地质力学学报

Tectonic evolution of the Sumatran Fault: synthesis and perspective

GUO Lin, CHU Yang, LIN Wei, LEI Yiyang, LIU Tanjie, GUO Yilin, MENG Lingtong

, Available online , doi: 10.12090/j.issn.1006-6616.2025067

Abstract (477) HTML (118) PDF (5012KB)(209)

Abstract:
Objective Oblique convergence between the Indo-Australian Plate and the Eurasian Plate produced a ~1,900-km-long dextral strike-slip fault—the Sumatran Fault—within the overriding plate. While previous studies have extensively examined its geometry, kinematics, and seismicity, the tectonic evolution of the fault remains poorly constrained. Methods This study integrates multidisciplinary evidence from structural geology, geomorphology, seismicity analysis, geodesy (GPS), low-temperature thermochronology (apatite and zircon (U-Th)/He dating), and volcanic distribution mapping. We systematically synthesize data on fault segmentation, slip rates, cumulative displacement, magmatic-tectonic relationships, and regional geodynamic models to evaluate the fault’s spatiotemporal evolution. Results The Sumatran Fault is a highly segmented dextral strike-slip system that can currently be divided into 19 segments based on geometric complexity and seismic activity. Slip rates along the fault are relatively uniform from south to north, with an average around 15 mm/yr, and a total cumulative displacement of approximately 20~25 km. Regionally, the distribution of active arc magmatism closely aligns with the trace of the fault, indicating a dynamic interaction between faulting and magmatism: while magma-induced crustal weakening facilitates fault development, extensional zones associated with normal faulting in turn influence the volcanic activity. Despite its tectonic significance, low-temperature thermochronological studies on the Sumatran Fault remain limited. Existing thermochronological data reveal a period of rapid uplift at ~2 Ma, likely driven by dip-slip motion along the fault. Conclusion A three-stage model is proposed. Before 2 Ma, oblique convergence was primarily accommodated by forearc faults (e.g., Mentawai Fault) and shear zones. Around 2 Ma, the Sumatran Fault initiated contemporaneously with the Mentawai Fault, manifesting strain localization in the overriding plate. At present, the Sumatran Fault accommodates the majority of the strain, while strike-slip motion on the Mentawai Fault has significantly diminished. The uplift phase correlates with the initial timing of the Sumatran Fault inferred from present-day slip rates and cumulative offsets, suggesting that the current through-going structure of the fault and the modern tectonic framework were established at the same time. [ Significance ] This study provides a comprehensive synthesis of multidisciplinary constraints on the Sumatran Fault and establishes a unified spatiotemporal framework for its tectonic evolution. By integrating fault segmentation, slip rates, thermochronological data, and magmatic–tectonic interactions, this study clarifies the timing of fault initiation and the development of the present-day tectonic architecture. The results offer new insights into strain partitioning and the formation of trench-parallel strike-slip faults at obliquely convergent margins, providing a valuable reference for understanding similar plate boundary systems and their associated seismic hazards.

Tectonic evolution of the WesternYangtze Block during the Ediacaran–Cambrian: Evidence from detrital zircon U-Pbgeochronology

Zhiqiang SHI, Le SUN, ZHANG Hong, PEI Jinyun, LI Wei

, Available online , doi: 10.12090/j.issn.1006-6616.2025065

Abstract (55) PDF (2116KB)(74)

