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Study on Precise Location and Structure of Earthquakes in the Shanxi Reservoir,Zhejiang Province
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作者 Zhu Xinyun Zhang Fan Yu Junyi 《Earthquake Research in China》 2011年第4期456-467,共12页
The Shanxi reservoir earthquakes are significant seismic events in southern Zhejiang Province in recent years, an area with fewer and weaker earthquakes. The seismicity showed an intermittent characteristic and group ... The Shanxi reservoir earthquakes are significant seismic events in southern Zhejiang Province in recent years, an area with fewer and weaker earthquakes. The seismicity showed an intermittent characteristic and group distribution. The epicenters located by the seismic network did not show a predominant direction and the seismogenic structure is not clear. In the study, the nonlinear imaginary wave travel time equation was linearized and solved, and the source position, initial imaginary velocity and travel time residuals were obtained. Then by doubling the standard deviation as time residuals, the maximum error generated from longitude, latitude, depth and imaginary velocity was calculated. The genetic population was structured using the maximum error and the end result of earthquake location was obtained by genetic algorithm. The result of relocation of the Shanxi reservoir earthquakes with this method shows that earthquakes are largely concentrated on a near-vertical, northwest oriented fault plane, and the included angles between the normal of the plane and the due north, due east and vertical directions are 46~, 44~, and 87~, respectively. The result is in agreement with that of comprehensive fault plane solutions of small earthquakes. The average depth of the earthquakes was 4.7km, the maximum depth 9.5kin, and the minimum depth 1.7km. The epicenters showed a northwestward narrow banded distribution, and the focal depth increased along the northwest direction. There was a discontinuous seismic gap of about 3.5km long at the northwest end of the strip. The characteristics of source parameters obtained by using the Borun model were not significantly different from that of tectonic earthquakes. Seismic stress drop was about 0.33MPa, and the average stress drop was 0.88MPa. According to the stress drop' spatial distribution, the seismic discontinuities segment at the northwest end of the strip is in a low stress drop zone. 展开更多
关键词 Reservoir induced earthquake Genetic algorithm Precise location Faultplane Stress drop
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Internal structures and high-velocity frictional properties of Longmenshan fault zone at Shenxigou activated during the 2008 Wenchuan earthquake 被引量:3
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作者 Yu Wang Shengli Ma +7 位作者 Toshihiko Shimamoto Lu Yao Jianye Chen Xiaosong Yang Honglin He Jiaxiang Dang Linfeng Hou Tetsuhiro Togo 《Earthquake Science》 2014年第5期499-528,共30页
This paper reports internal structures of a wide fault zone at Shenxigou,Dujiangyan,Sichuan province,China,and high-velocity frictional properties of the fault gouge collected near the coseismic slip zone during the 2... This paper reports internal structures of a wide fault zone at Shenxigou,Dujiangyan,Sichuan province,China,and high-velocity frictional properties of the fault gouge collected near the coseismic slip zone during the 2008 Wenchuan earthquake.Vertical offset and horizontal displacement at the trench site were 2.8 m(NW side up)and 4.8 m(right-lateral),respectively.The fault zone formed in Triassic sandstone,siltstone,and shale about 500 m away from the Yingxiu-Beichuan fault,a major fault in the Longmenshan fault system.A trench survey across the coseismic fault,and observations of outcrops and drill cores down to a depth of 57 m revealed that the fault zone consists of fault gouge and fault breccia of about0.5 and 250-300 m in widths,respectively,and that the fault strikes N62°E and dips 68° to NW.Quaternary conglomerates were recovered beneath the fault in the drilling,so that the fault moved at least 55 m along the coseismic slip zone,experiencing about 18 events of similar sizes.The fault core is composed of grayish gouge(GG) and blackish gouge(BG) with very complex slip-zone structures.BG contains low-crystalline graphite of about 30 %.High-velocity friction experiments were conducted at normal stresses of 0.6-2.1 MPa and slip rates of 0.1-2.1 m/s.Both GG and BG exhibit dramatic slip weakening at constant high slip rates that can be described as an exponential decay from peak friction coefficient lpto steadystate friction coefficient lssover a slip-weakening distance Dc.Deformation of GG and BG is characterized by overlapped slip-zone structures and development of sharp slickenside surfaces,respectively.Comparison of our data with those reported for other outcrops indicates that the high-velocity frictional properties of the Longmenshan fault zones are quite uniform and the high-velocity weakening must have promoted dynamic rupture propagation during the Wenchuan earthquake. 展开更多
