2014年8月3日云南鲁甸6.5级地震序列破裂过程研究

本文利用主地震相对定位法,对2014年鲁甸MS6.5地震序列中的8月3日—9月30日地震进行了重新定位,借助于时空图像分析方法,对本次地震破裂过程进行了分析,得到如下结果:(1)2014年鲁甸MS6.5地震主要沿NW向破裂,存在沿NE向破裂的成分,但是NE向破裂并不明显;(2)地震破裂时,主要从主震震中处往ES方向传播,破裂带长度大约为10km,破裂面近乎直立;(3)余震活动主要集中于主震上方区域,震源深度大于主震的余震稀少.根据上述结果,结合当地的地震构造情况和本次地震的震源机制解,分析表明,本次地震的破裂面为NW向,其发震断层为包谷垴—小河断裂的可能性很大.

Investigation on the rupture process of the Ludian MS6.5 earthquake sequence on 3 August, 2014 in Yunnan province

An M_S6.5 earthquake occurred in Ludian, Yunnan province. The rupture process has been analyzed by different researchers. From existing research results, it remains controversial that the seismogenic fault plane is NE or NW fault. Investigation of the aftershock distribution along the main fault is one of the important methods for analysis of earthquake rupture process. In this paper we use the master event relative location method. We select an earthquake with more accurate location than other earthquakes as the main earthquake or reference earthquake, then calculated aftershocks relative to the main location. Compared with absolute location method, this method is more suitable for analyzing the rupture process of earthquake sequence. To investigate the rupture process and seismogenic fault of Ludian M_S6.5 earthquake, we have selected the earthquake phase data recorded by Yunnan, Sichuan and nearby Digital Seismic Networks from 3 August 2014 to 30 September 2014. We use master event relative location method and have relocated the Ludian M_S6.5 sequence. We take the mainshock as the master event,and then obtain the aftershock's relative location. We analyzed the relocated result with the aid of spatial-temporal pattern analyzing method, the following result is obtained. (1) The rupture process for the Ludian M_S6.5 earthquake contains mainly the rupture in the direction of NW and a little one in the direction of NE; (2) The main shock ruptures from the epicenter of the main shock towards the southeast, and the rupture surface is nearly vertical with a rupture length of about 10 km; (3) Most of aftershocks are located in the upper region of the main shock, the aftershocks with the focal depth greater than that of the main shock are very few. According to the above results, combining with tectonic conditions and focal mechanism, we can infer that the rupture surface of the Ludian earthquake is along NW, and the possibility that Baogunao-Xiaohe fault could be the seismogenic fault is very large.