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四川省理县西山村滑坡运动变形过程中的微震研究

Abstract:

The Xishancun Landslide is located in the Longmenshan Mountains where the 2008 Wenchuan earthquake occurred. The 2008 Wenchuan earthquake triggered a large number of landslides in this region. Since then, the Xishancun Landslide is continuously deforming. In order to monitor slidequakes generated by the slope movement and the internal fracturing of the rock mass and to understand slip and strain pattern of the landslide, a seismic network with 30 seismometers was deployed on the landslide in the autumn of 2015. Firstly, we distinguish signals of slidequakes from those generated by human activities and local earthquakes through their onsets and waveform characteristics. Then we use the sliding-window cross-correlation method based on waveform matching to identify other slidequakes. We find 96 slidequakes recorded by all seismometers. We relocate the slidequakes using a grid-search algorithm by minimizing travel-time residuals. 80 events are located on the foot of the landslide while the others are located on the head, which indicates that considerable energy is accumulated in the foot and head of the landslide. Besides large slidequakes, there are smaller events which are only recorded by a few nearby stations. These small slidequakes occur in middle part of the landslide where less energy is released. Based on the distribution of those slidequakes, we find four seismically unstable regions which agree well with distinct deformation areas obtained from borehole data. The distribution of those slidequakes might be related to the internal structure and the movement of the landslide, indicating that seismic method is a useful tool to monitor landslide deformation and a powerful complement to other means.

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