Abstract:
[Objective] The Yangtze Block was a crucial component of the Gondwana supercontinent. During the Ediacaran-early Cambrian, its western margin underwent a marked transition from carbonate-dominated to siliciclastic-dominated depositional environments. However, the tectonic dynamics controlling this sedimentary facies shift of early Cambrian sedimentation remain poorly constrained. The exposed thick Early Cambrian terrigenous clastic rocks on the western Yangtze Block are key archives for tracing sediment sources and studying the geotectonic background of the Early Cambrian .[Method] This study carried out systematic detrital zircon U-Pb geochronology and whole-rock element analysis on the lower Cambrian Qiongzhusi Formation on the western Yangtze Block to study above question. [Results] The results indicate: (1) The clastic rocks exhibit high-field-strength elements (HFSEs) and large-ion lithophile elements (LILEs; e.g., Th, Zr, Hf, Ba, Pb) consistent with upper crustal compositions, whereas Sr, Sc, V, Cr, Cu, Ni, and Zn show depletion relative to upper continental crust (UCC)-particularly pronounced for Sr, Cr, V, and Cu. The immobile elements (Th, Sc, Hf, Zr, Ho) and rare earth elements (RREEs; e.g, La, Ce, Yb) suggest a dominantly felsic igneous provenance of the upper continental crust; (2) Primary age clusters of detrital zircon U-Pb ages in the Qiongzhusi Formation are ca.590-500Ma and ca.880-720 Ma, with subordinate groups at 1900-1500 Ma and 2500-2400 Ma. [Conclusions]Integrated with regional data and prior studies, we propose that the early Cambrian detritus was largely derived from the Ediacaran-Early Cambrian magmatic rocks in the Longmenshan tectonic belt (Ediacaran-early Cambrian), and the late Neoproterozoic felsic magmatic rocks of the Panxi-Hannan magmatic arc, Ailaoshan Magmatic Arc and the Jiangnan Orogen. The Proto-Tethyan Ocean's subduction beneath the western Yangtze during the Ediacaran-early Cambrian converted the western Yangtze from a passive to an active continental margin, and formed a late Ediacaran-early Cambrian magmatic arc. This arc supplied voluminous early Cambrian detritus, ultimately shifting the western Yangtze margin to a siliciclastic-dominated depositional system. [Significance]These findings reveal the provenance linkages between the western Yangtze and adjacent orogenic belts, thereby providing critical constraints for reconstructing the tectonic and paleogeographic evolution of the South China Block during the Ediacaran-Early Cambrian.

A 4400-Year-Old Extreme Paleo-Storm Surge Recorded in the Dongzhai Port Chenier, Hainan Island, China

ChaoQun WANG, DongXia SUN, YaoLing ZHANG, XiaoXiao YANG, Lei ZHANG, DaoGong HU

, Available online , doi: 10.12090/j.issn.1006-6616.2025073

Abstract (87) PDF (3542KB)(122)

Abstract:
Identifying paleo-storm surge deposits and extreme storm surge events holds significant scientific and practical importance for understanding the recurrence patterns of super typhoon-induced surges and predicting future storm hazards. Current research predominantly focuses on historical and modern storm surges, with less attention given to prehistoric extreme surges. This study investigates a 3.2-m-thick chenier at Wushu Village, Dongzhai Port, Hainan Island. Analyses of sedimentary structures, shell provenance, accelerator mass spectrometry (AMS)¹⁴C dating, and estimates of overtopping deposit elevation demonstrate that this chenier records an extreme storm surge event approximately 4400 years ago. The chenier's overtopping deposits accumulated on a Late Pleistocene alluvial plain landward of the Holocene highstand paleo-shoreline. Nine AMS ¹⁴C dates on shells range from 4402 to 6647 cal yr BP, exhibiting age reversals and co-occurrence of younger and older shells. The deposit is well-sorted and displays sedimentary structures diagnostic of high-energy deposition, including hummocky cross-stratification, current cross-stratification, and erosional scours. Comparative analysis of shell assemblages and ages between the chenier and underlying paleo-lagoon deposits within Dongzhai Port indicates that the chenier shells were reworked from these older lagoon sediments. The reconstructed paleo-elevation of the overtopping deposits indicates a storm surge height of 5.5 m above modern sea level. This exceeds the 4.58 m surge documented during the 2014 Super Typhoon Rammasun along the Dongzhai coast. Considering the potential influence of astronomical tides on total water levels, we infer that the extreme storm surge height 4400 years ago was likely superimposed on a contemporaneous high astronomical tide.

