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Deep tectonic setting of the 2.08 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 {2., Beijing 100081, china 2.earthquake {2. of sichuan province, chengdu 61004., china 1. Institute of Geophysics China Earthquake Administration Beijing 100081 China 2. earthquake administration of sichuan province Chengdu 610041 China

Teleseismic P-wave receiver functions at 2. 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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Average slip rate, earthquake rupturing segmentation and recurrence behavior on the Litang fault zone, western sichuan {2., 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 Geology, china earthquake {2., Beijing 10002., china 2. earthquake administration of sichuan province, chengdu 61004., 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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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 {2., Beijing 100039, china 2.earthquake {2. of Gansu province, Lanzhou 730000, china Institute of Geology China Earthquake Administration Beijing China earthquake administration of Gansu {2. 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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DEFORMATION RATE CHANGES OF TECTONIC BELTS ALONG BOUNDARIES OF YUNNAN SICHAUN BLOCK AND RELATION TO GROUPED STRONG earthquakeS

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大地测量与地球动力学 2003年第B12期23卷 101-107页

作者： Cheng Wanzheng and Yang Yongling (earthquake administration of {2. province, chengdu 61004., china) earthquake administration of {2. province Chengdu 610041 China

Deformation measurements such as short range leveling, short baseline, continuous cross fault strain measurement are carried out at different intervals from 1982.to *** these measurement sites are built across the boundary tectonic belts of Yunnan sichuan block. On the basis of these deformation data, the annual deformation rates at all sites are calculated and their change curves with time are plotted respectively. With these calculated results, we analyze the vertical and horizontal movements of tectonic belts of Yunnan sichuan block, and the relationship to grouped strong {2.s occurred in the block are discussed as well. These results show that the tectonic activities in the western and southeastern Yunnan are intensive. Along some eastern boundary belts: from Qujiang, Xiaojiang fault belts in the south of Yunnan to Xianshuihe fault belts in northwestern sichuan, present annual rate of horizontal deformation *** Xianshuihe, Xiaojiang and Longmenshan fault belts the rates of vertical deformation change are small,but the vertical deformation change rates along Anninghe and Zemuhe fault belts are comparatively large. The comprehensive analysis shows that grouped strong {2.s will occur probably when the deformation rate changes sharply. Thus we think that sharp changes of deformation rates may be one of the seismic precursors.

关键词：地震前兆变形率地表变形云南-四川板块边缘数据计算边缘区域的横向变形纵向变形聚集的强震

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Evaluation of Sustainable Land Management and Diagnosis of Obstacle at County Scale in sichuan Basin:Taking Lezhi County as Example

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Wuhan University Journal of Natural Sciences 2006年第4期11卷 1046-1051页

作者： CHEN Guangjian 1, 2. 3 , LIU Qing 1 1. chengdu Institute of Biology, Chinese Academy of Sciences, chengdu 61004., {2.,china 2. Graduate University of Chinese Academy of Sciences, Beijing 100049, china 3. Academy of Land Reconnaissance and Layout of {2. province , chengdu 610031, {2., china chengdu Institute of Biology Chinese Academy of Sciences Chengdu Sichuan China Graduate University of Chinese Academy of Sciences Beijing China Academy of Land Reconnaissance and Layout of sichuan province Chengdu Sichuan China

This paper established sustainable land resources evaluating indicators fit for hilly area in sichuan Basin, Southwest of china, and evaluated the case of sustainable land management of Lezhi County from 1990 to 2.01. The result showed that the land resource sustainable utilization ability in Lezhi County is belong to Second level （better sustainable）. Secondly, this paper diagnosed some years obstacles of sustainable land management of Lezhi County from base period to goal period and compared the obstacles factors in the indicators system. There were 16 indexes orderly become major affect factor to land sustainable utilization of Lezhi county in indicator system, of which there are 8 obstacles indexes exist both in 1990 and 2.01. The value of obstacles degree of five indicators exceeded 5 in 1990, but in 2.01, only two indicators＇ values were more than 5.

关键词： land resources sustainable land management assessment indicators diagnosis of obstacle

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Assessment of time-dependent seismic hazards on segments of active fault, and its problems

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Chinese Science Bulletin 1998年第23期43卷 1937-1950页

作者： WEN Xueze Seismological Bureau of sichuan province,{2., china Seismological Bureau of sichuan province Chengdu China

Assessment of time dependent seismic hazards on segments of active fault is one of the important techniques of long term earthquake forecast for specific locations. It is based on the data from quantitatively seismo geologic investigation in active faults and expresses seismic hazards of a fault segment with both the earthquake occurrence probability, which increases as the elapsed time increases, and the magnitude predicted. Through summing up and analyzing main technical steps in research of the recent decade, some defects in the current theory and model of this technique are pointed out. For instance, the probabilistic models for recurrence interval are based solely on the quasi periodic behavior of earthquake recurrence, ignoring behavior’s diversity that possibly exists. Variability of repeated rupture dimensions in various cycles is considered inadequately in fault segmentation research, etc. It is most important for improving the reliability of the result of seismic hazard assessment to reveal actual earthquake recurrence behavior and its generalities, and to update relevant models for evaluating probabilistic earthquake hazard based on the behavior and generalities.

关键词： active fault rupture segmentation time dependent hazard probabilistic model long term forecast.

