Tectonic Faults Research Articles

Evaluating heterogeneous lacustrine groundwater discharge of Hulun Lake using radium isotopes in Inner Mongolia, China

Study regionHulun Lake Basin, Northern China Study focusUnderstanding lacustrine groundwater discharge (LGD) is important for elucidating the hydrological cycle and sustainable use of water resources. Hulun Lake is the largest fresh water lake and has prominent ecological function in North China. However, the effect of groundwater discharge on the water balance and spatial distribution of LGD under different aquifers have not yet been evaluated in detail. Herein, radium (223Ra, 224Ra, and 228Ra) and stable isotopes (δD, δ18O) were used to identify the LGD locations and quantify the spatial LGD flux into the lake. New hydrological insights for the regionThe Ra isotope activities in groundwater from the fissured bedrock in the western part of the Lake are depleted relative to those from the east, underlain by the Quaternary unconsolidated sediments aquifer overlying granitic rocks. The spatial distribution of LGD under heterogeneous aquifers was revealed and groundwater discharge from fractured bedrock aquifer is the predominant source of the lake. The LGD flux is estimated to range from (1.07 ± 1.36)× 107 to (6.54 ± 1.89)× 107 m3/d, which exceeds that in the Quaternary aquifer by one order of magnitude due to the high permeability enlarged via tectonic faults and fractures. These findings promote scientific understanding of water balance in Hulun Lake and are instructional for LGD studies of freshwater lakes with complex water systems in cold and arid regions.

СТРУКТУРНО-ПЛОТНОСТНАЯ МОДЕЛЬ ЗЕМНОЙ КОРЫ ЗАПАДНОГО ШЕЛЬФА О-ВА САХАЛИН И ЕЕ ГЕОЛОГИЧЕСКАЯ ИНТЕРПРЕТАЦИЯ

Structural and density modeling of the Earth's crust carried out using a deep seismic sounding profile previously tested along the western shelf of Sakhalin Island offered a clearer view of the layered block structure of the main tectonic faults and their newtwork within the crust of the region, where a large number of strong crustal earthquakes are concentrated. The density structures of the resulting model were compared with geological data on the adjacent territory of Sakhalin Island. Our structural and density model made it possible to separate volcanic blocks and blocks of sialic crust and to trace the submerged prolongation of the largest geological complexes of the western edge of Sakhalin Island on the shelf. There are signs of spatial correlation between seismic events and some tectonic faults.

Seismic analysis of buildings with basements

This research work analyzes how seismic waves affect buildings with basements that are usually studied independently: In surface structures the inertial forces originated by the movement of their base and in subway structures the deformations due to ground motion are considered. The building located in the city of Quito with twelve elevated floors and five subfloors is studied using nonlinear finite element modeling, considering that the subsoil depends on seismic excitations in a dynamic soil-basement-structure set, for which it is modeled together with its geotechnical components. The superstructure is integrated to the infrastructure and a time-history analysis is included with the most representative earthquakes can affect the building. The present investigation has three basic components: seismic, geotechnical, and structural, which are merged by means of specialized 3D structural engineering programs. In the seismic component, local and regional information about tectonic faults within Ecuador is collected; the building is then located on a seismic risk map and the magnitudes, types, and other parameters of the site where the building is located are determined. Using the results of the Earthquake Risk Assessment Project for the city of Quito (TREQ) and the Pacific Earthquake Engineering Research Center (PEER) database, three relevant seismic events are chosen for the time-history analysis that meet the seismic risk data for the building. For the geotechnical soil component, the geotechnical parameters of the original design of the building foundation, stratigraphy, and characteristics of soil solids, among others, are used. The structural component considers the type of material, geometry, dimensions, joints between elements and others of the original design for both basements and superstructure. The connection of these three components is carried out using Midas Gen and Midas GTS NX. The results of deformations as a function of time are compared with similar standards, studies, and investigations.

