Study on shallow structural features in Changbaishan Tianchi volcanic region

A seismic survey by 10 shallow profiles and 6 ultra-shallow profiles was performed in Changbaishan Tianchi volcanic region in 2002. The result shows that there are three （in some areas as many as seven） stable interfaces in the survey region, but no reflection phases are found in depths greater than 500 m. The number of interfaces in the southwestern part is obviously greater than in the northwestern part of Tianchi volcano, which suggests that the faults in the southwest have a stronger controlling power over the flow direction of volcano-spewed lava as compared with those in the northwest. Six shallow faults exist in the survey region. The shallow faults are nearly vertical graben-like faults and are mostly distributed on the southwest of Tianchi crater, indicating that volcanic activities in the southwest are stronger than in the northwest. On this ground, it could be further deduced that the NE-trending major fault of Tianchi volcano （ the Liudaogou-Tianchi-Zengfengshan fault） is more active than the NW-trending Baishanzhen-Tianchi-Jince fault.