab rollback in the southern Tethys Ocean. In the Late Cenozoic (10–0 Ma), cooling and uplift reflect the influence of tectonic stresses from the India–Eurasia collision, which also drove the reactivation of the Kangbutiebao Fault. These findings suggest a complex interplay of tectonic processes driving exhumation in the SAMs from the Late Jurassic to the Early Paleogene.

Emanov A.F., Emanov A.A., Novikov I.S., Gladyshev E.A., Fateev A.V., Polyansky P.O., Shevkunova E.V., Ershov R.A., Arapov V.V., Krivov A.A.

Abstract —Years after the Chuya earthquake of 2003, geological structures adjacent to the focal area of the Chuya earthquake are still seismically active. The Aigulak focal area is one of them, but energetically the most pronounced. Detailed studies have been carried out with the network of stations of the Altai seismological testing site, supplemented by temporary stations. The region activated in the form of a local and compact structure measuring 10 × 10 km with focal depths from the first 100 m to 20 km. The focal area is not a subsequent activation along the same fault with the Chuya earthquake, but is located on a subparallel fault in the nodal region with its branching into three faults. The seismic activation of the Aigulak focal area is not an aftershock process after a major earthquake, but is an activated structure with a dynamically changing seismic process. An intensive process has formed since the earthquake in 2012 with ML = 6.1 with a gradual decrease in the number of earthquakes, and in 2019 the Aigulak earthquake with ML = 5.5 occurred with a very strong aftershock process after it. Our results of an area study of earthquake density in the focal zone indicate a change in the regime over time: from chaotic to self-organizing along short faults. We conclude that the focal area has not reached the maximum level of seismic energy release.

Jiang Y., Lu H., Yang R., Pang L., Jiao R., Wang Y., Pang J., Li Y.

Shalaginov A.E., Nevedrova N.N.

The article discusses the observation methodology, data interpretation, and results of electromagnetic monitoring with a controlled source for one of the seismically active regions of Siberia—Gorny Altai. Monitoring was carried out during the aftershock period in the epicentral zone of the destructive 2003 Chuya earthquake with M = 7.3. For regular observations, a measurement technique has been developed using several modifications of the transient electromagnetic field (TEM) method to determine variations in electrical resistance and the anisotropy coefficient. Long-term series of these two geoelectric parameters of the section are presented, compared with the characteristics of ongoing seismic events. As a result of the analysis, it was shown that variations in electrical resistance and the electrical anisotropy coefficient reflect the development and gradual decay of the aftershock activity of a powerful earthquake. The advantages of the TEM method and the selected technique for monitoring in complex areas are reflected.

Xiang D., Zhang Z., Chew D., Jolivet M., Malusà M.G., Zack T., Wu L., Guo C., Wang N., Xiao W.

AbstractCenozoic uplift in the Tianshan played an important role in driving Proto‐Paratethys Sea retreat and Asian aridification. However, most paleoclimate studies have focused on the Pamir‐Tianshan corridor, and frequently overlook the role of the entire Tianshan range in modifying the Central Asian climate during Cenozoic uplift. When and how Cenozoic deformation of Tianshan was initiated and propagated are intensively debated which makes its role in contributing to climate change in Central Asia more ambiguous. To address this issue, this study presents new detrital zircon U‐Pb and detrital apatite U‐Pb and fission track age data from Cenozoic sedimentary successions (54–0 Ma) in the northern margin of the Tarim Basin and integrates these data with published provenance data from adjacent regions. Our results show that deformation/uplift of the Baicheng‐Kuqa Depression and the South Tianshan occurred at ∼41–37 Ma and ∼24 Ma, when topographic growth of South Tianshan began to block the flow of sediment from the north. Continued uplift of the South Tianshan completely blocked fluvial transport from the Central Tianshan‐Yili Block by ∼10 Ma, as shown by the paucity of 380–310 Ma detrital zircons/apatites. Far‐field, north‐directed compressive stress resulting from the India‐Asia collision began to propagate toward the South Tianshan and its foreland during the Late Eocene, and continued to propagate into the South Tianshan and northward at the ∼24 Ma and 10 Ma. Finally, we suggest a two‐stage of aridification in the Tarim Basin which can be linked to two stages (∼24 and 10 Ma) of growth of the Tianshan.

