• Online First

    Select All
    Display Type: |
    • Characteristics of the Loess Seismic Subsidence in Qinyin Village, Shiyuan Town, Induced by the Jishishan M6.2 Earthquake

      Online: March 28,2024 DOI: 10.20000/j.1000-0844.20240208002

      Abstract (12) HTML (0) PDF 19.12 M (8) Comment (0) Favorites

      Abstract:The Jishishan M6.2 earthquake occurred on December 18, 2023, induced many loess seismic subsidence disasters. Characteristics of the seismic subsidence disaster are obtained through the field investigation of disaster area in Qinyin Village, Shiyuan Town, Jishishan County. Physical parameters characteristics, microstructure characteristics, and seismic subsidence behaviours of the loess in Qinyin Village were studied based on a series of laboratory tests. In addition, the main causes of seismic subsidence disasters were analysed combined with the field survey results. The results show that the loess in the seismic subsidence area of Qinyin Village is cracked and the cracks are developed. The loess layer is destroyed by anti-dip step-shaped seismic cracking. The maximum settlement is approximately 57 cm. The maximum length of the crack is about 300 m, and the maximum width is about 83 cm. The edges of the loess ridge collapses or slides, and the maximum extension length of the collapse is about 100 m. The loess in the seismic subsidence area is loose, the moisture content is relatively high, the micro-trellis pores are developed, and the particles cementation is weak. Thus, the soil conditions for generating seismic subsidence are met. Besides, the thickness of the loess layer in the seismic subsidence area is relatively large, and the equivalent dynamic stress of the earthquake is greater than the critical dynamic stress to produce seismic subsidence of the loess, and the duration and the predominant period of the ground motion is large, which causes a serious seismic subsidence damage in the site.

    • Analysis on the process and causes of debris flow in Zhongchuan Township induced by 6.2 earthquake in Jishishan in 2023

      Online: March 28,2024 DOI: 10.20000/j.1000-0844.20240113004

      Abstract (10) HTML (0) PDF 58.85 M (8) Comment (0) Favorites

      Abstract:Strong earthquake can easily induce the debris flow process in mountainous areas, but it needs to be supplemented by necessary geomorphological, geological, hydrological or climatic conditions. The 2023 debris flow in Caotan and Jingtian Village, Zhongchuan Township in Minhe County, Qinghai Province, has attracted much attention due to its severe disaster. Based on the comprehensive investigation of debris-flow gully and its surrounding areas of Caotan village, including the survey of geomorphological and quaternary-geological features, outcrop observation, grain-size and grain-shape analysis of debris flow source and deposits as well remote sensing, the disaster process characteristics, influencing factors and future prevention and control are analyzed and discussed. The erosion/accumulation thickness and its spatial distribution characteristics of debris-flow gully show that the source area is mainly concentrated in the tributary source of the right bank on the upper reaches of Caotan Village. The rich fine sand material in the source area and the traditional irrigation method provide favorable conditions for the trigger of the slump under earthquake-induced vibration; the field investigation shows that the source is mainly supplied by a large number of shallow (2~3m) slumps, and is gradually broken and dispersed during the migration process. The existence of the shallow stable water table and the exposure of the spring water provide continuous supply of water source for the material in the source area, and finally form debris flow. The both longitudinal and transverse profiles of the circulation area of gully in the pre-disasters are complex, there exist a local small reservoirs and gully are blocked by human structures, these increase the paroxysmal and destructive capacity of debris flow. The spatial distribution characteristics of residual debris and mud traces show that the debris flow has typical plug flow characteristics and shows great viscosity. The increasing potential energy eventually led to debris-flow breaking through the valley barrier to continue to flow. Erosion and accumulation coexist along the way, reshaping the debris-flow valley. The topography of the accumulation area is further open, leading to the dispersion and accumulation of debris flows. The intrusion of civil architecture into the valley is one of the causes of the disaster. In addition, the severe cold weather and the midnight occurrence of earthquake, as well as the lack of public awareness of the nature of the disaster, also aggravated the severity of the debris flow disaster to a certain extent. In view of the many small and medium-sized basins in the upper reaches of the Yellow River, with similar stratigraphic structure, landform and hydrological conditions, and similar human settlement environment and human-land relationship, this paper proposes to carry out the investigation step by step in combination with the characteristics of this disaster. On this basis, regular inspections and investigations will be carried out for the identified high-risk and hidden dangers to strengthen the prediction and early warning of major disaster risks. At the same time, add publicity and popularization to improve the public"s scientific awareness of earthquake-induced disasters.

