Table of Content

2025-07-31, Volume 45 Issue 3 Previous Issue   

Deformation Characteristics of the Sagaing Fault in Myanmar Revealed by GPS Observations WANG Yu-fan, MENG Guo-jie, WU Wei-wei 2025 (3):  1-12.  doi: 10.12196/j.issn.1000-3274.2025.03.001 Abstract ( )   PDF(3770KB) ( )   The Sagaing fault, situated within Myanmar, serves as the right-lateral strike-slip boundary between the Burma microplate and the Sunda plate. As a major structure accommodating the oblique convergence between India and Sunda, its kinematic characteristics are critical for seismic potential analysis. This study utilizes dense GPS observations from Myanmar and adjacent regions (1998—2024) to construct a horizontal velocity field referenced to the Sunda Plate through high-precision processing and ITRF framework alignment. Integrated with strain rate inversion via the VISR method, we systematically reveal the deformation characteristics and dynamic mechanisms of the Sagaing fault. The key findings include: ① The fault exhibits dominantly right-lateral strike-slip motion. The western block moves northwestward at 10~40 mm/a, while the eastern block shifts westward at <10 mm/a, forming a prominent velocity gradient zone. A velocity jump of 8~10 mm/a near Mandalay (~22°N) indicates deep fault locking, marking a critical segment for strain accumulation and major earthquake preparation. ② The strain rate analysis demonstrates that the northern segment (>21°N) undergoes shear-compression composite deformation, with a maximum compressive strain rate of -90×10-9 /a, correlating with historical seismic clusters. The central segment (18°N~21°N) hosts localized secondary strain concentration zones (e.g., an elliptical anomaly at 21°N, 97°E), reflecting complex internal strain partitioning. The southern segment (<21°N) exhibits steady strike characteristics, evidenced by dilatational strain rates (-30×10-9 /a~10×10-9 /a) and seismicity, modulated by Andaman Sea expansion. ③ Maximum shear strain rates (>120×10-9 /a) align spatially with historical large earthquakes (e.g., the 2012 Thabeikkyin MW6.8 earthquake and the 2025 Mandalay MS7.9 earthquake), confirming the control of high-strain gradients on seismogenesis. ④ The deformation patterns of the Sagaing Fault reveal the dynamic equilibrium between westward extrusion of the Burma microplate and boundary confinement under oblique Indian-Sunda plate convergence. The spatial correlation between velocity gradient discontinuities in the northern segment and historical seismic gaps establishes critical kinematic constraints for identifying both locked segments and regions of elevated seismic risk. Future research should prioritize quantifying strain accumulation rates within the northern locked segments (particularly the Sagaing and Meiktila segments) while systematically evaluating the seismic potential of secondary fault systems in the central segment.

Comparative Research of the 2016 MS6.4 and 2022 MS6.9 Earthquakes in Menyuan Based on the z-Value and PI Method SONG Cheng, ZHANG Yong-xian, BI Jin-meng, XU Ke, GAO Ye, ZHANG Ming-dong, XIA Cai-yun, TIAN Wei-xi, FENG Mao-ning 2025 (3):  13-30.  doi: 10.12196/j.issn.1000-3274.2025.03.002 Abstract ( )   PDF(4673KB) ( )   In this paper, two earthquakes, Menyuan MS6.4 in 2016 and Menyuan MS6.9 in 2022, were taken as research objects to conduct a comparative study on the change of regional seismic activity characteristics based on the seismic activity rate (z-value) and Pattern Informatics (PI) method. The results show that: ① z-value spatial scanning images obtained with different parameter models reflect the common feature of “abnormal seismic quiescence” in a large area around the epicenters of both earthquakes in the 6 a period before the Menyuan earthquakes. ② At the 1.0°×1.0° grid scale, based on different time window lengths, there are PI hotspots in the epicenter and Moore's adjacent grid of the two earthquakes, which are strong indicative function of the epicenters. Compared with the Menyuan MS6.9 earthquake, the hotspots associated with the 2016 Menyuan MS6.4 earthquake is more effective. ③ The combination of the spatial distribution of z-values and PI hotspots as well as the regional fault can narrow the forecast range of epicenter location of strong earthquakes further. The above study is of reference significance for summary of strong earthquake activity characteristics and the analysis of seismic activity trend at the northeastern margin of the Qinghai-Tibet block.

