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The tectonic settings and seismogenic tectonics of the M5.7 Jiujiang earthquake in 2005,Jiangxi Province,china

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Science china Earth Sciences 2008年第5期51卷 640-653页

作者： LI ChuanYou1, ZENG XinFu2 & ZHANG JianXi3 1 Institute of Geology, china earthquake administration, Beijing 100029, china 2 Jiangxi earthquake administration, Nanchang 330039, china 3 Beijing earthquake administration, Beijing 100080, china 1. Institute of Geology China Earthquake Administration Beijing 100029 China 2. Jiangxi earthquake administration Nanchang 330039 China 3. Beijing earthquake administration Beijing 100080 China

The M5.7 Jiujiang earthquake in 2005 was a mid-strong one, stronger than expected to occur in the region. This paper discusses the neo-tectonic settings of this earthquake, and it is thought that the earthquake region is located in the transitional belt, a potential area inducing weak to moderately strong earthquakes, between two large different tectonic units. The results of the reconnaissance work and on-the-spot investigation after earthquake indicate that the occurrence of the M5.7 Jiujiang earth- quake is closely related with the NE-trending fault on the western margin of Ruichang Basin. From its controlling to the landforms and Quaternary depositions, geological profiles, ESR dating, etc., the ac- tivity of the Dingjiashan-Langjunshan fault bounding the basin is discussed. It suggests that this fault displays an active one in Middle Pleistocene by the outcrop. Based on the activity of the fault, and the direction and location of the ground fissures, the isoseismal lines and the nodal plane of the focal mechanism solution, it is inferred that the Dingjiashan-Langjunshan fault is the seismogenic tectonics of the M5.7 Jiujiang earthquake, and the intersection point between this fault and the active NW ones is the possible origin of location of this earthquake. Our study shows that this earthquake is not an event exceeding expectation, and that the active and invisible characteristics of the causative fault are typical in the eastern area of china.

关键词： Jiujiang earthquake tectonic settings Dingjiashan-Langjunshan fault activity seismogenic tectonics

Two types of changes in apparent resistivity in earthquake prediction

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Science china Earth Sciences 2011年第1期54卷 145-156页

作者： DU XueBin1,2 1Lanzhou Institute of Seismology, china earthquake administration, Lanzhou 730000, china 2Lanzhou Base of earthquake Science Institute, china earthquake administration, Lanzhou 730000, china 1. Lanzhou Institute of Seismology China Earthquake Administration Lanzhou 730000 China2. Lanzhou Base of Earthquake Science Institute China Earthquake Administration Lanzhou 730000 China

Two types of changes in apparent resistivity (AR) have been linked to earthquake occurrences. This paper studies the changes and their causes, in detail with the ultimate purpose of developing and assessing a method of earthquake (EQ) prediction. The AR changes of the first type (CFT) are considered to be precursors related to earthquakes (EQs); these appear mostly in the medium-term period before EQs and in the short-term period preceding EQs. The changes of the second type (CST) are characterized by a turning anomaly of a long-trend AR variation or the drastically descending/ascending anomaly superimposed on such a variation; these appear synchronously in large areas, such as the Chinese mainland, and northern and northwestern china, ect. Their spatio-temporal clusters correspond well to high seismicities in the areas and distant great EQs around the Chinese mainland. Based on the behaviors of the two types of changes, the AR changes observed prior to the Ms8.0 Wenchuan EQ of 2008 are studied. The results show that in the medium-term period before the EQ, noticeable anomalies appeared synchronously at four stations around the Songpan-Ganzi active block, but only weak upward changes were observed in the short-term period preceding the EQ, which caused the prediction of the imminent EQ to fail.

关键词： strong earthquake apparent resistivity two types of changes spatio-temporal cluster Wenchuan earthquake

Source mechanism of strong aftershocks (M_s≥5.6) of the 2008/05/12 Wenchuan earthquake and the implication for seismotectonics

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Science china Earth Sciences 2009年第6期52卷 739-753页

作者： ZHENG Yong1,2,MA HongSheng3,Lü Jian4,NI SiDao5,LI YingChun6 & WEI ShengJi2 1 Institute of Geodesy and Geophysics,Chinese Academy of Sciences,Wuhan 430077,china 2 Institute of Geophysics,Chinese earthquake administration,Beijing 100086,china 3 Institute of earthquake Science,Chinese earthquake administration,Beijing 100086,china 4 earthquake administration of Jiangxi Province,Nanchang 330039,china 5 School of Earth and Space Science,University of Science and Technology of china,Hefei 230026,china 6 earthquake administration of Jiangsu Province,Nanjing 210014,china 1. Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China 2. Institute of Geophysics Chinese Earthquake Administration Beijing 100086 China 3. Institute of earthquake Science Chinese Earthquake Administration Beijing 100086 China 4. earthquake administration of Jiangxi Province Nanchang 330039 China 5. School of Earth and Space Science University of Science and Technology of China Hefei 230026 China 6. earthquake administration of Jiangsu Province Nanjing 210014 China