Evaluation of Source Rocks and Oil Source Correlation in Chang 7-Chang 6 Member of Yanchang Formation in Jingbian Area, Ordos Basin

SiWei TANG, Hui XUE, YouJun TANG, ShuMin WANG, GuangMing HU, Geng LI, FangTingYu SHI

, Available online , doi: 10.12090/j.issn.1006-6616.2025050

Abstract (90) PDF (2632KB)(118)

Abstract:
Objective The Chang 7 and Chang 6 Members of the Yanchang Formation in the Jingbian Area of the Ordos Basin constitute significant source rock intervals. However, systematic studies on their hydrocarbon generation potential and contributions to petroleum accumulation remain limited, which constrains further exploration efforts in this region. Therefore, this study integrates geochemical analytical methods to systematically characterize the distribution and the geochemical properties of the Chang 7 and Chang 6 source rocks in the Jingbian area, as well as the geochemical signatures of the crude oils from the Yan 9 and Chang 2 reservoirs in the Jingbian Oilfield. Methods By comparing the geochemical parameters between the local Chang 6 and Chang 7 source rocks and the Zhangjiatan Shale in the center of the basin, the potential sources of the oils in the Yan 9 and Chang 2 reservoirs were identified. Results The results demonstrate that the Chang 7 source rocks are high quality, with widespread distribution and considerable thickness. They are characterized by Type I-II₂ kerogen and are in the mature stage. The biomarker characteristics indicate mixed organic matter inputs, deposited in a reducing environment with low salinity. The low Pr/Ph and high C₂₇/C₂₉ regular sterane ratios further suggest that the organic matter is predominantly derived from aquatic algae and other lower organisms, consistent with a reducing, fresh to brackish water depositional environment. In contrast, the Chang 6 source rocks are of medium to high quality, containing Type II₂-III kerogen and are generally in the low-to-mature stage. The moderate Pr/Ph and low C₂₇/C₂₉ regular sterane ratios reflect a predominance of terrigenous higher plant input, deposited under a weakly reducing environment. The oil-source correlation results reveal that the Yan 9 and Chang 2 oils are of the same origin, primarily derived from the Chang 7 source rocks, with a minor contribution from the Chang 6 Member. Conclusion (1) the Chang 7 Member is the primary, high-quality source rock in the Jingbian area, superior to the Chang 6 Member in terms of thickness, lateral distribution, organic richness, and hydrocarbon generation potential. (2) Distinct biomarker signatures differentiate the Chang 7 (aquatic/algal, reducing), Chang 6 (terrigenous, weakly reducing), and distal Zhangjiatan (highly aquatic, strongly reducing) source rocks. (3) The Yan 9 and Chang 2 crude oils share a common origin and are primarily sourced from the local Chang 7 source rocks, with a possible minor contribution from the Chang 6 Member. The oils show no direct genetic link to the Zhangjiatan Shale in the basin center, supporting a predominantly local hydrocarbon sourcing model for the Jingbian area. Significance This study provides crucial geochemical evidence for a local hydrocarbon system within the Jingbian area, resolving previous ambiguities regarding oil sources and assessing the resource potential in the Jingbian Area, Ordos Basin.

Research on mechanical parameter prediction and modeling methods based on statistical regression and prestack inversion—Taking a particular area in the Bonan Depression as an example

Bin WANG, Han XIAO, XueMin NIU, RuiXuan ZHANG, Xing GE

, Available online , doi: 10.12090/j.issn.1006-6616.2025084

Abstract (133) PDF (1153KB)(193)

