Abstract: Based on waveforms from the Fujian regional seismic network, we obtained focal mechanisms of M_L≥4.0 distinct events in the Xianyou swarm earthquake sequence using the CAP method, While temporal and spatial evolution characteristics of the Xianyou earthquake swarm sequence activity was analyzed using the water level change of the Jinzhong reservoir. The results show that foca1 mechanisms of 5 M_L≥4.0 distinct events are similar. The NW plane of mechanisms solutions should be the focal rupture plane considering the distribution of the earthquake swarm sequence, and the dip angle is relatively steep. The type of focal rupture is right lateral slip, and the seismogenic structure of this sequence is the Shaxian—Nanridao fault system. Moreover, the focal depth of the first M_L≥4.0 event in this sequence is very shallow, only 4 km in depth, and the depth of the other 4 events are about 9~10 km. The entire swarm earthquake sequence shows clusters distribution in space, and the seismicity is controlled by water level in time. the Xianyou earthquake swarm sequence may be induced by the Jinzhong reservoir impounding.

Key words: Focal mechanisms, CAP method, Earthquake swarm sequence, Xianyou Reservoir