28 April 2013, Volume 31 Issue 12

    

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芦山地震专题
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  Focal Mechanism Solution of Lushan M_s 7.0 Earthquake, April 20, 2013

  ZENG Xiangfang;HAN Libo;SHI Yaolin

  . 2013, 31(12): 15-18. https://doi.org/10.3981/j.issn.1000-7857.2013.12.001

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  Focal mechanism provides key information on seismogenic fault and helps to understand tectonic stress field and . First-motion of direct P wave recorded at regional seismic station and teleseismic body wave were employed to invert focal mechanism of Lushan M_s 7.0 earthquake, April 20, 2013. The strike, dip and rake of fault planes of our results are 208°/41°/98°and 220°/46°/93°respectively. Both fault plane and centroid depth are close to results provided by other institutes with different methods and dataset.
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  Stress Changes on Major Faults Caused by M_s 7.0 Lushan Earthquake

  DONG Peiyu;CHENG Huihong;ZENG Xiangfang;SHI Yaolin

  . 2013, 31(12): 19-22. https://doi.org/10.3981/j.issn.1000-7857.2013.12.002

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  On April 20, 2013, a M_s 7.0 earthquake happened in Lushan, Sichuan Province, which killed and hurted hundreds of people, also resulted in huge financial loss. People usually cared about the changes of coulomb failure stress caused by the earthquake, and the effect on the adjacent faults, and subsequent progress after this earthquake. Based on seismic static triggering principle, the elastic dislocation theory, layered crustal model, we used the USGS focal mechanism solution, the coseismic coulomb failure stress is 1.0MPa to 0.1kPa from fault poane to 200km, stress was released in most of the area, however, the Daofu and Yulongxi segment of Xianshuihe fault became more dangerous.
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  Satellite Linear Clouds Anomaly Before M_s 7.0 Lushan Earthquake

  WU Lixin;ZHENG Shuo;ZHONG Xiaohong;QIN Kai

  . 2013, 31(12): 23-26. https://doi.org/10.3981/j.issn.1000-7857.2013.12.003

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  The analysis of the FY-2 satellite cloud images and the infrared radiation brightness temperature data within a month before Lushan earthquake discovered that there were two linear clouds with length of hundreds of kilometers, which developed along the eastern edge of Tibet Plateau at 06:30-09:30am on 17 April, 2013, 3 days before Lushan earthquake. The earthquake epicenter of Lushan earthquake was just located at the intersection point of these two linear clouds extension. As compared to the linear cloud anomalies occurred a few hours before Wenchuan Ms 8.0 earthquake, we suggested that the abrupt occurrences of linear clouds before strong earthquakes in Longmenshan faults region might be related with some unknown hidden structures and underground petroleum resources in the eastern edge of Tibet Plateau. The linear clouds had omens meaning for coming earthquake, which should be taken as a key point of satellite remote sensing monitoring. Subsequently, with the support of big data from GEOSS, and in consideration of the interaction between the multiple spheres of earth system and coupling effect in seismogenic process, we will analyze the spatio-temporal features and the relations of multi-parameters from remote sensing, so as to provide scientific foundations for uncovering the enigma of abnormal liner clouds in this region.
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  Strain Anomalies Before Wenchuan and Lushan Earthquakes Recorded by Component Borehole Strainmeter

  CHI Shunliang

  . 2013, 31(12): 27-30. https://doi.org/10.3981/j.issn.1000-7857.2013.12.004

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  China Earthquake Administration has installed a strain monitoring network of 40 sets four-component borehole strainmeters. One strainmeter located in Sichuan Guzan seismic station has recorded distinct tidal distortion and strain abnormity during the seismogenic process of Wenchuan and Lushan strong earthquakes. These abnormal changes basically met the three criteria of earthquake precursors, thus they were considered to be strain precursor of the seismogenic process of two strong earthquakes. In this paper, the related record information was analyzed, which would provide reference for the subsequent strong earthquake prediction.
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  Rapid Assessment of Earthquake Disaster and Rethink of M_s 7.0 Lushan Earthquake