Zhou Y., Wu Z., Liang Q., Xu H., Wang H., Xue W.

Scientific and reasonable emergency response initiation mechanisms can provide important support for decision making regarding the emergency management of urban floods. However, there is a lack of a unified paradigm on how to calculate the threshold for emergency response initiation and reasonably initiate emergency response. Therefore, this study proposes a loss-driven urban flood emergency response initiation framework from the perspective of combined disasters. A discrimination mechanism of the emergency response initiation level was established based on the optimal threshold and loss function. And the rainfall event that occurred in Zhengzhou, China, on July 20, 2021, was taken as an example to realize real-time emergency response discrimination and initiation driven by forecast data. Results showed that the initiation time of the Level I emergency response using the proposed method was 9.5 h earlier than the time of the government release, thereby significantly increasing the preparation time for flood management personnel. In addition, the results of the optimal threshold selection indicated that the Natural Breakpoint method was the optimal method for loss threshold partitioning, with the comprehensive evaluation index (CEI) being 3.56–9.53% higher than those of the K-means, Equal Interval, and Quantile method. These results constitute a reference for urban emergency management and related research.

Guo Q., Mao Y., Yan L., Chen W., Yang J., Xie X., Zhou L., Li H.

The nonferrous metal mines in China are rapidly depleting due to years of mining, and it has become difficult to identify new mineral resources in the periphery of the old mining area. In order to deal with this situation, advanced technologies and equipment must be deployed. The borehole transient electromagnetic method (TEM) has become a key technology due to its deep investigative capabilities within conductive geological structures. In the present study, in order to meet the exploration needs at depths of less than 3000 m, surface-borehole TEM exploration was used to analyze the characteristics of electromagnetic signals generated by a long wire source and a large loop source, providing essential data for the development of key technologies, such as sensor parameter design and signal gain optimization of the TEM system in the borehole. This study discussed in detail two key technical problems as follows: firstly, the efficient synchronization mechanism between the ground transmitter system and the borehole electromagnetic signal acquisition system ensured the accuracy and timeliness of data acquisition; and secondly, the realization of mass storage technology, which effectively solved the problem of mass storage and real-time transmission of data in a deep borehole environment. The effectiveness of the surface-borehole TEM systems with a long wire source and a large loop source was verified by tests in real mines. The surface-borehole electromagnetic signal acquisition system developed in this study effectively collected electromagnetic signals in the borehole, and the results accurately reflected the stratigraphic information of mineral resources in the study area. This study can pave a new technical path for the exploration of deep and peripheral areas of non-ferrous metal mines and provide valuable experience and insights for mineral resource exploration in similarly complex geological environments.

Rybin A., Bataleva E., Nepeina K.

The identification of hidden areas of active faults in the Earth’s crust that can generate earthquakes is the most urgent problem in assessing the seismic hazard of various regions. The main goal of this study was a detailed study of the geophysical characteristics in the zone of individual segments of active faults in the Northern Tien Shan with electromagnetic geophysical methods. The structural line of the Issyk-Ata fault is clearly, but fragmentary, revealed on the surface by geological methods, since the tectonic disturbance is hidden by loose deposits of the Cenozoic age. The results of inversion of detailed magnetotelluric soundings in the fault impact zone of the fault made it possible to determine the position of the upper edge, width, depth, strike and inclination of the fault zone. At the stage of complex construction of 2D geoelectric models of the Issyk-Ata fault zone, the results of field profile soundings by the method of surface electrical resistivity tomography were used. To study the dynamics of the constructed block model of the fault zone, we considered variations in the following electromagnetic parameters that reflect the response of the geomedium to a change in its stress–strain state: impedance and tipper components, apparent resistivity and impedance phase, time–frequency series, and anisotropic properties. Based on this, estimates of the correlation between variations in electromagnetic parameters and lunar-solar tides and the spatiotemporal distribution of seismicity were made. This work was supported by the Russian Science Foundation under grant No. 22–27-00567.

Guo X., Fan N., Liu Y., Liu X., Wang Z., Xie X., Jia Y.

