2008年汶川MS8.0地震和2013 年芦山MS7.0地震震源特征比较分析

Characteristics of the source parameters and the rupture processes for the 2 earthquakes in the Longmenshan fault zone: the 2008 MS8.0 Wenchuan earthquake and the 2013 MS7.0 Lushan earthquake

摘要:

2013年4月20日四川芦山发生了MS7.0地震，芦山地震震中距离2008年5月12日汶川MS8.0地震震中约85km，距离其余震密集分布区约60km。汶川地震和芦山地震均发生在龙门山断裂带上，震源机制均以逆冲为主，针对二者震源特征的比较分析，对解释龙门山地区强震特征意义显著。本文基于地震波辐射能及视应力与应力降的关系，对比讨论汶川地震和芦山地震的动态破裂过程，初步研究结果显示，汶川地震属于应力上调模式，而芦山地震则属于应力下调模式，通常应力上调模式的震后能量释放较为充分，应力下调模式则对应震后能量释放相对不够充分，余震空间分布相对集中。

Abstract:

The April 20，2013 MS7. 0 earthquake occurred in Lushan City，Sichuan Province， China，which was a result of east-west oriented reverse-type motion on a north-south striking fault． The source location suggests the event occurred on southern part of Longmenshan fault at a depth of 13km． And the great Wenchuan MS8． 0 earthquake of the May 12，2008 also occurred in Sichuan Province of the western interior China with an epicenter located at the longitude 103. 4°E and latitude of 31. 0°N． Both the 2 important earthquakes located on the Longmenshan fault zone， and the distance between 2 epicneters is 85km while the distance between aftershocks distribution of the 2 manshocks is 60km． In this study，the dynamic source process with the focal mechanism and empirical relationships was calculated and the related energy and apparent stress were analyzed，respectively． The results indicated that there was frictional undershoot behavior in the dynamic source process of Lushan earthquake，which is actually different from the overshoot activity of the Wenchuan earthquake． Moreover，the characteristics of the source parameters， radiated energy from the fault and the aftershocks distribution from 2 mainshocks were discussed． It indicated that the rupture process was under the influence of apparent stress and frictional behavior on the fault plane．