Abstract:
Abstract: [Objective] In the development of unconventional oil and gas, there exist problems such as complex reservoir structure and unclear rock mechanical properties. During the design of horizontal well trajectories and fracturing schemes, it is necessary to rely on rock mechanical models for segment and cluster division and design, thereby increasing the modification volume, reducing the risk of set changes, and achieving efficient development of unconventional oil and gas. The rock mechanics model can simultaneously reflect the continuous changes of mechanical parameters in the longitudinal and transverse directions with high resolution in the target area of the horizontal well trajectory. Therefore, in response to the model requirements, this paper provides a mechanical parameter prediction and modeling method based on statistical regression and prestack inversion. [Methods] Basing on the core test data and logging data, the quantitative relationship between elastic parameters and rock mechanical parameters is established and analyzed. Then, three-dimensional prestack inversion is performed using both drilling data and seismic data to obtain precise elastic parameters, including longitudinal wave velocity, density, Poisson's ratio, and Young's modulus. [Results] The application of this method in the tight glutenite reservoirs of the Bonan Sag has yielded significant and practical results. First, a robust quantitative relationship between mechanical and elastic parameters was established. The statistical regression relationship between Young's modulus and Uniaxial Compressive Strength (UCS) demonstrated a strong correlation (e.g., R² > 0.75), validating the feasibility of predicting rock mechanical strength from elastic parameters in this glutenite formation. Statistical analysis confirmed that the mechanical parameters of these highly compacted, low-porosity glutenites are primarily controlled by lithology and gravel content, exhibiting a very weak correlation with burial depth. This justifies the use of a unified predictive model across the entire studied depth interval. Second, a high-resolution 3D mechanical parameter model was constructed. A depth-domain structural model was built using logging data and a smoothed time-depth velocity field. Following attribute extraction, a comprehensive 3D mechanical parameter model for the target block was established. This model effectively overcomes the discreteness and non-continuity inherent in core and logging data, accurately characterizing the continuous lateral and vertical variations of mechanical properties. Third, the results are directed toward engineering application. To fully leverage the high vertical and lateral resolution of the mechanical parameter volume, the calculated seismic attributes were integrated into the 3D geological model based on engineering requirements. This outcome provides an accurate model for fracturing design, enabling precise assessment of the rock mechanical distribution along horizontal well sections, rational design of stage and cluster placement, optimization of pumping parameters, and enhancement of fracture conductivity. Consequently, it significantly increases the stimulated reservoir volume, effectively boosting single-well productivity and recovery rates. [Conclusion] The study leads to the following main conclusions: The integrated methodology of pre-stack inversion and statistical regression is a viable and effective solution for predicting 3D mechanical parameters in tight glutenite reservoirs. This method builds a bridge between petrophysical and seismological parameters, effectively resolving the challenge of poorly constrained rock mechanical properties in complex unconventional reservoirs. The constructed 3D mechanical parameter model provides a more reliable geological basis for optimizing well trajectories and fracturing designs. [Significance] The primary significance of this research lies in providing a reliable and scalable method for 3D rock mechanical parameter prediction and modeling, possessing substantial theoretical innovation and practical application value. It offers a dependable data foundation and a theoretical framework for defining mechanical boundaries and optimizing fracturing designs in heterogeneous tight reservoirs. This approach holds significant potential for improving fracturing efficiency and maximizing production in challenging tight glutenite formations.

MA Zhanrong, LI ZhenHong, LIU JianPing, HU AiPing, LinLin KOU

, Available online , doi: 10.12090/j.issn.1006-6616.2025031

Abstract (96) PDF (3282KB)(200)

Abstract:
[Objective] The dolomite of Ordos basin west margin complex tectonic belt Ordovician Kelimoli Formation as a high quality reservoir for natural gas exploration, its genesis mechanism and the relationship between sedimentary environment and tectonic superimposed transformation, there are still many disputes, which restricts the guidance of oil and gas exploration.[Methods] Based on comprehensive test and analysis including thin-section identification, cathodoluminescence, carbon-oxygen isotope, X-ray diffraction order, geochemical rare earth and trace elements, and strontium isotope, combined with the regional tectonic evolution process, this study explores the genetic mechanism of dolomite.[Results] Cathodoluminescence overall exhibits a relatively weak dark brown coloration with distinct ring bands, and authigenic quartz and saddle-shaped dolomite as hydrothermal minerals are visible, characterized by features of multi-stage recrystallization and burial origin. Carbon and oxygen isotope characteristics indicate that the dolomite has a burial origin. The overall order of the dolomite shows a relatively low degree, and the higher the temperature, the lower the order, suggesting that the dolomite formed in an environment with relatively high temperature and rapid crystallization rate. The rare earth element partitioning pattern is characterized by positive Ce and positive Eu anomalies, indicating that the formation process of dolomite is the result of internal fluid adjustment and redistribution within the diagenetic system under relatively closed, high-temperature, and high-pressure conditions. The lower the Sr content and the higher the Fe and Mn element contents, overall showing the characteristics of multi-stage superimposed modification under deep burial conditions. The strontium isotope values of medium to coarse-grained dolomite are significantly close to the average value of crustal source strontium isotopes, which may have been affected by crustal source strontium carried by synchronous tectonic activities.[Conclusion] Research indicates that dolomite formation is primarily attributed to deep burial, while also undergoing superimposed tectonic fluid modification. The evolution of Ordovician Krimolli Formation dolomite is closely linked to the deep fault system. During the co-deposition period, this fault system controlled the development of high-energy terraces. In the subsequent tectonic activity phase, the deep fault system became a fluid migration channel, facilitating the superimposed modification of dolomite bodies.[Significance] Research results can provide a fundamental support for the efficient exploration of oil and gas resources.

