2013年芦山M_S7.0地震和2008年汶川M_S8.0地震井水位同震变化的比较分析

COMPARISON AND ANALYSIS OF WELL WATER-LEVEL VARIATIONS CAUSED BY LUSAN M_S7.0 EARTHQUAKE IN 2013 AND WENCHUAN M_S8.0 EARTHQUAKE IN 2008

以芦山、汶川地震震中为中心,选择了8个井点,对2个地震引起的井水位同震变化进行了比较,重点分析了3口同震变化反向的井点,即重庆的荣昌华江井、北碚柳荫井和四川的泸沽湖井。为使对比研究结果可靠,进一步收集了2011年3月11日日本9.0级地震、2012年4月11日苏门答腊北部海域8.6级地震引起的井水位同震变化资料。对汶川、芦山地震引起的同震体应变的计算结果显示:汶川地震时,荣昌华江井、北碚柳荫井和泸沽湖井水位同震变化与井点位置处的同震体应变一致,即位于同震体应变压缩区的井水位上升,位于体应变膨胀区的井水位下降;芦山地震时,3口井的水位同震变化与同震体应变不一致,表现出与日本、苏门答腊地震时相似的同震变化特征。

With the Wenchuan and Lushan epicenters as the center, 8 wells were selected to make a comparative analysis of coseismic variations of well-water level caused by the two earthquakes. Emphasis was laid on the three wells, namely, the Huajiang well in Rongchang, the Liuyin well in Beibei, and the Luguhu well in Sichuan Province, where reverse coseismic variations of water-level were observed during the two earthquakes. We further collected the coseismic variations of water-level data of the three wells caused by two remote earthquakes, the Japan Ms9.0 earthquake in March 11, 2011 and the Sumatra northern sea area MsS. 6 earthquake in April 11, 2012. We also computed the coseismic volumetric strain caused by Wenchuan and Lushan earthquakes respectively in order to interpret the mechanisms. During the Wenchuan earthquake, the coseismic variations of water-level of the Huajiang well in Rongchang, the Liuyin well in Beibei, and the Luguhu well coincided with the coseismic volumetric strain at the wells, that is, the wells located in the compressed area of coseismic volumetric strain showed ascending in the coseismic variations of water-level, while the wells located in the dilatational area of the coseismic volumetric strain showed descending in the coseismic variations of water-level. During the Lushan earthquake, the coseismic volumetric strain and the coseismic water-level variations of the three wells were inconsistent, which are similar to the coseismic variations caused by the Japan and Indonesia earthquakes.