On January 7, 2025, a MS6.8 earthquake struck Dingri County in the Shigatse region of Xizang. In response to the event, it conducted field investigations and high-precision UAV aerial surveys, which indicate that the rupture extends from the central-northern segment of the Dengme Co (or Dingmu Co) fault to the eastern shore of Yangmudingcuomu Lake and the northern bank of the Pengqu River, totaling approximately 36.5 km. The surface rupture predominantly follows existing fault structures, with the southern end exhibiting multiple parallel faults and surface scarps up to 4 km wide. The rupture patterns are complex, combining seismic scarps and extensional fissures of varying dimensions. Notably, the northern section displays larger scarps, with maximum displacements reaching approximately (265±27) cm. Scarp heights vary significantly along the rupture, with minimal vertical displacement at north and south end. Our preliminary findings suggest that the surface rupture length and maximum displacement align closely with global empirical relationships between earthquake magnitude and rupture characteristics. Additionally, the characteristics of the Dingri earthquake's surface rupture offer valuable insights for studying the geomorphic evolution of single-event seismic scarps and their long-term cumulative effects.
To investigate the rupture mechanism of the MS6.8 earthquake in Dingri, Xizang, it inverted the rupture process of the mainshock using teleseismic waveforms and refined the hypocenter locations of the aftershock sequence through the double-difference relocation method. The results indicate that the rupture process lasted approximately 22 seconds, with unilateral propagation northward along the causative fault.The rupture extended for about 60 km, and the maximum slip reached 2.4 m, located roughly 30 km north of the mainshock, forming a co-seismic surface rupture zone that is consistent with the results of field geological surveys. The aftershock sequence exhibits a characteristic north-south distribution, which can be roughly categorized into three clusters. The earthquake distribution in the southern and central clusters indicates a complex fault structure and suggests the co-seismic activation of multiple secondary faults. Early aftershocks are concentrated in the low-slip regions at the periphery of the main rupture zone, complementing the high-slip areas (> 1.5 m), consistent with the "stress shadow" effect. Subsequent aftershocks migrated southward and formed conjugate clusters trending NE-SW and NW-SE, revealing a multi-directional stress adjustment process in the post-seismic stage. These findings suggest that the regional tectonic stress field plays a significant role in controlling the rupture process, and that the aftershock distribution is closely related to post-rupture stress redistribution and regional tectonics.
On January 7, 2025, an MW7.1 earthquake struck Dingri County, Shigatse City, Xizang Autonomous Region. The epicenter was located at the intersection of the southern segment of the Shenzha-Dingjie rift fault system and the South Tibetan detachment system, near the Dengmocuo fault. To investigate the seismogenic mechanism, slip distribution, and Coulomb stress disturbances of the earthquake, this study firstly utilized the Sentinel-1A data to obtain the coseismic deformation fields by InSAR (interferometric synthetic aperture rader) and POT (pixel offset tracking) techniques. Then, we employed the SDM program to invert the fault coseismic slip-distribution, and subsequently calculated the coseismic Coulomb stress disturbances with variable depth. The results indicate that the coseismic deformation of the Dingri earthquake is dominated by subsidence. The seismogenic fault strikes nearly north-south, with a dip angle of ~60°. The inverted coseismic slip-distribution suggests that the major rupture zone (slip > 1 m) extends ~40 km in length and ~14 km in width. The maximum slip is approximately 4.45 m, occurring at a depth of ~4.33 km. The average rake angle is approximately ‒76.81°, indicating that this earthquake was predominantly a normal faulting event with a slight left-lateral strike-slip component. Taken the shear modulus at 30 GPa, the inverted seismic moment is about 3.53×1019 N·m, equivalent to the moment magnitude MW7.0. Aftershocks predominantly happened around the periphery of the major slip zone. Additionally, the coseismic and postseismic Coulomb stress disturbances suggest significant increases (> 10 kPa) in the southern segment of Shenzha-Dingjie fault, the eastern segment of Zanda-Lhaze-Qongdojiang fault, the central-eastern segment of Dagyiling-Ngamring-Rinbung fault, and the central segment of Yarlung Tsangpo fault. The future seismic hazards on these fault segments warrant heightened attention.
