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Detection of ULF electromagnetic emissions as a precursor to two earthquakes in China 被引量:16
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作者 Qi Li Peiyu Zhu +1 位作者 Alimj an Mamatemin Xuegong Xu 《Earthquake Science》 CSCD 2011年第6期601-607,共7页
The geomagnetic data recorded by Kashi and Jinghai observatories in China were analyzed with improved polarization method. We compared the result around 0.01 Hz which is thought to be useful to detect the ULF anomaly ... The geomagnetic data recorded by Kashi and Jinghai observatories in China were analyzed with improved polarization method. We compared the result around 0.01 Hz which is thought to be useful to detect the ULF anomaly with the result around 0.1 Hz which was inferred from the earthquake depth according to the skin effect, and found that 0.1 Hz is more proper to detect the ULF anomaly for both earthquakes studied in this paper. 展开更多
关键词 ULF anomaly geomagnetic data polarization analysis earthquake precursor
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Seismotectonics of the 2008 and 2009 Qaidam Earthquakes and its Implication for Regional Tectonics 被引量:5
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作者 CHEN Guihua XU Xiwei +4 位作者 ZHU Ailan ZHANG Xiaoqing YUAN Renmao Yann KLINGER Jean-Mathieu NOCQUET 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2013年第2期618-628,共11页
Three magnitude 〉6 earthquakes struck Qaidam, Qinghai province, China, in November 10th 2008, August 28th and 31st 2009 respectively. The Zongwulongshan fault has often been designated as the active seismogenic struc... Three magnitude 〉6 earthquakes struck Qaidam, Qinghai province, China, in November 10th 2008, August 28th and 31st 2009 respectively. The Zongwulongshan fault has often been designated as the active seismogenic structure, although it is at odd with the data. Our continuous GPS station (CGPS), the Xiao Qaidam station, located in the north of the Qaidam basin, is less than 30 km to the southwest of the 2008 earthquake. This CGPS station recorded the near field co-seismic deformation. Here we analyzed the co-seismic dislocation based on the GPS time series and the rupture processes from focal mechanism for the three earthquakes. The afiershocks were relocated to constrain the spatial characteristics of the 2008 and 2009 Qaidam earthquakes. Field geological and geomorphological investigation and interpretation of satellite images show that the Xitieshan fault and Zongwulongshan fault were activated as left lateral thrust during the late Quaternary. Evidence of folding can also be identified. Integrated analyses based on our data and the regional tectonic environment show that the Xitieshan fault is the fault responsible for the 2008 Qaidam earthquake, which is a low dip angle thrust with left lateral strike slip. The Zongwulongshan fault is the seismogenic fault of the 2009 earthquakes, which is a south dipping back thrust of the northern marginal thrust system of the Qaidam basin. Folding takes a significant part of the deformation in the northern marginal thrust system of the Qaidam basin, dominating the contemporary structure style of the northern margin of the Qaidam basin and Qilianshan tectonic system. In this region, this fault and fold system dominates the earthquake activities with frequent small magnitude earthquakes. 展开更多
关键词 Qaidam earthquakes SEISMOTECTONICS Xitieshan fault Zongwulongshan fault structure style
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The Characteristics of Seismic Activity Before the Devastating Earthquake with M_W9.0 Off the West Coast of Northern Sumatra 被引量:1
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作者 Xue Yan Song Zhiping +1 位作者 Mei Shirong Liu Jie 《Earthquake Research in China》 2006年第2期118-126,共9页
The characteristics of seismic activity in different time-spatial domain before the M_W9.0 earthquake were studied. The results are as follows:The activity of the deep earthquakes in the north boundary zone of the Aus... The characteristics of seismic activity in different time-spatial domain before the M_W9.0 earthquake were studied. The results are as follows:The activity of the deep earthquakes in the north boundary zone of the Australian plate had been evidently strengthened since 1994, showing an increased frequency, magnitude and depth, especially in regards to the heterogeneous distribution of the earthquake depth (namely between 500km and 689km). Meanwhile the shallow earthquakes of M≥7.0 in the Sumatra island and its vicinity had been obviously strengthened too, and formed a strengthening area with a length of about 1000 km and width 300 km. ②The time distribution of global strong earthquakes with M≥7.0 shows that the character of anomalous seismic quiescence-activity one year before the M_W9.0 earthquake