ZHU Shu, ZHANG Quan, WANG Yanbing, LI Jin, LI Renjie, HUANG Yong, LI Benliang, LIU Fucai, YAN Yuping

, Available online , doi: 10.12090/j.issn.1006-6616.2025170

Abstract (169) PDF (2408KB)(225)

Abstract:
The Jiali Fault on the southeastern margin of the Tibetan Plateau is a key boundary structure for the southeastward extrusion of plateau material. Its geometric distribution and activity are crucial for understanding the tectonic evolution of the plateau and assessing regional engineering risks. However, the precise spatial location and Holocene activity of its southeastern segment (Guxiang to Gongrigabu section) have long been controversial due to rugged terrain and thick vegetation cover. Targeting this key contentious segment, this study integrated multiple methods, including high-resolution remote sensing interpretation, field geological and geomorphological surveys, drilling and trenching exposure, and magnetotelluric sounding, to systematically investigate the fault's spatial distribution, structural characteristics, and activity. The results indicate that the southern branch of the Jiali Fault Zone continuously extends along a line from south of Guxiang, through Gionala, Jinzhunongba, to Langqiunongba. Tectonic geomorphic evidence such as fault troughs, sag ponds, pressure ridges, bedrock fault mirrors, and horizontal slickensides were identified via remote sensing and field investigations. Magnetotelluric data revealed clear low-resistivity fracture zones, and drilling core samples exposed significant fault-related rocks. This evidence collectively confirms the existence and distribution of the fault within this segment. Combined with regional paleoseismic studies, it is concluded that this segment has the potential for Holocene activity. The research further systematically analyzed the deep engineering effects potentially triggered by fault activity, including surrounding rock deterioration, cosismic offset, high in-situ stress, seismic motion amplification, water inrush and mud gushing, geothermal anomalies, and secondary disasters at tunnel portals. The research results not only provide key geological constraints for improving the tectonic model of the southeastern Tibetan Plateau but also offer indispensable scientific basis for the planning, seismic design, and risk prevention and control of major projects (such as the Sichuan-Tibet Railway) traversing the fault zone.

Wu Chengjie^1,2，Zeng Huaien^1,2,3，Chen Jun⁴，FengYu⁵ , Li xi^2,3，WeiPengcheng^2,3,Yan Baorui^1,2

chengjie wu, HuaiEn CENG, jun chen, Yu FENG, xi li, pengcheng wei, baorui yan

, Available online , doi: 10.12090/j.issn.1006-6616.2025077

Abstract (294) PDF (1363KB)(199)

Abstract:
Accurate prediction of landslide displacement is a crucial component of landslide early warning systems. This paper proposes a landslide displacement prediction model based on Gaussian Process Regression (GPR) combined with diverse time-series feature engineering, achieving high-precision displacement prediction and uncertainty quantification. TAKING THE BAZIMEN LANDSLIDE AS AN EXAMPLE, During the feature engineering phase, displacement lag features, rolling mean of rainfall, rolling variance of reservoir water level, and displacement change rate are constructed. Additionally, temporal decomposition features including monthly and quarterly components are extracted. SUBSEQUENTLY, EMPLOY THREE-FOLD TIME SERIES CROSS-VALIDATION, ALONG WITH A GRID SEARCH SCHEME, TO OPTIMIZE HYPERPARAMETERS IN CONJUNCTION WITH THE TIME SERIES CROSS-VALIDATION STRATEGY, THEREBY MITIGATING THE RISK OF OVERFITTING IN THE SMALL-SAMPLE SCENARIO. The results demonstrate that after incorporating multi-source temporal features, the prediction coefficients of determination (R²) for monitoring points ZG110 and ZG111 at the Bazimen Landslide significantly increase to above 0.99. Metrics such as MAE, RMSE, and MAPE are substantially reduced, indicating a significant improvement in prediction accuracy. This study integrates probabilistic modeling with feature interpretability analysis. The proposed method achieves high-precision landslide displacement prediction in small-sample environments while simultaneously quantifying prediction uncertainty. It provides effective decision support for landslide risk early warning and engineering safety assessment.

