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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,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 3. 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.

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 {3. {3., Nanchang 3.003., china 3.Beijing {3. {3., Beijing 100080, china Institute of Geology China Earthquake Administration Beijing China Jiangxi earthquake administration Nanchang China Beijing earthquake administration Beijing 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

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,{3. 2. Institute of Geophysics,china earthquake administration,Beijing 100081,{3. 3. Beijing Research Center of {3. National Offshore Oil Corp.,Beijing 100027,{3. Institute of Crustal Dynamics China Earthquake Administration Beijing China Institute of Geophysics China Earthquake Administration Beijing China Beijing Research Center of china National Offshore Oil Corp. Beijing 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

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 43.077,china 2 Institute of Geophysics,Chinese {3. administration,Beijing 100086,china 3.Institute of {3. Science,Chinese {3. administration,Beijing 100086,china 4 {3. administration of Jiangxi Province,Nanchang 3.003.,china 5 School of Earth and Space Science,University of Science and Technology of china,Hefei 23.026,china 6 {3. 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 {3., 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.

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 73.000, china 2Lanzhou Base of {3. Science Institute, china earthquake administration, Lanzhou 73.000, china Lanzhou Institute of Seismology China Earthquake Administration Lanzhou China Lanzhou Base of earthquake Science Institute China Earthquake Administration Lanzhou 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 {{3., 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

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 {3. {3. 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

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 23.026, china 2 Institute of Geophysics, china earthquake administration, Beijing 100081, china 3.National earthquake Infrastructure Service, china earthquake administration, Beijing 10003., 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

Local and Global Character Sums

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Acta Mathematica Sinica,English Series 2000年第3期16卷 535-540页

作者： Chunlei Liu zhengzhou University of Information Engineering,zhengzhou 450002,P.R.{{3. zhengzhou University of Information Engineering Zhengzhou 450002 P. R. China

Hua’s estimate is established for character sums in a number field.A relationship between liftings of a character sum in a local field is also studied.

关键词： Character sum Exponential sum

Deep seismic sounding data reveal the crustal structures beneath Zoigê basin and its surrounding folded orogenic belts

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Science china Earth Sciences 2010年第2期53卷 203-212页

作者： JIA ShiXu,ZHANG XianKang,ZHAO JinRen,WANG FuYun,ZHANG ChengKe,XU ZhaoFan,PAN JiShun,LIU Zhi,PAN SuZhen & SUN GuoWei Geophysical Exploration Center,china earthquake administration,zhengzhou 450002.china Geophysical Exploration Center China Earthquake Administration Zhengzhou China

Songpan-Garze massif is located at the turning position of tectonics from the nearly west-east direction to the nearly north-south direction in the northeastern margin of Tibetan Plateau,with Zoigê basin in the centre of the *** this paper,we build a crustal structure model of Zoigê basin and its surrounding folded orogenic belts using the deep seismic sounding data in this *** also discuss structures and properties of the basement in Zoigê basin,tectonic relations between Zoigê upland basin and its surrounding folded orogenic belts,crustal deformation and thickening in the northeastern margin of Tibetan Plateau,and decoupling and relaxing processes in the *** results indicate that a special "Mesozoic basement" is formed of Triassic rocks with high density (2.65-2.75 g/cm3. and high velocity (5.6 km/s) in Zoigê ***-Garze tectonic massif was transformed into two types of tectonic units with different crustal structures,i.e.,relatively stable Zoigê upland basin and active folded orogenic belts around the basin,in the course of the crustal material of Tibetan Plateau flowing eastward and obstructed by surrounding stable *** thickening of the crust in the northeastern margin of Tibetan Plateau mainly occurred in the mid and lower crust,and the structure characterized by low velocities and multiple reflectors obviously appears in the folded orogenic belts around Zoigê *** implies that the mid and lower crust underwent a strong tectonic deformation in the folded orogenic *** thickness of the crust is about 50 km in Zoigê basin and the folded orogenic belts at the both southern and northern sides of Zoigê *** "Mountain root" cannot be *** is inferred that during the later orogenic period the eastwards flowing deep materials moved clockwise along the relatively relaxing southern side around the eastern tectonic knot under the obstructing of surrounding rigid massifs,and it resulted in the strong stretching action

关键词： Zoigê basin folded orogenic belt deep seismic sounding basement structure crustal structure and tectonics