Dozens of >M5, hundreds of >M4, and much more >M3 aftershocks occurred after the 2008/05/12 Wenchuan earthquake, which were well recorded by permanent and portable seismic stations. After relocated with P arrival, the >M3 aftershocks show two trends of distribution, with most of the aftershocks located along the north-east strike consistent with Longmenshan fault system, yet there is a north-west trend around the epicenter. It seems that substantially more aftershocks occur in regions with crystalline bedrocks. Then we collected waveform data from national Digital Seismograph Network and regional seismograph network of china, and employed 'Cut and Paste' method to obtain focal mechanisms and depths of the big aftershocks (M≥5.6). While most of those aftershocks show thrust mechanism, there are some strike slip earthquakes in the northern-most end of the rupture. Focal mechanisms show that the events located on the southern part of central Beichuan-Yingxiu Fault (BY) are mainly thrust earthquakes, which is consistent with initial mechanism of the main shock rupture. In the north part the aftershocks along the BY are also dominated by thrust slip, which is quite different from the right slip rupture of the main shock. Around Qingchuan-Pingwu Fault, the focal mechanisms are dominated by right-slip rupture with large depths (~18 km). So we suspected that in the north part the main shock might rupture on two faults: Beichuan Fault and Qingchuan-Pingwu Fault. The complex pattern of aftershock mechanisms argues for presence of a complicated fault system in the Longmenshan area.

关键词： focal mechanism seismotectonics Wenchuan earthquake cut and paste.

Evolution of terraces Ⅰ–Ⅲ along the Anning River, western Sichuan, based on pollen records and terrace structure

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Science china Earth Sciences 2011年第1期54卷 127-135页

作者： CHENG JianWu1,2 1 Institute of Geology, china earthquake administration, Beijing 10003., china 2 earthquake administration of Gansu Province, Lanzhou 730000, china Institute of Geology China Earthquake Administration Beijing China earthquake administration of Gansu Province Lanzhou China

This study reconstructs the long-term evolution of river terraces over large spatial scales along the Anning River, western Sichuan, and identifies external factors controlling terrace formation. Pollen record analysis and terrace structure indicate that formation of the middle section of terraces I-III resulted from the interaction of changing climates and uplift of the margins of the Qinghai-Tibet Plateau. The relative influence of climate and uplift in terrace formation changes in different periods. The terraces reveal multiple, gradual uplift events on the eastern Qinghai-Tibet Plateau, which is of great significance for determining uplift mechanisms across the entire plateau.

关键词： Anning River in western Sichuan terrace formation pollen paleoclimate

Upper crust structure of eastern A’nyemaqên suture zone: Results of Barkam-Luqu-Gulang deep seismic sounding profile

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Acta Seismologica Sinica(English Edition) 2007年第6期20卷 628-640页

作者：张先康Geophysical Exploration Center china earthquake administration 杨卓欣Geophysical Exploration Center china earthquake administration 徐朝繁Geophysical Exploration Center china earthquake administration 潘纪顺Geophysical Exploration Center china earthquake administration 刘志Geophysical Exploration Center china earthquake administration 王夫运Geophysical Exploration Center china earthquake administration 嘉世旭Geophysical Exploration Center china earthquake administration 赵金仁Geophysical Exploration Center china earthquake administration 张成科Geophysical Exploration Center china earthquake administration 孙国伟 Geophysical Exploration Center China Earthquake Administration

Barkam-Luqu-Gulang deep seismic sounding profile runs from north of Sichuan Province to south of Gansu Province. It is located at the northeastern edge of Tibetan Plateau and crosses eastern A＇nyemaqên suture zone. The upper crust structures around eastern A＇nyemaqên suture zone and its adjacent area are reconstructed based on the arrival times of refracted Pg and Sg waves by using finite difference method, ray tracing inversion, time-term method and travel-time curve analysis. The results show that the depth variation of basement along profile is very strong as indicated by Pg and Sg waves. The basement rose in Zoigê basin and depressed in eastern A＇nyemaqên suture zone, and it gradually rose again northward and then depressed. The results also indicate that eastern A＇nyemaqên suture zone behaves as inhomogeneous low velocity structures in the upper crust and is inclined to- ward the south. Hoh Sai Hu-Maqên fault, Wudu-Diebu fault and Zhouqu-Liangdang fault are characterized by low velocity distributions with various scales. The distinct variation in basement depth occurred near Hoh Sai Hu-Maqên fault and Zhouqu-Liangdang fault, which are main tectonic boundaries of A＇nyemaqên suture zone. Wudu-Diebu fault, located at the depth variation zone of the basement, possibly has the same deep tectonic background with Zhouqu-Liangdang fault. The strongly depressed basement characterized by low velocity distribution and lateral inhomogeneity in A＇nyemaqên suture zone implies crushed zone features under pinching action.