Lithospheric Layered Anisotropy in the Middle Part of Sichuan-Yunnan Block YANG Yi-wen, GAO Yuan, LI Xin-yi 2025 (3):  31-53.  doi: 10.12196/j.issn.1000-3274.2025.03.003 Abstract ( )   PDF(1891KB) ( )   The Sichuan-Yunnan secondary block is located in the forefront of the lateral extrusion of material from the Qinghai-Xizang Plateau and the contact with the South China primary block. It is strongly influenced by boundary faults of different activity characteristics, resulting in intense tectonic movements and seismic activity. Lijiang-Xiaojinhe fault and Jinpingshan fault (collectively referred to as the generalized Lijiang-Xiaojinhe fault system) within the middle of Sichuan-Yunnan block divide Sichuan-Yunnan block into two sub-blocks: northwestern Sichuan block and central Yunnan block, which exhibit distinct differences in tectonic activity intensity levels. Seismic activity along these faults is intense, and the regional lithospheric structure and deep deformation characteristics are critical scientific issues for understanding the lithospheric deformation and lateral growth mechanisms around the margins of the Qinghai-Xizang Plateau. The widespread existence of seismic anisotropy within the earth's interior is the key to accurately interpreting lithospheric structures and deformation. In this paper, based on the faults distribution, seismic activity, ground deformation, stress distribution and deep structures in the region, the deep deformation distribution with different depths and scales is obtained by comparing the anisotropic characteristics derived from S-wave splitting method for near-field earthquakes and teleseismic SKS series phases, and the anisotropic tomography results from composite waves, surface waves and full waveforms. Through analysis of deformation characteristics in the upper crust, entire crust and the lithosphere (including the middle and lower crust and the upper mantle), this study discusses the layered anisotropy and deformation coupled characteristics in the middle part of Sichuan-Yunnan block. These findings provide scientific references for further research into the evolution mechanisms and deep processes of the Qinghai-Xizang Plateau and its surrounding regions.

Volume Estimation of Loess Landslides Triggered by Strong Historical Earthquakes on the Loess Plateau: A Case Study of the Zhangling Landslide Induced by the 1556 Huaxian Earthquake in Shaanxi Province, Northwest China ZHAO Xin-yu, XU Yue-ren, TIAN Qin-jian, YUAN Rui-min, ZHANG Ji-yan 2025 (3):  54-72.  doi: 10.12196/j.issn.1000-3274.2025.03.004 Abstract ( )   PDF(6517KB) ( )   Accurately estimating the volume of loess landslides triggered by strong historical earthquakes on the Loess Plateau is crucial for a deeper understanding of earthquake-induced disaster mechanisms and the chain effects of seismic hazards. It also serves as an important indicator for quantitatively assessing the role of earthquakes in surface processes. This study focuses on the Zhangling Landslide (ZLLs), located within the epicentral region of the AD 1556 Huaxian M8.5 earthquake in Shaanxi Province. The Zhangling Landslide, a well-documented typical co-seismic landslide in historical records, was previously estimated to have a volume of 1.0×108 m3. In this study, we employed contemporary UAV (Unmanned Aerial Vehicle) surveying technology and obtained a Digital Elevation Model (DEM) with a resolution of 0.2 meters. By integrating these data with Keyhole satellite imagery, we accurately delineated the source, transport, and accumulation zones of ZLLs. Utilizing multiple methods, including the ellipsoid model, surface volume method, and profile estimation, the volume of the ZLLs was determined to be in the range of 6.23×106～11.7×106 m3, which is an order of magnitude smaller than the previously reported estimates. The investigation reveals that the source area of the Zhangling landslide developed within aeolian loess layers on the steep slope of the right bank terrace of the Weihe River, with its volume constrained by both the thickness of aeolian loess deposits and the interface with underlying bedrock strata. Furthermore, this study also compares the estimation results of loess landslide volumes from other recent researches, highlighting that UAV-based assessments are limited by variations in loess deposit thickness and slope erosion, a common issue in regional studies. While landslide interpretation typically focuses on affected areas, volume estimation must fully consider the scale of source areas and their control mechanisms governed by Quaternary loess thickness and bedrock interfaces. This study provides a reliable quantitative basis for evaluating the characteristics of coseismic loess landslides on the Loess Plateau.