  LI Zhifeng;WU Lixin;WANG Ran;WANG Qiuling;ZHENG Shuo;XU Zhihua;LI Jing

  . 2013, 31(12): 31-36. https://doi.org/10.3981/j.issn.1000-7857.2013.12.005

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  We initiated the disaster assessment of Lushan M_s 7.0 earthquake immediately after the shocking. The disaster situations including the ratio and distribution of affected population, the ratio of damaged houses, the distribution of casualties and the damaged roads were estimated for four times after seismic intensity was mapped. The whole assessment procedure, referring to the availability of data, was developed from qualitative assessment to quantitative assessment. As compared to the announced data from the Ministry of Civil Affairs, the accuracy of rapid assessment on affected population was 95%, that of damaged houses was 73.3%. The assessment system, including the models, methods and softwares, was validated to be practical after the successful assessment of Yushu earthquake, 2010. In addition, The problems existed in the assessment were rethought, and the solution and direction of the earthquake situations assessment were also put forward.
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  Airborne Union Observation and Disaster Enhanced Identification of M_s 7.0 Lushan Earthquake

  XU Zhihua;LIU Chunbo;WANG Ping;WANG Qiuling;LI Fashuai;WU Lixin;

  . 2013, 31(12): 37-41. https://doi.org/10.3981/j.issn.1000-7857.2013.12.006

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  Based on the Manned Aerial Vehicles (MAV) airborne remote sensing images of Sichuan Lushan M_s 7.0 earthquake acquired by the Institute of Remote Sensing and Digital Earth (RADI), Chinese Academy of Sciences (CAS), an enhanced disaster identification system was developed with Multiple Airborne Sensors Monitoring System(MASMS) supported with low-altitude unmanned aerial vehicles (UAV) sensors. The component of the MASMS and the technical process of the disaster monitoring were introduced. The MAV remote sensing and fixed-wing UAV were applied to joint monitor the disasters in Lushan County, which was badly suffered from Lushan M_s 7.0 earthquake. Taking the remote sensing images acquired by MAV and UAV into consideration synthetically, the details of typical building damage, the distribution of landslides and the destruction of power lines were analyzed comprehensively. The results showed that the MASMS can investigate the disaster situations of major electricity facilities, and meanwhile enhance the ability of disaster identification.
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  2010 Port-au-Prince, Haiti Earthquake Triggered Landslide Hazard Mapping and Its Validation

  XU Chong

  . 2013, 31(12): 42-47. https://doi.org/10.3981/j.issn.1000-7857.2013.12.007

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  Tens of thousands of landslides were triggered by the January 12, 2010 Port-au-Prince, Haiti earthquake (M_w 7.0). The main purpose of this study was to apply and verify the hazard mapping techniques of earthquake triggered landslide by Bivariate Statistics (BS) method, Geographical Information System (GIS) and remote sensing technologies in the Haiti earthquake stuck area. A total of 30828 landslides were delineated in the study area from visual interpretation of multi-source and high resolution remote sensing images pre- and post-earthquake. Eight factors, including elevation, slope angle, slope aspect, slope curvature, distance from drainages, Peak Ground Acceleration (PGA), distance from the Enriquillo-Plantain Garden Fault (EPGF) and distance along the Enriquillo-Plantain Garden Fault (EPGF) were selected as impact factors for the Haiti earthquake triggered landslide hazard mapping. The 30828 landslides were randomly partitioned into two subsets: A training dataset, which contained 70% (21579 landslides, with a total area of 11.18km²), was used for building the model; and a testing dataset containing 30% (9249 landslides, with a total area of 4.56km²) was used for model testing. Landslide hazard probability index map was then generated using the training dataset, the eight landslide impact factors, the weight index (Wi) modeling, a BS method, and GIS technology. The validation results showed a success rate of 84.966% between the hazard probability index map and the training dataset. The predictive rate of 84.547% was obtained from comparing the testing dataset and the landslides hazard probability index map. Both the success rate and the predictive rate showed sufficient agreement between the landslide hazard map and the existing landslides data. The resulting landslide hazard map showed five classes of landslide hazard, such as very high, high, moderate, low and very low. This paper showed weight index modeling, as a BS method in earthquake triggered landslide hazard mapping owned high predictive ability. The results of landslide hazard mapping might help planners to choose favorable locations for reconstruction in the Haiti earthquake struck area.
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  Textual Research of A.D. 600 Qin-Long Earthquake and Discussion on Its Seismogenic Structure