Tectonic stress field characteristics in Wushi , Xinjiang and the stress impact of the Wushi M7.1 earthquake

ZeYao SONG, YongGe WAN, PeiYuan GU, MingYue ZHOU

, Available online , doi: 10.12090/j.issn.1006-6616.2025085

Abstract (308) PDF (2767KB)(224)

Abstract:
[Objective] The Wushi region in Xinjiang is located at the intersection of multiple tectonic units, making it a key area for stress concentration and release. Although previous studies have revealed some characteristics of the tectonic stress field in this region, there is still a lack of in-depth and systematic analysis regarding the potential impact of the 23 January 2024 Wushi M 7.1 earthquake on the regional stress field. Therefore, adopt more systematic focal mechanism data to conduct a detailed analysis of the regional tectonic stress field characteristics and to explore the influence of the Wushi M 7.1 earthquake on the regional stress field. The aim is to provide more comprehensive scientific references for understanding the regional seismogenic environment and predicting future seismic activity.[Methods] Using the damped stress tensor inversion method and incorporating data from multiple institutions, we analyzed the stress field in different subregions of the study area and compared the changes in the tectonic stress field before and after the earthquake.[Results] The results of the stress field inversion show that, except for the area near the Jiashi seismic group, the R value is greater than 0.5, and the azimuth of the maximum principal compressive stress in the Wushi region gradually rotates from approximately NNW in the south to near N—S in the north, the azimuth is from 168.75° to 183.45°, and plunge angle is from 6.85° to 19.58°, it is in a compressive stress state. The Jiashi seismic area cluster shows a strike-slip feature of NNE—SSW compression and NWW—SEE extension.The northern area of the Jiashi seismic shows a thrust stress state, while the southern area presents a strike-slip stress state. By comparing and analyzing the regional stress field changes before and after the Wushi earthquake, it is found that the optimal principal compressive stress direction before the earthquake was N—S direction, and deviated by 12.53° in azimuth after the earthquake, with a spatial rotation angle of 15.06°. This indicates that this earthquake had a relatively small impact on the stress field of this area, which meaning that the stress field did not undergo significant changes after the earthquake, and still remains in the compressive stress system. [Conclusion] The tectonic stress field in the Wushi region is subject to N—S compression from the collision of the Indian plate with the Eurasian plate on the western margin of the Tibetan Plateau to form a strong near-north-south horizontal compression, and the stress from the plate collision is transmitted to the northeast to the Tian Shan orogenic belt, which leads to the shortening of the crust and retrograde thrusting between the Tarim Basin and the Tian Shan. The Wushi M 7.1 earthquake had a relatively minor impact on the regional stress field. The stress system of the entire area is still controlled by deep tectonic activities. The overall stress field is consistent, but the seismic cluster in northern Jiashi is located at the junction of the northern margin of the Tarim Plate and the Tianshan Mountains, presenting a thrust stress mechanism. This area is the plate tectonic transition boundary between the Tarim Basin and the Tianshan orogenic belt.[Significance] By analyzing the characteristics of the tectonic stress field in the Wushi region of Xinjiang and the impact of the Wushi M 7.1 earthquake on the regional stress field, the characteristics of the stress field and the effect of earthquakes on the regional stress field. This contributes to a deeper understanding of the tectonic relationship between the Tianshan orogenic belt and the Tarim Basin. In addition, the northern part of the Jiashi seismic exhibits a thrust stress mechanism, which is inferred to represent a tectonic transition boundary between the Tarim Basin and the Tianshan orogenic belt. This finding holds significant implications for regional tectonic segmentation and seismic hazard assessment.

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