On January 7, 2025, at 09:05, an MS6.8 earthquake struck Dingri County in the Xizang Autonomous Region, resulting in significant casualties and property damage. The epicenter of the main shock was located in the Dingmucuo graben, in the western segment of the southern Shenzha-Dingjie rift zone in the southern Tibetan Plateau, and the focal mechanism was identified as a typical normal faulting earthquake. The seismogenic fault is the normal faults in Dingmucuo graben, however, the distribution of surface rupture and geometry of normal faults, as well as the evolution model of this graben is relatively limited. This study discusses the seismogenic fault of the earthquake and the evolution model of the Shenzha-Dingjie rift through the interpretation of remote sensing images before and after the event, field investigations of surface ruptures, and the relocation of the seismic sequence. Earthquake investigations revealed significant surface ruptures developed on both the eastern and western sides of Dingmucuo, forming a typical graben structure, while the northern segment primarily developed in the eastern part of the Nixiacuo, exhibiting significant displacement and resembling a half-graben structure. Notably, the surface rupture extends about 30 km in the graben showing a migration of the graben boundary fault into the basin. Furthermore, based on the seismic phase data recorded by the permanent and temporary stations, 4 312 high-precision location results were determined by using a double-difference relocation method. The epicenter of the main shock was determined to be at 28.51°N, 87.52°E, with a focal depth of 11.3 km. The aftershock sequence was consistent with the direction of the surface rupture, showing a ~NS distribution, with depths concentrated around ~4‒17 km. The aftershock distribution revealed the coexistence of east-dipping and west-dipping fault characteristics. Based on the surface rupture and aftershock sequence, it concludes that the seismogenic fault for this earthquake is the eastern boundary fault of the Dingmucuo graben, with a dip angle of approximately 60°‒70°. The earthquake sequence is primarily concentrated in the upper crust and is likely a response to boundary stress resulting from the thrusting along Himalayan arc.
The MS6.8 Dingri earthquake in Xizang on January 7, 2025, exhibited a spatially extensive and complex aftershock sequence, with a relatively small maximum aftershock magnitude. Additionally, the lack of comparable historical earthquake data in the region posed significant challenges for strong aftershock prediction. This study utilizes phase reports from the regional seismic network in Xizang and applies the double-difference relocation method to precisely relocate the Dingri MS6.8 earthquake sequence. The results reveal that the aftershock zone extends along a north-south (NS) trend, spanning approximately 80 km in length, with the actual rupture length exceeding empirical estimates. The sequence displays distinct segmentation characteristics, with dense clusters at the northern and southern ends and sparse activity in the central section. The spatial distribution of aftershocks with magnitudes ML≥4.5 is highly complex, influenced and controlled by multiple factors, including heterogeneous coseismic slip, local stress conditions, fault geometry, tectonic setting, and historical seismic rupture patterns. The largest aftershock recorded was MS5.0, yielding a magnitude difference of 1.8 from the mainshock. This observation supports the empirical relationship that "larger rupture lengths correlate with greater magnitude differences between the mainshock and its largest aftershock."
Coseismic surface fractures triggered by earthquakes are of significant importance for understanding fault activity, seismic structural characteristics, and post-earthquake disaster assessment.This study combines high-resolution unmanned aerial vehicle (UAV) data and deep learning techniques to automatically identify and analyze the surface fracture characteristics of the 2025 MS6.8 earthquake in Dingri, Xizang, further revealing the surface fracture strike pattern and validating it through comparison with InSAR deformation data. Based on high-resolution images obtained by low-altitude UAVs, the ResPSP-CBAM model was used for intelligent recognition, successfully extracting the surface fracture distribution in the post-earthquake area. The ResPSP-CBAM model integrates the ResUNet residual structure, Pyramid Scene Parsing (PSP) module, and Convolutional Block Attention Mechanism (CBAM), significantly improving the accuracy and robustness of crack detection.The analysis indicates that the ResPSP-CBAM model performs excellently in accuracy, precision, recall, and F1 score, with respective values of 0.927, 0.829, 0.779, and 0.802. The identified surface fracture trends are highly consistent with the surface deformation directions interpreted from InSAR, further validating the effectiveness of this method.The ResPSP-CBAM deep learning model constructed in this study significantly improves the accuracy and efficiency of intelligent identification of seismic surface fractures. The identified surface fractures include both primary and secondary types, predominantly featuring primary fractures induced by fault ruptures. These fractures generally exhibit a north-south strike orientation, which aligns closely with the strike direction of the Dengmoco fault zone. This indicates that the surface fractures in the study area are closely associated with fault activity. This research provides a novel technical approach for intelligent identification of earthquake-induced surface fractures, offering robust support for understanding structural characteristics of seismic source faults, and delivering critical scientific evidence for earthquake prediction, early warning systems, and post-earthquake hazard assessments.
In order to understand the aftershock sequence and intensity distribution of the Dingri MS6.8 earthquake in 2025, the double-difference location method has been utilized to relocate the aftershocks within 72 hours and the standard deviation ellipse weighted by magnitude has been used to analyze the relocated aftershocks. Meanwhile, the instrumental intensities have been calculated with the strong-motion data within 150 km away from the epicenter. The relocated aftershocks are distributed in a north-south direction, and the distribution of aftershocks within 2 hours shows consistence with that of the 72 hours. The aftershock center and macroseismic epicenter are both located to the north of the epicenter, and the major-axis direction of the aftershock area is 5° different from that of the intensity Ⅸ of the isoseismal lines. The distribution length of the aftershocks along the major axis is 71 km. There are few strong motion stations around the epicenter, therefore only 4 calculated intensity values have been obtained in areas of intensity Ⅵ and above, 2 of which show agreement with the macroseismic intensities. Based on the spatial distribution of aftershocks and the focal mechanism solution, it is inferred that the nodal parameters of the seismogenic fault of the Dingri MS6.8 earthquake are 181°/51°/‒81° for strike/dip/rake angles. This earthquake shows a significant upper/lower wall effect, with greater high-intensity areas and a concentrated distribution of aftershocks in the upper wall.
