GPS连续观测站基线与地震危险性分析

根据中国地壳运动观测网络基准站1999—2009年的资料,文中应用小波方法对中国大陆的有关GPS基线时间序列进行了分离,通过对各个频段小波分解结果的分类分析,我们获得如下看法:①在2001年昆仑山口西Ms8.1级与2008年汶川Ms8.0级强震前,部分GPS基线小波分解中低频段(A8,D8,D7,D6,D5)在数月至1年以上的时间内发生较明显的变化,说明浅源大地震的孕育发生与大区域构造活动增强相关;②与北京十三陵(BJSH)相连的BJSH-YANC,BJSH-JIXN,BJSH-TAIN,HLAR-BJSH,CHUN-BJSH基线近期都存在一定程度的异常,显示北京周围地区压性活动增强,首都圈地区2006—2008年大面积垂直形变结果也反映该地区存在一定的异常。目前尚无足够的证据证明这种形变异常变化是否与汶川地震有关。但也许提示2008年华北北部地区的构造活动已从常态活动开始转向异态活动,有可能是强震孕育的信号,应给予密切跟踪研究。

Analysis of GPS Baseline of Continuous Stations and Earthquake Risk

By the use of the data of 1999—2009 from continuous stations of the Project of ＂China Crust Movement Measuring Network＂,the paper applies the wavelet method to separate the GPS baseline timeseries of continuous stations in the mainland of China,By classified analyzing of the results of different frequency,we gain opinions as follows：（1） Before the West Kunlun mountain Ms8.1 earthquake and the Wenchuan Ms8.0 earthquake,part of the medium-low frequency（A8,D8,D7,D6,D5） of GPS baselines showed obviously anomalous variations during a period of several months to more than a year early before the earthquake,which reflects that the occurrence of large earthquake with shallow focus is associated with the intensification of large-area tectonic movement;（2）There exists some anomalous variations of the baselines connected to BJSH,such as BJSH-YANC,BJSH-JIXN,BJSH-TAIN,HLAR-BJSH and CHUN-BJSH,which shows the increasing of compressive activities around the neighborhood of Beijing area recently,the vertical deformation results of Capital Area of 2006—2008 also reflects there exists certain anomalous variations in this area.Up to now,there was no sufficient evidence implying such deformation variation was induced by Wenchuan Earthquake.It maybe reminds us that the tectonic movement in northern region of North China is shifting from normal fashion to abnormal fashion since 2008.This might be a kind of signal of strong earthquake preparation which needs further investigattion and study.