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Joint exploration of crustal structure in Fuzhou basin and its vicinities by deep seismic reflection and high-resolution refraction as well as wide-angle reflection/refraction

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Science china Earth Sciences 2005年第7期48卷 925-938页

作者： ZHU Jinfang1, XU Xiwei2, ZHANG Xiankang3, HUANG Zonglin1, CHEN Xiangxiong1, FANG Shengming3, LIU Baojin3, ZHENG Rongzhang2,4 1. Seismological Bureau of Fujian Province,Fuzhou 350003,china 2. institute of geology,china earthquake administration,beijing 100029,china 3. Research Center for Exploration Geophysics,china earthquake administration,Zhengzhou 450002,china 4. State Key Laboratory of earthquake Dynamics,institute of geology,china earthquake administration,beijing 100029,china Seismological Bureau of Fujian Province Fuzhou 350003 China institute of geology China Earthquake Administration Beijing 100029 China Research Center for Exploration Geophysics China Earthquake Administration Zhengzhou 450002 China State Key Laboratory of earthquake Dynamics Institute of Geology China Earthquake Administration Beijing 100029 China

The Fuzhou basin and its vicinities are located at the northern end of the southeastern coastal seismic zone of the mainland of china. By the joint explorations of high-resolution seismic refraction and wide-angle reflection/refraction as well as deep seismic reflection in the region, which is the first synthetic profile in china, its fine velocity structure and geometric structure from the ground to Moho discontinuity is obtained. The result shows that the crust is obviously layered with a thickness of about 32 km. Basically, it consists of two parts: upper crust and lower crust. The velocity of the upper crust is 5.9-6.2 km/s in which there is a 3-4-km-thick weak low-velocity layer between the depths of 10-15 km, while the velocity of the lower crust in the range of 6.3-7.2 km/s. There exists a strong velocity gradient layer about 3 km thick above the Moho discontinuity whose velocity increases from 6.5 to 7.27 km/s. There exist high-angle normal faults that are small in size and extend only in the shallow crust. These faults are the secondary developed on the hanging wall of westward dipping low-angle normal faults. Thus, their seismogenic ability is limited, however, there exists a high-angle deep fault in the crust from Changle-Zaoan fault zone to seashore fault zone. This deep fault has cut the interface between the upper and lower crusts and Moho discontinuity, and may be the deep structure to trigger destructive earthquake source in future to affect Fuzhou City. These results have advanced the detecting precision of the deep structure in the southeastern coastal seismic zone of the mainland of china. In the aspect of the combined feature of the deep and shallow extensional structures that consist of the westward dipping low-angle normal faults and secondary normal faults on their hanging walls in the upper crust, it is firstly obtained that a united structural interpretation has deepened the knowledge about the deep dynamic process in the southeastern coasta

关键词： deep seismic reflection high-resolution seismic refraction wide-angle.

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Progress and review of the studies on the end-Triassic mass extinction event

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Science china Earth Sciences 2005年第12期48卷 2049-2060页

作者： DENG Shenghui1,2, LU Yuanzheng1,2,3 & XU Daoyi4 1. Research institute of Petroleum Exploration and Development, beijing 100083, china 2. Key Laboratory of Oil and Gas Reservoir of Petrochina, beijing 100083, china 3. china University of Geosciences, beijing 100083, china 4. institute of geology, china earthquake administration, beijing 100029, china Research institute of Petroleum Exploration and Development Beijing China Key Laboratory of Oil and Gas Reservoir of Petrochina Beijing China china University of Geosciences Beijing China institute of geology China Earthquake Administration Beijing China

The mass extinction at the end-Triassic is one of the five biggest in the Phanerozoic. However,it is the least well understood among these five events, and only till last decade it became a great academic interesting subject to geologists. The evidences for this event come obviously from bivalves, brachiopods, ammonites, corals, radiolaria, ostracods and foraminifera of marine habitats, and plants and tetrapods of terrestrial realm. By contrast, for some of other groups, such as marine gastropods and marine vertebrates, no mass extinction has been recog-nized yet. The extinction event is strongly marked at specific level but shown a complicated situa-tion at generic and family levels. Dramatic changing of the environment, such as the temperature raise due to the greenhouse effect, the marine anoxic habitats caused by a sudden transgression after the regression at the end of Triassic, has been claimed to be the main cause of the extinction. Many hypotheses have been suggested to demonstrate the mechanisms of the environment changing, among which two popular ones are the bolide impact and volcanic eruption. The Triassic-Jurassic (Tr-J) boundary mass extinction event is still poorly understood because no enough data have been obtained from the Tr-J boundary successional sections of both marine and terrestrial sediments, and most of these studies were regionally restricted. The basic aspects of the event and its associated environmental conditions remain poorly characterized and the causal mechanism or mechanisms are equivocal. Some authors even doubt its occurrence. china has many successionally developed terrestrial and marine Tr-J sections. Detailed studies of these sections may be important and significant for well understanding of the event.

