Evolution of 3D velocity structure before Dayao M=6.2 and M=6.1 earthquakes in 2003

• 作 者: 周龙泉 刘杰 张晓东
• 机 构: China Earthquake Networks Center China Earthquake Administration Beijing 100036 China,China Earthqu
• 出 处: Acta Seismologica Sinica(English Edition)
• 发表日期: 2007年01期
• 关键词: deviation Figure tectonic crustal perturbation epicenter approximate strike cont

In this paper the crustal velocity structure are imaged at the annual scale for determining the evolution of 3D ve- locity structure before the Dayao earthquakes in 2003, and the relation between physical variation of medium and cause of earthquake occurrence is discussed. Checkerboard resolution tests show that the spatial resolution at 15 km depth is approximate 0.6 around Dayao. Error analyses show that the error (Approximate 0.02 km/s) at the focus area is far smaller than the magnitude (approximate 0.15 km/s) of velocity variation. Results of the studies show that a NNW-striking juncture zone of high- and low-velocity is formed before Dayao earthquake, whose strike is basically consistent with that of aftershock distribution of Dayao earthquakes and the focal mechanism, and the hypocenters lie on the high-velocity side of juncture zone. Furthermore, there is a low-velocity body under the hypocenters after Dayao earthquakes. The evolution of velocity structure provides restriction for discussing the circumstances of earthquake gestating and occurring.

In this paper the crustal velocity structure are imaged at the annual scale for determining the evolution of 3D ve-locity structure before the Dayao earthquakes in 2003, and the relation between physical variation of medium and cause of earthquake occurrence is discussed. Checkerboard resolution tests show that the spatial resolution at 15 km depth is approximate 0.6 around Dayao. Error analyzes show that the error (Approximate 0.02 km / s) at the focus area is far smaller than the magnitude (approximate 0.15 km / s) of velocity variation. the studies show that a NNW-striking juncture zone of high- and low-velocity is formed before Dayao earthquake, whose strike is basically consistent with that of aftershock distribution of Dayao earthquakes and the focal mechanism, and the hypocenters lie on the high-velocity side of juncture zone. Furthermore, there is a low-velocity body under the hypocenters after Dayao earthquakes. The evolution of velocity structure provides restriction for discussing the circumstances of earthquake gestating and occurring.