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Lateral migration of fault activity in Weihe basin

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Acta Seismologica Sinica(English Edition) 2004年第2期17卷 190-199页

作者： FENG Xi-jie(冯希杰) DAI Wang-qiang(戴王强) earthquake administration of Shaanxi Province Xi''an 710068 China Earthquake Administration of Shaanxi Province Xi''an 710068 China

Lateral migration of fault activity in Weihe basin is a popular phenomenon and its characteristics are also typical. Taking the activity migrations of Wangshun Mountain piedmont fault toward Lishan piedmont fault and Weinan platform front fault, Dabaopi-Niujiaojian fault toward Shenyusi-Xiaojiazhai fault, among a serial of NE-trending faults from Baoji city to Jingyang county as examples, their migration time and process are analyzed and discussed in the present paper. It is useful for further understanding the structure development and physiognomy evolution history of Weihe basin.

关键词： lateral migration fault activity Weihe basin

Upper crustal velocity and seismogenic environment of the M7.0 Jiuzhaigou earthquake region in Sichuan, China

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Earth and Planetary Physics 2021年第4期5卷 348-361页

作者： DaHu Li ZhiFeng Ding Yan Zhan PingPing Wu LiJun Chang XiangYu Sun Chengdu Institute of the Tibetan Plateau earthquake Research China Earthquake AdministrationChengdu 610041China Institute of Geophysics China Earthquake AdministrationBeijing 100081China Institute of Geology China Earthquake AdministrationBeijing 100029China

On August 8,2017,a magnitude 7.0 earthquake occurred in Jiuzhaigou county,Sichuan Province,*** deep seismogenic environment and potential seismic risk in the eastern margin of Tibetan Plateau have once again attracted the close attention of seismologists and scholars at home and *** post-earthquake scientific investigation could not identify noticeable surface rupture zones in the affected area;the complex tectonic background and the reason(s)for the frequent seismicity in the Jiuzhaigou earthquake region are *** order to reveal the characteristics of the deep medium and the seismogenic environment of the M7.0 Jiuzhaigou earthquake region,and to interpret the tectonic background and genesis of the seismicity comprehensively,in this paper,we have reviewed all available observation data recorded by the regional digital seismic networks and large-scale,dense mobile seismic array(China Array)for the northern section of the North-South Seismic Belt around Jiuzhaigou earthquake *** double-difference seismic tomography method to invert the three-dimensional P-wave velocity structure characteristics of the upper crust around the Jiuzhaigou earthquake region,we have analyzed and discussed such scientific questions as the relationship between the velocity structure characteristics and seismicity in the Jiuzhaigou earthquake region,its deep tectonic environment,and the ongoing seismic risk in this *** report that:the P-wave velocity structure of the upper crust around the Jiuzhaigoug earthquake region exhibits obvious lateral inhomogeneity;the distribution characteristics of the shallow P-wave velocity structure are closely related to surface geological structure and formation lithology;the M7.0 Jiuzhaigou earthquake sequence is closely related to the velocity structure of the upper crust;the mainshock of the M7.0 earthquake occurred in the upper crust;the inhomogeneous variation of the velocity structure of the Jiuzhaigou earthquake area and

关键词： the M7.0 Jiuzhaigou earthquake 3D P-wave velocity structure deep tectonic seismogenic environment

A τ_c magnitude estimation of the 20 April 2013 Lushan earthquake, Sichuan, China

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Science China Earth Sciences 2014年第12期57卷 3118-3124页

作者： PENG ChaoYong YANG JianSi ZHENG Yu JIANG XuDong XU ZhiQiang GAO Yu Institute of Geophysics China Earthquake Administration

A crucial part of proposed earthquake early warning systems is a rapid estimate for earthquake *** of these methods are focused on the first part of the P-wave train,the earlier and less destructive part of the ground motion that follows an earthquake.A method has been proposed by using the period of the P-wave to determine the magnitude of a large earthquake at local distance,and a specific relation for the Sichuan region was calibrated according to acceleration records of Wenchuan *** Mw 6.6 earthquake hit Lushan county,Sichuan,on April 20,2013 and the largest aftershocks provide a useful dataset to validate the proposed relation and discuss the risks connected to the extrapolation of magnitude relations with a poor dataset of large earthquake waveforms.A discrepancy between the local magnitude(ML)estimated by means ofτc evaluation and the standard ML(6.4 vs.7.0)suggests using caution when ML vs.τc calibrations do not include a relevant dataset of large *** from large residuals could be mitigated or removed by introducing selection rules onτc function,by regionalizing the ML vs.τc function in the presence of significant tectonic or geological heterogeneity,and by using probabilistic and evolutionary methods.