    • SIMULATION STUDY OF THE 6.9 MAGNITUDE STRONG GROUND MOTION IN MENYUAN, QINGHAI ON JANUARY 8, 2022

      Online: March 28,2024 DOI: 10.20000/j.1000-0844.20230920001

      Abstract (4) HTML (0) PDF 9.32 M (9) Comment (0) Favorites

      Abstract:In this study, to meet the new requirements of emergency response in the digital age, we developed a method based on the stochastic finite fault modeling. Using the subsurface three-dimensional velocity structure model and vS30 data from the Menyuan region of Qinghai Province, we applied the step by step iterative ray-tracing method, the Green"s function displacement analytical solution of phase spectra and the finite fault method to calculate strong ground motion simulation data with amplification response at the ground surface. Taking the 6.9 magnitude earthquake in Menyuan, Qinghai as an example, we created PGA and intensity distribution simulation maps for the study area. Comparing these simulated results with actual PGA records from monitoring stations and the field intensity survey, we found that the intensity zonation ranges are basically consistent. This process also verified that this method can be utilized for the rapid assessment of future earthquake disasters, thereby providing a reference for the post-disaster emergency rescue.

    • Analysis of seismic response of ultra-high head lock with different water simulation methods under oblique incidence of SV waves

      Online: March 07,2024 DOI: 10.20000/J.1000-0844.20221027001

      Abstract (65) HTML (0) PDF 8.59 M (33) Comment (0) Favorites

      Abstract:Based on the viscous-spring artificial boundary and oblique incident ground motion input method, plane SV waves at different angles is simulated, and the acoustic structure coupling method and additional mass method are used to simulate the water inside the lock chamber respectively. The aim is to investigate the seismic response of the ultra-high head lock chamber in terms of displacement, stress, and plastic damage, and compare the similarities and differences of the calculation results of the two methods. Results reveal that: (1) The seismic response results calculated by the two methods are basically consistent with the incident angle. The maximum tensile damage of the left lock wall appears at 15°, and the maximum tensile damage of the right lock wall appears at 35°. The incident angle of seismic waves has a great influence on the dynamic response of ultra-high head locks. Therefore, the influence of oblique incidence of seismic waves should be considered in the design process. (2) When the incidence angle is larger, the extremum values of relative displacement, the extremum values of principal stress and tensile damage results of the lock walls calculated by the acoustic structure coupling method are relatively larger, which is safer for the lock design. (3) Two calculation methods are recommended for cross-referencing and calibration, and the biased safety result is recommended for the design of ultra-high head locks.

    • Earthquake disaster defense; Risk survey; Service platform; Gansu Province; Three levels of province, city and county

      Online: March 05,2024

      Abstract (98) HTML (0) PDF 16.37 M (58) Comment (0) Favorites

      Abstract:Gansu is one of the provinces in China with high seismic intensity. Although some achievements and progress have been made in the informatization of earthquake disaster defense in Gansu province in recent years, the technical systems for earthquake disaster defense at the municipal and county levels have still not been established, resulting in problems such as ineffective integration of resources across the province and a low level of data information services. Building on the foundation of the earthquake disaster risk survey work in Gansu Province, this paper aims to construct a comprehensive earthquake disaster defense service platform at the three levels of province, city, and county, integrating the display, query, and services of achievements in earthquake hazard, disaster-bearing bodies, and earthquake disaster risk assessment. The platform facilitates the unified aggregation and service of risk survey results at the provincial, municipal, and county levels. Through various forms such as web pages, maps, statistical charts, etc., the platform provides informatization services for earthquake disaster risk prevention and control throughout the province, maximally meeting the operational needs of earthquake departments at all levels and comprehensively enhancing the seismic damage prevention and control service capabilities across the entire province. Key words:Earthquake disaster defense; Risk survey; Service platform; Gansu Province; Three levels of province, city and county