In this study, the rupture process of the 2025 Dingri 6.8 magnitude earthquake in Xizang is rapidly determined based on a dense far-field seismic array, and the seismic intensity distribution and potential casualties are rapidly assessed based on the rupture process. First, the back-projection technique is used to obtain the spatial and temporal distribution characteristics of the energy release in the seismic source area, which reveals the dynamic evolution process of the rupture of the seismic source. Then, combining the rupture process with the ground shaking parameter attenuation model based on the shortest distance from the fault, the spatial distribution of the seismic intensity is quickly calculated, and the scope and intensity of the disaster impact are clarified. Based on this, the casualty assessment model is used to make a preliminary estimation on the casualties that may be caused by the earthquake. The results show that the rapid seismic intensity assessment method based on dense seismic array has high reliability and practical application value in the rapid assessment of post-earthquake disaster, which can provide important reference for government decision-making, emergency command and rescue deployment.
The stress triggering of the 2015 Nepal MW7.8 and MW7.2 earthquakes on the 2025 Dingri MW6.8 earthquake and its seismogenic fault are analyzed and discussed in this study, based on the rupture models of the two Nepal earthquakes and a layered viscoelastic crustal velocity model. The results show follows: (1) The 2015 Nepal MW7.8 earthquake caused a Coulomb stress change of 0.003 9 MPa at the source location of the Dingri earthquake, which was significantly greater than the stress modulation caused by solid tides, indicating that it played a promoting role in the occurrence of the Dingri earthquake. The combined Coulomb stress changes from the 2015 Nepal MW7.8 and MW7.2 earthquakes at the source location of the Dingri earthquake amounted to 0.010 4 MPa, exceeding the seismic stress triggering threshold of 0.01 MPa, suggesting that the joint effect of the two earthquakes significantly promoted the occurrence of the Dingri earthquake. (2) During the Dingri earthquake, both the MW7+ earthquakes caused positive Coulomb stress changes on its seismogenic fault plane, with an average Coulomb stress change of 8 837 Pa. Especially at the source of the Dingri earthquake, the Coulomb stress change exceeded the stress triggering threshold of 0.01 MPa, indicating that the two earthquakes effectively increased the stress level on the seismogenic fault plane of the Dingri earthquake, having a significant triggering effect on the source location of the Dingri earthquake. (3) Considering the two MW7+ earthquakes in 2015, along with the two MS5.9 earthquakes in Dingri in 2015 and 2020, it was found that the 2015 Dingri earthquake had a suppressing effect on the Dingri earthquake, while the 2020 MS5.9 Dingri earthquake had a promoting effect. The combined Coulomb stress changes from these four earthquakes amounted to 0.01 MPa, which triggered the Dingri earthquake. The results of this study provide basic data and information for understanding the seismic hazard analysis of the fault where the Dingri earthquake occurred, with significance for the seismic activity at the boundary of the Indian Plate and the Eurasian Plate, as well as the tectonic evolution of the Tibetan Plateau.
In the southern Tibetan rift zones, there are several approximately north-south trending rifts distributed from west to east. As important tectonic extensional zones within the blocks, these rifts have developed a series of normal faults and experienced multiple strong earthquakes. Since the Late Quaternary, this region has exhibited intense tectonic activity with frequent earthquakes causing serious disasters. For instance, the January 7, 2025 Mw7.1 (CENC: Ms6.9) Tingri earthquake demonstrated the characteristics of "small earthquake with major disaster consequences". To assess the seismogenic potential of normal faults within the rift zones and understand their disaster-inducing competence, this study divides 92 normal fault zones based on geometric characteristics and statistically analyzed fault trace lengths. Under the assumption of full-length surface rupture along fault traces during earthquakes, combined with empirical relationships between normal fault rupture length and moment magnitude, we estimated the maximum potential magnitudes of normal faults in the rift zones. Results indicate that these normal faults have upper seismogenic limits ranging from Mw6.5 to Mw7.5, with numerous historical seismic gaps. While generally demonstrating strong seismogenic competence, they exhibit an eastward-increasing strength pattern. Bounded by major fault zones to the north and south, and considering multiple historical seismic gaps along the southern magethrust (particularly in the context of accelerated Coulomb stress loading following the 2015 Nepal Mw7.8 earthquake and potential interaction/triggering effects between major boundary faults), the normal faults south of Yarlung Tsangpo River, especially those in the Tingri-Nyalam and Xiongqu fault, show high potential for future strong earthquakes.
