2012年4月11日苏门答腊8.6级地震前后川滇地区波速变化研究

利用2012年1~6月川滇地区(21°～34°N, 97°～108°E)99个测震数字地震台的连续波形资料, 采用背景噪声层析成像方法反演了2012年4月11日苏门答腊8.6级地震前后川滇地区的波速变化, 同时研究了该地震前后川滇地区地震活动的变化特征。 结果表明, 川滇地区波速结构呈现龙门山断裂带南段至元谋—绿汁江断裂带和安宁河断裂带波速降低而两侧波速升高的特点。 同时, 波速变化与地震活动性变化具有明显的相关性: 在宁蒗—木里和乐山—雅安一带波速增高显著, 地震活动速率也增加; 在龙门山断裂带南段至安宁河断裂带上则表现为明显的波速降低, 而安宁河断裂带也是地震活动速率降低区域。 这表明本研究得到的波速变化的结果有一定的可信度, 也为背景噪声方法应用到地震预测提供了一种可能的途径。

Wave Velocity Changes in the Sichuan-Yunnan Region before and after the April 11, 2012 Sumatra MS8.6 Earthquake

Velocity changes before and after the April 11, 2012 Sumatra M_S8.6 earthquake have been inverted by ambient tomography method, using continuous waveform records of 99 stations in Sichuan seismic network and Yunnan seismic network from Jan., to Jun., 2012. The characteristics of seismicity in the Sichuan—Yunnan region are also analyzed during the earthquake. Results show that the velocity from the southern segment of Longmenshan fault to Yuanmou—lvzhijiang fault zone and Anninghe fault zone decreased, while the velocity of both sides increased. At the same time, wave velocity changes have a significant correlation with the changes of seismicity. The wave velocity increased together with the seismicity rate in Ninglang—Muli and Leshan—Yaan regions. Wave velocity decreased from the southern segment of Longmenshan Fault zone to Anninghe Fault zone. The seismicity rate of Anninghe Fault zone was also decreased. These show that the results of the velocity change are credible to some extent.