    • Stress change on surrounding faults and stress triggering of aftershocks by 2023 Jishishan Ms 6.2 earthquake in Gansu

      Online: March 05,2024 DOI: 10.20000/j.1000-0844.20240101001

      Abstract (59) HTML (0) PDF 9.78 M (41) Comment (0) Favorites

      Abstract:On December 18, 2023, an Ms 6.2 earthquake occurred in Jishishan County, Linxia Prefecture, Gansu Province, China. The earthquake was located in the Lajishan fault. To deeply into the static Coulomb stress impact of this earthquake on the surrounding faults and aftershocks, the static Coulomb Failure Stress(CFS) changes induced by the Jishishan Ms6.2 earthquake at various depths along the major surrounding faults are calculated by using elastic half-space medium and the co-seismic rupture model. And the future potential seismic hazard on the study region is estimated based on the CFS changes.The results indicate that the event significantly increased the CFS on segments of the Qinghainanshan-Xunhuananshan fault, Lajishanbeiyuan fault, and Lajishannanyuan fault. Particularly, the eastern segment of the Qinghainanshan-Xunhuananshan fault experienced a CFS increase well beyond the static stress triggering threshold, reaching 0.022 MPa, indicating a potentially higher seismic hazard. Other faults also exhibited various degrees of CFS changes, with stress unloading amounts reaching tens of thousands of Pascals on segments of the Lajishanbeiyuan fault and Lajishannanyuan fault, and hundreds of Pascals on the other segments of Nanshan-Xunhua Nanshan fault in Qinghai except the eastern segment and Zhuanglanghe fault. Furthermore, a comparative analysis of CFS changes on faults at different depths revealed a significant influence of depth variations on the CFS pattern of the earthquake. However, the increase in CFS along the Qinghainanshan-Xunhuananshan fault remains highly significant. This study provides a reference for evaluating the possibility and risk of future earthquakes in study region. Moreover, the CFS changes induced by the earthquake on the fault planes of the larger aftershocks are calculated. The CFS changes on the fault planes of the three subsequent Ms≥4 earthquake are estimated as 0.024 MPa, 0.033 MPa, and 0.034 MPa, respectively, which surpassing the triggering threshold and it shows that the Ms6.2 earthquake has obvious triggering effect on these three earthquakes.

    • The Causes and Destructive Effects Analysis of the liquefied earthflow triggered by the 2023 Jishishan Ms 6.2 earthquake, Zhongchuan Township Gansu Province

      Online: February 21,2024 DOI: 10.20000/j.1000-0844.20240110001

      Abstract (110) HTML (0) PDF 30.71 M (103) Comment (0) Favorites

      Abstract:At 23:59 on December 18, 2023,an Ms 6.2 seismic event? struck the Jishishan County in Linxia Prefecture, Gansu Province, triggering numerous geological disasters. Among them, the sand-soil liquefaction mudflow disaster in Zhongchuan Township caused significant economic losses and casualties, and it is urgent to analyse and determine its characteristics, causes and destructiveness. After the earthquake, we went to Zhongchuan Township in Gansu Province, which is the most destructive area of the earthquake, to carry out emergency scientific research, and obtained high-precision and high-resolution digital results of DOM and DSM. Through image interpretation, ground surveys, and on-site inspections, we conducted a comprehensive analysis of the post-earthquake mudflow disaster. The results show that: ① Loess soil, prone to sliding and saturated with water, experienced a rapid increase in pore water pressure under the seismic load, leading to sand-soil liquefaction. This ultimately destabilized and destroyed the soil layer, causing the collapse of the plateau"s edge and seismic landslides. The soil-water mixture, under the influence of gravity, flowed down the slopes and valleys, forming a liquefaction-type landslide-mudflow disaster; ② The disaster phenomenon is not a single mudflow, but the liquefaction of sand and soil led to mudflow and sand-bursting at the same time, the probability of both occurring at the same time is very low, the devastation is very great; ③ This earthquake exemplifies the "small and medium quake, large disaster" scenario, where, despite its moderate magnitude, it caused greater destruction and casualties compared to other earthquakes of similar scale. This geological disaster has both particularity and abnormality.