关键词 Wenchuan earthquake - Longmenshan faultsystem - Shenxigou fault zone Fault zone structures High-velocity friction
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Simultaneous Inversion of Earthquake Relocation and Velocity Structure in the Shanxi-reservoir,Wenzhou 被引量:1
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作者 Zhong Yuyun Zhang Zhenfeng Kan Baoxiang 《Earthquake Research in China》 2011年第4期468-476,共9页
Using the data of P-wave network and Zhejiang and travel time recorded at the Shanxi-reservoir seismological Fujian local networks, we implemented a simultaneous inversion of earthquake relocation and velocity struct... Using the data of P-wave network and Zhejiang and travel time recorded at the Shanxi-reservoir seismological Fujian local networks, we implemented a simultaneous inversion of earthquake relocation and velocity structure and determined the new locations of earthquakes in the Shanxi-reservoir. The results show that: (1) the overall epicenter distribution is NW directed, and the Shanxi reservoir induced seismicity has a close relationship to the Shuangxi-Jiaoxiyang fault; (2) the focal depth of the Shanxi reservoir induced seismicity is 5.4km in average, less than the average focal depth in the South China earthquake zone; (3) the focal depth is shallower on the reservoir shore and deeper in the reservoir inundation area. At the beginning of the reservoir induced seismicity, the focal depth increased gradually. This may be due to the gradual penetration of water into a larger depth that induced deeper earthquakes; and (4) there is a low P-wave velocity anomaly in the study area, located at the intersection of multiple faults in the reservoir inundation area. The Shanxi reservoir induced seismicity mostly occurred in this lowvelocity anomaly zone. This may be related to water penetration. 展开更多
关键词 Shanxi reservoir Velocity structure Simultaneous inversion Earthquake location
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Detecting the Earthquake Excited Spheroidal Free Oscillation of the Earth by Use of Observational Data at Huzhou Seismic Station
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作者 Fang Yanxun Bian Genfa +1 位作者 Hui Ruoyu Sun Zongqiang 《Earthquake Research in China》 CSCD 2016年第4期584-593,共10页
By using the digital observations of the pendulum tiltmeter, water tube tiltmeter,extensometer and volumetric strainmeter at Huzhou station and with the power spectrum density estimation method,we acquired the_0S_5-_0... By using the digital observations of the pendulum tiltmeter, water tube tiltmeter,extensometer and volumetric strainmeter at Huzhou station and with the power spectrum density estimation method,we acquired the_0S_5-_0S_50 fundamental sphere free oscillations caused by the Japan earthquake on March 11,2011,then compared it with the PREM model. The relative errors are mostly bigger than 1.2‰. The extensometer and volume strainmeter can clearly detect _0S_2,_0S_3and_0S_4,which are closely related to the deep structure and earth's interior. 展开更多
关键词 Pendulum tiitmeter Water tube tiitmeter EXTENSOMETER Volumetric strainmeter Free oscillation of the earth
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Envelope Functions of Time Histories in Seismic Safety Evaluation and Scenario Earthquakes
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作者 Shen Jianwen Yu Zhan Shi Shuzhong 《Earthquake Research in China》 2008年第3期297-303,共7页
It has been a period of time since the concept of scenario earthquake was proposed, but this concept has rarely been used in seismic safety evaluation in China since then. Meanwhile, because of the uncertainties of ma... It has been a period of time since the concept of scenario earthquake was proposed, but this concept has rarely been used in seismic safety evaluation in China since then. Meanwhile, because of the uncertainties of magnitudes-distances pairs, there is large arbitrariness while determining the envelope function of time histories in seismic hazard analysis. In this paper, we describe a method to control the envelope functions of the time histories by introducing the most-likely combinations of magnitude and distance of the scenario earthquakes based on a probabilistic method, revise the software of the ellipse model for seismic hazard analysis, and give a computation example. 展开更多
关键词 Scenario earthquake Envelope functions of time history Seismic hazard analysis
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Late Quaternary Tectonic Deformation of the Eastern End of the Altyn Tagh Fault 被引量:4
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作者 YU Zhongyuan MIN Wei +2 位作者 CHEN Tao LIU Yugang SU Peng 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2015年第6期1813-1834,共22页