The rapid mapping of secondary effects triggered by strong earthquakes is crucial for understanding the disaster-causing mechanisms of mainshock events. The Tibetan Plateau, characterized by its higher altitude, sparse population, and challenging field conditions, presents significant difficulties for on-site investigations. Consequently, it is significant to analyze the distribution of earthquake-induced landslides and soil liquefaction utilizing post-earthquake emergency satellite imagery. We aim to systematically identify the spatial distribution characteristics of secondary hazards triggered by the MS6.8 Dingri earthquake on January 7, 2025. We utilized emergency imaging data from high-resolution Chinese satellite images. We employed manual visual interpretation through a comparative analysis of pre- and post-earthquake imagery supplemented by field investigations. The following results are obtained: (1) The mainshock triggered 2 869 coseismic landslides, with two major concentration zones in the north and south. Approximately 60% of these landslides occurred in high-altitude regions between 5 000-6 000 m, predominantly manifesting as slope debris flows and collapses with limited effect for far away the residents. (2) The mainshock also induced about 400, 000 soil liquefaction pits, primarily concentrated in the floodplains and low terraces of the Pengqu River at elevations of 4 100-4 300 m. These liquefaction sites are distributed across the Democuo Basin, Guojia Basin, and Dingjie Basin, with some occurrences in Quaternary tills at elevations reaching 5 200 m. The distribution pattern of coseismic landslides, primarily as slope debris flows in higher-altitude (about 5 000 m) areas, suggests a possible correlation with the topographic amplification effect. Meanwhile, the spatial extent of soil liquefaction, spanning three basins in the southern section of the Dingjie-Shenzha Rift system, indicates that single secondary-fault rupture event within a single basin can significantly impact other adjacent secondary-faulted basins, leading to severe secondary disasters, even the controlled faults without coseismal faulting.
Sand liquefaction is one of the main forms of post-earthquake disasters, so it is of great significance to conduct a detailed surface survey of the distribution patterns and development characteristics of sand liquefaction after an earthquake. To reveal the characteristics of sand liquefaction caused by the Dingri earthquake, detailed remote sensing interpretation and field investigation were carried out in the Dingri area after the earthquake, and the following results were obtained: (1) During the MS6.8 Dingri earthquake on January 7, 2025, sand liquefaction was observed in the southern Pengqu Valley, along the shores of Dingmu Co in the central area, and on the southeast side of Kongmucuo in the northern region, which suggests the formation of a widely distributed liquefied sand layer in the strata during this earthquake. In this event, ground failures caused by sand liquefaction along both banks of the Pengqu River and on the east shore of Dingmu Co were mainly characterized by lateral spreading. In contrast, ground failures in the riverbed of Pengqu, the edge of the alluvial fan on the east shore of Dingmu Co, and the southeast side of Kongmucuo were dominated by liquefaction-induced sand dunes. (2) Field observations and analysis of the tectonic stress field suggest that the sand liquefaction deformation in this earthquake underwent a dynamic developmental process. Under the influence of tectonic stress and gravity, north-south oriented tensional fractures formed. The sand liquefied due to the librations, and some liquefied material was ejected along these north-south fractures, resulting in lateral spreading due to the gentle slope. Blocks on the surface collided and compressed with each other. In some locations, intense compression and collision led to the formation of east-west oriented tensional fractures, through which liquefied material surged out, forming nearly east-west oriented linear liquefaction sand dunes.
To improve the accuracy of peak ground motion (peak ground acceleration (PGA) and peak ground velocity (PGV) prediction in Chinese instrument seismic intensity calculation for on-site earthquake early warning (EEW), a prediction method of on-site peak ground motion based on machine learning and transfer learning is proposed. A pretrained on-site peak ground motion prediction model was established using neural networks based on strong motion data recorded by the K-NET network in Japan. Based on strong motion data from China and the pretrained on-site peak ground motion prediction model, an on-site peak ground motion prediction model for China was established through transfer learning. For the Japanese and Chinese test dataset and Luding M6.8 eathquake, at 3 s after the arrival of P-wave, compared to traditional on-site peak ground motion prediction method, the method proposed in this study has smaller mean absolute error and standard deviation for PGA prediction and PGV prediction. The results indicate that the method proposed in this study can improve the reliability of predicting peak ground motion in on-site EEW to a certain extent, which is of great significance for the development of on-site EEW systems.
Peak Ground Velocity (PGV) is one of the parameter commonly used to measure the damage potential of ground shaking to building structures, and real-time prediction of PGV is a key technology in emergency response to major engineering earthquakes. To further improve the accuracy of PGV prediction, in this paper it proposes an onsite PGV prediction model based on Extreme Gradient Boosting (XGBoost). The model takes five characteristic parameters, including peak acceleration (Pa), peak velocity (Pv), peak displacement (Pd), cumulative absolute velocity (CAV), and predominant period (Tpd) in the first 3 seconds of the P-wave observed at the station as inputs, and the PGV observed at the station as the prediction target. 6 918 sets of acceleration records from 102 earthquakes recorded by the K-NET station network in Japan were used for model training, and 3 430 sets of acceleration records from 89 earthquakes were used to test the generalization ability of the model. The results show that, within the same dataset, the PGV prediction model based on XGBoost has a predictive value that is closer to a 1:1 ratio with the actual measured values compared to the PGV prediction models based on Pd and support vector machines. Additionally, the standard deviation of the prediction errors is smaller, the mean of the prediction residuals is closer to zero, and the model performs well on actual earthquake cases in China. The PGV prediction model based on XGBoost can be used for the prediction of peak ground motion in local earthquake early warning systems.
