【作者】 孙尧；

【导师】 龙长兴； 安美建；

【作者基本信息】 中国地质科学院 ， 地球探测与信息技术， 2014， 博士

【摘要】 位于中国西南的川滇地区在印度板块和欧业板块持续碰撞的动力学背景下,第四纪以来构造活动强烈,并且形成了由川滇外弧带和滇西内弧带构成的独特的双弧型旋扭活动构造体系。其中滇西内弧带是我国构造格局最复杂,地震活动性最高的区域之一。基于地表的调查资料难以判断活动断裂的深部产状和延伸范围,中国地质科学院地质力学研究所于2010年3月至2011年3月在瑞丽及其周边部署了由24个短周期地震台站组成的台阵,目的是通过所观测到的大量微地震的空间分布来研究区域上断裂带的空间展布、相互关系以及地震活动性。通过地震定位与误差分析等常规的处理,得到了一年以来瑞丽地区共计527个地震事件的震源参数。在分析这些地震事件的水平展布与深部剖面分布后,认为瑞丽地区在近期总体上地震活动性不强,就当地的主要活动断裂而言畹町断裂的地震活动性要强于龙陵——瑞丽断裂,而且在瑞丽市的东南方向还存在‘个地震密度相对较高的近南北向的次级构造带。除此以外我们的短周期地震台阵还记录了台阵北北西方向约60km处的2011年3月10日盈江5.9级地震的前震和余震信息,在分别利用Hypo71绝对定位和HypoDD双差分相对定位方法对所记录到的地震进行了高精度定位后。地震时空分布显示,盈江地区的地震活动自2010年12月起开始逐渐增强；2011年3月10日Ms5.9级主震前存在3次密集震群、且有多次4级以上前震和余震发生;Ms5.9级主震及4级以上的前震均发生在苏典断裂与大盈江断裂的交汇处。从地震垂直分布上看,在北东走向大盈江断裂与苏典断裂交汇处的前震和余震呈向南东倾的带状分布,表明大盈江断裂在本次主震发生区域的倾向为南东。虽然地震的震源机制解显示大盈江断裂为主震断裂,但是由于多数小于4级的前震和余震主要沿近南北向苏典断裂呈带状分布,据此可以推测苏典断裂可能是2011年盈江地震及其前震和余震的控震构造。那么,控制前震和余震发生的控震构造与主震断裂归属走向不同的断裂。为深入分析两者差异的本质原因,这里对2008年至2010年间区域大地震活动与2011年盈江地震的关联性进行了库仑应力变化分析,首先,这些大地震均使沿苏典断裂断裂5km左右深度的库仑应力增强,这应该是盈江地震前震和余震多沿苏典断裂分布的根本原因。在大盈江断裂与苏典断裂交汇处,这些大地震(尤其是在苏典断裂发生的6级地震)对盈江地震震源机制两个破裂而中沿大盈江断裂方向的破裂面在10km深度以上的库仑应力都有增强作用,而对沿另一个与苏典断裂走向接近的破裂面的库仑应力的增强作用较弱,这解释了为什么虽然苏典断裂比大盈江断裂具有更强的地震活动性,但大盈江断裂仍然是盈江地震的主震断裂的原因。更多还原

【Abstract】 Controlled by geodynamic background of India-Eurasia collision, Sichuan and Yunnan area in southwestern China develops intensive tectonic activities, and develops double arc rotational tectonic system which comprised by Sichuan Yunnan outer arc zone and western Yunnan inner arc zone. Western Yunnan inner arc zone is one of the area which has the most complex tectonic framework and strongest seismic activity.For the surface geology investigation is hard to decide the attitude of active faults in depth, a portable seismic network with dense short-period seismeters deployed by Inst. Geomechanics, CAGS in Ruili during2010.3-2011.3, and the purpose is research the spatial distribution, correlations and seismic activity of major active faults in the area by microearthquake data. We got527microearthquakes and their focal parameters in Ruili area through generic processing such as earthquake location and error analysis. By analysis of the spatial distribution of these microearthquakes, we suggest that the seismic activity in Ruili area is not strong recently, and the activity of Wanding fault is higher than Longling-Ruili fault. Besides, there shows a high seismic activity N-S tectonic belt, southeast of Ruili.Fortunately, our seismic network recorded the Ms5.9earthquake occurred at the Yingjiang town on March10th,2011.-60km far away from Ruili, but also recorded the foreshocks and aftershocks. All the earthquakes were located firstly with the HYPO71and then relocated by HYPODD. The results show that seismic activity in the Yingjiang area became higher since December,2010; then three earthquake swarms and several foreshocks stronger than Ml4.0occurred before the mainshock; Both the mainshock and all the foreshocks stronger than Ml4.0occurred at/around the intersection of the NNW-SSE Sudian Fault and the NE-SW Dayingjiang Fault. Vertically, foreshocks and aftershocks aligned in a SE-dipped belt around the intersection of the two faults, indicates that the Dayingjiang fault dips SE at/around the mainshock. Although Focal mechanism of the main shock indicated that the Dayingjiang Fault is the seismogenic fault of the mainshock, however, most foreshocks and aftershocks distribute as a belt along the NNW-SSE Sudian Fault, indicating that the seismicity of Yingjiang during2010-2011is mainly controlled by the Sudian Fault. In order to understand why mean that the seismogenic fault of the mainshock is different with the regional active seismogenic fault, we analyzed the relationship between regional strong shocks happened in2008-2010and the2011Yingjiang earthquake by Coulomb Stress analysis. At first, the strong shocks increased coulomb stress in a plane parallel to the Sudian fault in a large area along/close to the Sudian fault at the depth of-5km, which can interpret why the foreshocks and aftershocks of the2011Yingjiang earthquake distributed along the Sudian Fault. The three strong shocks, especially the Ms6.1earthquake occurred at Sudian Fault, increased coulomb stress at the intersection of the Sudian Fault and the Dayingjiang Fault, at both the possible fault planes of the2011-Yingjiang-earthquake focal mechanism down to10km deep, however, the increase of coulomb stress along the plane parallel to the Dayingjiang fault is obviously higher than the other plane which is close to the strike of the Sudian Fault, which can interpret that although the seismic activity of the Sudian Fault is stronger than the Dayingjiang Fault, the Dayingjiang Fault is the seismogenic fault of the mainshock更多还原