2011年5月中国东北M_w5.7深震的非同寻常震源机制:区域波形反演与成因探讨

Anomalous focal mechanism of the May 2011 M_w5.7 deep earthquake in Northeastern China:regional waveform inversion and possible mechanism

本研究利用中国区域宽频地震台的波形数据,应用gCAP(generalized Cut And Paste)方法反演了2010年2月18日和2011年5月10日中国东北中俄边界附近发生的两个深震的矩张量解,与全球地震矩张量测定机构的结果对比分析,证实了2011年5月深震具有显著的补偿线性单力偶矢量(CLVD)成分,表明基于区域波形资料的gCAP反演可获得较可靠的深震震源机制结果.结合研究区1977—2010年的深震震源机制数据反演确定的日本俯冲带前缘的区域应力场方向,分析认为2011年5月深震的非同寻常震源机制,可能是由于日本东北近海Mw9.0地震造成南东东向拉张应力的变化而造成的,属于日本俯冲带动力作用过程中的响应活动.

Based on digital seismic waveform records of 10 regional broadband stations in Northeastern China and using the generalized ＂Cut and Paste＂ （gCAP） method,we obtained full moment tensors of the deep earthquakes occurred on February 10,2010 and May 10,2011 near the China-Russia border.In comparison with moment tensor results provided by international agencies for global earthquakes,our results for the 2011 deep earthquake confirmed the Global Centroid-Moment-Tensor （gCMT） result,i.e.,it has a significant non-double couple component.This study shows that the gCAP method works very well for obtaining reliable focal mechanisms of deep earthquakes.We also determined the regional stress regime using 23 gCMT solutions of deep earthquakes between 1977 and 2010 within our study area by the Linear Stress Inversion with Bootstrapping resampling method.The regional stress shows that the anomalous non-double couple source component of the 2011 deep earthquake was caused by the dynamic effect of the Japan subduction zone in response to the tectonic stress adjustment after the 11 March 2011 Mw9.0Tohoku-oki earthquake.