The Quaternary activity of the faults at the eastern end of the Altyn Tagh fault, including the Dengdengshan-Chijiaciwo, Kuantanshan and Heishan faults, was studied on the basis of interpretation of satellite images, ... The Quaternary activity of the faults at the eastern end of the Altyn Tagh fault, including the Dengdengshan-Chijiaciwo, Kuantanshan and Heishan faults, was studied on the basis of interpretation of satellite images, trenching, geomorphologic offset measurements and dating. The Altyn Tagh fault has extended eastwards to Kuantanshan Mountain. The left-slip rates of the Altyn Tagh fault decreased through the Qilianshan fault and were transformed into thrust and folds deformation of many NW-trending faults within the Jiuxi basin. Meanwhile, under NE-directed compression of the Tibetan plateau, thrust dominated the Dengdengshan-Chijiaciwo fault northeast of the Kuantanshan uplift with a rate lower than that of every fault in the Jiuxi basin south of the uplift, implying that tectonic deformation is mainly confined to the plateau interior and the Hexi Corridor area. From continual northeastward enlargement of the Altyn Tagh fault, the Kuantanshan uplift became a triangular wedge intruding to the east, while the Kuantanshan area at the end of this wedge rose up strongly. In future, the Altyn Tagh fault will continue to spread eastward along the Heishan and Jintananshan faults. The results have implications for understanding the propagation of crustal deformation and the mechanism of the India-Eurasian collision. 展开更多
关键词 slips rate tectonic deformation Kuantanshan fault Dengdengshan fault Altyn Tagh fault
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Seismic reflection and transmission coeffi-cients at an air-water interface of saturated porous soil
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作者 周新民 夏唐代 +1 位作者 徐平 邹振轩 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2006年第4期397-405,共9页
Based on the modified Biot's theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences... Based on the modified Biot's theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences between air-saturated soils and water-saturated soils were theoretically discussed, and the theoretical formulas of reflection and transmission coefficients at an air-water interface were derived. The characteristics of propagation and attenuation of elastic waves in air-saturated soils were given and the relations among the frequency, the angle of incidence and the reflection, transmission coefficients were analyzed by using numerical methods. Numerical results show that the propagation characteristic of the wave in air-saturated soils is great different from that in water-saturated soils. The frequency and the angle of incidence can have great influences on the reflection and transmission coefficients at interface. Some new cognition about the wave propagation is obtained and the study suggests that we may carefully pay attention to the influence of air on the dynamic analysis of seismic wave. 展开更多
关键词 seismic wave air-saturated soils propagation characteristics reflection and transmission
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Teleseismic receiver function using stacking and smoothing of multi seismic-records at a single station
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作者 Yi Yang Fuhu Xie 《Earthquake Science》 CSCD 2012年第1期75-81,共7页
Receiver functions (RFs) obtained using teleseismic wave records at a seismic station and synthetic seismograms indicate that RF with a single teleseismic wave record is related to the selection of record section an... Receiver functions (RFs) obtained using teleseismic wave records at a seismic station and synthetic seismograms indicate that RF with a single teleseismic wave record is related to the selection of record section and to the calculating parameters of the RF. The scatter noise contained in the seismogram also affects the quality of RF. A new method for calculating receiver function, stacking and smoothing multi-seismic records in a single station, is presented in this paper. The RF results using some records and some synthetic seismograms with different noises indicate prominent mantle discontinuity and thus prove that the method is effective and satisfied. 展开更多
关键词 receiver function mantle discontinuity DECONVOLUTION stability
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A Research on the 2014 Wenzhou M4.2 Earthquake in the Shanxi Reservoir
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作者 Zou Zhenxuan Ma Zhijiang +3 位作者 Zhou Xinmin Zhang Fan Li Jun Li Jinlong 《Earthquake Research in China》 CSCD 2017年第4期455-462,共8页