AbstractOcean mining activities have been ongoing for nearly 70 years, making great contributions to industrialization. Given the increasing demand for energy, along with the restructuring of the energy supply catalyzed by efforts to achieve a low-carbon economy, deep seabed mining will play an important role in addressing energy- and resource-related problems in the future. However, deep seabed mining remains in the exploratory stage, with many challenges presented by the high-pressure, low-temperature, and complex geologic and hydrodynamic environments in deep-sea mining areas, which are inaccessible to human activities. Thus, considerable efforts are required to ensure sustainable, economic, reliable, and safe deep seabed mining. This study reviews the latest advances in marine engineering geology and the environment related to deep-sea mining activities, presents a bibliometric analysis of the development of ocean mineral resources since the 1950s, summarizes the development, theory, and issues related to techniques for the three stages of ocean mining (i.e., exploration, extraction, and closure), and discusses the engineering geology environment, geological disasters, in-situ monitoring techniques, environmental protection requirements, and environmental effects in detail. Finally, this paper gives some key conclusions and future perspectives to provide insights for subsequent studies and commercial mining operations.

Zhao Z., Luo Z., Sun H., Li H., Liu Q., Liu H.

Capillary rise tests were conducted on soil columns containing of three layers of sandy soils with coarser over finer over coarser sandy soil to investigate the effect of the relatively finer soil interlayer. The capillary rise height, rate, and water distribution were observed in laboratory tests of four layered soil columns, with two homogeneous (without the interlayer) soil columns serving as the controls. The final maximum height of the capillary rise in the soil column with the interlayer was larger than that of the column without the interlayer when the interlayer was laid around the water entry value of the underlying soil. The water content was not continuous in the entire soil profile with the interlayer, and a small matric suction gap was observed in the relatively fine soil between the soil column with and without the interlayer.

Ziganshin E., Nourgaliev D., Bayuk I., Kadyrov R., Nguyen T.H.

Carbonate rocks have a wide variety of pore shapes and different types of grains, which greatly affect the elastic properties and characteristics of the reservoir. This causes certain difficulties in petroelastic modeling. One of the problems is the scale of the input data, which is then used to build the rock physics model. The paper presents the results of studying three core samples of carbonate rocks of the Upper Devonian and Lower Carboniferous age, which are located in the South Tatar arch (Volga-Ural oil and gas basin (Russia)). To evaluate the structural characteristics of the pore space, the effective medium theory is used. The input data are the results of laboratory studies that include measurements of the velocities of longitudinal and transverse waves, porosity, and thin section and computed tomography analysis. When using the computed tomography, the core samples are analyzed at different resolution (12–37 µm/voxel). The tomography studies of pore space at different scales provide rather different values of porosity and pore aspect ratio. The tomography-based porosity estimations also differ from the experimentally measured porosity (up to 10%). The pore space characteristics provided by different datasets are used to build a rock physics model for the studied rocks that helps to estimate the elastic wave velocities with three different methods of effective medium theory (self-consistent approximation, differential effective medium (DEM), and the Kuster–Toksöz method). A comparison of the velocity estimations with their experimental analogs for dry rocks may indicate the presence of microcracks whose size is beyond the tomography resolution. Improved rock physics models incorporating both pores and microcracks are then used to predict the elastic wave velocities of fluid-saturated rock in a wide porosity range. It is demonstrated that the predicted values significantly differ (up to 30%) from those provided by the rock physics (RP) models constructed without the support of the tomography results. Moreover, other types of models are considered in which the difference in experimental and theoretical velocities is attributed to changes in the host matrix properties as compared to the calcite polycrystal, which are caused by various reasons.

Vargas C.A., Caneva A., Solano J.M., Gulisano A.M., Villalobos J.

We applied multi–temporal 1D magnetotelluric (MT) surveys to identify space–time anomalies of apparent resistivity (ρa) in the upper lithosphere in the Antarctic Peninsula (the border between the Antarctic and the Shetland plates). We used time series over several weeks of the natural Earth’s electric and magnetic fields registered at one MT station of the Universidad Nacional de Colombia (RSUNAL) located at Seymour–Marambio Island, Antarctica. We associated resistivity anomalies with contrasting earthquake activity. Anomalies of ρa were detected almost simultaneously with the beginning of a seismic crisis in the Bransfield Strait, south of King George Island (approximately 85.000 events were reported close to the Orca submarine volcano, with focal depths < 20 km and MWW < 6.9). We explained the origin of these anomalies in response to fluid migration near the place of the fractures linked with the seismic swarm, which could promote disturbances of the pore pressure field that reached some hundreds of km away.