  SHI Zhigang;;YUAN Daoyang;LI Tingdong;GENG Shufang;LEI Zhongsheng;LIU Xingwang;HE Wengui;JIN Qing;

  . 2013, 31(12): 48-52. https://doi.org/10.3981/j.issn.1000-7857.2013.12.008

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  A.D. 600 December 16, a strong earthquake occurred in an area including Tianshui, Gansu Province and Longxian, Shaanxi Province, which caused serious damage and social impact. For a long time, there were different understandings of its exact magnitude, epicenter and epicentral intensity, the seismogenic structure was also unclear. The Qin-Long area was a transitional zone between the southwestern margin of the Ordos block and the Qilian fault fold belt of northeastern Qinghai-Tibet block. It was significant to detailedly study A.D. 600 Qin-Long earthquake and discuss its seismogenic structure. The historical datum on A.D. 600 Qin-Long earthquake were collected and the previous works done by other scholars were also consulted. In Addition, A few of supporting information that was possibly related to this earthquake was discovered. Through studying the historical datum and analyzing the damages on this earthquake, the epicenter of A.D. 600 Qin-Long earthquake may located between Tianshui and Longxian, which is closer to the latter. Its epicentral intensity was inferred as IX and magnitude was about 6(3/4). The orientation of the long axis of the meizoseismal area was roughly consistent with Longxian-Baoji fault zone. By conducting the field investigation and comprehensively analyzing datum of this earthquake, the seismogenic structure of A.D. 600 Qin-Long earthquake may be concluded as Badu-Longwei segment of Guguan-Xiangong fault zone.
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  Performance Evaluation and Test Note of Earthquake Simulation Shaking Table Array System

  GUO Wei;YU Zhiwu;JIANG Lizhong

  . 2013, 31(12): 53-58. https://doi.org/10.3981/j.issn.1000-7857.2013.12.009

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  Considering the risk caused by the frequently occurrence of strong earthquakes, and the development of earthquake simulation shaking table and related technologies, the construction of shaking table device has entered into a boom period in China in order to improve the experimental conditions for carrying out in-depth study on the damage mechanism of buildings in the earthquake. Firstly, the present development state and trends of shaking table are introduced. And then based on the shaking table array system located at Central South University that has passed the acceptance recently, the performance indexes, design ideas, and evaluation method of the overall array system are clearly described. Furthermore, key testing contents of the system are pointed out, the performance acceptance and usage essentials of shaking table array system are also given.
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  Seismic Response Analysis of Steel Through Arch Bridge Considering Effects of Nonlinearity

  XU Qingchun;XU Tao;LI Jia

  . 2013, 31(12): 59-63. https://doi.org/10.3981/j.issn.1000-7857.2013.12.010

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  Nonlinear seismic response analysis was carried out to study the dynamic response and damage mechanism of long span steel through arch bridges which were subjected to strong earthquake. Taking the Beijing-Hangzhou canal bridge in Xuzhou as an example, the seismic response and damage of the bridge under strong earthquake were calculated. The results showed that steel through arch bridges had preferable seismic resistant ability and yielded only limited damage under strong earthquake action. The moment for out of plane significantly increased when considering the geometric and material nonlinear state, while the effect of the geometric and material nonlinear state on the transversal and the vertical displacement response was consistent. Steel through arch bridge was prone to be damaged at arch base, lateral bracing and arch rib. Lateral bracings were the weakness of the structure under the lateral earthquake action. We should pay more attention to these weak parts in case this type of bridge is built in a high earthquake intensity area.
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  Refinement Simulation Study on the Elastoplastic Seismic Time History Analysis of Subway Station Interior Column