Complete records of more than 3,000 earthquake events in the Shanxi, Wenzhou reservoir earthquake sequence were recorded from August to November,2014 by the high-density,high-resolution monitoring stations of the Zhej... Complete records of more than 3,000 earthquake events in the Shanxi, Wenzhou reservoir earthquake sequence were recorded from August to November,2014 by the high-density,high-resolution monitoring stations of the Zhejiang Regional Digital Seismic Network and the reservoir earthquake monitoring network,with a maximum magnitude of M4. 2. Based on 3-D epicenter location, focal mechanism solutions, and in combination with the geological and tectonic characteristics of the reservoir area,the earthquake sequence is discussed in this paper. The linear fitting of the Hypo SAT location results show that the main shock occurred in the NW trending fault and the earthquake sequence is concentrated in bands along the active faults,with a strike of305 °,dipping SW with dip angle of 85 °. By using P-wave first motion symbols, we obtained the average focal mechanism of M ≥ 3. 5 earthquakes,with a strike 308 ° and dip 84 ° for nodal plane II. The field geological survey and research show that the strike,dip and rake of nodal plane II are roughly consistent with the occurrence of the Shuangxi-Jiaoxi fault. The comprehensive analysis reveals that the NW-trending Shuangxi-Jiaoxi fault is the seismogenic structure of the earthquakes. 展开更多
关键词 RESERVOIR EARTHQUAKE Monitoring network The FAULT structure The FOCAL mechanism SOLUTION
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Numerical Simulation of the Response Features of Apparent Seismic Wave Velocity Ratio in a Horizontal Layered Medium
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作者 Qian Jiadong Yu Xuejun +1 位作者 Cao Aimin Li Shaonong 《Earthquake Research in China》 2013年第4期427-439,共13页
This paper deals with the response features of AR(apparent ratio of seismic wave velocities to the changes of TR(true ratio of wave velocities)in the horizontal layered model by mathematical modeling.The results show ... This paper deals with the response features of AR(apparent ratio of seismic wave velocities to the changes of TR(true ratio of wave velocities)in the horizontal layered model by mathematical modeling.The results show that:(1)the response features of AR are associated with the parameters of the structure and its dynamic changes,and the relative position between the hypocenters and the monitoring networks,showing complicated patterns strongly related to the concrete paths of propagation of seismic waves from the source to the receiver in the observatories of the network;(2)the depth of the seismic source would have important influence on the response features of AR,especially the capacity to carry the anomalous information in the condition of the earth media,being in the anomalous state would be greater for those earthquakes which occur inside the anomalous layers than those underneath the anomalous layers;(3)the response features of AR are clearly related to the changes of TR(true ratio of wave velocities)instead of changes of wave velocities themselves,i.e.the response could be small as the changes in TR is small even in the case of large changes in the wave velocities.It is suggested that more attention must be paid to all these features in combination with detailed investigation of the velocity structure of the earth media in the study region and best fitting of precise hypocenter locations when one wants to obtain the reliable precursors from the changes in AR. 展开更多
关键词 Apparent ratio of seismic wave velocities True ratio of seismic wavevelocities Response features Simulation
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Levels of Probability of Exceedance for Current Code Spectra in China
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作者 Shen Jianwen Liu Zheng Shi Shuzhong 《Earthquake Research in China》 2008年第2期131-136,共6页
Long-period acceleration spectra determined by seismic safety evaluation for project sites are generally lower than that given by relative code spectra.In this paper,we discuss the recurrence periods corresponding to ... Long-period acceleration spectra determined by seismic safety evaluation for project sites are generally lower than that given by relative code spectra.In this paper,we discuss the recurrence periods corresponding to the code spectra of different periods,by using ground motion attenuation laws for sites of types Ⅰ and Ⅲ.We show the results that the longer the periods of code spectra are commonly the more conservative the seismic level is.As for the project examples in this paper,when the periods are longer than 3.7 or 5.2 seconds for sites of types Ⅰ or Ⅲ,the recurrence periods corresponding to the code spectra are longer than 5000 years.We suggest that some problems need to be further discussed,including the reliability of the present attenuation laws,the performance of those project structures that suffer long period seismic waves and have been designed according to the conservative codes,and the effects of ground motion parameters such as velocity and displacement on seismic design. 展开更多
关键词 Seismic design Code spectra Probability level of exceedance
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