Earthquake Engineering

• Early-warning algorithm for imminent sliding of unstable layered-soil slopes under bidirectional seismic action

  WANG Xu, NI Hongjiang

  2026,48(4):751-760, DOI: 10.20000/j.1000-0844.20241225001

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  Abstract:

  Earthquakes cause not only horizontal displacements and shear forces but also vertical vibrations on the ground surface. Accordingly， this study proposes an early-warning algorithm for the imminent sliding of unstable layered soil slopes under bidirectional seismic loading. Based on grey relational analysis， early warning indicators are identified， and multiple regression analysis is conducted under bidirectional seismic loading conditions. The tangent angle is calculated from the predicted displacement； when it exceeds a preset threshold， the slope is considered to have entered the imminent sliding deformation stage. The results show that slope stability gradually decreases with increasing moisture content. Under three different bidirectional seismic loading conditions， slope displacement increases over time， initially slowly and then at an accelerating rate. The maximum error at the warning point is 0.7 m， which meets the accuracy requirements for early warning of unstable layered soil slopes. These findings demonstrate that the proposed algorithm achieves good predictive performance， high warning accuracy， and strong monitoring capability.

• Detection technology and application for deep-buried river-crossing pipelines based on hammer-drilled preborehole vertical profiling

  XU Tao, YUAN Zhongming, PENG Gongxun, SHEN Xuzhang

  2026,48(4):761-768, DOI: 10.20000/j.1000-0844.20240118003

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  Abstract:

  River-crossing pipelines constructed by trenchless methods are deeply buried with weak signals， posing challenges for surface-water detection. In this practical research， a hammerdrilled pre‐borehole approach was employed to strategically arrange detection points without compromising pipeline structural integrity. Electromagnetic vertical profiling measurements and subsequent data fitting successfully acquired the precise spatial coordinates of target pipelines. When applied to a power pipeline beneath the Pearl River where surface signals were undetectable， this method achieved the highprecision localization of ultradeep pipelines （＞24 m burial depth）. The detection principle， implementation framework， and operational protocols established herein provide a reference for the detection of deep-buried river-crossing pipelines in navigable waterways.

• Seismic adaptability analysis of graded crushed stone foundations for seismic category Ⅰ underground galleries

  YIN Xunqiang, CHEN Xu, YANG Weilong, ZHAO Min

  2026,48(4):769-775, DOI: 10.20000/j.1000-0844.20241013002

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  Because nuclear waste liquid transport and discharge galleries are classified as seismic category Ⅰ items， seismic adaptability analysis is required when graded crushed stone is used for soft soil foundation treatment of these galleries. Considering the foundation treatment of a waste liquid discharge gallery at a domestic nuclear power plant as the background， a viscous artificial boundary considering near-field heterogeneity is adopted to dissipate scattered wave energy and achieve seismic motion input. An equivalent linear method is employed to simulate the nonlinear dynamic characteristics of graded crushed stone material， and Goodman elements are introduced to account for the contact effect between the soil and gallery structure， thereby establishing a dynamic interaction analysis model for the underground gallery and graded crushed stone foundation. On this basis， seismic adaptability analysis of the underground gallery foundation is performed， and various indicators， such as structural acceleration response spectrum， internal forces， inter-story drift ratio， and relative deformation of joints， are comprehensively evaluated. The results indicate that the graded crushed stone foundation exhibits good seismic reliability and engineering practicality. The findings of this study can provide a technical reference for the engineering design of seismic category Ⅰ underground galleries.

• Comparative study on the lateral loading response of monopile foundations in unsaturated and saturated sands

  LI Shuzhao, ZHANG Hui, SUN Guodong, CUI Jianbin, TIAN Gengping, GUO Peng, ZHANG Youhu

  2026,48(4):776-785, DOI: 10.20000/j.1000-0844.20240830001

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  Abstract:

  Large-diameter monopiles are prevalent foundations for offshore wind turbines. Most experimental studies on the lateral bearing behavior of monopile foundations are currently conducted in unsaturated sand， whereas the seabed soil is saturated. Therefore， it is necessary to investigate whether the response of monopile foundations in unsaturated sand can reflect their true characteristics in saturated sand. To this end， two series of comparative lateral loading model tests on monopile foundations were conducted in unsaturated and saturated sands， with each series including one monotonic loading and two cyclic loading conditions. The lateral load was applied to the extended upper section through a servo motor and transferred to the monopile foundations. The test results indicate that the monotonic lateral response of monopile foundations in unsaturated and saturated sands is relatively similar， but considerable differences are observed under cyclic loading conditions. In unsaturated sand， the presence of matric suction causes the soil around the pile to gradually form gaps under cyclic loading conditions， resulting in a pronounced degradation of pile-soil stiffness. Meanwhile， in saturated sand， soil fissure development is not pronounced， and the cyclic degradation effect of pile-soil stiffness is insignificant. The findings reveal the causes of the cyclic degradation effect in sand， which can reduce the design cost of offshore wind turbine foundations in saturated sand and hold paramount implications for practical engineering.

