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earthquake relocation and 3-dimensional crustal structure of P-wave velocity in central-western China

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Acta Seismologica Sinica(English Edition) 2004年第1期17卷 20-30页

作者： YANG Zhi-xian(杨智娴) YU Xiang-wei(于湘伟) ZHENG Yue-jun(郑月军) CHEN Yun-tai(陈运泰) NI Xiao-xi(倪晓晞) Winston CHAN Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Crustal Dynamics China Seismological Bureau Beijing 100085 China Institute of Geophysics China Seismological Bureau Beijing 100081 China Multimax Inc. MD 20774 USA Multimax Inc. MD 20774 USA

A simultaneous inversion of earthquake relocation and three-dimensional crustal structure of P-wave velocity in central-western China (21癗~36癗, 98癊~112癊) were performed in this paper. The crustal P-wave velocity model and earthquake relocation for this region are obtained using Pg and Sg phase readings of 9 988 earthquakes from 1992 to 1999 recorded at 193 seismic stations within central-western China by SPHYPIT90 and SPHREL3D90 programs. A lateral inhomogeneous structure of P-wave velocity in this region was obtained. Ob-vious contrast of P-wave velocities was revealed on both sides of active fault zones. Relocated epicenters of 6 459 events show clear lineation along active faults, which indicated a close correlation between seismicity and the active faults in this region. Focal depths of 82% relocated events ranged from 0 to 20 km, which is in good agreement with that from double-difference earthquake location algorithm.

关键词： simultaneous inversion 3-D P-wave velocity structure earthquake relocation central-western China

Analysis of seismic activity in the crust from earthquake relocation in the Central Tien Shan

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Analysis of seismic activity in the crust from earthquake re...

Rapid report of source parameters of 2023 M6.2 Jishishan,Gansu earthquake sequence

中国科学院地质与地球物理研究所2006学术年会

作者： Steve W.Roecker Department of Earth and Environmental Sciences Rensselaer Polytechnic InstituteTroyNY 12180

Using P and S wave arrivals from local earthquakes recorded by a temporary broadband seismic network(GHENGIS) and a Kyrgyzstan broadband seismic network(KNET), we determined the source parameters of 1938 earthquakes occurring from 1997 to 1998 in the central Tien Shan and adjacent areas,based on one-dimensional and three-dimensional velocity *** results indicate that seismic activity is not restricted to only central Tien Shan,but also penetrates into the edges of the Kazakh platform and the Tarim basin to the north and south, *** implies that most range-bounding faults in the central Tien Shan are active and they play a significant role in the tectonic activity of the mountain ***,seismic activity of the Talas-Fergana fault in the study area is different:its central segment seems more active than its eastern *** infer that this part of the fault may be activated by neighboring faults, while its eastern segment could be temporally *** earthquakes at the depths of 30-40km beneath the east-central Tien Shan reveal an interaction between the upper and mid-lower crust. This suggests that brittle failure is possible to greater depth within the *** possibility is that the seismic activity in the mid-lower crust is affected by a positive buoyancy force created by mantle upwelling of this *** observations indicate that dynamic processes such as small-scale mantle convection or mantle upwelling,which resulted in Hthospheric thinning or removal,still occur beneath the central Tien Shan.

关键词： Central Tien Shan earthquake relocation Seismic activity

来源： cnki会议评论

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Earth and Planetary Physics 2024年第2期8卷 436-443页

作者： ZhiGao Yang Jie Liu YingYing Zhang Wen Yang XueMei Zhang China earthquake Networks Center Beijing 100045China

The M6.2 earthquake in Jishishan,Gansu Province,on December 18,2023,caused extraordinary earthquake *** was located in the northern part of the north−south seismic zone,which is a key area for earthquake monitoring in *** newly built dense strong motion stations in this area provide unprecedented conditions for high-precision earthquake relocation,especially the earthquake focal *** paper uses the newly built strong motion and traditional broadband seismic networks to relocate the source locations of the M3.0 and above aftershocks and to invert their focal *** horizontal error of earthquake location is estimated to be 0.5−1 km,and the vertical error is 1−2 *** focal depth range of aftershocks is 9.6−14.6 km,distributed in a 12-km-long strip with SSE *** in the south are more concentrated horizontally and vertically,while aftershocks in the north are more *** focal mechanisms of the main shock and aftershocks are relatively consistent,and the P-axis orientation is consistent with the regional strain *** is a seismic blank area of M3.0 and above,about 3−5 km between the main shock and *** is suggested that the energy released by the main shock rupture is concentrated in this *** on the earthquake location and focal mechanism of the main shock,it is inferred that the Northern Lajishan fault zone is the seismogenic structure of the main shock,and the main shock did not occur on the main fault,but on a secondary *** initial rupture depth and centroid depth of the main shock were 12.8 and 14.0 km,*** source rupture depth may not be the main reason for the severe earthquake disaster.