关键词： progress, review, end-Triassic, mass extinction, mechanism, Tr-J boundary.

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Discussion on moment tensor solution and seismogenic structure of Ruichang-Yangxin earthquake on 10 September 2011

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earthquake Science 2012年第3期25卷 229-234页

作者： Lifen Zhang1,2, Guichun Wei and Wulin Liao1 1 Key Laboratory of earthquake Geodesy, institute of Seismology, china earthquake administration, Wuhan 430071, china 2 institute of Geophysics, china earthquake administration, beijing 100081, china Key Laboratory of earthquake Geodesy Institute of Seismology China Earthquake Administration Wuhan China institute of Geophysics China Earthquake Administration Beijing China

Ruichang-Yangxin earthquake is another moderate earthquake in Yangxin-Jiujiang area since 2005 Jiujiang-Ruichang M5.7 earthquake. In order to more understand the seismic activities in this area, we study the moment tensor solution and the seismogenic structure of the Ruichang-Yangxin earthquake. Precise earthquake relocation shows that the mainshock occurred on the southwestern part of the NE-trending fault and aftershocks are distributed not only along the NE-trending fault but also along its conjugated NW-trending fault. By comprehensive analysis on the earthquake distribution, characteristics of isoseismal curve, focal mechanism, and regional structure characteristics, it is inferred that this earthquake is caused by the NE-trending Tanlu fault. In addition, it has close relationship with the conjugated NW-trending fault as well. Many researches have shown that the junction area is the earthquake-prone area, and should be paid more attention to. And our study also proves this viewpoint.

关键词： moment tensor inversion Ruichang-Yangxin earthquake seismogenic structure

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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 institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China institute of Geophysics Chinese Earthquake Administration Beijing China institute of earthquake Science Chinese Earthquake Administration Beijing China earthquake administration of Jiangxi Province Nanchang China School of Earth and Space Science University of Science and Technology of China Hefei China earthquake administration of Jiangsu Province Nanjing 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.

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Deep tectonic setting of the 2008 Wenchuan M_s8.0 earthquake in southwestern china―Joint analysis of teleseismic P-wave receiver functions and Bouguer gravity anomalies

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Science china Earth Sciences 2009年第2期52卷 166-179页

作者： LOU Hai1, WANG ChunYong1, L ZhiYong2, YAO ZhiXiang1, DAI ShiGui2 & YOU HuiChuan1 1 institute of Geophysics, china earthquake administration, beijing 100081, china 2 earthquake administration of Sichuan Province, chengdu 610041, china institute of Geophysics China Earthquake Administration Beijing China earthquake administration of Sichuan Province Chengdu China

Teleseismic P-wave receiver functions at 20 broadband seismic stations in the Longmenshan fault zone (LMFZ) and its vicinity were extracted, and the crustal thickness and the P- and S-wave velocity ratio were calculated by use of the H-k stacking algorithm. With the results as constraints, the S-wave ve-locity structures beneath each station were determined by the inversion of receiver functions. The crustal structure of the Rear-range zone is similar to that of the Songpan-Garze Block, whereas the velocity structure of the Fore-range zone resembles that of Sichuan Basin, implying that the Central Principal Fault of LMFZ is the boundary between the eastern Tibetan Plateau and the Yangtze Block. Lower velocity zone exists in lower crust of the Songpan-Garze Block and the central-southern seg-ment of the Rear-range zone, which facilitates the detachment of the material in upper and middle crust. Joint analysis of the receiver functions and the Bouguer gravity anomalies supports the thesis on the detachment-thrust mode of the LMFZ. A double-detachment pattern is suggested to the tectonic setting in the Songpan-Garze Block. The upper detachment occurs at the depth of 10-15 km, and represents a high-temperature ductile shear zone. There is a lower detachment at the depth of about 30 km, below which the lower crust flow exists in the eastern Tibetan Plateau. Interpretation of the Bouguer gravity anomalies indicates that the Sichuan Basin is of higher density in upper and middle crust in compari-son with that of the Songpan-Garze Block. The LMFZ with higher density is the result from the thrusting of the Songpan-Garze Block over the Sichuan Basin. In the lower crust, higher P velocity and higher density in the Sichuan Basin are related to more rigid material, while lower S velocity and lower density in the Songpan-Garze Block are related to the softened and weakened material. The higher density block beneath the Sichuan Basin obstructs the eastward flow of lower crustal ma

