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On March 13,2007,two earthquakes with M4.7 and M4.6 occurred in Zhengfang Village,Shunchang,Fujian.The M4.7 earthquake is the most intensive one in the Fujian region since the establishment of the Fujian digital seismic networks.These two earthquakes provide us with valuable first-hand observation data for seismological research.This paper analyzes their wave-forms and concludes that(1)the crustal thickness in the seismic region is estimated to be about 40km according to the observed head-wave critical distance;(2)there is a salient difference between the ratios of S-wave’s maximum amplitudes of these two earthquakes;(3)the focal depth of the M4.7 earthquake is estimated to be 8.4km according to the clear depth phrase sPn in waveforms,which is the same with the result of other determination methods.
On March 13, 2007, two earthquakes with M4.7 and M4.6 occurred in Zhengfang Village, Shunchang, Fujian.The M4.7 earthquake is the most intensive one in the Fujian region since the establishment of the Fujian digital seismic networks.These two earthquakes provide us with valuable first-hand observation data for seismological research.This paper analyzes their wave-forms and concludes that (1) the crustal thickness in the seismic region is estimated to be about 40km according to the observed head-wave critical distance ; (2) there is a salient difference between the ratios of S-wave’s maximum amplitudes of these two earthquakes; (3) the focal depth of the M4.7 earthquake is estimated to be 8.4km according to the clear depth phrase sPn in waveforms , which is the same with the result of other determination methods.