Joint Study of the Xishancun Landslide, Sichuan, Using Seismological and Electromagnetic Methods

Monday, 15 December 2014: 3:14 PM
Risheng Chu1, Sidao Ni1, Xiangyun Hu2, Feng Bao1, Ping Lu3 and Zhiwei Li1, (1)Institute of Geodesy and Geophysics, Wuhan,Hubei, China, (2)China University of Geosciences Wuhan, Wuhan, China, (3)Tongji University, Shanghai, China
Xishancun Landslide is located about 20 km northwest of Wenchuan County, where the great 2008 Ms8.0 Wenchuan earthquake occurred. The landslide, approximately 8.5x107 m3, is continuously deforming and poses great hazard to life and properties near the populated area. In order to investigate three-dimensional structures of the landslide and its internal fractures, scientists deployed a dense seismic array consisting of 19 broadband sensors and 5 electromagnetic profiles for two weeks. Seismic studies include thickness of the sediment from the H/V spectral ratio method and identification and relocation of micro-seismicity. During the seismic deployment, broadband seismic stations recorded 3 M>3 earthquakes and many small local events within 30 km of the array. Seismic data from these earthquakes are also used to constrain the sediment thickness of the landslide. The electromagnetic approaches involve high-density-resistivity method and transient electromagnetic (TEM) method. Results from both seismic and electromagnetic studies will be compared to and calibrated by borehole observations. Our preliminary results show a sediment thickness of 20~50 m and a low resistivity layer underneath the sediment, which may be related to water-bearing material. We also indentified and relocated some possible microseismic events. More details will be presented in the meeting.