关键词： Jishishan earthquake earthquake relocation focal mechanism strong motion data

relocation and seismogenic structure of the 1998 Zhangbei-Shangyi earthquake sequence

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Acta Seismologica Sinica(English Edition) 2002年第4期15卷 383-394页

作者：杨智娴陈运泰张宏志 Institute of Geophysics China Seismological Bureau Beijing China

On January 10, 1998, an earthquake of ML=6.2 occurred in the border region between the Zhangbei County and Shangyi County of Hebei Province. This earthquake has been the most significant event occurred in the northern China in the recent years. Historical seismicity in the Zhangbei-Shangyi region was very low. In the epicentral area no active fault capable of generating a moderate earthquake like this event was found. The earthquake locations of the main shock and its aftershocks of the Zhangbei-Shangyi earthquake sequence given by several agencies and authors were diverse and the resulted hypocentral distribution revealed no any dominant horizontal lineation. To study the seismogenic structure of the Zhangbei-Shangyi earthquake, in this paper the main shock and its aftershocks with ML3.0 of the Zhangbei-Shangyi earthquake sequence were relocated using the master event relative relocation algorithm. The relocated results show that the epicentral location of the main shock was 41.145癗, 114.462癊, which was located 4 km to the NE of the macro-epicenter of the main shock. The relocated focal depth of the main shock was 15 km. The hypocenters of the aftershocks distributed in a nearly vertical N20E-striking plane and its vicinity. The relocated results of the Zhangbei-Shangyi earthquake sequence clearly indicated that the seismogenic structure of this event was a nearly N-S- to NNE-SSW-striking fault with right-lateral and reverse slip, and that the occurrence of this event was associated with the horizontal and ENE-oriented compressive tectonic stress, which was compatible with the tectonic stress field in the northern China.

关键词： Zhangbei-Shangyi earthquake earthquake relocation seismogenic structure source process

relocation of the 1998 Zhangbei-Shangyi earthquake sequence using the double difference earthquake location algorithm

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Acta Seismologica Sinica(English Edition) 2004年第2期17卷 125-130页

作者： YANG Zhi-xian(杨智娴) CHEN Yun-tai(陈运泰) Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Geophysics China Earthquake Administration Beijing 100081 China

On January 10, 1998, at 11h50min Beijing Time (03h50min UTC), an earthquake of ML=6.2 occurred in the border region between the Zhangbei County and Shangyi County of Hebei Province. This earthquake is the most significant event to have occurred in northern China in the recent years. The earthquake-generating structure of this event was not clear due to no active fault capable of generating a moderate earthquake was found in the epicentral area, nor surface ruptures with any predominate orientation were observed, no distinct orientation of its aftershock distribution given by routine earthquake location was shown. To study the seismogenic structure of the Zhangbei- Shangyi earthquake, the main shock and its aftershocks with ML3.0 of the Zhangbei-Shangyi earthquake sequence were relocated by the authors of this paper in 2002 using the master event relative relocation technique. The relocated epicenter of the main shock was located at 41.145癗, 114.462癊, which was located 4 km to the NE of the macro-epicenter of this event. The relocated focal depth of the main shock was 15 km. Hypocenters of the aftershocks distributed in a nearly vertical plane striking 180~200 and its vicinity. The relocated results of the Zhangbei-Shangyi earthquake sequence clearly indicated that the seismogenic structure of this event was a NNE-SSW-striking fault with right-lateral and reverse slip. In this paper, a relocation of the Zhangbei-Shangyi earthquake sequence has been done using the double difference earthquake location algorithm (DD algorithm), and consistent results with that obtained by the master event technique were obtained. The relocated hypocenters of the main shock are located at 41.131癗, 114.456癊, which was located 2.5 km to the NE of the macro-epicenter of the main shock. The relocated focal depth of the main shock was 12.8 km. Hypocenters of the aftershocks also distributed in a nearly vertical N10E-striking plane and its vicinity. The relocated results using DD algorithm cl

关键词： Zhangbei-Shangyi earthquake double difference earthquake location algorithm earthquake relocation seismogenic structure source process

Intermediate-depth earthquakes beneath the Pamir-Hindu Kush Region:Evidence for collision between two opposite subduction zones

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earthquake Science 2009年第6期22卷 659-665页

作者： Xiaoting Lou Chen Cai Chunquan Yu Jieyuan Ning Department of Geophysics School of Earth and Space Sciences Peking University Beijing 100871 China

We employed a double-difference algorithm （hypoDD） to relocate earthquakes within the region bounded by 66°E-78°E and 32°N-42°N in the period of 1964-2003 reported by the International Seismological Center （ISC）. The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt. Based on this feature and other evidences, we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zones with opposite dip directions.

关键词： continental dynamics Pamir-Hindu Kush intermediate seismic zone earthquake relocation

relocation of earthquakes in the Northeastern Tianshan Mountains Area and Improvement of Local 1-D Crustal Velocity Model

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earthquake Research in China 2012年第3期26卷 321-334页

作者： Sun Anhui Chen Qifu Chen Yong Li Gang Zhang Zhiqiang Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of earthquake'Science China Earthquake Administrat'ion Beijing 100036 China China earthquake Networks Center Beijing 100045 China

We apply three methods to relocate 599 earthquake events that occurred from August 2004 to August 2005 in the northeastern Tianshan Mountains area ( 85°30' ～ 88°30'E,43°00' ～ 44°40' N ) by using travel times recorded by regional seismic network and 10 portable seismic stations deployed around the Urumqi city. By comparing the reliability of different results,we determined a suitable location method,and an improved 1-D crustal velocity model of the study area. The uncertainty of earthquake location is significantly reduced with combined data of seismic network and portable stations. The relocated events are clearly associated with regional tectonics of the northeastern Tianshan Mountains area, and are also in agreement with the existence of active faults imaged by deep seismic reflection profile. The relocated seismicity discovers some potential traces of buried active faults,which need to be validated further.

关键词： earthquake relocation Velocity model The northeastern Tianshan Mountains area Active faults