关键词： earthquake early warning systems τc method Lushan earthquake magnitude

Study on the characteristics of earthquake's impact on cities

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Acta Seismologica Sinica(English Edition) 2004年第2期17卷 222-229页

作者： PAN Hua(潘华) ZHAO Feng-xin(赵凤新) GAO Meng-tan(高孟潭) Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Geophysics China Earthquake Administration Beijing 100081 China

Firstly, the impact of historical earthquakes on 34 China province-level capital cities is evaluated by using historical earthquake catalog. The distribution of affected intensity shows, about 53% of cities have even not been affected by earthquake intensity VI, and 44% of cities have been hit by earthquake intensity VII to IX. For most of the cities, occurrence frequency of affected intensity VI is usually higher than that of affected intensity larger than VI, and the value of affected intensity with maximal occurrence frequency may be very different among cities. So both the maximal affected intensity and the affected intensity with maximal occurrence frequency should be taken into account when the prevention seismic intensity needs to be determined. Secondly, considering the incompleteness of records of historical earthquakes, a method of earthquake catalog computer simulation is introduced to study the features of affected intensity of big cities. 69 county-level cities of Fujian Province are selected to be statistical objects. The statistical result shows, for different risk levels the seismic intensity changes greatly among cities, the seismic intensity of 2% probability of exceedance in 50 years can be regarded as the characteristic affected intensity of city, and can be the basis of determining the city special earthquake prevention level and a proper indicator of future earthquakes impact on cities.

关键词： city group affected intensity characteristics earthquake probability of exceedance

The 2018 M_S 5.9 Mojiang earthquake:Source model and intensity based on near-field seismic recordings

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Earth and Planetary Physics 2019年第3期3卷 268-281页

作者： Xu Zhang Zhen Fu LiSheng Xu ChunLai Li Hong Fu Institute of Geophysics China Earthquake Administration earthquake administration of Yunnan Province

On September 8, 2018, an M_S 5.9 earthquake struck Mojiang, a county in Yunnan Province, China. We collect near-field seismic recordings(epicentral distances less than 200 km) to relocate the mainshock and the aftershocks within the first 60 hours to determine the focal mechanism solutions of the mainshock and some of the aftershocks and to invert for the finite-fault model of the *** focal mechanism solution of the mainshock and the relocation results of the aftershocks constrain the mainshock on a nearly vertical fault plane striking northeast and dipping to the southeast. The inversion of the finite-fault model reveals only a single slip asperity on the fault plane. The major slip is distributed above the initiation point, ～14 km wide along the down-dip direction and ～14 km long along the strike direction, with a maximal slip of ～22 cm at a depth of ～6 km. The focal mechanism solutions of the aftershocks show that most of the aftershocks are of the strike-slip type, a number of them are of the normal-slip type, and only a few of them are of the thrust-slip *** average, strike-slip is dominant on the fault plane of the mainshock, as the focal mechanism solution of the mainshock suggests, but when examined in detail, slight thrust-slip appears on the southwest of the fault plane while an obvious part of normal-slip appears on the northeast, which is consistent with what the focal mechanism solutions of the aftershocks display. The multiple types of aftershock focal mechanism solutions and the slip details of the mainshock both suggest a complex tectonic setting, stress setting, or both. The intensity contours predicted exhibit a longer axis trending from northeast to southwest and a maximal intensity of Ⅷ around the epicenter and in the northwest.

关键词： 2018 MS 5.9 Mojiang earthquake near-field seismic recording finite-fault model intensity prediction focal mechanism solution

Relocation of the 1998 Zhangbei-Shangyi earthquake sequence using the double difference earthquake location algorithm

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Acta Seismologica Sinica(English Edition) 2004年第2期17卷 125-130页

作者： YANG Zhi-xian(杨智娴) CHEN Yun-tai(陈运泰) Institute of Geophysics China Earthquake Administration Beijing 100081 China Institute of Geophysics China Earthquake Administration Beijing 100081 China

On January 10, 1998, at 11h50min Beijing Time (03h50min UTC), an earthquake of ML=6.2 occurred in the border region between the Zhangbei county and Shangyi county of Hebei Province. This earthquake is the most significant event to have occurred in northern China in the recent years. The earthquake-generating structure of this event was not clear due to no active fault capable of generating a moderate earthquake was found in the epicentral area, nor surface ruptures with any predominate orientation were observed, no distinct orientation of its aftershock distribution given by routine earthquake location was shown. To study the seismogenic structure of the Zhangbei- Shangyi earthquake, the main shock and its aftershocks with ML3.0 of the Zhangbei-Shangyi earthquake sequence were relocated by the authors of this paper in 2002 using the master event relative relocation technique. The relocated epicenter of the main shock was located at 41.145癗, 114.462癊, which was located 4 km to the NE of the macro-epicenter of this event. The relocated focal depth of the main shock was 15 km. Hypocenters of the aftershocks distributed in a nearly vertical plane striking 180~200 and its vicinity. The relocated results of the Zhangbei-Shangyi earthquake sequence clearly indicated that the seismogenic structure of this event was a NNE-SSW-striking fault with right-lateral and reverse slip. In this paper, a relocation of the Zhangbei-Shangyi earthquake sequence has been done using the double difference earthquake location algorithm (DD algorithm), and consistent results with that obtained by the master event technique were obtained. The relocated hypocenters of the main shock are located at 41.131癗, 114.456癊, which was located 2.5 km to the NE of the macro-epicenter of the main shock. The relocated focal depth of the main shock was 12.8 km. Hypocenters of the aftershocks also distributed in a nearly vertical N10E-striking plane and its vicinity. The relocated results using DD algorithm cl