Watson C.S., Elliott J.R., Amey R.M., Abdrakhmatov K.E.

Earth observation (EO) data can provide large scale, high-resolution, and transferable methodologies to quantify the sprawl and vertical development of cities and are required to inform disaster risk reduction strategies for current and future populations. We synthesize the evolution of Bishkek, Kyrgyzstan, which experiences high seismic hazard, and derive new datasets relevant for seismic risk modeling. First, the urban sprawl of Bishkek (1979–2021) was quantified using built-up area land cover classifications. Second, a change detection methodology was applied to a declassified KeyHole Hexagon (KH-9) and Sentinel-2 satellite image to detect areas of redevelopment within Bishkek. Finally, vertical development was quantified using multi-temporal high-resolution stereo and tri-stereo satellite imagery, which were used in a deep learning workflow to extract buildings footprints and assign building heights. Our results revealed urban growth of 139 km2 (92%) and redevelopment of ~26% (59 km2) of the city (1979–2021). The trends of urban growth were not reflected in all the open access global settlement footprint products that were evaluated. Building polygons that were extracted using a deep learning workflow applied to high-resolution tri-stereo (Pleiades) satellite imagery were most accurate (F1 score = 0.70) compared to stereo (WorldView-2) imagery (F1 score = 0.61). Similarly, building heights extracted using a Pleiades-derived digital elevation model were most comparable to independent measurements obtained using ICESat-2 altimetry data and field-measurements (normalized absolute median deviation < 1 m). Across different areas of the city, our analysis suggested rates of building growth in the region of 2000–10,700 buildings per year, which when combined with a trend of urban growth towards active faults highlights the importance of up-to-date building stock exposure data in areas of seismic hazard. Deep learning methodologies applied to high-resolution imagery are a valuable monitoring tool for building stock, especially where country-level or open-source datasets are lacking or incomplete.

Rybin A.K., Bataleva E.A., Aleksandrov P.N., Nepeina K.S.

Abstract—Electromagnetic investigation of stress-strain state dynamics in the geological medium is based on the analysis of two groups of physical phenomena. The first group includes phenomena associated with the dynamics of electrical properties of rocks caused by a change in their fracturing, porosity, fluid content, structure and texture, temperature and pressure, etc. The second group covers the effects of generation of endogenous (geodynamic) sources of electromagnetic field under irreversible deformations of the geological medium. In this paper, we present the practical results of the studies of the Earth’s natural electromagnetic field that have been carried out at the Research Station of the Russian Academy of Sciences in Bishkek over 40 years of operation of the Bishkek Geodynamical Test Site of the Research Station and aimed at gaining new insights into the present-day geodynamics of the Tien Shan lithosphere. The results of the experimental study of the first group of phenomena are based on the analysis of temporal changes in the magnetotelluric transfer functions. In this analysis it is assumed that the present-day geodynamic processes including catastrophic ones, e.g., earthquakes, trigger the crack formation processes which, in turn, changes the pore-fracture space of the rocks and causes fluid redistribution in them, thus resulting in the changes in the electrical conductivity of the geological medium. The practical results of the studies of the second group of phenomena are based on the notion that the geodynamic processes induced in the Tien Shan crust by irreversible deformations of rocks create sources of electromagnetic radiation leading to the variations in the endogenous electromagnetic field which can be observed on the ground.

Bataleva E.A.

The results of monitoring studies of the fault structures of the Northern Tien Shan are presented, where regime (regular) observations by the magnetotelluric sounding method are carried out over the state of the geological environment under the influence of geodynamic processes. Fault zones identified from geological and electromagnetic data appear in the upper part of the section as subvertical objects with high electrical conductivity due to increased fracturing and have a good correlation with lunisolar tidal effects. The relationship between the behavior of geophysical fields variations and the stress-strain state of the Earth's crust in the seismically active regions of the Tien Shan is considered based on the analysis of correlations between the components of lunar-solar tidal influences, variations in electromagnetic parameters, and the distribution of seismic events.

