The Longnan MS5. 5 Earthquake on September 12, 2008:A Very Shallow Event Probably Triggered by the Wenchuan Earthquake

作者：LUO Xinyu,ZENG Xiangfang,DONG Peiyu,ZHOU Yong,WEI Xing,CHENG Huihong

摘要：The 2008 Wenchuan earthquake has a significant impact on the seismicity of nearby regions. The Longnan earthquake which occurred on September 12,2008 in Gansu Province was out of the aftershock zone. Reliable source parameters are essential for understanding the seismogenic process of this earthquake. Therefore,three approaches are adopted to study the source parameters of this event. The focal mechanism is obtained with the g CAP method that takes non-Double-Couple(non-DC)component into account. The two fault planes are NP1:150°/45°/81° and NP2:342°/45°/98°,while the non-DC component is about 53%. The focal depth is 1. 6 km,which indicates the Longnan earthquake is a shallow event. Furthermore,this result is also in good agreement with results obtained with two other approaches:amplitude spectra of Rayleigh wave and surface displacement from In SAR measurement. To analyze the cause of the event,coulomb failure stress change caused by the Wenchuan earthquake on the Longnan earthquake fault plane is calculated. The result shows that coulomb stress change is 30 k Pa around the Longnan earthquake hypocenter,which exceeds the typical triggering threshold of 10 k Pa. The research indicates that the Wenchuan earthquake probably promote the happening of the Longnan earthquake.

发文机构：School of Earth and Space Sciences State Key Laboratory of Geodesy and Earth's Dynamics Hubei Earthquake Agency Department of Earth and Space Sciences School of Geodesy and Geomatics China Earthquake Networks Center CAS Key Laboratory of Computational Geodynamics

关键词：LongnanEARTHQUAKESourceparameterRAYLEIGHwaveAMPLITUDEspectraSurfaceDISPLACEMENTCOULOMBfailurestress

分类号： P31[天文地球—固体地球物理学][天文地球—地球物理学]