| 2008年汶川Ms8.0地震前龙门山—岷山构造带的地震活动性参数与地震视应力分布 |
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| 引用本文： | 易桂喜,闻学泽,辛华,乔慧珍,龙锋,王思维.2008年汶川Ms8.0地震前龙门山—岷山构造带的地震活动性参数与地震视应力分布[J].地球物理学报,2011,54(6):1490-1500. |
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| 作者姓名： | 易桂喜 闻学泽 辛华 乔慧珍 龙锋 王思维 |
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| 作者单位： | 1. 四川省地震局,成都 610041;
2. 中国地震局预测研究所,北京 100036 |
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| 基金项目： | 国家重点基础研究计划(973)，中国地震局“中国大陆7～8级地震危险性中-长期预测研究”(M7)专项共同资助 |
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| 摘 要： | 本文利用网川区域台网最近30多年的地震资料,计算了2008年四川汶川MS8.0地震前沿龙门山—岷山构造带的多个地震活动性参数(包括震级-频度关系中的a、6与a/6值,复发间隔丁r值),同时,计算了震前2年多的时间内ML≥3.5地震的视应力.在此基础上分析了地震活动性参数值和地震视应力的空间分布与汶川主震破裂范围、MS≥...
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| 关 键 词： | 龙门山—岷山构造带 汶川地震 地震活动性参数 视应力 余震 |
| 收稿时间： | 2010-12-09 |
Distributions of seismicity parameters and seismic apparent stresses on the Longmenshan-Minshan tectonic zone before the 2008 MS8.0 Wenchuan earthquake |
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| YI Gui-Xi,WEN Xue-Ze,XIN Hua,QIAO Hui-Zhen,LONG Feng,WANG Si-Wei.Distributions of seismicity parameters and seismic apparent stresses on the Longmenshan-Minshan tectonic zone before the 2008 MS8.0 Wenchuan earthquake[J].Chinese Journal of Geophysics,2011,54(6):1490-1500. |
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| Authors: | YI Gui-Xi WEN Xue-Ze XIN Hua QIAO Hui-Zhen LONG Feng WANG Si-Wei |
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| Institution: | 1. Earthquake Administration of Sichuan Province, Chengdu 610041, China;
2. Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China |
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| Abstract: | Using the seismic data from the Sichuan Seismic Network, we calculate several seismicity parameters (including the a and b values in the frequency-magnitude relationship, the ratio of a and b, and the recurrence interval Tr) on the Longmenshan-Minshan tectonic zone for the last 30 years before the 2008 MS8.0 Wenchuan, Sichuan, earthquake. We also calculate the apparent stresses of ML≥3.5 earthquakes in the study area for the last over 2 years just before the Wenchuan earthquake. Based on the calculations, we analyze the relationships between the distributions of the seismicity-parameters and the apparent stresses and both the extent of the Wenchuan mainshock's rupture and the distribution of the MS≥5.0 aftershocks. The result mainly shows that, (1) Before the Wenchuan earthquake, the spatial distributions of seismicity parameters and the apparent stresses were significantly heterogeneous on the Longmenshan-Minshan tectonic zone. The sections of Mianzhu-Maoxian and Jiangyou-Pingwu of the central and northern segments of the Longmenshan fault zone were of anomalously low b-values that were much lower than the regional mean one, low a-values, relatively high a/b values and relatively short recurrence intervals Tr. Such a parameter combination suggests that these two fault-sections seemed to have been locked under high stress and to have higher probability for strong or major earthquakes occurring than the other segments before the Wenchuan earthquake. Actually, these two fault sections have become the central segment of the rupture and suffered severe damage during the Wenchuan mainshock. (2) Before the Wenchuan earthquake, the Beichuan fault section, that is between the above mentioned two fault sections, had the parameter combination of relatively high b and a values, as well as relatively low a/b values, implying that it was a fault section with not-high stress level. Following the Wenchuan mainshock, this section has shown relatively low level of aftershock activity without MS≥5.0 aftershock events. (3) From the distributions of the seismicity parameters and the apparent stresses it has been suggested that the stress level cumulated on the southwestern segment of the Longmenshan fault zone seemed to be lower than that on the central and northern segments of the fault zone before the Wenchuan earthquake. This difference of the background stress levels on the southwestern and the central to northern segments could be related with the unilateral and northeastward rupture propagation of the Wenchuan mainshock. In addition, the seismicity parameter value combination also suggests that there may be little chance for a major earthquake occurring on the southwestern segment of the Longmenshan fault zone in the near future. |
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| Keywords: | Longmenshan-Minshan tectonic zone Wenchuan earthquake Seismicity parameters Apparent stress Aftershocks |
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