Seite - 461 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 5 The results of double-difference location algorithm for 2014 seismic cluster 4. CONCLUSION Consider the features of seismic activities and geological conditions in Shanxi reservoir, conclusions could be summarized as follows. 1. The seismic frequency of Shanxi reservoir region increases significantly after the impoundment, and the seismic activities shown a periodic change in every 4 years. 2. More than 99% of the seismic events are weak or micro earthquakes, and the maximum magnitude is ML4.6. 3. The seismic events after the impoundment are mainly distributed in the area near fault F2 and F3. 4. The results of double-difference location algorithm suggest that the branch fault F3-3 is the causative fault of 2014 seismic cluster. 5. The preferably infiltration conditions of fault F3 (steep dip and higher permeability) is the control factor of the seismic activity in Shanxi reservoir. At last, we suggest that the changing rate of water level in dam operation should be controlled in a relative low level, especially for the water level decreasing rate must be limited to no more than 2m/day. 461