关键词： Longmenshan fault zone (LMFZ) Wenchuan Ms8.0 earthquake deep tectonic setting teleseismic receiver function

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The April 14th, 2010 Yushu earthquake, a devastating earthquake with foreshocks

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Science china Earth Sciences 2010年第6期53卷 791-793页

作者： NI SiDao1, WANG WeiTao2 & LI Li3 1 School of Earth and Space Sciences, University of Science and Technology of china, Hefei 230026, china 2 institute of Geophysics, china earthquake administration, beijing 100081, china 3 National earthquake Infrastructure Service, china earthquake administration, beijing 100036, china School of Earth and Space Sciences University of Science and Technology of China Hefei China institute of Geophysics China Earthquake Administration Beijing China National earthquake Infrastructure Service China Earthquake Administration Beijing China

In the early morning of April 14th, 2010, a strong earth- quake (Ms7.1, http://***; Mw6.9, http://neic. ***) occurred in Yushu district, Qinghai Province, china. More than 2000 lives were lost and over 100000 injured,

关键词： Figure Yushu earthquake a devastating earthquake with foreshocks The April 14th 2010 very than

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Virtual ChuanDian--A parallel numerical modeling of Sichuan-Yunnan regional strong earthquake activities: Model construction and parallel simulation

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Science china Earth Sciences 2009年第10期52卷 1585-1598页

作者： ZHANG Huai1, WU ZhongLiang1,2, ZHANG DongNing2, LIU Jie2, WANG Hui2, YAN ZhenZhen1,2 & SHI YaoLin11 Laboratory of Computational Geodynamics, Graduate University of Chinese Academy of Sciences, beijing 100049, china 2 institute of Geophysics, Chinese earthquake administration, beijing 100081, china Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Beijing China institute of Geophysics Chinese Earthquake Administration Beijing China

Reasonable use of mathematical modeling and numerical simulation of regional earthquake activities has attracted more and more attentions in realistic seismicity studies in recent years. The inherent nature of their attendant multi-scale properties, from either the temporal or the spatial direction, necessitates the use of the cutting-edge massive parallel data processing techniques. Our study here is focused on the model construction and numerical simulation of the regional stress evolution after large earthquake sequences along the fault zones in Sichuan and Yunnan areas, using large-scale parallel finite element approximations with tens of millions of unstructured meshes on the distributed systems. The objective of our study is to provide a state-of-the-art model and a large-scale numerical simulation platform, on which estimation of the risk of large earthquake triggering sequences can be carried out in a middle or long-term time scale with realistic data and constrains inputted from field observation and geological survey.

关键词： Sichuan-Yunan area seismic processing parallel simulation initial stress field

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Post-earthquake assessment of building damage degree using LiDAR data and imagery

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Science china(Technological Sciences) 2008年第S2期51卷 133-143页

作者： LI ManChun1,cheng Liang1,2,GONG JianYa2,LIU YongXue1,CHEN ZhenJie1,LI FeiXue1,CHEN Gang1,CHEN Dong1 & SONG XiaoGang3 1 Department of Geographic Information Science,Nanjing University,Nanjing 210093,china 2 State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University,Wuhan 430079,china 3 State Key Laboratory of earthquake Dynamics,institute of geology,china earthquake administration,beijing 100029,china Department of Geographic Information Science Nanjing University Nanjing China State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan China State Key Laboratory of earthquake Dynamics Institute of Geology China Earthquake Administration Beijing China

