汶川8.0级地震前龙门山断裂带的地震活动性和构造应力场特征

研究了2008年5月12日汶川8.0级地震前龙门山断裂带及其附近地区的地震活动.利用区域地震台网和流动测震台的数字地震波资料，测定了震源机制解.结果表明，震中所在的龙门山断裂带震前地震活动平稳，未出现显著异常增强或平静现象.根据汶川8.0级地震前地震活动求出的震源机制解，其主压应力P轴方位为WNE——ESE向，震源断层面呈NE向与NW 向两组节面走向.其中NE向节面呈N50deg;——70deg;E，断面倾角均陡，达60deg;——70deg;,震源力学作用方式多呈逆倾型，少部分呈走滑型．震前地震活动呈现的主压应力方位、震源断面走向及其错动类型，与汶川8.0级地震给出的解是一致的.巨大地震发生前沿龙门山断裂带微破裂呈现的平均应力场与主震一致．起始破裂区东侧20km内是紫坪铺水库水域区，这一区域发生小震活动增加的现象处于水库放水的卸载阶段.本文研究了汶川8.0级地震起始破裂区附近的小震活动，其震源参数表明，震源位于8.0级地震之上的5——14km深度，其震源参数与8.0级地震给出的解也是一致的． 

Seismicity and tectonic stress of the Longmenshan fault zone before 2008 Wenchuan M_S8.0 earthquake

Seismicity of the Longmenshan fault zone and its vicinity before the 12 May 2008 Wenchuan MS8.0 earthquake is studied. Based on the digital data of seismic waveform observed from regional seismic networks and mobile stations, earthquake focal mechanism solutions are determined. The results obtained show that the seismicity of Longmenshan fault zone before the 12 May 2008 Wenchuan MS8.0 earthquake were in a stable state. No obviously intensified seismic activity appeared. According to focal mechanism solutio...