    • Sliding process and causative mechanisms of the Jintian-Caotan landslide-mudflow hazard chain induced by the 2023 Jishishan Earthquake

      Online: January 31,2024 DOI: 10.20000/j.1000-0844.20240113003

      Abstract (138) HTML (0) PDF 56.27 M (138) Comment (0) Favorites

      Abstract:At 23:59 on December 18, 2023, a magnitude Ms6.2 earthquake occurred in Jishishan County, Gansu Province. This earthquake triggered a severe landslide-debris flow disaster in Caotan Village, Zhongchuan Town, Minhe County, Qinghai Province. Based on the detailed geological survey, low-altitude photogrammetry, onsite engineering geology mapping, and soil water content experiments, basic characteristics, dynamic development process, as well as causes of the landslide disaster were investigated and analyzed. The results suggest that the landslide initiated in a phased and block-wise manner, undergoing six significant sliding stages. This progression exhibits a characteristic of progressively retreating slip. The analysis suggests that the landslide was predominantly attributed to such composite factors: prolonged irrigation activities undertaken by local inhabitants culminated in the establishment of saturated loess layers beneath the surface. Subsequent to the strong earthquake shaking, the pore water pressure within these saturated loess layers experienced a rapid escalation, inducing a state of liquefaction in the loess.

    • Structure design and experiment of ocean bottom cabled seismometer node

      Online: January 03,2024 DOI: 10.20000/j.1000-0844.20230330001

      Abstract (145) HTML (0) PDF 6.60 M (117) Comment (0) Favorites

      Abstract:The ocean bottom seismometer is an important marine seismic observation equipment. In view of the characteristics of high noise of ocean currents and frequent human activities in China"s offshore shallow ocean, the chained seismic observation method is proposed and the mechanical structure of ocean bottom cabled seismometer node is designed. Firstly, the overall structure of node is designed according to the size and layout of the internal components. Then the shell thickness, end cover thickness and sealing size are determined by theoretical calculation and finite element simulation. Finally, the pressure test verifies that the pressure resistance and water tightness of the designed seismometer node structure meet the requirements, and the seismic observation comparison test verifies its ability to receive natural earthquakes. The ocean bottom cabled seismometer will be applied to the actual seismic observation in the offshore area of Zhejiang Province to provide real-time and continuous seismic observation data.

    • Overview of the Current Situation of Earthquake Monitoring in the United States

      Online: January 03,2024 DOI: 10.20000/j.1000-0844.20230802001

      Abstract (216) HTML (0) PDF 22.90 M (198) Comment (0) Favorites

      Abstract:The earthquake monitoring work in the United States started early and has been in a leading position in network design, equipment development, software development, standard formulation, data management, and new technology application. In recent years, with the development of mobile internet and the advancement of projects such as strong earthquake observation, earthquake early warning, and large-scale seismic arrays, earthquake data products in the United States have achieved a leap from singularity to diversification and customization. Although the earthquake monitoring work in China started late, in recent years, with the implementation of a series of major projects such as the national earthquake intensity quick report and early warning, the ‘Belt and Road’ seismic monitoring network and the Chinese seismic experimental site, China has achieved leapfrog development in terms of seismic station density, monitoring and early warning ability, intelligent processing of seismic data, service level and new technology application. In order to better understand the current situation of international earthquake monitoring, this paper introduces the progress of earthquake monitoring in the United States from five aspects: earthquake monitoring architecture, seismic network layout, data processing system, Earthquake warning system and data products, and makes a comparative analysis with China"s earthquake monitoring, which can provide reference for the planning and development of China"s earthquake monitoring and early warning cause.

    Prev 1 2 Next Last
    Result 15 Jump to Page GO