四川丹巴梭坡滑坡微震信号初探

与滑坡变形相关的微震称作滑坡震,反映了滑坡上不稳定区域对外界环境因素的响应,分析滑坡体微震事件的地震学性质能够为理解滑坡的动力学过程、进行滑坡稳定性分析以及灾害防治提供关键信息。放置在滑坡上的地震仪不但能记录到和滑坡变形相关的微震,可能还会记录到一些人类活动信号。滑坡上的人类活动产生的震动事件给滑坡震探测带来挑战。梭坡滑坡位于四川省丹巴县大渡河左岸猴子岩水库库尾,是丹巴县古碉群的集中分布区之一,近年来滑坡灾害频发,其稳定性对古碉群保护和水库蓄水位的选择均十分重要。为监测该滑坡体局部破裂产生的微震信号,2017年2月至3月在滑坡上布设了34台三分量短周期地震仪。基于信号到时和波形特征确定几类模板事件,采用滑动时窗互相关的方法检测微震事件,并对信噪比较高的事件进行定位。根据事件的位置和到时信息,估算出滑坡体东西部浅层沉积层面波速度结构存在一定差异,表明了滑坡浅层沉积层物质分布的横向不均匀。根据这些事件的发生时间和波形特征,认为除了滑坡震,梭坡滑坡上还存在燃放烟花造成的震动事件。

Preliminary Study on Microseismic Signals of Danba Suopo Landslide in Sichuan Province

Microseisms caused by the landslide deformation are called slidequakes,which are the response of unstable areas on the landslide to external environmental factors. Analyzing the seismological properties of slidequakes helps to understand the dynamics of landslides,to analyze landslide stability and to prevent potential disasters. The seismometers deployed on the landslide can record the microseisms related to the deformation of the landslide along with some human activity signals. However,events generated by human activities on landslides pose challenges for slidequake detection. The Suopo landslide is located at the end of the Houhouyan Reservoir on the left bank of the Dadu River in Danba County,Sichuan Province,where is famous for ancient blockhouses in Danba County. In recent years,landslide disasters have occurred frequently on Suopo landslide. So the stability of Suopo landslide is key to the protection of the ancient blockhouses and the determination of water level of local reservoirs. In order to monitor the microseismic signal generated by the local rupture of the landslide,we deployed 34 three-component short-period seismometers on the landslide from February to March 2017. Based on the signal arrival time and waveform characteristics several types of template events are determined firstly,then the sliding time window cross-correlation method is used to detect microseismic events,and the events with high signal-to-noise ratio are located. According to the location and time information of the event,we find that there exist certain differences in the wave velocity structure of the shallow sedimentary layer between the east and the west of the landslide,indicating the lateral unevenness of the material distribution in the shallow sedimentary layer of the landslide. Based on the time and waveform characteristics of these events,we believe that in addition to slidequakes,there are also vibration events caused by fireworks on the Suopo landslide. Our results provide a reference for the detection of slidequakes and the inversion of shallow structures of landslides.