In order to improve surface wave in the narrow space of the lateral resolving power, a method is proposed to the two-dimensional surface wave phase velocity profile, firstly using linear Radon transform to extract the surface waves in seismic records, then using two adjacent phase difference method to calculate the surface wave dispersion curves, and finally explaining it with half wave. A model of abnormal body at low speed is established in random medium, in the case of a short order. Through data processing of seismic wave records from finite difference numerical simulation of wave equation, it is found that the area of low-velocity abnormal body in velocity profile is obvious and its location is accurate. This technique has been applied to the detection of underground air-raid shelters in Zhengzhou City and the detection of seepage in the Yellow River levee, and the positions of air-raid shelters and seepage channels have been found. This technique has high lateral resolution and is suitable for non-destructive ground detection in urban narrow space.
In order to limit the timing of Mesozoic folds in the eastern coast of South China and study the formation mechanism, in this paper it studies the folds of the Late Triassic to Middle Jurassic strata in the northern section and analyzes the geochronology of related geological bodies. Fossils of ferns, pinnules, bivalves found in the strata confirm the sedimentary age from the Late Triassic to the Middle Jurassic. The NE fold is invaded by the Late Jurassic volcanic rock (zircon U-Pb age at 163-148 Ma). The NW fold is invaded by the Late Jurassic granite (zircon U-Pb age at 157-154 Ma). Combined with the previous debris zircon U-Pb age obtained in the formation (171-173 Ma), comprehensive analysis indicates that the fold was formed in the middle and late Middle Jurassic. NE fold is longitudinal bending fold, which is the product of regional NW-SE extrusion; NW fold is formed by shear fold, which is the product of NW transverse fault in the fold reverse zone. The different trending Jurassic folds in the northern section of Lianhuashan fault, Guangdong, are the tectonic response of South China block to the subduction of the Paleo-Pacific plate.
The occurrence and genetic mechanism of residual uranium in uranium reservoirs after CO2 + O2 in-situ leaching of uranium are highly important for improving the in-situ leaching process and leaching efficiency of uranium, but few studies have been conducted in this field. Therefore, this work takes mineralized sandstones and drilling core samples after in-situ leaching of uranium as the research object in the Qian II block of the Qianjiadian uranium deposit in Inner Mongolia. Three types of residual uranium were identified via SEM-EDS analyses: uranium minerals, adsorbed uranium and minerals containing uranium. In the samples after in-situ leaching, uranium minerals include coffinite and pitchblende, which are mainly distributed in the dissolved pores of clastic particles or inside and around clay minerals such as kaolinite. The adsorbed uranium is adsorbed mainly by clay minerals and carbonaceous debris, whereas minerals containing uranium include mainly monazite containing uranium, zircon containing uranium and titanium minerals containing uranium. A comparison of the occurrence of uranium in the mineralized sandstones before and after in-situ leaching reveals the following. (1) In the types of uranium minerals associated with clastic particles, the residual uranium minerals inside the quartz, feldspar, rock debris and carbonaceous debris were observed, whereas no residual uranium minerals at the edge of clastic particles, or inside the mica joints were observed. (2) In the uranium minerals associated with interstitial material, residual uranium minerals associated with pyrite and kaolinite were observed, and no residual uranium minerals associated with siderite were observed.(3) Uranium adsorbed by kaolinite and carbonaceous debris was retained. (4) Minerals containing uranium retains between clastic particles. On the basis of above observations and analyses, four genetic mechanisms of uranium residue in uranium reservoirs during in-situ leaching are proposed. (1) Because of the lack of effective interconnected pores, the in-situ leaching solution has difficulty flowing through the uranium minerals inside the clastic particles, resulting in formation of the uranium residual uranium minerals.(2) Kaolinite can block fluid transport channels, making it difficult to leach uranium minerals associated. (3) Kaolinite has adsorption properties and is stable under acidic conditions, which makes it difficult for the adsorbed uranium to be leached out. Uranium cannot be leached in areas rich in carbonaceous debris because of its strong reduction ability, adsorption capacity and poor circulation in the area. (4) Minerals containing uranium have difficulty reacting with the leaching agent, which results in incomplete leaching. This research has shown that the occurrence of uranium in the mineralized sandstone is an important factor affecting its leaching, and the results provide a mineralogical basis for improving in-situ leaching processes and enhancing uranium leaching efficiency.