Machine learning estimation of rock masses displacement

This paper presents a comprehensive analysis of the factors affecting landslide occurrence in Iran based on a dataset containing information on more than 4000 landslide cases. Both natural (slope, height, rainfall, distance to rivers and faults) and anthropogenic (type of land use) factors were studied. A random forest model was used to predict landslide risk and assess the significance of various factors. The results show that the most significant factors are terrain slope, elevation and distance to water bodies and tectonic faults. These findings can be used to develop preventive measures and improve landslide risk management strategies in the region.

Experimental and analytical investigation of geomechanical dynamics of coal mining near tectonic faults

Experimental and analytical investigation of geomechanical dynamics of coal mining near tectonic faults

Construction of the geological model of the “Knurów” deposit and its application to the exploitation design

The “Knurów” deposit is characterized by intense and rich fold and fault tectonics. The model of the “Knurów” deposit includes 11 seams belonging to the Orzesze, Ruda Śląska and Siodłowe layers. Each of these seams is recognized by boreholes, but also properly documented by mining, which greatly facilitates the modelling of its surface. The article addresses selected issues related to the construction of a three-dimensional model of the deposit. The method of modelling the surface of the terrain and the erosion surface of the Carboniferous is presented, which are used to calculate the location of subcrops of modelled seams and to predict the deformation of the terrain under the influence of mining. The general principles of fault modelling are presented, and so are ways of designing mining surfaces in longwalls passing through a fault. In the analysed deposit there are also seam splits. The article discusses the principles adopted for the development of the deposit model and its visualization, as well as the use of a dedicated algorithm for calculating the location of mining surfaces in such zones.

РАСПРЕДЕЛЕНИЕ И ГЕНЕЗИС УГЛЕВОДОРОДНЫХ ГАЗОВ ДОННЫХ ОТЛОЖЕНИЙ ЛАПТЕВО-СИБИРОМОРСКОЙ ЗОНЫ ВОСТОЧНО-АРКТИЧЕСКОГО ШЕЛЬФА

Gases from bottom sediments of the Laptev–Siberian Sea zone contain methane (up to 8.3047 cm3/kg) and its homologues (down to and including pentane) totaling 0.0259 cm3/kg. The established values of the carbon isotope composition of methane (δ13С), the molecular weight of the hydrocarbon fraction, the weight concentrations of С1–С5 hydrocarbons and their ratios, the «wetness» and «transformation» coefficients of the hydrocarbons fraction, indicate the presence of various syngenetic and epigenetic gases in bottom sediments. Potential gas sources are modern sediments, peat, coal, gas and gas hydrate? deposits, solid bitumen, igneous rocks, and inferred oil and gas accumulations. It has been established that the distribution of hydrocarbon gases in sediments vertically and horizontally depends on the influence of a complex of geological factors – fold and fault tectonics, magmatism and seismic activity in the region, coal, oil and gas potential and bituminosity, organic saturation and lithological composition, hydrogeological, geocryological, and other conditions for accumulation of gases or their degassing.

DIFFERENT-SCALE HETEROGENEITIES IN SEGMENTS OF SEISMOGENIC FAULTS AND THEIR INFLUENCE ON SLIP MODES

The paper presents some multidisciplinary research results on the structure of slip surfaces in segmented sections of tectonic faults in the Baikal region and Mongolia. The properties of subsurface (modern) and deep slip planes that came to the earth’s surface as a result of many-kilometer denudation in the upper part of the earth’s crust are studied at different levels-from macroscale to nanocrystals. Other types of heterogeneities characterizing the structure of fault slip zones are also considered. The presented data indicate a heterogeneous structure of tectonic faults. Their slip zones show both low friction in sections where strong mineral phases are replaced by weak minerals, and potentially unstable patches with high frictional resistance. The results obtained in a comprehensive study of geological conditions, under which different-scale heterogeneities emerge in exhumed fault segments, should be taken into account when developing rock mass models suitable for numerical simulation of earthquake preparation processes at the micro-, mesoand macroscales.