Progress on Borehole Strain in Seismic Observation Researches SU Peng, FU Guo-chao, ZHU Xiao-yi, XUE Bing, ZHANG Bing 2025 (3):  73-86.  doi: 10.12196/j.issn.1000-3274.2025.03.005 Abstract ( )   PDF(2194KB) ( )   This paper introduced the domestic and foreign research progress on borehole strain, explored the influencing factors of borehole strain, and provided an introduction and summary of borehole strain data identification, reliability, and analysis methods. The study analyzed the earthquake precursor anomalies, co-seismic responses, and earthquake models based on borehole strain data, finding that current borehole strain observations are insufficient to meet all seismic observation needs, with seismic precursor observations still in need of confirmation and verification. It is recommended to establish a comprehensive subsurface monitoring system and integrating other observation methods to address the shortcomings of borehole strain observations, thereby better understanding the patterns and characteristics of borehole strain for future seismic monitoring reference purposes.

Quantitative Analysis of Disturbance Caused by Metal Pipes in Xiangyun Apparent Resistivity Station HAN Ying, FAN Ye, YU Chen, XIE Tao 2025 (3):  87-100.  doi: 10.12196/j.issn.1000-3274.2025.03.006 Abstract ( )   PDF(4438KB) ( )   From April 30 to August 2022, the apparent resistivity observed along the EW- and NS- arrays at Xiangyun Station exhibited a rapid decline resembling a pre-seismic anomaly. This synchronous drop in the data did not recover afterward, and the amplitude of annual variation increased significantly compared to previous levels. Based on the on-site environmental investigation, it was found that metal pipes for farmland irrigation were laid in the survey area during the period of rapid decline. By integrating electrical sounding data from Xiangyun Station, this study employs the finite element numerical calculation method to analyze the static and dynamic effects of metal pipes on observation data. The analysis results show that the calculated changes in apparent resistivity before and after the installation of metal pipes are consistent with the actual observed variations, indicating that the decrease was caused by interference from the metal pipelines, rather than abnormal changes before the earthquake; when the resistivity of shallow media decreases in summer, the influence of metal pipelines on the observations increases. When the resistivity of shallow media increases in winter, the influence decreases, leading to an increase in the annual variation amplitude of the observation data. The calculated results align with the actual observed variation trend.

Earthquake Spontaneous Rupture Simulation and Its Application Progress in the Qinghai-Xizang Plateau XIONG Hai-cheng, LI Yan-chuan, WANG Zhen-jie, SHAN Xin-jian, ZHANG Guo-hong, QU Chun-yan 2025 (3):  101-120.  doi: 10.12196/j.issn.1000-3274.2025.03.007 Abstract ( )   PDF(786KB) ( )   The Qinghai-Xizang Plateau, characterized by active tectonic movements and frequent seismic activity, serves as a natural laboratory for seismic research. Physics-based spontaneous rupture simulations are crucial in uncovering the dynamics and mechanisms of earthquake rupture. In this study, we review the advancements in spontaneous rupture simulation, focusing on fault modeling and numerical methods. We summarize the influence of factors such as fault geometry, initial stress, frictional criteria, and medium properties on rupture propagation, slip distribution, and final earthquake magnitude. Furthermore, we discuss the challenges faced in dynamic rupture simulations, particularly in constraining stress distribution on fault planes, medium properties, and frictional behavior. Additionally, we review the application of dynamic rupture simulations in reconstructing major earthquake scenarios, predicting seismic hazards, and assessing disaster risks. Looking forward, there is a need to develop dynamic rupture models with extended time scales and spatial coverage, incorporating earthquake cycles and interactions, and combine the kinematic inversion results, such as fault interseismic locking model within the Qinghai-Xizang Plateau. Such models would provide a more reliable scientific basis for construction earthquake rupture scenarios and disaster risk assessment.

Noise Level Analysis of the Lanzhou Array LI Xin-rui, HAO Chun-yue 2025 (3):  121-135.  doi: 10.12196/j.issn.1000-3274.2025.03.008 Abstract ( )   PDF(6823KB) ( )   LZDM is one of the 50 primary stations of the International Monitoring System (IMS), and the capacity to monitor microseismic activity in Lanzhou and its surrounding areas has been significantly enhanced by LZDM. Welch average periodogram method was used to estimate the background noise level of LZDM. The continuous waveform data recorded by nine elements of LZDM during 2018—2022 were systematically processed, and two methods, Power Spectral Density and Power Spectral Probability Density Function, were used to analyze the background noise in different time dimensions. The characteristics of noise in the frequency domain and cyclical variation were analyzed, and the noise sources were surveyed. Finally, suggestions on data processing were put forward considering the actual situation of Lanzhou Array. The research result shows that the power spectral density of long-period noise for nine elements showed significant annual variation with periodicity: It decreased from May to September and increased from September to May of the next year. The power spectral densities of short-period noise for nine elements were relatively high and showed significant diurnal and annual variation. The noise level near 3 Hz reached the peak and could be suppressed by narrowband filtering. Because A0 and B2 were affected by road traffic, the PSD values between 7 and 20 Hz were relatively high for the two elements, which reached -100 dB and -110 dB respectively, and could be suppressed by low-pass filtering or beamforming techniques. There were more instrument malfunctions with B4 compared to the other elements, and its data could be excluded when necessary. The research results of this paper could provide important references for the data processing and operation and maintenance of Lanzhou array.