Jizhong depression is located in the west of Bohai Bay basin. Its Carboniferous-Permian coaly source rocks have great resource potential, of which related oil and gas reservoirs have been explored in Suqiao-Wen'an area in the depression. However, the hydrocarbon generation characteristics and petroleum resource potential of the coaly source rocks still remain unclear in the Jizhong depression, which seriously affects the oil and gas exploration. On the basis of previous research, in this paper it makes a detailed analysis of organic geochemical characteristics of the Carboniferous-Permian coaly source rocks. The hydrocarbon generation potential and mechanism of selected coaly source rocks from Taiyuan Formation and Shanxi Formation are also explored by the experiment of high temperature and high pressure hydrocarbon generation kinetics. The research shows that the organic abundance of coal source rocks in the study area is high, indicating good hydrocarbon generation potential. The organic matter types of Taiyuan Formation are mainly type II2 and type II1, and the organic matter types of Shanxi Formation are mainly type II2 and type III, which are mostly in the mature stage.The oil and gas generation capacity of Taiyuan Formation is stronger than that of Shanxi Formation, but the activation energy of coal in Shanxi Formation is lower and it is easier to generate gas. The development of coal-bearing source rocks is controlled by sedimentary environment, paleoclimate and paleoplant factors. The coal of Taiyuan Formation is mainly formed in the coal-forming environment of lagoon peat swamp, and the coal of Shanxi Formation is mainly formed in the coal-forming environment of delta plain peat swamp. On this basis, a coal accumulation model suitable for the study area has been established. This study plays an important supporting role in the evaluation of oil and gas resource potential in the study area.
Based on the geological, seismic, and analytical data obtained from the exploration of Paleozoic oil reservoirs in the southern section of the western margin thrust belt in the Ordos basin and based on the first Paleozoic industrial oil flow Well YT3 discovered in 2022, combined with the tectonic sedimentary background of the Wulalike Formation and Yanghugou Formation oil-bearing series, this study conducts a comparison of Paleozoic oil sources, quantitatively restores the structural evolution process, systematically analyzes the genesis and reservoir-structure coupling relationship of Paleozoic oil reservoirs, constructs unconventional oil reservoir accumulation models, predicts and evaluates favorable exploration areas.The study shows follows. (1) The crude oil of the Lower Paleozoic Wulalike Formation is "single source" from the same layer of mudstone source rocks, and the oil sand of the Upper Paleozoic Yanghugou Formation is "dual source", contributing to the joint contribution of the Wulalike Formation mudstone source rocks and the Yanghugou Formation coal-bearing source rocks. Both sets of source rocks have the ability to generate oil, and in comparison, the Wulalike Formation source rocks have a greater potential for oil generation. (2) The construction quantitative restoration of the balanced profile method reveals that the differential settlement effect during the Hercynian-Indosinian period is the fundamental reason for the differences in maturity of the source rocks of the Wulalike Formation in the Yindongzi and Shajingzi thrust faults, which is high in the west and low in the east, as well as the differences in oil and gas phases. (3) A "dual source and dual storage" stereoscopic reservoir formation model of unconventional oil reservoirs is constructed through the study of source and reservoir configuration relationship. The Wulalike Formation has developed "self generating and self storing" oil reservoirs, while the Yanghugou Formation has developed "bottom generating and upper storing" and "source in" oil reservoirs. (4) The geological seismic multi-attribute fusion prediction area has a favorable exploration area of 400 km2 for the Wulalike Formation shale and 300 km2 for the Yanghugou Formation.The volume method estimates the total resource potential of the Upper and Lower Paleozoic oil reservoirs in the southern section of the western margin to be 1.0×108 t, which is a realistic target replacement area for Paleozoic reservoir exploration.
The potential of continental shale oil resources in China is enormous, and the lower member of the Xingouzui Formation (LXF) from the Early Eocene serves as the primary target for shale oil exploration in the Jianghan basin. Previous research has mainly focused on hydrocarbon generation potential and reservoir characteristics, while discussions regarding its depositional environment evolution and mechanisms of organic matter enrichment remain relatively scarce.This study takes the Early Eocene LXF from the SKD1 and CY1 boreholes as the main research object. Based on lithofacies, elemental, and isotopic geochemical analyses, it investigates the paleoenvironmental changes and organic matter enrichment mechanisms of the LXF. The results indicate that organic matter content in the LXF is relatively low, with an average total organic carbon (TOC) of 0.9%. During the Paleocene-Eocene Thermal Maximum (PETM), rapid warming and oxidative conditions accelerated the decomposition of organic matter, resulting in relatively low organic matter content, with a TOC of only 0.5%. In contrast, during arid climatic periods, increasing lake salinity led to the sequential deposition of evaporative minerals such as anhydrite and glauberite. Under high-salinity conditions, halophilic organisms contribute to part of the productivity. High salt and hypoxic environment promotes the production and preservation of organic matter, with average TOC increaing to 2.56%. These findings indicate that organic matter enrichment in the Jianghan basin during the Eocene was primarily controlled by synergy of productivity and preservation conditions. This study provides insights into the mechanisms of organic matter preservation in continental saline lacustrine basins under greenhouse climate conditions and provides a theoretical basis for identifying favorable stratigraphic intervals for future oil and gas exploration.
