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The tectonic settings and seismogenic tectonics of the M5.7 Jiujiang earthquake in 2.05,Jiangxi Province,china

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, {2., china 2.Jiangxi earthquake administration, Nanchang 3.003., 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 {2. Beijing 100080 China

The M5.7 Jiujiang earthquake in 2.05 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

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A circum-earth shear zone at low-latitudes and episodic large earthquakes in it and the circum-Pacific seismic zone

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Science china Earth Sciences 2006年第9期49卷 897-903页

作者： MA Zongjin1, DU Pinren1, REN Jinwei2.& GAO Xianglin1 1. Institute of geology, china earthquake administration, {2., china 2. Institute of earthquake Science, china earthquake administration, beijing 10003., china 1. Institute of geology China Earthquake Administration Beijing 100029 China 2. Institute of earthquake Science China Earthquake Administration Beijing 100036 China

Because of the differential motions between the Northern and Southern Hemispheres of the Earth, there exists a motion discordant zone between them. On the surface this zone consists of 13.large faults dominant with strike-slip. We call it a global shear zone at low-latitudes (E system). By statistical analysis of temporal distribution of earthquakes Mw≥7.5 in the E system and the circum-Pacific (P system) during 1900―2.03. we find that there exist quasi-episodic and alternative activities in and between these two systems. This phenomenon is likely associated with the half-sphere oscillation in dilation and contraction and the change of the Earth’s rotation rate.

关键词： shear zone, circum-Pacific zone, great earthquake, quasi-episode.

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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 3.0003.china 2. Institute of geology,{2.,beijing 100029,china 3. Research Center for Exploration Geophysics,{2.,Zhengzhou 450002.china 4. State Key Laboratory of earthquake Dynamics,Institute of geology,{2.,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 3.2}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 7.2. 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 {2. 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. {3. 2. Key Laboratory of Oil and Gas Reservoir of Petro{3., beijing 100083. {3. 3. {3. University of Geosciences, beijing 100083. {3. 4. Institute of geology, china earthquake administration, {13., {3. 1. Research Institute of Petroleum Exploration and Development 100083 Beijing China 2. Key Laboratory of Oil and Gas Reservoir of Petrochina 100083 Beijing China 3. china University of Geosciences 100083 Beijing China 4. Institute of geology China Earthquake Administration 100029 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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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, {2. 10003., china 2.earthquake administration of Gansu Province, Lanzhou 73.000, 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

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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,{2. 2. Institute of Geophysics,china earthquake administration,beijing 100081,{2. 3. beijing Research Center of {2. National Offshore Oil Corp.,beijing 10002.,{2. 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 2.0 and 1000 - 2.00 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

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Characteristics and origin of mafic and ultramafic xenoliths in trachyandesite lavas from Heikongshan volcano,Tengchong,Yunnan Province,china

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Science china Earth Sciences 2010年第9期53卷 1295-1306页

作者： YU HongMei, LIN ChuanYong, SHI LanBin, XU JianDong & CHEN XiaoDe Institute of geology, china earthquake administration, {2., {3. 1. Institute of geology China Earthquake Administration Beijing 100029 China

The trachyandesite lavas from Heikongshan volcano of the Tengchong volcanic cluster, Yunnan Province contain relatively abundant mafic and ultramafic small xenoliths comprising mainly gabbro, pyroxenite and rare lherzolites, all less than 2.5 cm in size. Gabbro xenoliths are characterized by "open" texture represented by relatively abundant vesicles and ground-mass fillings, while pyroxenite xenoliths are characterized by equigranular and poikilitic texture. Their mineral compositions (clinopyroxene ± orthopyroxene ± plagioclase) are similar to those of phenocrysts in lavas, and their equilibration temperature (1000-112.°C) is consistent with the crystallization temperature of the phenocrysts (998-1108°C). Thus, the textures and compositions of these xenoliths are different from those of lower crustal and mantle xenoliths, and were derived from the magma chamber. Among them, the gabbroic xenoliths come from the crystal-bubble-liquid zone at the top of the magma reservoir, while the pyroxenite xenoliths come from the cumulates in the bottom of magma reservoir. The studied single lherzolite xenolith with porphyroclastic texture has similar mineral compositions to the mantle xenoliths from eastern china, and is considered to be of upper mantle origin. It was brought into magma reservoir by replenishment magma, and might have experienced a cooling event before eruption. The formation of xenoliths in trachyandesite flows largely reflects the ascent, storage, evolution and eruption processes of magma.