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Monitoring the Cultivated Slope Land in the Three Gorges Reservoir Area Based on Remote Sensing and GIS

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Wuhan University Journal of Natural Sciences 2006年第4期11卷 915-921页

作者： ZHOU Jieming1, ZHOU Qigang 2. 3 ,HUANG Zhiqin 2. 3, 4 1. The Faculty of Geography and Resources Science, sichuan Normal University, chengdu 610066, sichuan, china 2. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, chengdu 61004., sichuan, china 3. Graduate University of the Chinese Academy of Sciences, Beijing 100049, china 4. Information Center of Land and Resources Department of sichuan province, chengdu 61004., sichuan, china The Faculty of Geography Resources Science Sichuan Normal University 610066 Chengdu Sichuan China Institute of Mountain Hazards Environment Chinese Academy of Sciences 610041 Chengdu Sichuan China Graduate University of the Chinese Academy of Sciences 100049 Beijing China Information Center of Land Resources Department of sichuan province 610041 Chengdu Sichuan China

By means of combining auto-extraction with manual interpretation, the current distribution information about cultivated land is obtained. The distribution information of 1992.is extracted from the dynamic polygons of 2.02. The monitoring mini-system of the cultivated slope land is established. In the system, detailed surveys, focused on the resources of cultivated slope land, are carried out. The results indicate that the area of the cultivated slope land is very large. Meanwhile, there are lots of cultivated steep slopes with gradient above 35°. The areas of steep land cultivated had been slowly reduced from 1992.to 2.02. At the same time, the pressures of returning farm land to forestry are great in all counties. The conflicts between population growth, insufficient grain supply and stagnant economic development sharpen increasingly. It is inevitable to improve the agricultural structure.

关键词： slope land cultivated remote sensing geography information system (GIS) the pressure of returning farm land to forestry Three Gorges Reservoir Area

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Research on evolution and prevention of the No.1 large-scale dangerous slope of Erlang Mountain on the sichuan-Tibet Highway

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Science china(Technological Sciences) 2003年第z1期46卷 42-51页

作者： ZHANG Xiaoyan The Transportation Department of sichuan province,{2., china Transportat Dept sichuan Prov Chengdu 610041 Peoples R China

sichuan-Tibet Highway traverses the two principal geomorphic units and their transition belt in western china; it has some hazardous slopes characterized by high altitude and chilliness, high elevation, large scale and complexity. Various hazards usually concur in groups. The integrated hazards of these slopes cannot be reflected by any single hazardl they act on one another and develop at the same time, like many other things experiencing a recurrent evolving course from growth to demise. Based on the mechanisms of the typical dangerous No.1 slope of Erlang Mountain on the sichuan-Tibet Highway, various simulations through geotechnical test, numerical calculation, and in-situ monitoring have been carried out to control and regularize the last phase of evolution of the slope. The text shows that such slopes have developed under geological and engineering conditions that might have enforced the potentiality of hazards; interactions between different hazards are of more menace than any single factor; structures in cooperation with the hazardous bodies may be effective for preventing such calamities.

关键词： hazards of large slope evolution, hazards concurring in group, structure control.

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Research on the relationship between site function and environment at the site of Zhongba,Chongqing City,china

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Chinese Science Bulletin 2008年第S1期53卷 58-73页

作者： SUN ZhiBin Institute of Cultural Relics and Archaeology of sichuan province,{2. 61004.,china 1. Institute of Cultural Relics and Archaeology of sichuan province Chengdu 610041 China

The Zhongba site has been demonstrated to be a location of salt production based on multi-disciplinary research including salt archaeology,environmental archaeology,zooarchaeology,paleobotany,and other natural science *** continuity of salt production from the Han Dynasty to the present day as understood primarily from ancient texts can now be traced back to even earlier times. Based on the characteristics of cultural layer deposits,features,and artifacts,Zhongba can be clearly distinguished from known settlements,and from bronze,iron,pottery and porcelain *** to various natural science examinations,the major impurities in local salt brine are also found in floor features,brine troughs,and rounded bottom pots at the site even though NaCl itself was not *** traces were left over from the salt production process rather than being naturally *** and its constituent features and artifacts share many common characters with other salt production sites around the ***,the Zhongba site can be confidently identified as a salt production site where activity continued for several thousand *** formation of the site cannot be separated from salt production,and it is also highly related to its natural environment.

关键词： Zhongba site function salt production environmental relationships

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Discovery of seismites in Upper Sinian stratiform lead-zinc deposits in Dadu River valley, sichuan, china: Implication for ore genesis

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Science china Earth Sciences 2006年第11期49卷 1135-1146页

作者： LIN Fangcheng1,2.& PAN Guitang2.1. Geoscience College, chengdu University of Technology, chengdu 610059,{2. 2. chengdu Institute of Geology and Mineral Resources, chengdu 610082.{2. 1. Geoscience College Chengdu University of Technology Chengdu 610059 China 2. chengdu Institute of Geology and Mineral Resources Chengdu 610082 China

A number of lead-zinc sulphide deposits have been discovered in recent years in dolo- mitic rocks of the Upper Sinian Dengying Formation in the Dadu River valley region, sichuan province,{2.. The lead-zinc mineralization is closely associated with a black siliceous exhalite that has been traced over 50 km of strike. This makes Dadu River valley the most extensive stratiform non-ferrous sulphide horizon having been discovered to date in{2.. In a previous study by the first author (LIN), these deposits were recognised as belonging to the broad spectrum of lead-zinc sedimentary exhala- tive (SEDEX) deposits. In this paper, seismites and seismogenetic structures occurring in close association with the Dadu River valley mineralized zone are described. The close spatial and temporal relationship between the seismites and mineralization provides strong evidence for the hypothesis that the lead-zinc SEDEX deposits formed in direct response to earthquake activities around the Sinian-Cambrian boundary. The earthquakes are postulated to be an effective dynamic mechanism for triggering the upward migration of deep circulating ore fluids along synsedimentary growth faults and their exhalation onto the sea-floor to form the extensive deposits of stratiform lead-zinc sulphide ore.

关键词： seismites, earthquake, lead-zinc deposit, hydrothermal exhalation, Upper Sinian Dengying Age.

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