利用同震滑坡分析2014年鲁甸地震震源性质与破裂过程

摘要

The 201 4 Ludian MS 6.5 /MW 6.1 earthquake in Yunnan,China caused significant causalities andserious disasters.It also triggered at least 1 024 landslides with areas equal to 1 00m2 or larger.The purpose of thisstudy is to utilize the spatial distribution and scalechanges of coseismic landslides to analyze the source andrupturing process of the 201 4 Ludian earthquake.Base on the northwest strike direction of the long axis of thelandslidedistribution area and the regional tectonic distribution of the earthquake affected area,the seismogenicfault of the Ludian earthquake is considered to be the BaogunaoXiaohe fault.Most of the landslides occurred in theareas southeast to the epicenter,which indicates the rupturing direction is from northwest to southeast.Thelandslides in the northwest part of the affected area is characterized by more,smallerscales,and larger distributionarea,whereas those of the southeast part are few,largerscales,and distributed in a smaller area.Landslidestriggered by blindruptured earthquakes always show more quantity,smallerscale,and larger distributionarea than those of surfaceruptured earthquakes.It can be inferred that the rupturing plane is relatively deep in the northwestsection of the seismogenic fault and probably did not generate surface ruptures.The southeast section of theseismogenic fault should be relatively shallower and rupture the ground surface.These inferences have beenvalidated by field investigations.It is concluded the seismic rupturing started from depth in northwest,then spreadupward to the shallow subsurface in the southeast,which produced the surface rupture at the terminal of the ruptureplane.Such a rupturing process can also explain the unusually serious disasters caused by the Ludian earthquake.%2014年8月3日，发生在中国云南省鲁甸县的 MS6.5（Mw6.1）级地震造成了严重的灾难，本次地震还触发了至少1024处面积大于100m2的滑坡。本文的目的是利用同震滑坡的空间分布与规模分布特征分析本次地震的震源性质与破裂过程。鲁甸地震同震滑坡分布区域的长轴展布方向呈北西—南东方向，结合区域活动构造分布，认为其发震构造是北西—南东方向的包谷垴—小河断裂。地震滑坡多分布在震中的南东方向，表明了其破裂方向是自北西向南东扩展。滑坡分布区北西部分滑坡分布较分散，规模总体较小；而南东部分滑坡分布相对集中，且有几处规模较大。由于隐伏断裂型地震比地表破裂型地震触发滑坡分布面积广、数量多，但规模较小，因此判断发震构造的北西部分可能由于破裂面较深而隐伏于地下，而南东部分可能产生了地表破裂且破裂面较浅。这一判断得到了野外调查结果的验证。鲁甸地震破裂自北西向南东是由深部向浅部斜向上扩展的，这种破裂面斜向上扩展的破裂特征或许是导致鲁甸地震灾害非常严重的重要原因之一。