关键词： eastern A'nyemaqên suture zone deep seismic refraction upper crust structures

A preliminary study on seismic design criteria of offshore platforms in Bohai Sea of china

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earthquake Engineering and Engineering Vibration 2010年第2期9卷 223-231页

作者： Peng Yanju1,Lu Yuejun1,Yan Jiaquan2,Tang Rongyu1,Wang Junqin3 and Li Jiagang3 1. Institute of Crustal Dynamics,china earthquake administration,Beijing 100085,china 2. Institute of Geophysics,china earthquake administration,Beijing 100081,china 3. Beijing Research Center of china national Offshore Oil Corp.,Beijing 100027,china Institute of Crustal Dynamics China Earthquake Administration Beijing 100085 China

This paper analyzes the seismicity in Bohai Sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea,a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method,a scheme of two seismic design levels is proposed,and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings,it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000 - 2500 years,respectively. The validity of these proposed values is discussed. Finally,the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea.

关键词： fixed offshore platform seismic design level seismic design objective return period Bohai Sea

Prilimary result of temperature distribution and associated thermal stress in crust in Tianshui, china

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Acta Seismologica Sinica(English Edition) 2007年第6期20卷 641-655页

作者：刘耀炜高安泰Lanzhou Institute of Seismology china earthquake administration 施锦Lanzhou Institute of Seismology china earthquake administration 苏鹤军Lanzhou Institute of Seismology china earthquake administration School of Water Resources and Environment China University of Geosciences

The heat flow in crust and the thermal stress generated by the flow play a very important role in earthquake occurrence. Different crustal structure has different effect on heat distribution and associated thermal stress. In all of typical seismogenic crustal structure models, including the bulge of Moho surface, the deep-large fault in the mid-lower crust, low-velocity and high-conductive layer in the middle crust, and the typical crustal structure in mid-upper crust, the thermal stress produced by deep heat disturbance may move up to the mid-upper crest. This leads to upper brittle part of crust break and hence, strong earthquakes. This result is constructive in enhancing our understanding of the role of deep fieat flow in curst in development of earthquake and its generation, as well as the generation mechanism of the shallow flowing fluid.

关键词： earthquake crust structure thermal stress numerical simulation geothermal field

The Wenchuan earthquake creation of a rich database of building performance

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Science china(Technological Sciences) 2010年第10期53卷 2668-2680页

作者： SUN BaiTao & ZHANG GuiXin Institute of Engineering Mechanics, china earthquake administration, Harbin 150080, china 1. Institute of Engineering Mechanics China Earthquake Administration Harbin 150080 China

After the Wenchuan earthquake,The Institute of Engineering Mechanics (IEM) performed an extensive and comprehensive damage survey of the large area affected by the earthquake. Seismic codes in china were revised and updated after the catastrophic 1976 Tangshan earthquake. However,until the Wenchuan earthquake the seismic code provisions were not tested by a large earthquake. Some 5000 buildings,exposed to intensities VI to XI,were investigated in great detail immediately after the earthquake. The investigation and the surveys covered both seismically designed (fortified) buildings and non-code compliant buildings. In the process a comprehensive and documented database of building performance was compiled,which would be very valuable for further research,improvement of the seismic code,improvement of the construction practices,and disaster mitigation planning and management. The database dominantly contains the most prevalent structural types in the region: 1) reinforced and un-reinforced masonry structures; 2) masonry buildings with reinforced frame in the lower stories,and 3) reinforced concrete frame structures. Observed damage characteristics of various structural types were studied and documented,damage patterns analyzed,and corresponding damage probability matrices derived from the data collected during this survey. It is our hope that this investigation and the published material will be utilized for the revision of the seismic codes,leading to a higher level of life safety and damage reduction in future earthquakes.

关键词： Wenchuan earthquake building damage vulnerability damage probability matrices

Surface deformation at the epicenter of the May 12,2008 Wenchuan M8 earthquake,at Yingxiu Town of Sichuan Province,china

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Science china(Technological Sciences) 2008年第S2期51卷 154-163页

作者： DONG ShaoPeng,HAN ZhuJun & AN YanFen national Center of Seismic Fault Study,Institute of Geology,china earthquake administration,Beijing 100029,china 1. national Center of Seismic Fault Study Institute of Geology China Earthquake Administration Beijing 100029 China

Surface deformation,along national Highway 213.at the epicenter of Wenchuan M8 earthquake,at Yingxiu Town of Sichuan Province,china,is surveyed and measured in *** results show two distinct *** is that no horizontal displacement displays,or dextral strike-slip component at the observation point can not be found basically,the other is that uplift amount is 2.72 m,and the short-ening amount is 0.38 m,which reflects thrust shortening deformation is not *** crust uplift amount of 2.71 m is distributed in a belt with width of 60 *** model of lower crustal flow proposed by Royden et al.(1997) about the dynamic process in eastern margin of the Tibetan Plateau seems more suitable to explain the seismic surface deformation characteristics at Yingxiu Town,the epicenter of the May 12,2008 Wenchuan M8 earthquake.

关键词： Wenchuan M8 earthquake Yingxiu Town surface deformation