• Rapid prediction method for local site amplification effects based on integrated batch numerical simulation and machine learning

  YANG Xiaomei, CHEN Yuantao, WU Sheng, CHEN Xin, WANG Yushi

  2026,48(4):786-799, DOI: 10.20000/j.1000-0844.20250423002

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  Abstract:

  Traditional numerical simulation methods based on single physical models generally suffer from limitations such as computational complexity and high resource consumption when analyzing complex site effects. To address these issues， this study takes a typical inverted trapezoidal sedimentary basin as the research object and integrates batch numerical simulations with machine learning techniques to develop an efficient prediction framework for local site amplification effects. First，3 312 standard finite element models of the sedimentary basin were constructed. Second， a large-scale database containing 11 types of input parameters and spectral responses （totaling 977 010 data entries） was built through systematic seismic response analysis. Third， three types of machine learning algorithms—convolutional neural networks， long short-term memory networks， and decision tree regression—were employed to train intelligent prediction models of surface amplification effects. All data processing was automated using self-developed Python programs， with the dataset split into training and testing sets in an 8∶2 ratio to ensure model generalizability. Empirical analysis based on a typical profile of the Mygdonian Basin in Greece demonstrated that the proposed model rapidly and accurately assessed local site effects. Compared with traditional numerical simulation methods， this approach established direct mapping between inputs and outputs through machine learning algorithms， significantly reducing computational complexity. While maintaining engineering accuracy， the approach markedly improved computational efficiency， providing a reliable technical foundation for the rapid assessment of seismic responses at practical engineering sites.

• Story drift ratio limit of shear wall structures under horizontal seismic action

  HAO Huimin, FANG Xinxin, CHEN Yuexiang, ZHOU Weiliang

  2026,48(4):800-809, DOI: 10.20000/j.1000-0844.20250410001

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  Abstract:

  Employing the ETABS software， this study comprehensively investigates the seismic performance of shear wall structures under horizontal earthquake action. ETABS software incorporates various nonlinear factors to calculate the story drift ratio of the structures， thereby demonstrating an improved analysis method for their story drift ratio limits under horizontal seismic action. Adopting a regional shear wall structure as a case study， four sets of natural seismic waves and one set of artificial waves are generated. The results show that the maximum story drift ratio of the shear wall structure is approximately 0.000 8 rad under different seismic-wave actions， remaining within the 1/1 000 limit. This indicates that the shear wall structure maintains good integrity and stability under horizontal seismic action， effectively resisting a certain degree of seismic damage. By analyzing the story drift reserve ratio， the drift limit of the wall is relaxed to 1/500. Under the artificial horizontal seismic wave action， the maximum damage factor for the wall structure is approximately 0.45， indicating minor damage and compliance with safety requirements. Therefore， the feasibility of relaxing the story drift ratio limit to 1/500 is demonstrated. Classifying the time-frequency data of seismic waves using the proposed method enables accurate distinction between high-and low-frequency components. Furthermore， the contribution rates of each seismic wave to the story drift ratio limit of the shear wall structure all exceed 93%， reaching a maximum of 98.55%. These results demonstrate the high accuracy of the proposed method in analyzing the story drift ratio limits of shear wall structures.

• Seismic performance of assembled single-coupling beam structures with I-shaped mild steel dampers

  ZHENG Bo, LI Weibin, LIU Ya, YU Tong, AI Yayi, CHEN Yan, ZHOU Chengzong

  2026,48(4):810-819, DOI: 10.20000/j.1000-0844.20241126001

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  Abstract:

  Herein， we propose a design scheme to address the issues related to the poor seismic performance and low construction efficiency of coupling beam connections in prefabricated concrete structures. The proposed scheme employs metal dampers for the connection of precast shear walls and coupling beams. Using the ABAQUS finite element software， we investigated the mechanical performance of 24 structures with assembled single-coupling beams equipped with I-shaped mild steel dampers under low-cycle reciprocating loading. Specifically， we analyzed the effects of different parameters on the load-displacement （P-Δ） skeleton curves， stiffness degradation curves， and strength degradation curves of the assembled single-coupling beam structures. The results showed that the grout strength and web thickness of an I-shaped mild steel damper slightly affect the P-Δ skeleton curves； the variation in bearing capacity does not exceed 10%. In contrast， the shear wall thickness and web height of the damper significantly affect the P-Δ skeleton curves； the bearing capacity variations exceed 40% and 15%， respectively. The web height and thickness of the mild steel damper and the grout strength considerably affect the initial stiffness of the coupling beam； however， their effect on stiffness degradation is minimal. The strength degradation curves generally exhibit an initial increase， followed by a gradual decrease. The proposed design scheme is applicable to engineering applications and meets the multifunctional coordination requirements of load-bearing， energy dissipation， and assembly of the structure. The design results can be used as a reference for the engineering application of prefabricated frame-shear wall structures.

