2001～2006年兰州—天水—武都地区重力场时变小波分析

Wavelet Analysis of the Temporal Gravity Variation in Lanzhou-Tianshui-Wudu Area from 2001 to 2006

对2001～2006年兰州—天水—武都地区5期重力场时变资料进行小波分解,结合2003年11月岷县5.2级地震、2004年9月岷县5.0级地震以及2006年6月武都、文县间5.0级地震进行分析。探讨了无震年份、有震年份及较长时段的重力场时变资料小波分解结果与地震活动之间的关系,结果表明:用小波分解方法可有效分离重力场时变的不同波长成分;该地区不同层次的重力场时变异常反映了一定尺度意义上不同深度的介质密度的动态变化分布,说明兰州—天水—武都地区中深部地质构造活动所引起的重力异常变化的2阶、3阶小波细节对2003、2004、2006年3次MS≥5.0地震反应明显。

In this paper, we adopt wavelet analysis method to separate different components with different wave length of gravity changes in Lanzhou-Tianshui-Wudu area from 2001 to 2006. The gravity changes were related to the recently-occurred earthquakes, such as Ms5.2 Minxian Earthquake on November 2003 ; Ms5.0 Minxian Earth- quake on September 2003, Ms5.0 Wudu-Wenxian Earthquake on June 2006. Then we discuss the relationship between gravity variations, earthquake activities and tectonic activities. The results show that we can distinguish different gravity changes with different wavelet components by wavelet decomposition, among which 2-order and 3-order wavelet decomposition parts can expose the middle and deep geological and tectonic activities.