Micro Events around Zipingpu Reservoir before 2008 Wenchuan Earthquake: Possible Influence of Impoundment

After the 2008 Ms8 Wenchuan Earthquake (WE) occurred on Longmenshan thrust fault in the western Sichuan region in China, a long-time debate has arisen on whether there are some correlations between this huge earthquake and a large water reservoir, the Zipingpu Reservoir (ZR), which locates only about 10 km away from this event. Many geophysicists have studied the ZR issue but got different conclusions. So it is worth our attention to make more thorough investigation to figure out the possible effect of ZR impoundment on 2008 WE.

We investigate this issue by applying Matched Filter Technique (MFT) in the region around ZR, to better understand the local seismicity in this area.

MFT is originally used to detect duplicated events, thus is not able to find new events with different locations. So we make some improvement on this method. Firstly we adopt the idea proposed by David Shelly et al. (Nature, 2007) to conduct a strong detection and a weak detection simultaneously, which enables us to find more micro-events. Then, we relocate the detected events, which provides us with more accurate spatial distribution of new events as well as the geometry of related faults, comparing with traditional MFT. In the meeting, we will introduce the temporal variation of spatial distribution of earthquakes around ZR from the initial impoundment of the reservoir in August, 2004 to the WE in May, 2008, and tell how the ZR might be involved with the destructive event.