First reports on the genetic diversity and phylogenetic relationships of bathynellids (Malacostraca: Bathynellidae) from Lake Baikal

Within the fauna of Lake Baikal, two species of bathynellids are known: Bathynella baicalensis Bazikalova, 1954 and Baicalobathynella magna (Bazikalova, 1954), both originally described from the southern basin of the lake. The authors’ findings indicate that bathynellids are prevalent across all three basins of the lake, occuring on habitats such as methane seeps, mud volcanoes and hydrothermal vents. A comprehensive analysis of the COI (mtDNA) and 18S rRNA (nuclear DNA) gene fragments from bathynellids collected at tectonic fault sites in the northern basin of the lake revealed the absence of any representatives of the genus Bathynella Vejdovsky, 1882 among them. Instead, individuals identified as Baicalobathynella cf. magna comprise two genetic lineages at the species level, which diverged from a common ancestor approximately 7 Ma. The genus Altainella Camacho, 2020, whose representatives inhabit the interstitial hyporheic zone of the Onon river in Mongolia and Aktru mountain river of Altai, is designated as the closest relative of the Baikal bathynellids studied.

Preparation of initial seismic data for modeling tectonic fault in coal body

Preparation of initial seismic data for modeling tectonic fault in coal body

ОБРАБОТКА РЕЗУЛЬТАТОВ GPS-МОНИТОРИНГА ПРИ ИНТЕНСИВНЫХ ДВИЖЕНИЯХ ЗЕМНОЙ КОРЫ В СЕЙСМОАКТИВНЫХ РЕГИОНАХ КАЗАХСТАНА

The article presents the results of GPS-monitoring studies in the zone of major tectonic faults on the territory of Almaty. It has been established that monitoring the movement of the Earth's crust is necessary to understand the processes preceding earthquakes and to develop forecasting models. Knowledge of the movement of the Earth's crust is important to ensure the safety of infrastructure such as roads, bridges and residential buildings. The results of the study can be useful for conducting scientific research (when monitoring, analyzing and predicting the movement of the Earth's crust in regions with increased seismic activity) related to the structure of the Earth's crust and the tectonics of the region.

Investigation of tectonic faults in coal seams using horizontal directional drilling from temporary roadways

Investigation of tectonic faults in coal seams using horizontal directional drilling from temporary roadways

Structural and tectonic features of the Transcarpathian trough according to gravity and magnetic data

Based on the analysis and interpretation of gravity and magnetic field anomalies, we studiedthe peculiarities of fault tectonics, structural-tectonic structure (including salt dome tectonics) of the Transcarpathian trough. We identified signs of the manifestation of deep faults and other large structural-tectonic elements in anomalies of gravity and magnetic fields. We then traced these structural-tectonic units by comparing the morphology, intensity, dimensions, and directions of the typical anomalous zones in the gravitational and magnetic fields with the tectonic structure of the region.
 We used digital maps of gravitational and magnetic fields; averaging transforms and relief-shadow images, we mapped local gravimagnetic anomalies. Analysis of the spatial structure of the original gravimagnetic fields and their transforms and structural-tectonic maps yielded a reflection of large tectonic elements of fault tectonics, anticlinal and salt dome structures in the gravimagnetic fields. Based on gravimagnetic data, the tectonic structure of the Transcarpathian trough was clarified, and the boundaries of tectonic zones and microplates were traced. The zone of the Transcarpathian deep fault is identified as a tectonic zone traced by a band of intense local positive anomalies of the gravity field along the Flysch Carpathians to the border of the Marmarosh massif. It is limited by high gradients from the southwest and northeast and is a reflection of the Pieniny and Marmarosh rock zones. The zone of the Transcarpathian deep fault is considered a suture zone of the Inner and Flysch Carpathians. In the structure of the anomalous gravity field of the Transcarpathian trough, a number of local anomalies associated with salt stocks, as well as individual anomalies, expected to be connected to salt-bearing deposits, werefound.
 We confirmed the effectiveness of gravimagnetic methods in the geological conditions of the Transcarpathian trough to detect anticlinal structures, basement protrusions, which create favorable conditions for oil and gas traps in sedimentary strata. Interpreting anomalous gravimagnetic fields in combination with geological and tectonic materials is an important condition for the integral process of studying the geological and tectonic structure of the Earth’s crust in the Transcarpathian region.