During the fault growth process, a fault zone with complex three-dimensional structure is formed. The fault zones occupying a very small volume in the Earth's crust have a significant impact on the migration of fluids within the crust. The study of the interaction between fluids and solids in these fault zones is of great geological and engineering importance. Over the past 30 years, multidisciplinary research has been conducted on the characteristics of fault zones, permeability, and fluid migration patterns in sedimentary clastic rock. However, there is a lack of understanding and efforts in systematically comparing and comprehensively explaining the findings across different disciplines. In this paper, it summarizes the types, formation mechanisms, and geometric characteristics of fault zone. It systematically reviews data on the permeability of fault zones, analyzes three categories of factors influencing permeability changes, and elucidates the fluid migration behavior within fault zones, including dominant pathways, migration velocity, periodic frequencies, critical conditions, and multi-field coupled migration mechanisms. By summarizing the research progress over the past 30 years, in this paper it is expected to deepen our understanding of the complex geological processes of fault-fluid-mineralization. It is important to note that further interdisciplinary collaboration is needed to conduct more in-depth research on the fluid migration within fault zones.
The CO2 geological storage technology in salt water layer is an important supporting technology for achieving China's carbon peaking and carbon neutrality goals. However, the current 3D geological modeling technology based on oil and gas development purposes is difficult to meet the requirements of CO2 geological storage. Numerical simulation and safety evaluation of CO2 geological storage in salt water layers require a geological model of all strata from the ground to the target layer. Taking the Gaoji area of the Subei basin as an example, using Petrel software and various deterministic and stochastic modeling methods, it conducted research on the three-dimensional modeling technology of the entire strata from the target strata to the surface. The main achievements are as follows. Propose to use the Structural framework method to solve various fault modeling problems caused by complex fault contact relationships, and use the stepped grid method to solve the grid requirements for whole formation modeling. Propose a method of sequentially simulating porosity, permeability, and other models using different geostatistical methods under the constraint of lithological models, and ensure that the number of grids in the entire geological model is less than ten million. Based on the characteristics of the geological model of the entire formation, the accuracy of the geological model of the entire formation in the Gaoji area was tested using the comparison method of reservoir development characteristics. Overall, it is believed that the results of the random modeling in the Gaoji area have high credibility. The geological modeling method proposed in this study can provide a reliable and complete geological model for the numerical simulation and safety inspection of CO2 geological storage in salt water layers, which is of great significance for the development of CO2 geological storage in salt water layers.
It is an important method to simulate P- and S-wave velocities using digital core obtained from X-ray CT images. However, since it is impossible to differentiate clay and grains, and abundant micro-pores exist in shaly tight sandstones, simulating P- and S-wave velocities using digital core is a challenge. In this study, 2D digital core models are constructed and simulated using finite element method to understand the effect of clay content and distribution, amount of micro-pores on the rock elastic properties. The results will be used to assist the construction of a 3D model that can be used to simulated P- and S-wave velocities of shaly sandstones. The results show that dispersed clay and framework clay have minor effects on the bulk modulus, while interstitial clay shows large effect on bulk modulus. Effects of the different clay distributions on shear modulus are similar. Clay distribution has larger effect on bulk modulus than clay content, whereas clay content has larger effect on shear modulus than clay distribution. Micro-pores related to dispersed clay have minor effect on rock elastic properties, however micro-pores related to framework clay and grain-grain contact clay are sensitive to rock elastic properties. In addition, micro-pores have larger effect on shear modulus than bulk modulus. Based on the above results, a 3D digital core model using 3D watershed method on the X-ray images has been built and the results show good match with the measured velocities.
Soil-groundwater organic pollution in key industrial sites is a critical problem to be solved urgently in restoration of water and soil environment. The distribution of microbial communities in the soil-groundwater system plays an important role in the migration, transformation and biodegradation of these organic pollutants. Taking a typical vertical profile of a petrochemical site in the Loess Plateau in Northwest China as an example, based on 16S rRNA gene high-throughput sequencing technology, this study finely describes the vertical distribution characteristics of microbial communities structure, diversity and their metabolic function differences in the soil-vadose zone-phreatic aquifer-aquitard continuous heterogeneous media field, and reveals the impact of lithological composition and depth on the vertical distribution of microbial community structure and function.The results suggested that there were significant differences in the vertical distribution of microbial community structure and diversity in the media field of the soil-groundwater system, which exhibited different metabolic functions and degradation modes of petroleum pollutants.Propionibacteriales in the vadose zone layer and Betaproteobacteriales in the phreatic aquifer were not only the dominant species, but also the biomarker species among the groups, which contributed to the main relevant different metabolic functions.Depth and lithology separately affected different metabolic functions. Microorganisms in the vadose zone, aquifer and its underlying aquitard acted synergistically to degrade petroleum pollutants with aromatic compounds degradation and dark hydrogen oxidation, respectively.
