Using EH4 audio-magnetotelluric sounder to detect the gigantic Qiaojia paleo-landslide and its structural characteristics

Abstract

In this study, we used the EH4 audio-magnetotelluric sounding, combining with the drilling data, to detect and define the spatial electrical properties and structural characteristics of the Qiaojia paleo-landslide. Based on the detection results, the average depth of the main sliding surface is considered to be 250 m and six faults (F1-F6) were identified, among which the Xiaojiang fault zone (F1) is the main active fault. Meanwhile, it is inferred from the sounding results and drill date that the terrace along the Jinsha River fall into four layers from the surface (Qh) to the deep, namely the sandy clay layer, gravel layer, broken limestone layer, and complete limestone bedrock. The broken limestone layer and the complete limestone bedrock are in the bedrock outcrop area from the surface to the deep. The comprehensive analysis shows that the paleo-landslide is temporarily stable at present, but along with large earthquake activity in the north section of Xiaojiang fault zone in the future, whether the paleo-landslide is likely to revive or similar paleo-landslides will reoccur in this region needs further study. Our study proved the effectiveness of the EH4 audio-magnetotelluric method in detecting gigantic paleo-landslide.

Keywords

• xiaojiang fault zone
• gigantic paleo-landslide
• eh4 audio-magnetotelluric method
• sliding surface
• qiaojia