PECULIARITIES OF THE GROUNDWATER CHEMICAL COMPOSITION WITHIN THE SAKSAGANSK-SURSK ORE DISTRICT OF THE DNIPROPETROVSK REGION

The purpose of the research: to study the groundwaters in the Saksagansk-Sursk ore district of the Dnipropetrovsk region, which are used to ensure the economic and drinking needs of the local population. Data and Methods: A wide range of methods of obtaining, processing and interpreting of ecological-hydrogeochemical data, including field, chemical-analytical, comparative and graphical, were used. Mathematical and statistical methods were used in the processing of the obtained data. Visualization of the general chemical composition was performed with the help of specialized software tool GW_Chart. Results. The chemical composition of underground waters was studied, an assessment of their quality and suitability for potable use was made, the range of risks for the health of local residents-consumers of water was outlined, and the rationale for possible reasons for changes in their chemical composition during 42 years of operation (from 1978 to 2020) was provided. During the research, the authors found signs of metamorphosis of the chemical composition of groundwater. On the other hand, in the multi-year section, a general regularity was observed regarding the restoration of the state of the studied waters resources to the natural one, which is probably related to the decrease in the level of man-made load on the water environment over 42 years due to a significant decline in the rate of industrial development of uranium and iron ores within the Dnipropetrovsk region in general and the Saksagansk-Sursk ore district in particular. A preliminary conclusion was obtained that the ecological-hydrogeochemical conditions of the studied groundwater are primarily determined by: insignificant occurrences of water-bearing rocks (up to their emergence to the surface), close hydraulic connection with surface waters and adjacent aquifers, weak protection against surface pollution due to the lack of regionally sustained confining bed in its roof, the chemical composition of water-bearing rocks, as well as the tectonic conditions of the territory. The authors consider it necessary in further research to take into account the structural and geological features of the crystalline foundation of the studied area in connection with the spread of a wide range of metamorphic rocks and their weathering products, as well as the presence of tectonic faults within the first structural floor.

Использование вероятностных методов обработки геолого-геофизических данных на территории Восточно-Сибирской платформы для прогноза нефтегазовых перспектив концентрических структур

The study aims in showing the results of forecasting oil and gas prospects of some concentric structures in the East Siberian Platform area. The research was conducted using probabilistic data processing methods based on the use of preliminary analysis of various geological and geophysical data (histograms of the thickness of the Earth's crust, lithosphere, sedimentary layer, geothermal gradient, density of tectonic faults), evaluated for the main oil and gas basins in the Russian Federation. The results obtained were used to forecast oil and gas prospects of concentric structures in the East Siberian Platform area. In particular, probabilistic processing methods using five geological and geophysical types of data in the region were used to calculate probability values for fifteen different concentric structures. The results of using probabilistic methods for processing various types of geological and geophysical data, measured within several concentric structures on the territory of the East Siberian Platform are considered. According to the calculated probability values, the areas of three concentric structures (Nepsko-Botuobinskaya, Angarskaya, Sayano-Yeniseyskaya), located in the south of the East Siberian Platform promising for the search for new areas with hydrocarbon deposits, were predicted. Six other concentric structures (Kureyskaya, Tungusskaya, Bakhtinskaya, Kamovskaya, Yenisey-Khatangsk, Zabaikalskaya) require more comprehensive geological prospecting, as their individual sectors may be promising for oil and gas exploration.

