Difference between focal mechanisms of Dayao earthquake doublet sequence

Using the maximum amplitude ratios of vertical component of P and S waves recorded by a regional network, 921 focal mechanisms of Dayao earthquake doublet sequence are determined by means of synthetic seismograms of a point source of dislocation in a plane layered medium. Among them, 389 focal mechanisms are in the aftershock sequence of M6.2 earthquake occurred on 21 July, 2003 and the other 532 focal mechanisms are in the aftershock sequence of M6.1 earthquake occurred on 16 October, 2003 in Dayao, Yurman. The focal mechanism consistent parameter a of the two aftershock sequences are calculated and analyzed. According to the focal mechanism consistent parameter a, the focal mechanisms of the first aftershock sequence are more consistent than those of the second. According to the comparison of CMT solutions of the two M6 earthquakes, the physical mechanism of the doublet in the intra-plate earthquake is very complex, and many processes are involved and interacted with each other. This doublet provides insights into earthquake clustering, triggering and stress cycling.