关键词： magma chamber xenoliths geothermo-barometry trachyandesite Heikongshan volcano Tengchong

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Anatexis in Himalayan crust:Evidence from geochemical and chronological investigations of Higher Himalayan Crystallines

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Science china Earth Sciences 2005年第9期48卷 1347-1356页

作者： YANG Xiaosong1, JIN Zhenmin2.& MA Jin1 1. State Key Laboratory of earthquake Dynamics, Institute of geology, {2., beijing 100029, china 2. Faculty of Earth Sciences, china University of Geosciences, Wuhan 43.074, china 1. State Key Laboratory of earthquake Dynamics Institute of Geology China Earthquake Administration 100029 Beijing China 2. Faculty of Earth Sciences China University of Geosciences 430074 Wuhan China

Migmatization in Higher Himalayan Crystallines (HHC) results from anatexis. The widely distributed migmatites in HHC are an important clue to investigate the relationship be- tween anatexis and the origins of Higher Himalayan leucogranites (HHL), and to understand the effect of anatexis on crustal evolution during the post-collision period. We studied in detail the chemical features of three basic constituent parts of the migmatites, i.e. leucosome, mesosome and melanosome, and determined the K-Ar ages of leucosomes. Our studies indicate that type-I leucosome is the product of crystallization of melt generated by partial melting of mesosome at source region, but type-II leucosome and HHL probably underwent crystallization differentiation of plagioclase during melt aggregation and migration. The age of 2..67 Ma of Type-I leucosome, which is a little older than the beginning of MCT movement, indicates that anatexis may have played an important role in the formation of MCT. That the ages of type-II leucosome (ranging from 14.82.to 18.3. Ma) are consistent with that of HHL provides new chronological evidence for the relationship between migmatization and HHL. We obtained a very young age of 6.2. Ma of Type-II leucosome that provides new time constraint on magma activity in the central segment of Higher Himalayas.

关键词： Higher Himalayan Crystallines, migmatite, anatexis, leucosome, K-Ar age.

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Average slip rate, earthquake rupturing segmentation and recurrence behavior on the Litang fault zone, western Sichuan Province, china

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Science china Earth Sciences 2005年第8期48卷 1183-1196页

作者： XU Xiwei1, WEN Xueze2. YU Guihua1, ZHENG Rongzhang1, LUO Haiyuan2.& ZHENG Bin2.1. Institute of {3., china earthquake administration, {2., china 2. earthquake administration of Sichuan Province, Chengdu 610041, china 1. Institute of geology China Earthquake Administration 100029 Beijing China 2. earthquake administration of Sichuan Province 610041 Chengdu China

The Litang fault zone (LFZ) is an active fault zone within the northwestern Sichuan sub-block. Field investigation reveals new evidence for its late Quaternary offset, neoteric earthquake ruptures and surface-rupturing segmentation, from which long-term slip-rates, char-acteristic earthquake magnitudes and recurrence intervals on the fault zone are estimated. This study shows that the LFZ consists of three subordinate faults, and they are the northern Maoyaba fault, Litang fault and Kangga-Dewu fault, respectively. All of them are dominated by left-lateral strike-slip with reverse dip-slip component on different segments. Based on offset landforms and ages of relevant deposits collected from seven sites, it is estimated that the average left-lateral slip-rate on the LFZ reaches 4.0±1.0 mm/a in the past 14 ka BP, and vertical (reverse) dip-slip rate in the range of 0.1―1.8 mm/a. Three subordinate faults are independent earthquake rup-turing segments, on which the maximum moment magnitude of the characteristic earthquakes is estimated to be 7.0―7.3. and their average recurrence interval to be 500―1000 a. The latest earthquake ruptures occurred 119±2.years ago on the northern Maoyaba fault, about 1890 AD on the Litang fault, and in 1948 AD on the Kangga-Dewu fault, and this may indicate a unidirectional migration for surface rupturing earthquakes along the Litang fault zone, related to stress trigger-ing between the segments.

关键词： Litang fault zone, slip rate, earthquake rupturing segmentation, recurrence interval.

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An experimental study on variation of thermal fields during the deformation of a compressive en echelon fault set

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Progress in Natural Science:Materials International 2007年第3期17卷 298-304页

作者： LIU Peixun, MA Jin, LIU Liqiang, MA Shengli and CHEN Guoqiang (Laboratory of earthquake Dynamics, Institute of geology, {2., {3., china) [a]Laboratory of earthquake Dynamics Institute of Geology China Earthquake Administration Beijing China

The temperature variations during deformation of a compressive en echelon fault set in a rock sample were measured by a surface measurement system with multi-point platinum resistance thermometers and an infrared thermal image system. The measurements obtained by the two systems were in agreement with each other, indicating a relationship between temporal-spatial variations of the thermal field and changes of stress and strain. At varied structural positions of the rock sample, the rising of the temperature was different, implying distinct stress distributions at these positions. In the experiment, the deformation process of the sample included three stages: elastic deformation, stick-slip, and rupture. Correspondingly, the variation process of temperature had also three stages, each of which had its own temperature rising profile. And the thermal radiation field showed a similar process. These phenomena mean that the dominant mechanisms of temperature rising in all stages of deformation are different. Experimental results provide a physical basis for the study of current fault activities by using data of satellite infrared images.

关键词： en echelon fault set stick-slip thermal infrared radiation temperature mechanism of temperatnre rising.

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