and during its active period, the strong earthquakes formed a seismic belt striking in NWW direction. At the same time, there is a seismic gap formed by earthquakes of M≥5.0 in the epicenter and its neighboring region. ③Two deep earthquakes of M≥7.0 occurred in the west and in the east of the north boundary zone of the Australian plate half year ago. It is notable that one of them occurred in the Sumatra island where no deep earthquake with M≥6.0 has occurred in the past thirty years. ④The space distribution of moderate shocks occurring three days ago exhibited a NWW-strike seismic belt along the north boundary zone of the Australian plate. ⑤The activity of volcanoes distributed in the north boundary zone of the Australian plate had been strengthened in the past 4 years, especially several months before the occurrence of the M_W9.0 earthquake. 展开更多
关键词 地震 活动性 苏门答腊岛 裂隙 火山
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Characteristics of seismic activity before the M_S8.0 Wenchuan earthquake
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作者 Yan Xue Jie Liu +1 位作者 Shirong Mei Zhiping Song 《Earthquake Science》 CSCD 2009年第5期519-529,共11页
The characteristics of spatio-temporal seismicity evolution before the Wenchuan earthquake are studied. The results mainly involve in the trend abnormal features and its relation to the Wenchuan earthquake. The wester... The characteristics of spatio-temporal seismicity evolution before the Wenchuan earthquake are studied. The results mainly involve in the trend abnormal features and its relation to the Wenchuan earthquake. The western Chinese mainland and its adjacent area has been in the seismically active period since 2001, while the seismic activity shows the obvious quiescence of M≥7.0, M≥6.0 and M≥5.0 earthquakes in Chinese mainland. A quiescence area with M≥7.0 has been formed in the middle of the North-South seismic zone since 1988, and the Wenchuan earthquake occurred just within this area. There are a background seismicity gap of M≥5.0 earthquakes and a seismogenic gap of ML〉4.0 earthquakes in the area of Longrnenshan fault zone and its vicinity prior to the Wenchuan earthquake. The seismic activity obviously strengthened and a doughnut-shape pattern of M≥4.6 earthquakes is formed in the middle and southern part of the North-South seismic zone after the 2003 Dayao, Yunnan, earthquake. Sichnan and its vicinity in the middle of the doughnut-shape pattern show abnormal quiescence. At the same time, the seismicity of earthquake swarms is significant and shows heterogeneity in the temporal and spatial process. A swarm gap appears in the M4.6 seismically quiet area, and the Wenchuan earthquake occurred just on the margin of the gap. In addition, in the short term before the Wenchuan earthquake, the quiescence of earthquake with ML≥4.0 appears in Qinghai-Tibet block and a seismic belt of ML〉3.0 earthquakes, with NW striking and oblique with Longmenshan fault zone, is formed. 展开更多
关键词 Wenchuan earthquake background seismicity gap seismogenic gap earthquake swarm seismic belt QUIESCENCE
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3-D rheologic model of earthquake prepa-ration (III): Precursor field
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作者 宋治平 梅世蓉 尹祥础 《Acta Seismologica Sinica(English Edition)》 CSCD 2006年第1期20-29,共10页
On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for t... On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for the three-dimensional rheologic model of earthquake preparation. We derive the viscoelastic analytical expressions of the ground tilt, underground water level, earth resistivity at an arbitrary point (x, y, z) in the rheologic medium, and analyzed the earth resistivity preliminarily, providing a certain theoretical basis for the precursor analysis of seismogenic process. 展开更多
关键词 elastic inclusion theory rheologic inclusion theory viscoelastic analytical expression ground tilt underground water level earth resistivity
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Characteristics of seismic activity before several large Sumatra, Indonesia, earthquakes
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作者 薛艳 宋治平 +1 位作者 梅世蓉 马宏生 《Acta Seismologica Sinica(English Edition)》 CSCD 2008年第3期325-329,333,共6页
Two great earthquakes of MS8.5 and MS8.3 determined by the China Earthquake Networks Center (CENC) occurred successively on September 12 and 13, 2007 in the sea area to the south of Sumatra, which is another group of ... Two great earthquakes of MS8.5 and MS8.3 determined by the China Earthquake Networks Center (CENC) occurred successively on September 12 and 13, 2007 in the sea area to the south of Sumatra, which is another group of large earthquakes after MS8.7 event on December 26, 2004 and MS8.5 event on March 29, 2005. The 展开更多