Qi T., Zhang F., Pei X., Feng G., Wei H.

Water inrush disasters poses a great threat to the safe exploitation of coal resources. To solve this problem, the transient electromagnetic method (TEM) was proposed to accurately detect the water accumulation in the goaf. The electromagnetic response characteristics of different water-filled goaves were studied by electromagnetic field theory, numerical simulation and field verification. Through the models of 100% water accumulation, 50% water accumulation, 0% water accumulation, 100% water accumulation with collapsed rock, 50% water accumulation with collapsed rock and 0% water accumulation with collapsed rock goaf, the characteristics of induced voltage attenuation curves were studied. Meanwhile, the relationship between the attenuation voltage value and area of the transmitting coil, the depth of the goaf, the background resistivity, and the delay time were also simulated. The results illustrate that the attenuation curve of induced voltage presented a regular exponential decay form in the 0% water accumulation model but existed abnormal exaltation for voltage in water-filled model. Through the linear fitting curve, it can be seen that the abnormal intensity of the induced voltage becomes stronger as the distance between the measuring point and the center of the target decrement. Moreover, the abnormal amplitude of the induced voltage increases with the rise of the water accumulation and collapsed rock will weakly reduce the low-resistivity anomalous effect on the water-accumulated goaf. In addition, the response value of the attenuation voltage increased as the area of the transmitting coil increases, but decreased with increasing delay time and increasing background resistivity and depth of the target body. The field detection results of the Majiliang coal mine also confirmed the theoretical analysis and the numerical simulation.

Lin T., Zhou K., Cao Y., Wan L.

• Air-core coil sensors are important magnetic measurement tools for surface geophysical technology. • Detailed design process of induction coil and air-core coil sensor is presented. • Optimization methods for air-core coil sensors in TEM and SNMR applications are reviewed. • Research prospects of sensor technology in surface geophysical exploration are examined. In the field of surface geophysical detection, electromagnetic technologies represented by transient electromagnetic methods (TEMs) and surface nuclear magnetic resonance (SNMR) use air-core coil sensors as magnetic detection devices because of their high sensitivity, simple fabrication, robustness, and low cost. To clarify the application of air-core coil sensors in these fields, we review the design process and research directions of these devices. First, we introduce the detection principles and parameters of induction coils. Second, we summarize the structure, equivalent model, amplitude–frequency characteristics, and noise level of air-core coil sensors. Third, the characteristics of the air-core coil sensors used in TEMs and SNMR are introduced respectively, and the optimization of parameters such as the noise level, sensitivity, and size of these magnetic detection devices according to actual application conditions is then discussed in detail. Finally, we propose directions for future research based on existing problems in the use of air-core coil sensors, and provide ideas for their further development in geophysical detection.

Bataleva E.

The results of geophysical monitoring of seismically hazardous regions are of undoubted interest for studying the deep structure of the lithosphere, regional seismicity, modern geodynamics, etc. The work used experimental material, including the results of magnetotelluric monitoring and the catalogs of the KNET (Kyrgyzstan Telemetered Network), KRNET (Kyrgyz Republic Digital Network) and ISC (International Seismological Center) networks obtained in the seismically active zones of the Bishkek Geodynamic Proving Ground (Northern Tien Shan). The analysis of electromagnetic monitoring results of the Northern Tien Shan seismic generating zone was carried out in a wide frequency range. The data on the parameters of the electromagnetic field of the Earth’s crust in the Northern Tien Shan are generalized and systematized. Based on the analysis of these data, the dependence of the response of seismic events in electromagnetic parameters on the distance of earthquake epicenters was studied. The most likely reason for the occurrence of anomalous changes in the electromagnetic field is the activation of deformation processes during the preparation of strong earthquakes. The results of the time-frequency analysis are presented and the features of manifestation are considered depending on the location of the hypoand epicenters of seismic events and their magnitude. Regularities have been established in the behavior of tipper variations for remote and regional earthquakes for the first quarter of 2016 with an energy class from 6 to 10.

Nevedrova N.N., Sanchaa A.M., Shaparenko I.O.