关键词： Zhangbei-Shangyi earthquake double difference earthquake location algorithm earthquake relocation seismogenic structure source process

Textual research of 1219 A.D. Guyuan earthquake in Ningxia Hui Autonomous Region,China and discussion on its causative structure

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earthquake Science 2008年第6期21卷 652-664页

作者：袁道阳雷中生张俊玲刘百篪梁明剑 Lanzhou Institute of Seismology China Earthquake Administration Lanzhou Base of Institute of earthquake Science China Earthquake Administration

On the basis of textual research on the historical earthquake data and the field investigation of 1219 *** earthquake,we suggest that there is only one strong earthquake occurred in Guyuan area in 1219 A.D.,instead of two or three strong *** further suggest that the earthquake parameters recorded in the present earth-quake catalogs are not definite and should be *** occurrence time of this earthquake should be about 11 am,August 7,1219 *** the heavily-damaged area of this earthquake,the VIII intensity area,should be lo-cated among the regions of Guyuan,Pingliang and Longde county *** epicenter area should be near Gu-yuan *** magnitude of this earthquake is about 7 and it has intensity about larger than or equal to IX within the epicenter *** major axis direction of the heavily-damaged area strikes in north-northwest that is ap-proximately consistent with the strike of the Liupan Shan thrust fault *** new tectonic activity of the Liupan Shan thrust fault zone resulted in the M7 Guyuan earthquake in 1219 A.D.

关键词： 1219 A.D.Guyuan earthquake textual research of historical earthquake causative structure eastern Liupan Shan piedmont fault

Analysis of landslide damage caused by the 2008 Wenchuan earthquake using strong motion data: A case study in the Beichuan county town

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earthquake Science 2012年第4期25卷 307-313页

作者： Xiuying Wang Gaozhong Nie Song Wang Institute of Crustal Dynamics China Earthquake Administration Institute of Geology China Earthquake Administration China earthquake Networks Center

The county town of Beichuan county, China, experienced catastrophic destruction due to landslides induce by the 2008 Wenchuan earthquake. In consideration of the special location of the county town, this paper selected the landslides induced in the town as representative of large-scale near-rupture landslides, and quantitatively analyzed why the landslide damage was so destructive in the town by using strong motion data obtained from the Wenchuan earthquake in the Longmenshan area. Three methods were employed to estimate the landslide damage using strong motion data. （1） Peak ground accelerations （PGAs） on the hanging wall were used to evaluate the PGAs on the landslide sites in the town. The evaluated average PGAs were all greater than I g, indicating that the ground motion intensity was very strong during the earthquake. （2） Acceleration time histories, from another station with similar geological conditions to the town, were used to evaluate the critical acceleration changing range, and the estimated values showed the geological conditions were very susceptible to earthquakes. （3） Acceleration time histories, from two stations on the hanging and foot walls of the rupture, and near the town, were used to calculate the Newmark displacements, and all the evaluated displacements indicated that landslides were very likely. The results show that the slopes, susceptible to earthquakes in the Beichuan county town, were easily triggered under such strong ground-motion intensity and developed into large-scale catastrophic events.

关键词： Wenchuan earthquake landslide strong motion evaluation critical acceleration

New characteristics of intensity assessment of Sichuan Lushan “4.20” M_s7.0 earthquake

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earthquake Engineering and Engineering Vibration 2014年第S1期13卷 123-139页

作者： Sun Baitao Yan Peilei Chen Xiangzhao Key Laboratory of earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake Administration Professor PhD PhD Candidate

The post-earthquake rapid accurate assessment of macro influence of seismic ground motion is of significance for earthquake emergency relief,post-earthquake reconstruction and scientific research. The seismic intensity distribution map released by the Lushan earthquake field team of the China earthquake administration(CEA) five days after the strong earthquake(M7.0) occurred in Lushan county of Sichuan Ya’an City at 8:02 on April 20,2013 provides a scientific basis for emergency relief,economic loss assessment and post-earthquake reconstruction. In this paper,the means for blind estimation of macroscopic intensity,field estimation of macro intensity,and review of intensity,as well as corresponding problems are discussed in detail,and the intensity distribution characteristics of the Lushan '4.20' M7.0 earthquake and its influential factors are analyzed,providing a reference for future seismic intensity assessments.

关键词： Lushan earthquake intensity assessment damage index remote sensing strong earthquake record