Using a two-dimensional seismic attenuation tomography technique, the crustal Q S dynamic variation in Zipingpu reservoir area, Sichuan Province, was obtained by inverting S-wave data from relocated earthquakes from 16 Aug. 2004 to 11 May 2008 with the double-difference algorithm. Monthly moving average Q S value in different-sized regions and earthquake frequency for different magnitude range
... [Show full abstract] were compared with the water level of the Zipingpu reservoir, respectively (the window length is 1 year and the step length is 1 month). The result shows that low-Q S region expanded and Q S value dropped significantly around the reservoir area during the first fast water-loading period. In particular, Q S value varied remarkably in the southwestern, northeastern and middle parts of the reservoir area. Monthly moving average Q S values for different-sized regions in the Zipingpu reservoir area decrease with elapsed impoundment time and increased water level, and the Q S value in the middle reservoir area dropped sharply. Furthermore, the impoundment enhanced seismic activity in the reservoir area, and mainly increased activity of small earthquakes of M L0.0-2.0.