Abstract In this paper we present the results of our studies of sections of the Uimon basin in Gorny Altai (Russia) using a complex of electrical prospecting methods. The areas of Baratal Formation at the surface have been investigated. This areas explored in order to understand the stages of formation of the depression. In addition, the possibilities of the electrotomography method for regular observations in seismoactive regions are shown. Comparison of the amplitudes of the resistivity variations based on repeated ERT measurements in different zones of the Terekta fault indicates the activity of its eastern part, which is expressed in significant resistivity variations exceeding 100%. At the same time, the variations in the northwestern part of the fault, reaching 15% on average, are many times smaller.

Mukhamadeeva V.A.

Abstract The article presents the results of electromagnetic monitoring and geomagnetic observation during increased seismic activity in eastern part of Bishkek geodynamic range (Northern Tien-Shan) in 2017. It includes brief description of seismic conditions of the territory being researched, as well as analyses of the correlation between changes in geophysical field parameters and the earthquakes.

Tang H., Wei W., Song X., Liu F.

In this article, we formulate an anisotropic elastoplastic Cosserat continua model for shear failure in stratified geomaterials. Considering the dip angle between local and global coordinates of a formation, a Cosserat elastic anisotropy constitutive matrix under plane strain condition is derived, and cohesion anisotropy is reflected using a microstructural tensor combined-stress invariant method. A Cosserat continuum finite element model and consistent algorithm are developed to consider the characteristics of elastic anisotropy, strength anisotropy, and strain softening. The simulation of a stratified geomaterial sample under uniaxial compression condition shows that the elastic anisotropy has an evident influence on the deformation pattern. It is also demonstrated that dip angle could significantly impact macroscopic failure modes, uniaxial compressive strength, and macroscopic equivalent elastic modulus. The stability analysis of a layered slope demonstrates that the strength anisotropy has a considerable influence on the overload safety factor of the slope and can be a trigger of the formation of shear bands in such slopes. Furthermore, the dip angle of the structural plane also affects the stability of the stratified slope, which is controlled by both the block and structural surface. By comparing the numerical results of the classical continuum model and the Cosserat continuum model, it is proved that the numerical model considering the elastoplastic anisotropy and strain softening under the Cosserat continuum theory overcomes the ill-posedness of mesh sensitivity and maintains the well-posedness of the strain localization problem. Thus, the proposed model is useful for modeling shear failure in stratified geomaterials. • An anisotropic elastoplastic Cosserat model for stratified geomaterials is presented. • Elastic and strength anisotropy, strain softening are included in the model. • The microstructural tensor combined-stress invariant is used for cohesion anisotropy. • Stability of stratified slope is controlled by both the block and structural surface. • The ill-posedness of the strain localization problem is overcome with the model.

Kanaun S.

The effective field method is applied to solution of the homogenization problem for anisotropic media containing random sets of thin inclusions of low conductivity (crack-like inclusions) or cracks. The derived expression for the tensor of effective conductivity of cracked media on the one hand, takes into account peculiarities of shapes and conductivity of thin inclusions, and on the other hand, reflect statistical properties of the inclusion distributions in the host medium. The crucial part of realization of the method is solution of the so-called one-particle problem that is the conductivity problem for an isolated inclusion embedded into an anisotropic host medium and subjected to a constant external field. This problem is reduced to solution of the integral equation for the potential jump on the middle surface of a thin inclusion. An efficient numerical method of solution of this equation is proposed. The integral equation is discretized by Gaussian approximating functions and reduced to a linear algebraic system for the coefficients of the approximation (the discretized problem). For Gaussian functions, the elements of the matrix of the discretized problem are calculated in explicit analytical forms (for isotropic host media) or they reduce to a standard 1D-integral (for arbitrary anisotropic host media) that can be tabulated. As a result, the matrix of the discretized problem is calculated fast. For inclusions with planar middle surfaces and regular grids of approximated nodes, this matrix has Toeplitz’ structure, and fast Fourier transform algorithm can be used for iterative solution of the discretized problem. The cases of a strongly anisotropic medium with circular, annular and square cracks are considered. Examples of solution of the homogenization problems for the medium containing cracks of various shapes are presented.