关键词 seismic gap strengthened seismic activity deep earthquake activity Wadati-Benioff belt
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Study on the Precise Location of the Xinjiang Yutian M_S7.3 Earthquake
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作者 Zhan Xiaoyan Song Xiuqing +4 位作者 Chen Xiangjun Wang Jun Miao Fajun Liu Shuangqing Zhu Yuanqing 《Earthquake Research in China》 CSCD 2015年第1期57-67,共11页
The seismic waveform of the Yutian MS7.3 earthquake,Xinjiang on February 12,2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang,Qinghai,Tibet,and Xinjiang Hotan array,so the method of ... The seismic waveform of the Yutian MS7.3 earthquake,Xinjiang on February 12,2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang,Qinghai,Tibet,and Xinjiang Hotan array,so the method of joint location by regional seismic network and seismic array can be used to accurately determine the earthquake source location.The following technologies were used in the process of location:(1) We selected seismic stations equally located around the epicenter of the MS7.3 earthquake with an average interval of about 15 degrees in the initial location.(2) The recording waveforms of Yutian seismic station were rotated to the radial and tangential directions to precisely obtain the arrival time of S-waves to determine the epicentral distance.(3) The velocity model was used in the determination of location of the epicenter,based on the historical records of earthquakes in the area within a radius of 1.0° from the source as the center,and the velocity model is obtained after re-fitting and calibration.(4) Based on the waveform records of the Hotan seismic array,the method of waveform beaming was used to determine the azimuths and perform the correction of the epicenter location with these azimuths.(5) The deterministic method was used to measure the source depth.Finally,it is concluded that the Yutian MS7.3 main shock hypocenter location is 36.197°N,82.467°E,focal depth 12 km and original time 17:19:48.2 p.m.February 12,2014. 展开更多
关键词 地震波形 新疆和田 精确位置 数字地震台网 区域地震台网 震源位置 时间间隔 震中位置
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Study on the Recurrence Probability of Strong Earthquakes of Faults
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作者 Zhu Yuanqing Xie Chaodi +1 位作者 Song Xiuqing Qin Haowen 《Earthquake Research in China》 2014年第2期152-163,共12页
Based on the physical model of Brownian passage time,the probabilities of recurrence of strong earthquakes on the major active faults in China are calculated in different predictive time spans,based mainly on the anal... Based on the physical model of Brownian passage time,the probabilities of recurrence of strong earthquakes on the major active faults in China are calculated in different predictive time spans,based mainly on the analysis of the earthquake preparation process before a strong earthquake occurs. Furthermore,the seismic risks on active faults are studied. The results show that the earthquake probabilities on the Xianshuihe fault,the Altyn Tagh fault,the east Kunlun fault and Xiaojiang fault are significantly greater than other faults in the Chinese mainland,which indicates that the level of stress accumulation on these faults are higher than on other faults. Therefore,these faults may have a seismic risk for strong earthquake in future. 展开更多
关键词 活动断层 概率计算 强震 鲜水河断裂带 复发 地震孕育过程 阿尔金断裂带 东昆仑断裂带
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Research on the Result of Calibration for the Location of the Seismic Array in Shanghai
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作者 Yu Haiying Zhu Yuanqing Zhao Shuli 《Earthquake Research in China》 2007年第1期55-61,共7页
The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have... The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have been drawn; the difference of calibration results between Hokkaido and Honshu region in Japan is investigated. And calibration results of different directions, different epicenter distances and different magnitudes are probed into. The result shows that the location of earthquakes on the Shanghai seismic array is greatly improved. 展开更多
关键词 上海地震台阵 标定结果 地址 定位
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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 地震 安全设备 评价 历史记录
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Support vector machine method for fore-casting future strong earthquakes in Chinese mainland 被引量:1
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作者 王炜 刘悦 +4 位作者 李国正 吴耿锋 马钦忠 赵利飞 林命週 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2006年第1期30-38,共9页
