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Journal: Earthquake Research In China  2019 No.3  Share to Sinaweibo  Share to QQweibo  Share to Facebook  Share to Twitter    clicks:307   
Title:
The Longnan MS5.5 Earthquake on September 12, 2008: A Very Shallow Event Probably Triggered by the Wenchuan Earthquake
Author: LUO Xinyu1, ZENG Xiangfang2, DONG Peiyu3, ZHOU Yong4,5, WEI Xing6, CHENG Huihong2,7
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Abstract:
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 gCAP 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 1.6km, 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 InSAR 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 30kPa around the Longnan earthquake hypocenter, which exceeds the typical triggering threshold of 10kPa. The research indicates that the Wenchuan earthquake probably promote the happening of the Longnan earthquake.

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