Structures of the Xishancun landslide in Lixian County,Sichuan,inferred from seismic ambient noise autocorrelations
The seismic ambient noise autocorrelation method is widely used to detect interface structures at different scales because it can obtain shallow underground reflection responses without artificial sources or natural earthquakes.However,the thickness of most soil landslides ranges from a few meters to a hundred meters with complex internal structures,despite significant difference in physical properties between the weathered layer and the bottom bedrock,the application of ambient noise autocorrelation is less common in detecting landslide structures.Therefore,we take the Xishancun landslide in Lixian County,Sichuan Province as an example,and try to apply the autocorrelation method to horizontal component seismic ambient noise to detect the landslide structures.Firstly,we cut the continuous noise data into segments with a time window of 3600 s,and adopt time domain normalization and spectral whitening to each segment.We then calculate autocorrelation functions and bandpass filter them to the frequency range of 1～15 Hz.Next,we extract the first and multiple S-wave reflection responses of the interface between the landslide and the bedrock directly beneath each station.The results show that the two-way travel time of the interface reflected S-wave extracted from the autocorrelation function of the E component of 22 stations in the Xishancun landslide is between 0.14～0.25 s.The thickness of the Xishancun landslide is 57～102 m.Because the landslide is relatively thin,the two-way P-wave travel times between the free surface and underground interface are less than 0.1 s,which makes it impossible to distinguish P-wave reflection responses from eigenvalues of the autocorrelation functions.This study provides more thickness constraints on the sediment layer at some monitoring stations in the Xishancun landslide.The results of this article indicate that the the Quaternary deposits of Xishancun landslide are thick in the north and thin in the south.Based on the result of electrical profile and receiver function,there is a large area of low resistivity and high Poisson's ratio aquifer within a depth range of 100 m inside the landslide,which has poor anti-slide ability.If there are heavy rainfalls or earthquakes,the gravel deposits in the north are prone to detachment,which will cause significant losses to the gathering areas of the southern villages.
Ambient noise autocorrelationS-wave reflectionXishancun landslide in Lixian CountyDepth of sliding surface
万方数据
维普