Various methods have been developed to detect and assess building's damages due to earthquakes using remotely sensed *** the launch of the high resolution sensors such as IKONOS and QuickBird,it becomes realistic to identify damages on the scale of individual *** the low accuracy of the results has often led to the use of visual interpretation ***,it is very difficult to estimate the degree of building damage(*** damage,moderate damage,or severe damage) in detail using the existing ***,a novel approach integrating LiDAR data and high resolution optical imagery is proposed for evaluating building damage degree *** approach consists of two steps:3D building model reconstruction and rooftop patch-oriented 3D change ***,a method is proposed for automatically reconstructing 3D building models with precise geometric position and fine details,using pre-earthquake LiDAR data and high resolution ***,focusing on each rooftop patch of the 3D building models,the pre- and post-earthquake LiDAR points belonging to the patch are collected and compared to detect whether it was destroyed or not,and then the degree of building damage can be identified based on the ratio of the destroyed rooftop patches to all rooftop *** novelty of the proposed approach is to detect damages on the scale of building's rooftop patch and realize quantitative estimation of building damage degree.

关键词： post-earthquake assessment building damage degree rooftop patch LiDAR imagery

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Lithospheric seismic fabrics of Sulu ultrahigh-pressure metamorphic belt

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Science china Earth Sciences 2005年第5期48卷 585-600页

作者： YANG Wencai 1 , YANG Wuyang 1 , JIN Zhenmin 2 & cheng Zhenyan 1 1. institute of geology, Chinese Academy of Geological Sciences, beijing 100037, china 2. china University of Geosciences, Wuhan 430074, china Chinese Academy of Geological Sciences Institute of Geology Beijing China china University of Geosciences Wuhan China

Calibration of seismic reflectors appearing in the crust of the Chinese continent sci- entific drilling site can be completed through the correlation studies between direct evidences, such as the drill cores, and geophysical signatures; therefore the interpretation of geophysical data could produce reliable results of crustal structure and composition. On the other hand, there are two Cenozoic volcanoes close to the scientific drilling site; analyzing composition of xenoliths existent in the volcanoes and evaluating their seismic velocities can also offer information about the mantle and lower crust. After the calibration via cores and well-logging data, the seismic re- flectors appearing in the UHP belt can be caused by lithological changes within the UHP rock slice, ductile shearing rock-suites, and later fracture zones. Among these sources, ductile shearing resulted in displacement and detachment of original rock-sheets, producing some rock-interbeds of several hundred meters thick that are named the ductile shearing rock-suites. A suite consists of mylonized gneiss and eclogite slices that underwent shearing, becoming the major mechanism responsible to generate regional strong reflections. The UHP rock-slice is characterized by complicated structures and high density, high seismic velocity and high electri- cal resistivity, its thickness is usually less than 11 km. Velocity and density of the gneiss-layer beneath gradually tend to normal with increasing depth. Based on the xenoliths we can infer that the middle crust contains a lot of gneisses, and the lower crust consists of different granulites. The lithospheric mantle has multi-layer structures and consists mainly of spinal lherzolite and harzburgite, implying late Mesozoic lithospheric thinning. The seismic fabrics with different ori- gins were possible products of different geodynamic processes. For instance, the UHP rock-slice was produced by the UHP metamorphic process and the exhumation of subducted supe

关键词： deep seismic reflection, ultrahigh-pressure belt, Sulu china, calibration of reflectors, lithospheric fabrics.

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Plumb line variation at Tangshan during 1987―1998 and its relation with the earthquakes around

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Science china Earth Sciences 2009年第1期52卷 101-107页

作者： LI ZhengXin1,2 & LI Hui3 1 Shanghai Observatory,Chinese Academy of Sciences,Shanghai 200030,china 2 institute of Geodesy and Geophysics,Chinese Academy of Sciences,Wuchang 430077,china 3 institute of Seismology,china earthquake administration,Wuchang 430071,china Shanghai Observatory Chinese Academy of Sciences Shanghai China institute of Geodesy and Geophysics Chinese Academy of Sciences Wuchang China institute of Seismology China Earthquake Administration Wuchang China

Plumb line variations(PLV) at Tangshan during the years of 1987―1998 are determined by using the 46 batch repeated gravity observations of the beijing-Tangshan *** has been found that PLV at Tangshan are related with the 38 earthquakes in this *** appears that the time of an earthquake around Tangshan is usually quite the same when PLV at Tangshan begins moving in opposite direction.

关键词： plumb line variations network in northern china variations of local gravity field earthquakes

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