Statistical learning theory is for small-sample statistics. And support vector machine is a new machine learning method based on the statistical learning theory. The support vector machine not only has solved certain ... Statistical learning theory is for small-sample statistics. And support vector machine is a new machine learning method based on the statistical learning theory. The support vector machine not only has solved certain problems in many learning methods, such as small sample, over fitting, high dimension and local minimum, but also has a higher generalization (forecasting) ability than that of artificial neural networks. The strong earthquakes in Chinese mainland are related to a certain extent to the intensive seismicity along the main plate boundaries in the world, however, the relation is nonlinear. In the paper, we have studied this unclear relation by the support vector machine method for the purpose of forecasting strong earthquakes in Chinese mainland. 展开更多
关键词 statistical learning theory support vector machine artificial neural networks earthquake situation
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Primary component analysis method and reduction of seismicity parameters
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作者 王炜 马钦忠 +2 位作者 林命周 吴耿锋 吴绍春 《Acta Seismologica Sinica(English Edition)》 CSCD 2005年第5期68-77,132,共11页
In the paper, the primary component analysis is made using 8 seismicity parameters of earthquake frequency N (ML≥3.0), b-value, η-value, A(b)-value, Mf-value, Ac-value, C-value and D-value that reflect the character... In the paper, the primary component analysis is made using 8 seismicity parameters of earthquake frequency N (ML≥3.0), b-value, η-value, A(b)-value, Mf-value, Ac-value, C-value and D-value that reflect the characteristics of magnitude, time and space distribution of seismicity from different respects. By using the primary component analysis method, the synthesis parameter W reflecting the anomalous features of earthquake magnitude, time and space distribution can be gained. Generally, there is some relativity among the 8 parameters, but their variations are different in different periods. The earthquake prediction based on these parameters is not very well. However, the synthesis parameter W showed obvious anomalies before 13 earthquakes (MS≥5.8) occurred in North China, which indicates that the synthesis parameter W can reflect the anomalous characteristics of magnitude, time and space distribution of seismicity better. Other problems related to the conclusions drawn by the primary component analysis method are also discussed. 展开更多
关键词 primary component analysis method data mining EIGENVECTOR contribution rate
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The characteristics of Quaternary activity of faults in the sea area near the Yangtze River mouth
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作者 ZHANG Zhen-quan(章振铨) +5 位作者 HUO En-jie(火恩杰) LIU Chang-sen(刘昌森) WANG Feng(王锋) 《Acta Seismologica Sinica(English Edition)》 CSCD 2004年第4期473-479,共7页
By shallow seismic prospecting, it is showed that the faults in the sea area near the Yangtze River mouth are mainly the NE and NW-trending faults. The main activity time of fault is Pliocene to Early Pleistocene, and... By shallow seismic prospecting, it is showed that the faults in the sea area near the Yangtze River mouth are mainly the NE and NW-trending faults. The main activity time of fault is Pliocene to Early Pleistocene, and the latest activity is up to Middle Pleistocene. The maximum of fault is generally several tens meters with the throw decreased upward. The dislocation near the bottom of Middle Pleistocene is 12~13 m. The average vertical dis-placement rate is on a level of 10-3 mm/a. 展开更多
关键词 FAULT ACTIVITY sea area near the Yangtze River mouth
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Performance Metrics and Delay Thresholds for Multi-Link Cluster Monitoring in Seismic Profession
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作者 王小明 李德敏 +1 位作者 汤海涅 张光林 《Journal of Donghua University(English Edition)》 EI CAS 2016年第3期439-443,共5页
Seismic cluster nodes can be monitored by monitoring system,but thresholds for link failure alarm in monitoring systems are not determined presently,especially in different types of cluster links.Communication link ty... Seismic cluster nodes can be monitored by monitoring system,but thresholds for link failure alarm in monitoring systems are not determined presently,especially in different types of cluster links.Communication link types are discussed in seismic profession.By analyzing the characteristics of various links,the main performance metric,network latency,was proposed,which influenced states of communication links and gave the monitoring results deviation formula for judging the cluster monitoring system at different delay thresholds settings based on multiple-link delay error ratio analysis algorithm we offered.From the final experimental data of the monitoring system,fault alarm thresholds settings were posed under five different communication links,which had the instruction significance to the cluster monitoring in seismic profession. 展开更多