Lithotectonic architecture of the Paleoproterozoic intracratonic Kaladgi rift basin, southwestern India: Inference from a magnetotelluric study

Peninsular India is traversed by several major Paleoproterozoic rift basins, among which the Kaladgi rift basin is a prominent one. Here, we present results from Magnetotelluric (MT) studies in the eastern section of this rift basin. The data were acquired along a ∼120 km long profile passing through Belavanik-Bagalkot-Ukkali regions covering the Paleoproterozoic intracratonic Kaladgi rift basin, the Cretaceous Deccan volcanic province and the Archean gneisses/granites/greenstones of the Dharwar craton. The lithospheric electrical structure was obtained from joint inversion of TE- and TM-modes data using a 2-D nonlinear conjugate gradient algorithm. The results reveal that the Kaladgi sediments are ∼500–1000 m in thickness overlying a highly fractured crystalline basement. Proterozoic sediments are exposed beneath the Deccan basalt cover and in the shallow fractured zones. The conductive-resistive transitions in the model at the crustal depths correspond to major tectonic faults and deformed crustal rocks. The transition boundary at ∼50 km depth defines the electrical Moho. At the same time, a ∼25 km wide, steep conductive feature from ∼75 km to upper mantle lithosphere depths (∼180–200 km) is interpreted as the trace of the Chitradurga Suture Zone (CSZ). The observed crustal heterogeneity, conductivity variations, and resistive lithosphere are attributed to the geological history of the region, including Archean collisional events and subsequent reactivation associated with the Reunion hotspot. The crustal conductors are associated with mafic intrusions from the underplated basalts, and also the high conductivity may be due to the sulfide mineralization in the fault zones. The MT study provides valuable insights into the deep tectonic framework of the region.

Seismic-induced landslide hazard analysis of the recreational area of the Makiling Botanic Gardens, Los Baños, Laguna, Philippines

The Makiling Botanic Gardens (MBG) is an educational and eco-tourism site located within the vicinity of Mount Makiling, a dormant volcano susceptible to landslides, and located less than 20 km away from at least two tectonic faults. The study assessed the seismic-induced landslide hazards in the recreational area of MBG mainly based on three parameters: factor of safety (FS), yield acceleration (ay), and slope displacement (Dn). Dynamic Cone Penetration Test (DCPT) served as the primary method for obtaining the shear strength of the soil within the area. Meanwhile, other relevant parameters, including material unit weight and internal angle of friction, were determined through laboratory testing, correlations, and available data and models. Moreover, the Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) values were obtained through an interpretation of a probabilistic seismic hazard analysis (PSHA) study of the Philippines. Using the ArcGIS software, an FS map, yield acceleration map, and slope displacement map were generated. Results showed that the slopes within the area exhibit static stability. However, in the event of an earthquake, it is expected that the amplified PGA will exceed the expected yield acceleration values of the slopes in some parts of the recreational area, which could result in dynamic instability and slope displacements as high as 130 mm. Thus, the recreational area of MBG possesses some susceptibility towards a seismic-induced landslide.

GIS modeling to investigate environmental change and degradation in Kohima district, North East Hill (NEH) region of India.

As a part of the Himalayan mountains, the North East Hill (NEH) region of India is geophysically dynamic and seismotectonically active since its formation about 55 million years ago with a head-on collision of the Indian plate and the Eurasian plate. The region still has been underthrusting at a rate of 4.5-5cm/year causing the reshaping and changing of its geophysical characteristics (geology, geomorphology, relief, slope gradient, drainage system, etc.), whereas anthropogenic activities, particularly shifting cultivation and technological intervention, have caused changes or degradation of the ecological environment (air, land, water, vegetation, crop pattern, climate, wildlife, etc.). Addressing this burning geoecological problem, a geospatial technology-based case study from the Kohima district of Nagaland in the North East Hill region of India is presented here. Through the development and integration of multiple GIS modules, this reconnaissance study suggests that continuous seismic activities (about 27 seismic events/year) along tectonic faults, thrusts, and lithological shear zones have been reshaping and changing the geophysical environment, whereas the ecological environment has been changing or degrading due to decreasing natural landscape and habitats (forest area, water bodies, and shrubs) at an annual rate of 5.91 km2 (0.60%), increasing built-up area, agricultural land, and wasteland at an annual rate of 2.73 km2 (0.28%), 2.69 km2 (0.27%), and 0.49 km2 (0.05%) respectively. Results also suggest that environmental degradation results in accelerated trends of climate change (rising temperature at the rate of 0.13°C/year, decreasing annual rainy days at the rate of 2days/year, decreasing annual rainfall at the rate of 9.55cm/year, mounting climatic zones at the rate of 175m/year) and its adverse impacts (increasing extreme rainfall events at the rate of 3 events/year and causing cloud burst, erosion, landslides, and floods) in the region.

