2008年汶川8.0级地震前川青块体及邻区地震活动性分析

Seismicity analysis on the Qinghai-Sichuan Blocks and proximity before the 2008 Wenchuan M8.0 Earthquake

本文简要分析了2008年5月12日汶川8.0级地震前川青块体及邻区的地震活动性特征。结果表明,汶川地震发生的龙门山断裂本身历史地震活动水平不高,其周边的鲜水河断裂、岷江断裂、虎牙断裂等历史上强震多发;汶川8.0级地震前龙门山断裂带3级以上中小地震活动增强或平静异常现象不明显,地震活动参数值均在正常变化区间内;4级以上地震异常平静,形成了地震空区;2007年底到2008年初位于龙门山断裂带及其附近台站的0.1级以上小震月频度增强明显。

The seismicity characters of the Qinghai-Sichuan Blocks and proximity before the 2008 Wenchuan MS. 0 Earthquake are summarized. Analyzing results show that the active level of historical earthquakes along the Long- mensban faults is not high and a lot of strong earthquakes occurred along following faults： Xianshuihe, Mingjiang and Huya. The seismicity level of small and moderate magnitude more than M3.0 along Longmenshan Faults in- creased and these anomalous items were not clear before the 2008 Wenchuan M8.0 Earthquake. The seismicity pa- rameters were in the normal level and the seismieity of magnitude M4.0 earthquakes is quiet. A gap of magnitude M4.0 earthquakes was formed. The active rate of events per month with magnitude more than 0. 1 earthquakes in- creased from 2007 to 2008 before the 2008 Wenchuan MS. 0 Earthquake.