关键词 CLUSTER communication link DELAY THRESHOLD monitoring
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Study on the Crustal Velocity Model of Xinjiang and Its Subareas
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作者 Chen Xiangjun Shangguan Wenming +4 位作者 Song Xiuqing Wang Jun Liu Shuangqing Miao Fajun Zhu Yuanqing 《Earthquake Research in China》 2014年第4期436-447,共12页
In this paper,we firstly analyze the "3,400 travel time table "used for a long time in Xinjiang Seismological Network to obtain the velocity structure models in accord with the table by fitting. Then we fit ... In this paper,we firstly analyze the "3,400 travel time table "used for a long time in Xinjiang Seismological Network to obtain the velocity structure models in accord with the table by fitting. Then we fit the velocity of all seismic phases recorded in Xinjiang region in January 2009 ~ December 2013. Simulation analysis is done on the reliability and stability of the velocities,and a concept is proposed for building subarea crustal velocity models according to partitioning of seismic cluster regions. The crustal velocity model suitable for the Yutian area is fitted with the data of all phases of seismic events within a radius of 1°around the 2014 Yutian M_S7.3 earthquake since January 2009,and the model is applied to the relocation of the Yutian M_S7.3 earthquake and determination of focal depths of the earthquake sequence. 展开更多
关键词 地壳速度模型 新疆地区 地震台网 内区 结构模型 仿真分析 地震事件 模型应用
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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 地震 设计 代码光谱 概率水平
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Discussion of rupture mechanisms on the seismogenic fault of the 2008 M_s8.0 Wenchuan earthquake 被引量:19
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作者 DENG QiDong CHEN GuiHua ZHU AiLan 《Science China Earth Sciences》 SCIE EI CAS 2011年第9期1360-1377,共18页
The May 12, 2008, Ms8.0 Wenchuan earthquake was the outcome of a recent movement of an active intra-continental thrust fault zone. The seismogenic fault of this earthquake underwent oblique-slip faulting along the cen... The May 12, 2008, Ms8.0 Wenchuan earthquake was the outcome of a recent movement of an active intra-continental thrust fault zone. The seismogenic fault of this earthquake underwent oblique-slip faulting along the central fault and pure thrust faulting along the range-front fault of the Longmenshan fault zone. The former had a steep dip and large vertical displacement, and the latter had a gentle dip and little vertical displacement. The fault zone consisted of compressive double fault ramps rup turing with right-lateral strike-slip components resulting from strain partitioning of a deep oblique slip fault in the brittle zone of the upper crust. The kinematic pattern and rupture mechanisms are complex for the seismogenic fault, as indicated by the geometric pattern of its surface ruptures, the coseismic displacement distribution and focal mechanisms of the main shock and aftershocks. As a tear fault, the NW-trending, left-lateral, strike-slip Xiaoyudong fault zone has accommodated NE-trending displacements with different shortening amounts. However, because of intense compression on the southwestern segment of the seismogenic fault, the left-lateral, strike-slip Xiaoyudong fault also carries a clear compression component. Normal faulting with a strike-slip component controls the formation of a fault-trough along the central fault, which is characterized by thrusting with a strike-slip component and strike-slip with thrusting. The fault-troughs are the product of the interaction of slip and grav ity on the seismogenic fault under specific geological and geomorphic conditions. Gravitational force exaggerated the vertical component of fault displacement, which by no means represents the actual maximum vertical displacement of the seismogenic fault. 展开更多
关键词 发震断层 破裂机制 地震 汶川 龙门山断裂带 走滑断裂带 垂直位移 垂直分量
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Statistical study on great geomagnetic storms during solar cycle 23
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作者 Qi Li Yufen Gao +2 位作者 Peiyu Zhu Huaran Chen Xiuling Zhang 《Earthquake Science》 CSCD 2011年第4期365-372,共8页
Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number fr... Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak. 展开更多
关键词 geomagnetic storms solar cycle 23 sunspot number 4.5 solar cycles peak Dst andpeak Bz
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青藏高原东缘汶川地震断层陡坎类型与级联破裂模型(英文)
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作者 Guihua Yu 徐锡伟 +10 位作者 Yann Klinger Guilin Diao Guihua Chen Xiangdong Feng Chenxia Li , Ailan Zhu Renmao Yuan Tingting Guo Xinze Sun Xibin Tan Yanfeng An 《国际地震动态》 2010年第6期26-27,共2页