Contrasting Effects of Tectonic Faults on Vegetation Growth along the Elevation Gradient in Tectonically Active Mountains

Long-term tectonic movements have shaped the geomorphological features and hydrothermal conditions of mountains, influencing their vegetation growth patterns in both positive and negative ways. However, little is known about the effect of fault development on the spatio-temporal variation in vegetation along the elevation gradient in mountainous regions. To address this issue of montane tectonic ecology, this study selected the tectonically active mid-altitude zone (1000–3500 m) of the Chinese Western Tianshan Mountains. The role of tectonics is investigated by fault length density maps calculated from zonal statistics of region-scale fault survey data (1:250,000). The normalized difference vegetation index (NDVI) was chosen as an indicator to analyze the growth status of vegetation. The spatial distribution of fault length density, elevational, and interannual characteristics of the NDVIs from 2000 to 2020 and their relationships along the elevation gradient were investigated. The results show that the faulting zone accounts for 32.6% of the study area and the high faulting zone exhibits a unimodal distribution along the elevation gradient, with the maximum occurring at elevations of approximately 2000 m. The NDVIs of forests and high-coverage grassland show a unimodal distribution with elevation, with the maximum occurring at elevations of approximately 2000 m, coinciding with that of fault length density. In the elevation range of 1000–2500 m, the NDVI of the faulting zone is lower than that of the non-faulting zone, whereas that of the elevation range of 2500–3500 m is higher—a difference that is particularly evident in forests. This elevation-dependent contrasting effect of faults on vegetation growth could be attributed to more favorable hydrothermal conditions for vegetation in fault valleys and reduced landslide susceptibility with increasing elevation. This study highlights the need to consider fault distribution in understanding vegetation distribution and growth in tectonically active mountains.

Tectonism and fracture-related dissolution induced the formation of the large-scale metamorphic granite reservoir: Implications from Bozhong 26–6 Precambrian bedrock trap, offshore Bohai Bay basin, Northern China

Crystalline rocks in basins are unconventional sites for hydrocarbon exploration. Owing to the lack of primary pores in the bedrock, it remains unclear how later tectonism and dissolution alter crystalline rock within large-scale reservoirs. Notably, the recent discovery of a 200 million-ton oil field of Precambrian metamorphic granite in the Bonan buried hill, Bohai Bay Basin, China provides an important opportunity for exploring this mechanism. Herein, the relationship between fractures and the regional tectonic evolution of this buried metamorphic granite mass, as well as the accompanying phenomena of dissolution and vein filling (which record related fluid interactions contributing to second pore formation from tight crystalline rocks) were investigated. The results indicated that the reservoir space was primarily composed of tectonic fractures and associated dissolution pores (maximum porosity ≤18%). The densely interlaced fractures with dominant NWW-trending flat surfaces indicated that the majority of Precambrian bedrock fractures were induced by Indosinian tectonic compression. The Cenozoic north–south tectonic extensional fault obliquely intersects these NWW-trending fractures, accounting for 73% of the previous dense shearing fractures transformed into open fractures. The dissolution pores were primarily distributed along the fractures and increased the porosity of these fracture-related reservoirs by ≤ 12%. The carbon and oxygen isotopes of the calcite fillings within the fractures suggested that atmospheric freshwater was the primary dissolution fluid, whereas some pores were formed by the dissolution action of deep hydrothermal and organic acid fluids. Thus, regional compressive stress is a necessary tectonic mechanism for the formation of densely interlaced fractures in tight crystalline rocks. The later extensional setting contributing to fracture release and fracture dissolution in the epi-diagenesis stage are two immediate factors in the formation of permeability and storage capacity within buried bedrock traps.