• Prediction of residual deformation in frame structures based on MLP-RF

  LI Jing, ZHAI Shixin, ZHANG Zhaojin, CHEN Jianyun

  2026,48(4):820-827, DOI: 10.20000/j.1000-0844.20240826001

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  Abstract:

  Residual deformation is an optimal parameter for evaluating structural damage after an earthquake. To investigate the relationship between ground motion parameters and structural residual deformation， this study focuses on frame structures. A large dataset of class-Ⅰ ground motions recorded on-site was selected， and ground motion parameters were calculated and then applied to finite element models established in ABAQUS for nonlinear time-history analysis， from which the converged structural residual deformations were extracted. By employing machine learning theory， an ensemble multilayer perceptron （MLP）-random forest （RF） learning model （MLP-RF） was developed. The processed ground motion parameters and structural characteristics were used as inputs，with structural residual deformation as the output. MLP-RF was trained to predict the overall structural residual deformation and interstory residual drift. Based on a comparison of prediction performance， the ground motion parameters exerting the greatest influence on residual deformation were identified. The results show that the prediction accuracy of MLP-RF is higher than that of the stand‐alone MLP and RF models. The Newmark sliding displacement， Riddell displacement index， and mean acceleration response spectrum are the most influential ground motion parameters for residual deformation. The findings of this study provide invaluable insights into the underlying mechanism governing the relationship between residual deformation and ground motion parameters.

• Mixed-mode Ⅰ-Ⅱ fracture characteristics of ASCB compacted clay samples considering the effect of fulcrum friction

  LI Yuqiao, LI Xudong, LIU Zhong, CHEN Fang, MA Luhan, LI Xiaolei, JIANG Xiulan

  2026,48(4):828-835, DOI: 10.20000/j.1000-0844.20241026002

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  Abstract:

  To investigate the influence of support friction on the mixed-mode Ⅰ-Ⅱ fracture characteristics of compacted clay using asymmetric semi-circular bending （ASCB） specimens， the ABAQUS finite element software was employed to study the effects of dimensionless crack length （a/R）， support span ratio （S₂/R）， and support friction coefficient （f） on the dimensionless stress intensity factors Y_Ⅰ and Y_Ⅱ and the dimensionless T-stress （T*）. In addition， three-point bending tests were conducted on compacted clay to examine the effect of support friction on fracture toughness. The results indicate that under non-pure mode-Ⅱ loading，Y_Ⅰ ，Y_Ⅱ ， and T* exhibit a certain degree of reduction with increasing f. Under pure mode-Ⅱ loading， increased f induces stress concentration， altering the stress state at the crack tip and resulting in a transition from pure mode-Ⅱ to mixed-mode Ⅰ-Ⅱ loading. The three-point bending tests revealed that when support friction is considered， the use of traditional stress intensity factors results in an overestimation of fracture toughness values. Therefore， when employing fixed supports in three-point bending fracture tests on compacted clay， fracture toughness must be calculated based on dimensionless parameters corrected for friction.

• Seismic dynamic response of bridges in the permafrost region of the Qinghai-Xizang Railway under near-fault ground motions

  XIAO Ruixin, YAN Wujian, KANG Lin, GUO Dingnan, WANG Yali

  2026,48(4):836-847, DOI: 10.20000/j.1000-0844.20250422002

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  Abstract:

  In permafrost regions， the dynamic characteristics of railway bridges subjected to near-fault seismic actions exhibit marked variations between the cold and warm seasons. A railway bridge in the permafrost region of the Golmud—Lhasa section of the Qinghai-Xizang Railway was considered the research object to study these characteristics. By establishing a three-dimensional finite element model of the bridge pile-permafrost-structure system and using the near-field bedrock seismic waves from the Jishishan earthquake as the ground motion input， the dynamic response characteristics of the bridge under frozen and unfrozen states of the active layer were compared. The research results indicate the following.（1）Under near-fault seismic action， the unfrozen active layer substantially amplifies the structural dynamic response， with the peak bridge superstructure acceleration increasing by 58% compared with the frozen state.（2）When the active permafrost layer is unfrozen， soil stiffness degradation reduces the constraining capacity， further amplifying the displacement response， with the maximum displacement occurring at simply supported beams. （3）Acceleration and displacement responses show a clear amplification trend as the soil depth decreases， with particularly pronounced dynamic amplification effects in the active layer and superstructure. This study clarifies the differences in the dynamic characteristics of railway bridges under different states of the active layer in permafrost regions， providing theoretical support for the seismic design of bridges in such regions and offering invaluable insights for enhancing railway engineering seismic resilience and operational safety.