The transformation of arsenic in hot springs is significantly affected by biotic sulfur oxidization. However, the effects of different types of sulfur-oxidizing microorganisms on arsenic transformation are still not well understood. In this study, it compared the effects of anthiosulfate-oxidized bacterium Anoxybacillus flavithermus DB-1 and anelemental sulfur-oxidized archaea Sulfolobus tengchong RT8-4 on arsenopyrite, a typical sulfur-arsenic-bearing mineral from hot springs. The results show that strain A. flavithermus DB-1 could oxidize 60% of As(Ⅲ) at an initial concentration of 0.1 mmol/L in two days, but not elemental sulfur at 50 ℃, pH 7.0-8.0. Strain S. tengchong RT8-4 was able to oxidize 54.3% of Fe(Ⅱ) at an initial concentration of 0.1 mmol/L within 8 days, but could not oxidize sulfur ions and arsenic under the conditions of pH 3.0 and 75 ℃. Co-culture of A. flavithermus DB-1 with arsenopyrite promoted the release of arsenic and sulfur, and the final concentration of arsenic released into the solution was 1.8 mmol/L, SO42- concentration was 10.4 mmol/L, and no secondary mineral was produced. With S. tengchong RT8-4, 12.8 mmol/L of arsenic, SO42- 87.7 mmol/L and 8.5 mmol/L Fe(Ⅲ) were released, and the secondary minerals such as jarosite, yavapaiite and scorodite were generated. These findings suggest that different sulfur-oxidizing microorganisms can affect arsenic migration and transformation in different ways in hot springs, which improves our understanding of arsenic and sulfur biogeochemistry in hot springs.
South China Block is a natural laboratory for the study of paleogeographic environmental changes and biological evolution since it has myriad records of major biological evolutionary events in the Paleozoic. However, the paleogeographic location of South China during this period remains controversial. In this paper it selects and evaluates different paleogeographic reconstruction models of the South China Block in the Middle Paleozoic by using of the paleomagnetic data, paleontological evolution pattern, paleogeographic environmental changes and other indicators. It is difficult for the existing models to match most of these indicators. On the basis of the newly proposed paleogeographic reconstruction of South China at the end of Ordovician based on true polar wandering, it established the paleogeographic location model of South China at four different periods from the Late Ordovician to Devonian. The model shows that the relationship between South China and the Gondwana is dynamically evolving, with a movement from near to far and from far to near. Moreover, this model can well match the existing data of paleomagnetism, paleontology, tectonic evolution and paleogeographic environment changes in South China, which provides a high accuracy paleogeographic reconstruction for the further study of the Paleozoic environment and paleontological evolution in South China.
In order to understand the relationship between the transformation of Longshan culture to Erlitou culture in the Luoyang basin and the hydrological climate, in this paper it collects and analyzes the location and scale information of the settlements (quantity, grade and the largest settlement area) in the two cultural periods, the Holocene paleoclimate records and the paleoflood events at ca. 4 000 a BP. The results show follows. (1) During the Longshan Culture period (4 900-4 000 a BP), the scale of settlements grew, which may be closely related to the stable and suitable climate in the late Middle Holocene. In the turning stage of Longshan Culture to Erlitou Culture (4 000-3 750 a BP), the 4 200 a BP climatic event triggered extreme floods in the basin, which destroyed many settlements and prompted residents to move to the surrounding highlands or other places. (2) During the Erlitou Culture period (3 750-3 500 a BP), the extreme floods did not occur again, the superior geographical location and geomorphic conditions in the basin provided a broad space for large-scale agricultural production and settlement construction. The results are of great significance for exploring the relationship between the evolution of Longshan Culture-Erlitou Culture in Luoyang basin and the hydrological climate.
Ocean tide is the dynamic basis driving the hydrodynamic changes of groundwater. In order to explore the influence of ocean tide on the groundwater dynamics in Naozhou Island, Guangdong Province, the groundwater level and salinity were used as the main indicators, and the frequency characteristics of groundwater dynamics relative to tides were analyzed by power spectrum. Moreover, the amplitude and phase of groundwater dynamics were analyzed by combining wavelet transform and cross-correlation methods. The results show follows: (1) The response of groundwater to tidal loading has a certain spatial range. The horizontal influence of ocean tide on the groundwater level in Naozhou Island is about 400-500 m. (2) The distance from the sea and the aquifer properties are the main factors affecting the hydrodynamic response to the tide. (3) The channel connecting groundwater and seawater in Naozhou Island is distributed in the Quaternary medium sand layer. When the aquifer has a good hydrodynamic response to the tide and good connectivity with seawater, the seawater salt is more easily transmitted to the groundwater. The response analysis of groundwater dynamics to ocean tides can identify the influence range of ocean tides effectively, providing an important basis for the salinity phenomenon of groundwater in the island or nearshore areas.