The post-earthquake field investigations reveal that the MW7.9 Wenchuan earthquake of 12th May 2008 ruptured three NE-striking imbricate reverse faults and another NW-trending reverse fault, along the middle Longmensh... The post-earthquake field investigations reveal that the MW7.9 Wenchuan earthquake of 12th May 2008 ruptured three NE-striking imbricate reverse faults and another NW-trending reverse fault, along the middle Longmenshan fold-and-thrust belt at the eastern margin of the Tibetan plateau. The fault-scarp features can be categorized into eight groups: simple thrust scarp, hanging-wall collapse scarp, simple pressure ridge, dextral pressure ridge, fault-related fold scarp, back-thrust pressure ridge, local normal fault scarp and crocodile-mouth-like scarp. The local normal scarp is first discovered in the reverse-faulting earthquakes as ever reported in the world. Field observation indicates that the Wenchuan earthquake surface rupture is dominated by reverse faulting with a minus right-lateral component, but the relative ratio varies from site to site. Also, the surface ruptures can be divided, for the first order, into two segments, the Yingxiu and Beichuan segments, corresponding to MW7.8 and MW7.57 events, respectively. The two segments further can be divided, for the second order, into four sub-segments in total, which are equivalent to four sub-events of MW7.46, MW7.69, MW6.99 and MW7.52, respectively. The fault segmentation, for different orders, shows a cascade-rupturing pattern and can explain why the quake time of the Wenchuan earthquake was so long as up to 100 second. Aftershock focal mechanisms are also used to constrain the fault geometry for the sub-segments, indicating that the seismogenic faults are listric at depth and in general, the fault plane becomes steeper northward, which enables the fault to accommodate larger strike-slip motion. This earthquake also confirms that the crustal shortening across the Longmenshan fold-and-thrust belt should be responsible for the growth of high topographic relief along the eastern margin of the Tibetan Plateau. 展开更多
关键词 断层陡坎 汶川地震 青藏高原东缘
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Branched tetraether lipids in Chinese soils:Evaluating the fidelity of MBT/CBT proxies as paleoenvironmental proxies 被引量:10
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作者 ZHENG FengFeng ZHANG ChuanLun +6 位作者 CHEN YuFei LI FuYan MA CenLing PU Yang ZHU YuanQing WANG YongLi LIU WeiGuo 《Science China Earth Sciences》 SCIE EI CAS CSCD 2016年第7期1353-1367,共15页
The ubiquitous occurrence of branched glycerol dialkyl glycerol tetraethers(br GDGTs) in soils has allowed development of new proxies for reconstruction of past climate and environment. The methylation and cyclization... The ubiquitous occurrence of branched glycerol dialkyl glycerol tetraethers(br GDGTs) in soils has allowed development of new proxies for reconstruction of past climate and environment. The methylation and cyclization degrees of br GDGTs, expressed as MBT and CBT, respectively, are reported to be mainly controlled by mean annual air temperature(MAAT) and soil p H. However, the br GDGT-derived temperatures and soil p H scatter widely when data from different environmental conditions are considered. In this study, we collected over 300 soil samples from China, which are representative of humid(Xishuangbanna, Guangzhou, and Shanghai), semi-arid(Dongying) and semi-arid/arid(Lanzhou, Tibetan Plateau) regions. Collectively we have the most extensive dataset that broadly characterizes the distribution of br GDGTs according to climate zones in China. The overall data demonstrate that the MBT/CBT derived temperatures better match the measured MAATs in humid and non-alkaline regions than those from regions of low MAP(<400 mm/yr) and above neutral soil p H(>7.0–7.5). Similarly, CBT describes soil p H much better in humid and non-alkaline soils than in semi-arid/arid and alkaline soils; the semi-arid/arid and alkaline soils tend to show a positive correlation between soil p H and CBT, which contradicts that in the humid and non-alkaline soils. While soil p H, MAAT and mean annual precipitation(MAP) are dominating factors controlling the br GDGT distribution across all climate zones, conductivity, total organic carbon and total nitrogen, as well as soil water content can also play an important role locally. Removing br GDGT-II resulted in a revised CBT index that provides more accurate estimation of p H, especially in semi-arid/arid and alkaline soils. The overall Chinese dataset demonstrates that continental air temperature derived from br GDGT-proxies can vastly deviate from real measurements and should be used with extreme caution in paleo-climate or-environment studies. 展开更多
关键词 中国土壤 环境指标 CBT MBT 代理 碱性土壤 年平均气温 保真
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