• Horizontal dynamic response of end-bearing friction piles subjected to vertical load

  MU Zhengxiang, DING Nansheng, SONG Chunyu, GAO Xuejun, LI Yingcong

  2026,48(4):848-856, DOI: 10.20000/j.1000-0844.20240917001

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  To investigate the effect of end-bearing ratio （EBR） on the horizontal dynamic response of piles， an analytical method for end-bearing friction piles considering the second-order effect of vertical load is proposed. Based on continuum mechanics theory， a simplified solution for the pile axial force function is first derived using the Boussinesq solution. Next， an analytical solution for the horizontal dynamic response of piles， accounting for EBR， is obtained using the Novak thin-layer element and Adomian decomposition methods. The proposed method is validated by comparing the calculated degenerate solution results of no vertical load with existing literature data. In addition， its applicability is verified by comparing calculated results with experimental findings. Further analysis explores the effects of vertical load and EBR on the horizontal dynamic response of piles. The results show that the horizontal dynamic response undergoes considerable redistribution under vertical load. Further， an increase in EBR results in a downward shift of the neutral displacement point， thereby enhancing pile stability. This analytical method provides a theoretical basis for a more comprehensive understanding of the impact of EBR on the horizontal dynamic response of piles and elucidates the substantial influence of vertical load on this response.

• Seismic subsidence characteristics of loess in different engineering geological zones

  WU Songhan, ZHONG Xiumei, CHEN Peng, LI Chen, WANG Jun, WANG Qian

  2026,48(4):857-865, DOI: 10.20000/j.1000-0844.20250815001

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  Abstract:

  Loess seismic subsidence is a settlement phenomenon caused by pore compression and structural collapse under dynamic loading. To investigate the seismic subsidence behavior and controlling factors of loess in different engineering geological zones， microstructural analysis and seismic subsidence tests were conducted on loess samples from the Longxi， Guanzhong—Tianshui， and Long‐dong regions. Subsequently， regional variations in microstructural characteristics were analyzed， and the relationships between physical parameters （dry density and moisture content） and seismic subsidence were examined. The results indicated significant differences among the three regions in microstructural and seismic subsidence behavior， with seismic subsidence closely linked to physical properties. As dynamic stress increases， loess seismic subsidence becomes increasingly pronounced. The study also found that the effects of moisture content and dry density on susceptibility to subsidence vary by region. Longxi loess exhibits the highest sensitivity， whereas Longdong loess shows the greatest stability. Microstructural analysis reveals that large overhead pores and point contacts in Longxi loess are key factors contributing to its high susceptibility to subsidence. The greater resistance of Guanzhong—Tianshui loess to seismic subsidence is attributed to more face contacts and coagulated structures， whereas transitional features in Longdong loess result in moderate susceptibility. This study offers valuable insights for the prevention and mitigation of seismic subsidence hazards in loess regions.

• Seismic disaster risk analysis of the Maijishan Grottoes

  ZHAO Cheng, SHI Yucheng, LU Yuxia, LIU Kun

  2026,48(4):866-876, DOI: 10.20000/j.1000-0844.20260212001

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  Grotto temples are important cultural heritage sites in China and are mostly distributed in seismically active regions， making the study of earthquake disaster risk assessment and mitigation of great importance. To address the problems of strong subjectivity and limited applicability of existing methods， this study proposes a probabilistic seismic risk analysis framework that integrates seismic hazard and structural vulnerability， and validates it using the Maijishan Grottoes as a case study. The framework first quantifies site ground motion parameters through probabilistic seismic hazard analysis to obtain the exceedance probability of ground motion intensity. Then， in the seismic capacity analysis， vulnerability curves for statues （based on a lognormal distribution） and a slope stability model （using the limit equilibrium method and reliability theory） are constructed， and reliability indices and failure probabilities are introduced to characterize the structural dynamic response. Finally， the risk values under different ground motion intensities are calculated using an integration method. The results show that the annual exceedance probabilities for various damage states of the statues and for slope instability at the Maijishan Grottoes increase significantly with increasing ground motion intensity， indicating an extremely high overall earthquake disaster risk. The proposed method is both objective and universally applicable， providing a theoretical basis for earthquake risk quantification and disaster prevention decisionmaking for grotto temples and other geotechnical heritage sites.