  LI Xibing;WANG Zewei;PENG Kang;LIU Zhixiang

  . 2013, 31(12): 64-68. https://doi.org/10.3981/j.issn.1000-7857.2013.12.011

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  The paper has analyzed the mid-column section and come up with the idea of displacement response which was applied on rigorous component model. Three-dimensional elastic-plastic time history analysis of subway station mid-column under earthquake action was achiered. The subway station was submitted to sectional elastic-plastic time history analysis,and relative displacement time history response of both ends of the mid-column was obtained. Then relative displacement time history response was applied to the both ends of elaborate model of mid-column to achieve the time history response in the earthquake action. The results showed that mid-column generated a large-scale plastic zone when rare earthquake was applied at 3.94s. In addition, the concrete of the end portion of mid-column failed, even fell off, and the plastic hinge fully formed at 4.6s and 5.0s. The results of refinement simulation of mid-column was in accordance with that of section simulation of subway station. Moreover it was very similar to the actual earthquake damage.
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  The Prediction of Risk Range and Short-term Catastrophic Timing for Tailings Debris Flowof in West Ditch

  ZHOU Zhichao;LI Xiangquan;LIU Lingxia;HOU Xinwei;LI Jiebiao;WEN Xiaohui

  . 2013, 31(12): 69-74. https://doi.org/10.3981/j.issn.1000-7857.2013.12.012

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  The main research achievements in the area of risk assessment, hazardous dimension, and catastrophic prediction of debris flow are reviewed and summarized. The environmental geological condition of tailings debris flow in west ditch is introduced by the method of field survey and local observation. By taking use of the experiment model established based on 31 sets of debris flow experiment data, the hazardous dimension of debris flow is predicted, and the maximum accumulation length and area in West Ditch is obtained, comparing with the results of field investigation, it could be concluded that the experiment model method is more suitable for predicting the hazardous dimension of tailings debris flow. The gray system forecast model is used to predict the recently disaster time sequence, the credibility is good enough as contrasted with the monitor result, it is able to provide a reference for the risk assessment and disaster mitigation of debris flow. It is also able to provide new ideas for the disaster prevention and mitigation assessment caused by tailings debris flow.
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  The Safety Coefficients Determination for Shear Strength Reduction Method Based on Orderly Clustering

  LIU Aihua;WU Junping;MA Chunde

  . 2013, 31(12): 75-79. https://doi.org/10.3981/j.issn.1000-7857.2013.12.013

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  In order to accurately obtain the mutation point of displacement-reduction coefficient curve when using shear strength reduction method, the method of orderly clustering analysis is brought in for the safety coefficient determination. First, the strength reduction method and criterions of instability are introduced. In view of the system model changes before and after the mutation breakdown point, especially displacement and plastic strain increase sharply, the orderly clustering analysis is used to find out the mutation point. Since conventional Fisher optimal segmentation is not applicable to the progressive trend sequence, by integrating the regression clustering thought, using fitting a polynomial as clustering center, the sum of squared residuals as regression class diameter, a new orderly regression clustering method is set up. Based on the method, the displacement-reduction coefficient sequence is divided into a stable segment and a buckling segment, therefore the mutation point is able to be ascertained, and the corresponding reduction factor is the safety factor of the system. The typical examination question of EX1(a) from ACDAS is used to prove the feasibility of the method, the result for the method is consistent with that for solve fos method of Flac3D and closes to the standard answer. Finally, a discriminant of the system state is established, it is more convenient and practical.