Study on Quaternary Stratigraphy of the Kaifeng Area, Henan Province ZHANG Zhe, ZHANG Yang, LI Tao, BI Zhi-wei, DONG Wang-gang, SUN Jie, ZHAO Xian-gang 2025 (3):  136-155.  doi: 10.12196/j.issn.1000-3274.2025.03.009 Abstract ( )   PDF(7921KB) ( )   The division of the Quaternary system is of great significance for regional stratigraphic correlation and the study of paleogeographic evolution. Due to the relatively limited research on complete Quaternary strata in Henan Province, this study conducted a drilling project (with a depth of 401.2 m) in Kaifeng, Henan Province. Paleomagnetic, AMS14C, optically stimulated luminescence (OSL), and electron spin resonance (ESR) dating methods were applied. Combined with the characteristics of the borehole lithology and sporopollen assemblages, a comprehensive study was carried out on the Quaternary strata from the Kaifeng BK1 borehole. Paleomagnetic results show that the BK1 borehole core recorded the Brunhes positive polarity chron (Brunhes), the Matuyama negative polarity chron (Matuyama), the Gauss positive polarity chron (Gauss) and Blake polarity subchron corresponding to depths of 0~167.5 m, 167.5~362.5 m, 362.5~401.2 m, and 44.1~46.7 m, respectively. Based on magnetic chronology and dating results, and combined with lithological sedimentation and sporopollen assemblage characteristics, the boundary depths of the Holocene, Upper Pleistocene, Middle Pleistocene, and Lower Pleistocene were determined to be 19.8 m, 50.9 m, 167.5 m and 362.5 m, respectively. By comparing with previous studies and analyzing the sedimentary characteristics of the drill core, the Quaternary paleogeographic evolution of the Kaifeng area was reconstructed. During the Early Pleistocene, ancient lakes developed in the Kaifeng-Puyang area, depositing lacustrine strata, with the western boundary of the lake located in the Xinxiang area. In the Middle Pleistocene, the Yellow River alluvial fan developed, the lake gradually shrank and eventually disappeared, and fluvial sediments developed in the Kaifeng area, with a significant increase in sand body thickness. From the Late Pleistocene to the Holocene, the region remained influenced by the Yellow River alluvial fan, inheriting previous fluvial sedimentary characteristics.

Study on the Relationship between the Distribution of Geomagnetic Daily Ratio Anomaly Current Source and Earthquake in Xinjiang Area, China ZHANG An-he, AISA·Yisimayili 2025 (3):  156-167.  doi: 10.12196/j.issn.1000-3274.2025.03.010 Abstract ( )   PDF(4338KB) ( )   The geomagnetic daily ratio anomaly plays an important role in earthquake prediction in Xinjiang, China, but the spatial relationship between the abnormal current source and the earthquake is not clear. In this paper, nearly 30 geomagnetic daily ratio anomalies and more than 40 subsequent corresponding earthquakes in the middle and western sections of the Tianshan Mountains in Xinjiang since 2015 are used. Based on the Biot-Safar theorem, the relationship between the current source of the geomagnetic daily ratio anomaly in Xinjiang and the earthquake is analyzed. The following conclusions are obtained: ① Compared with the currently used area enclosed by the threshold line as the earthquake prediction area, the area enclosed by the anomalous current line is generally smaller than the threshold line, and the predicted area in the middle section of the Tianshan Mountains is reduced by 64.8%. The anomalous current line can significantly reduce the area of the prediction area. ② From the spatial relationship between earthquakes and abnormal current lines, more than 50% of the epicenters are closer to the abnormal current lines, and the distance between earthquakes and current lines in the middle of Tianshan Mountains is reduced by 57.7% compared with the threshold line. The earthquakes in the western section of the southern Tianshan may be more likely to occur at the end of the abnormal current line and its extension line, while the middle section of the Tianshan does not show a clear dominant seismogenic area. ③ Earthquakes with magnitude above 6 are prone to occur at or near the intersection of multiple daily abnormal current lines. The above results show that the geomagnetic diurnal variation anomaly source current positioning method can effectively reduce the prediction area in Xinjiang, China, and the research is conducive to further improving the existing prediction indicators.