Earthquake Research

• Experimental study on geoelectric field observation using a cross-shaped array

  NIU Yanping, YE Qing, ZHANG Yuanfu, HU Yuan, CHEN Jianjun, LIU Jun, CHEN Junying, SHI Wenbing

  2026,48(4):877-888, DOI: 10.20000/j.1000-0844.20250917001

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  To address the limitations of traditional geoelectric field observation devices， which typically utilize a single-quadrant electrode layout， this study propose a “cross-shaped” observation array with multiple azimuths and electrode distances and conducts a field test in Gaotai County， Gansu Province. Comprehensive processing and analysis of the experimental data collected from June 2023 to June 2024 indicate that this new observation array achieves full 360° coverage of geoelectric field observations across all four quadrants. Its primary advantage over traditional devices lies in its ability to accurately capture the planar omnidirectional potential distribution and effectively separate the natural electric field from the telluric electric field. An in-depth examination of the spatiotemporal variation characteristics of the geoelectric field in the test area reveals a significant spatial distribution pattern of the geoelectric field vectors， predominantly oriented between 15° and 30° south by east， with a background intensity of approximately 60 mV/km. Local variations reflect the lateral inhomogeneity of the subsurface medium. The natural electric field shows a distinct annual variation， with higher values in summer and lower values in winter. On geomagnetically quiet days， the telluric electric field displays a clear diurnal variation pattern characterized by two peaks and one trough， whereas on geomagnetically disturbed days， it effectively records electromagnetic disturbances linked to solar activity. This study provides technical support for vector characterization， component separation， and signal identification of the geoelectric field， reveals the spatiotemporal variation patterns in small-scale environments， and offers a reference for the development of modern unattended observation networks.

• Medium-and long-term seismic risk assessment of the BeijingTianjin-Hebei and Bohai area based on fault activity analysis

  LIN Yi, CAO Jingquan, YAN Chengguo, ZHANG Wenpeng, CAO Ying, ZHANG Andong, YAO Xinqiang, LIU Hongyan, JI Jing, CONG Pengli

  2026,48(4):889-898, DOI: 10.20000/j.1000-0844.20240123002

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  Abstract:

  Accurate and reliable regional medium-and long-term seismic risk assessments are crucial for guiding earthquake disaster prevention efforts. To develop a scientific and efficient evaluation method and obtain precise assessment results， the Beijing-Tianjin-Hebei and Bohai area—known for its active faults and frequent seismic activity—was selected as the study area. Statistical and gridbased analysis methods were employed to assess medium-and long-term seismic risk based on fault activity， considering factors such as the faults’ tectonic setting， activity history， activity characteristics， strike， and dip angle. The results indicate that areas with relatively high seismic risk in the Beijing-Tianjin-Hebei and Bohai region are mainly concentrated in the Zhangjiakou—Bohai fault zone， the northern part of the Shanxi graben system， and the middle part of the Tan-Lu fault zone. Additionally， NE-trending faults exhibit a higher likelihood of seismic activity and therefore demand continuous attention. The innovative ideas and methods for seismic risk assessment introduced in this study could significantly enhance the accurate assessment of seismic risk and support the science-based development of earthquake prevention and disaster mitigation strategies.

• Measured dynamic response characteristics of the Liujiaxia Reservoir Dam during the Jishishan M_S6.2 earthquake

  WANG Wencai, SHI Wenbing, JIN Jie, XIE Junju, ZHANG He, ZHANG Rong, GOU Miaomiao, ZHANG Jiajing

  2026,48(4):899-909, DOI: 10.20000/j.1000-0844.20250821003

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  Abstract:

  On December 18，2023， an M_S6.2 earthquake struck Jishishan County， Linxia Hui Autonomous Prefecture， Gansu Province. The strong motion observation array at the Liujiaxia Reservoir Dam， located approximately 50 km from the epicenter， recorded a complete set of seismic data. Conventional processing was performed on the three-component acceleration records obtained from 13 observation points of the dam array. The horizontal-to-vertical spectral ratio （HVSR） and horizontalto-vertical instantaneous polarization spectral ratio methods were used to estimate the natural frequency of the dam and to analyze the directional characteristics of ground motion effects. The results indicate that the recorded peak ground acceleration at the dam’s structural array ranged from 24.1 cm/s2 to 330.0 cm/s2， peak ground velocity from 0.55 cm/s to 4.75 cm/s， and peak ground displacement from 0.12 cm to 0.22 cm， with instrumental intensities between 4.8 and 6.9. The HVSR curves for the foundation points were relatively flat and showed no distinct predominant frequency， whereas the predominant frequency for points on the dam body ranged from 4.90 Hz to 5.20 Hz. The ground motion amplitude in the east-west direction was generally greater than that in the north-south and updown directions at the same location， indicating that the cross-river direction was the dominant ground motion direction. Furthermore， the ground motion amplitude at the central point of the same dam elevation was typically greater than that at points on either side. The dam structure exhibited a significant amplification effect on ground motions. Compared to the middle level and the foundation， records from the top level of the dam body showed larger amplitudes.

