Reservoir Induced Seismicity Types in the Three Gorges Project

Abstract

Reservoir Induced Seismicity(RIS) is a common phenomenon needed to be focused in the construction and operation of water conservancy project. The Three Gorges reservoir has a digital telemetry seismic network to monitor the earthquakes in this region. According to the correlation between water impoundment and earthquakes, the reservoir induced seismicity can be divided into rapid response and delayed response. The two types can be found in the Three Gorges area as well. In 2003, soon after the first stage of water impoundment, micro earthquake swarm occurred, which is so called rapid response type and water loading is the main factor. And delayed effect is the most observed phenomenon in RIS, in which pore diffusion controls the earthquakes. Double difference relocation results show that the earthquakes can be generally divided into three regions. And the earthquakes controlled by the active faults are called tectonic type RIS, while those related with karst, landslide, etc are nontectonic type. In region A, some earthquakes are related with the Gaoqiao active fault, and some have relationship with karst. The earthquakes in region B are controlled by some coalmines, landslide, and so on. And the earthquakes in region C belong to tectonic type RIS, which have certain relationship with the Xiannvshan fault and Jiuwanxi fault. Different RIS types have different mechanisms and controlling factors, furthermore have different earthquake trending.