Research on Taylor Polynomial Model Based on FHD Stations in Jiangsu Province SUN Jun-song, WU Ying-yan, LI Hong-yu, WANG Li, YANG Jie, CHEN Hua-yuan 2025 (3):  168-179.  doi: 10.12196/j.issn.1000-3274.2025.03.011 Abstract ( )   PDF(4673KB) ( )   A Taylor polynomial model for Jiangsu region was established using the F, H, and Z components of 11 proton vector magnetometers (FHD). The calculation results of the model were compared with those of the IGRF13 model in the region, as well as the measured values of the proton vector magnetometer (FHD). The comparison results showed that: ① The difference between the measured values of proton vector magnetometer (FHD) stations in Jiangsu region and the IGRF13 model is between -208.27~176.74 nT, which is consistent with the global estimation accuracy of 50~300 nT of the model studied by previous researchers. ② The Taylor polynomial model constructed in Jiangsu region is generally consistent with the IGRF13 model, and the Taylor polynomial model in Jiangsu region can better highlight local geomagnetic features. ③ The accuracy of the Taylor polynomial model in the region is higher than that of the IGRF13 model. Combined with continuous observation data in the region, it can provide useful references for the construction of regional geomagnetic maps.

Spatiotemporal Order Analysis of MS≥7.0 Earthquakes in Tianshan Region, Xinjiang, China HAN Xin-zhuo, WANG Yun 2025 (3):  180-192.  doi: 10.12196/j.issn.1000-3274.2025.03.012 Abstract ( )   PDF(1985KB) ( )   The phenomenon of strong earthquakes occurring in a specific spatiotemporal range following a certain pattern is referred to as seismic spatiotemporal orderliness. In this study, the commensurability method and three-dimensional ordered structure were applied to analyze MS≥7.0 earthquakes in the Tianshan region since 1700. The commensurability equations were derived, and the three-dimensional ordered structure was constructed to enhance the reliability of trend analysis for strong earthquake occurrences. Furthermore, the occurrence trends of strong earthquakes in this region over the next 50 years were predicted. The results indicate that: ① MS≥7.0 earthquakes in the Tianshan region of Xinjiang exhibit significant spatiotemporal orderliness, with a clear commensurability in occurrence times; ② The potential occurrence years for MS≥7.0 earthquakes in this region within the next 50 years are 2026, 2028, and 2056; ③ Future strong earthquakes in the region are likely to migrate eastward.

Study on the Prediction of Seismic Hazard and Seismic Risk Assessment for the Next 10 Years in the Chinese Mainland SHAO Zhi-gang, WANG Wu-xing, LIU Qi, DOU Ai-xia, WANG Xiao-qing, WU Yan-qiang, JI Ling-yun, ZHANG Ling-xin, XU Wei-jin, XU Chong, WANG Peng, WEI Wen-xin, PAN Zheng-yang, LIU Xiao-xia, YIN Xiao-fei, FENG Wei, SUN Ke 2025 (3):  193-218.  doi: 10.12196/j.issn.1000-3274.2025.03.013 Abstract ( )   PDF(9946KB) ( )   This paper elaborates on the specific tasks and research content involved in determining the Key Earthquake Monitoring and Preparedness Zones (ZFP) for the 2021—2030 period. With the fundamental goal of enhancing regional earthquake prevention and disaster mitigation capacity, the core work encompasses conducting research on long-term earthquake forecasting and earthquake disaster prediction, along with systematically analyzing regional seismic risks and potential disaster scenarios. Building on this foundation, the work fully integrates the current status and developmental needs of regional socio-economy to scientifically formulate the technical plan for delineating the boundaries of the ZFP. The objectives are to: Provide disaster prevention policies for governments at all levels to guide effective public participation in earthquake prevention and mitigation efforts; Establish well-defined strategic target areas for the deployment of focused initiatives within the earthquake monitoring system; Systematically develop and promote the implementation of a series of comprehensive countermeasures, aiming to elevate the overall earthquake prevention and disaster mitigation capacity and practical effectiveness of the region. The determination of these Key Zones will serve as a crucial reference for effectively conducting subsequent ZFP-related activities, including decadal updates, five-year rolling adjustments, and annual tracking.