• Relationship between surface deformation and mining-induced seismicity in mining areas based on InSAR technology

  ZHANG Yusheng, YIN Xinxin, QIU Jiangtao

  2026,48(4):910-917, DOI: 10.20000/j.1000-0844.20241022003

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  This study investigates the correlation between surface deformation and mining-induced seismic activity within a mining area in Gansu Province， China. Using the SBAS-InSAR technique，ascending and descending track synthetic aperture radar data from 2020 to 2024 were processed to derive high-precision surface deformation fields. The spatiotemporal relationship between deformation characteristics and mining-induced seismicity was analyzed using data from the seismic monitoring network. The results demonstrate that surface deformation in the mining area exhibits significant localized and regional characteristics： localized deformation （peak vertical rate：24 cm/a） is concentrated in two rectangular mining zones and correlates directly with mining activities， whereas regional deformation manifests as gradual mountain subsidence. Temporally， three distinct episodes of rapid deformation were observed from 2020 to 2024， each lasting approximately one month， followed by an adjustment period， exhibiting an alternating pattern of rapid and slow deformation. Notably，125 seismic events were recorded between January and May 2024， where three high-energy events exhibited typical characteristics of seismicity induced by mining under extremely thick overburden. These highenergy events temporally corresponded to transition phases from slow to accelerated deformation and were primarily concentrated within zones of accelerated deformation along mining boundaries. These results confirm distinct spatiotemporal evolution patterns of surface deformation closely linked to mining seismicity. They provide a critical scientific basis for the construction of geological hazard earlywarning systems and mining safety management while offering new insights into the coupling mechanism between surface deformation and mining-induced seismicity in mining areas.

• Mechanism of travel-time anomalies observed by active sources before strong earthquakes

  LI Tong, ZHANG Yuansheng, LIU Xuzhou, QIN Manzhong, GUO Xiao, SONG Ting, ZOU Rui

  2026,48(4):918-925, DOI: 10.20000/j.1000-0844.20250126003

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  In this study，“active source” refers to large-volume airgun controllable sources. China has successively established four active source excitation platforms in regions including Yunnan， Xinjiang， and Gansu， through which long-term continuous observation data have been obtained. Monitoring of multiple strong earthquake preparation processes has revealed significant anomalous changes in subsurface medium wave velocity prior to earthquakes， with seismic phase travel times exhibiting a characteristic “V”-shaped variation. To reveal the physical mechanism of this phenomenon， this study employs a rock crack wave velocity model to divide the stress evolution process in rocks into Stage Ⅰ and Stage Ⅱ and investigates the dynamic variation patterns of rock compressibility factor， fragmentation degree factor， wave velocity， stress， and crack development in these two stages. Using the mathematical formulas of this model， the actual variation trends of medium wave velocity and seismic phase travel time in both stages were calculated. The calculation results show that the theoretical outcomes are not only highly consistent with rock mechanics theory and experimental data but also align with the “V”-shaped travel-time variation characteristics observed by active sources. This research （i） provides theoretical support for the quantitative interpretation of precursory wave velocity anomalies before strong earthquakes and （ii） enhances the understanding of the mechanisms behind subsurface medium changes prior to earthquakes， thus holding significant scientific importance for mediumto short-term earthquake prediction.

• Spital characteristics and tectonic implications of geomorphic indices in the western piedmont of Zhuozishan

  GUAN Yehao, LIANG Kuan, LEI Xuanyue, MA Baoqi

  2026,48(4):926-939, DOI: 10.20000/j.1000-0844.20250106002

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  The Wuhai Basin is located along the northwestern edge of the Ordos Block， with its eastern boundary marked by the Zhuozishan West Piedmont fault （ZWPF）， a fault active during the Holocene. As urban expansion increasingly approaches this fault zone， gaining a detailed understanding of ZWPF activity has become increasingly important. Using 12.5 m resolution digital elevation model data， this study extracted and analyzed geomorphic parameters—including the relief degree of land surface， channel steepness index， stream length-gradient index， and hypsometric integral （HI）—on the western flank of Zhuozishan Mountain using ArcGIS and MATLAB. Combined with field geological surveys， the study examined the spatial distribution characteristics of these geomorphic indices and their implications for fault activity. The results show that the ZWPF displays clear segmentation in tectonic activity. The northern segment， divided by the Xinwusu trench， shows relatively weaker tectonic activity， characterized by lower geomorphic index values. In this segment， fault rupture often follows the existing fault plane， creating prominent fault scarps and triangular facets. In contrast， the southern segment shows stronger activity， with higher geomorphic indices， a broader fault zone， and a series of fault stepovers， with the fault located closer to the basin side. Both the northern and southern segments show higher HI values in the tectonic mountains and lower values in the basin areas. Drainage basins in the northern segment reach HI values up to 0.691 in tectonically uplifted zones. The overall HI distribution highlights the significant impact of the ZWPF on vertical crustal movements within the study area.

