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Institute of Geology completed underwater detection of active faults for the first time

2017/10/18 15:31:19

On June 2017 14-22, Lu Renqi, Cai Minggang, Wu Xiyan et al., Key Laboratory of Active Tectonics and Volcanology carried out for the first time an underwater sonar detection of faults in the Qionghai area, Xichang, Sichuan Province. This work was based on the study of the seismic hazard assessment of active faults in focused monitoring areas in China mainland.

The results of this survey show that the E’zhanghe fault at Hainan Township, Xichang City extends to the west of Qionghai, which is the northernmost end of the 1850 Xichang 7.5 earthquake rupture zone. Whether this fault crosses the Qionghai  area? Are there any other unknown active faults there? These questions were unsolved before the survey. The research team deployed 10 profiles through the entire Qionghai watershed about 50km in total. Analysis on the track of more than 60 kilometers of the sonar measurement permitted them to obtain high-quality underwater detection data of hidden faults.

Sonar detection has many influencing factors including speed, generator output power, engine eddy, and multiple interference. In the study, the influence of various factors were fully considered and eliminated, and the reliability of the detection results was guaranteed. The detection results include three interface data sets on underwater depth, underwater topography, and Quaternary shallow cover. The results of the study,to some extent, reflect the anomalies related to the E’zhanghe fault below the Qionghai's water and other possible faults. At present, these data need to be further processed. In combination with the existing geological and drilling data in the study area, the subsequent comprehensive analysis will allow us to achieve the expected research objectives.

During this filed work, we received many supports and help from the Xichang Municipal Government, Lushan-Qionghai Administration of Xichang City, ,Xichang Earthquake Prevention and Disaster Mitigation Agency, and Xichang Panxi Geological Prospecting Institute. We are very grateful to them.