• Seismic fragility analysis of immersed tunnels under near-fault pulse-like ground motions

  HUANG Junchao, SU Lei, MENG Qingxu, WANG Jianfeng, ZHENG Yewei, CHEN Weiyun, LING Xianzhang

  2026,48(4):940-949, DOI: 10.20000/j.1000-0844.20241231001

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  As critical transportation links connecting coastal urban agglomerations， the seismic design and safety assessment of underwater immersed tunnels are essential. Therefore， this study considered the Hong Kong-Zhuhai-Macao Bridge immersed tunnel （a two-hole and one-duct structure） as the research object. First， a two-dimensional finite element model of the tunnel-soil system was established using the OpenSees open-source numerical platform， the physical and mechanical parameters of soil layers were determined according to the site conditions， and three types of ground motions were selected as seismic inputs. Second， the relative deformation ratio， inter-story drift ratio， and transverse inclination angle of tunnel bores were chosen as damage measures （DMs） to characterize seismic performance； the corresponding ground motion intensity measures （IM） were determined based on a probabilistic seismic demand model. Finally， seismic fragility curves for the immersed tunnel were derived using an incremental dynamic analysis method. The results indicate the following.（1） The peak ground velocity is the optimal IM for the selected DMs.（2） According to the fragility curves， the damage probability for the relative deformation ratio is the highest， whereas those for the inter-story drift ratio and transverse inclination angle are relatively close.（3） The damage severity of the immersed tunnel follows the order of near-fault pulse-like ground motions ＞ near-fault nonpulselike ground motions ＞ far-field ground motions. The numerical modeling approach， analysis methods， and conclusions of this study can provide invaluable references for the seismic performance evaluation and risk analysis of immersed tunnels.

• Regional seismic economic loss prediction model considering soil-structure cluster interaction

  ZHANG Weijie, SU Peiyang, Lü Yang, XIONG Feng

  2026,48(4):950-958, DOI: 10.20000/j.1000-0844.20241107002

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  Abstract:

  In this study， we propose an innovative method for developing a regional seismic economic loss prediction model by integrating regional building characteristic parameters with ground motion intensity measures， enabling rapid generation of large-scale seismic loss data to provide reliable data support for regional seismic risk assessment. The research workflow comprises three core modules： foundational data construction， data augmentation， and model development.（1） For foundational data construction， a seismic damage simulation framework is established based on a simplified multidegree-of-freedom structural model considering soil-structure cluster interaction， achieving highprecision calculation of building component damage and loss by following FEMA P-58.（2） For data augmentation， an improved data augmentation algorithm is proposed to address the bottleneck of insufficient sample data in traditional methods by generating high-fidelity simulated loss data through feature space reconstruction and distribution optimization techniques. （3） In model development， a regional loss prediction model based on Gaussian process regression is established， which effectively characterizes spatial correlation mechanisms of building cluster losses by incorporating feature variables， such as building functional type and spatial distribution. Empirical studies conducted on a university campus demonstrate that， compared with traditional data augmentation methods， the improved algorithm considerably enhances the fidelity of simulated data， and that neglecting interbuilding loss correlations may result in the underestimation of total regional loss predictions. Through the integration of physical-and data-driven approaches， this model effectively resolves prediction biases due to sample insufficiency and neglected correlations in traditional data augmentation methods while maintaining computational efficiency， providing a new technical pathway for urban seismic resilience assessment.

• Interseismic deformation of the northern margin of the West Qinling fault derived from GNSS and InSAR data

  HUANG Shilong, GE Weipeng, ZHANG Bo, PING Zifei, YUAN Naikang

  2026,48(4):959-971, DOI: 10.20000/j.1000-0844.20251027002

  Abstract(90) HTML(0) PDF(24.35 M)( 10) Collect

  Abstract:

  Active tectonics and geodesy currently present inconsistent views on the seismic hazard assessment of the northern margin of the West Qinling fault. The Longxi M_S5.6 earthquake that occurred in September 2025 indicates that this fault zone still has the potential to generate moderate earthquakes. In this context， this study integrates high-precision global navigation satellite system （GNSS） observations and time-series interferometric synthetic aperture radar （InSAR） deformation results from the northeastern Qinghai-Xizang Plateau to analyze the present-day interseismic deformation characteristics and locking state of the fault， and to explore the spatial segmentation of fault activity and its implications for seismic hazard. The results reveal distinct spatial segmentation of presentday crustal deformation along the northern margin of the West Qinling fault： the left-lateral strike-slip rate is 0.5—0.9 mm/a for the Guomatan segment，0.3—0.6 mm/a for the Zhangxian segment，0.6— 0.9 mm/a for the Wushan—Gangu segment， and 0.6—1.0 mm/a for the Tianshui—Baoji segment. The geodetically derived present-day slip rates are generally lower than the Late Quaternary geological slip rates， suggesting that the fault may be in a phase of stress accumulation on a short timescale. Elastic dislocation modeling and strain rate analysis further indicate that the Wushan—Gangu and Tianshui—Baoji segments exhibit relatively low slip rates and larger locking depths. Considering the long elapsed time since the last major earthquake in the region， it is inferred that these segments are likely in a stage of energy accumulation and pose a high potential seismic hazard.

• Influence of mainshock-aftershock sequence directionality on soil slope response

  ZHANG Chengda, ZHANG Jiangwei, CHI Mingjie, LI Xiaojun, ZHU Baoqiang

  2026,48(4):972-982, DOI: 10.20000/j.1000-0844.20240908001

  Abstract(31) HTML(0) PDF(2.91 M)( 3) Collect

  Abstract:

  Directionality is a key feature of seismic ground motion and significantly influences slope response. However， research on the directionality of mainshock-aftershock sequences （MASs） remains limited， and the superposition and coupling mechanisms between the mainshock and aftershock directions are not well understood. To address this issue， this study combines numerical simulation with mathematical analysis to investigate the directional effects of MASs on soil slopes. The superposition and coupling effects of mainshock and aftershock directions are considered， and the response mechanisms under single mainshock directionality and MAS directionality are compared. The results indicate that single-mainshock directionality affects both slope displacement response and acceleration amplification， producing larger responses in the along-slope direction than in the reverseslope direction. Compared with the single-mainshock scenario， the directional effect of MASs is more complex. MASs exert a more pronounced influence on slope displacement， whereas their influence on slope acceleration is comparable to that of a single mainshock. The response magnitude follows the order： MAS along-slope direction ＞ mainshock along-slope direction + aftershock reverse-slope direction ＞ mainshock reverse-slope direction + aftershock along-slope direction ＞ MAS reverseslope direction. In addition， aftershocks produce an incremental damage effect on the slope. These findings reveal the response differences of a double-sided slope under MASs and provide a reference for evaluating the seismic performance of soil slopes under mainshock-aftershock conditions.

• Preliminary study on the structure of the Lenglongling fault based on a dense seismic array and methane gaseous detonation source

  GUAN Xujie, QIN Manzhong, SHEN Xuzhang, LIU Xuzhou, WANG Yahong, SUN Dianfeng, WU Baichen, WEN Shulin

  2026,48(4):983-993, DOI: 10.20000/j.1000-0844.20251212001

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  Abstract:

  To investigate the structure and attenuation properties of the Lenglongling fault， this study deployed a linear dense seismic array consisting of 118 short-period seismometers along the Daogou segment of the Lenglongling fault， which is the seismogenic fault of the January 8，2022， Menyuan M_S6.9 earthquake. New methane gaseous detonation sources were excited at the northern， middle， and southern sections of the array， respectively. The results show that the dominant frequency band of the methane gaseous detonation signals is 5 to 50 Hz， with an effective propagation distance of up to 7 km. Significant travel-time delays were recorded at stations near the rupture； these delays indicate a low-velocity zone approximately 400 m wide， the location of which is consistent with the surface rupture of the Menyuan M_S6.9 earthquake. The maximum P-wave travel-time delay caused by this fracture zone is about 85 ms， and the delay on the north side is significantly higher than that on the south side， indicating asymmetry in the velocity structure across the fault， which is consistent with the geological background of exposed bedrock on the south side and unconsolidated sediments on the north side. Normalized spectral analysis shows that after the wavefield passes through the fracture zone， the dominant frequency band becomes lower and narrower， and its high-frequency components exhibit more significant attenuation when propagating in the low-velocity fracture zone. This study preliminarily constrains the heterogeneity and medium attenuation properties on both sides of the Lenglongling fault zone， validates the effectiveness of the methane gaseous detonation source in active fault detection， and provides a reference for subsequent high-resolution velocity structure imaging.