Characteristic outline of P wave velocity structure in the depth beneath the Sulu-Dabie region.

The velocity structures to 200 km deep beneath the Sulu-Dabie and the surrounding were discussed in the present analysis. The characteristics of velocity structure in the horizontal sections for several different layers between the 50 and 200 km were investigated in detail. The results suggest that the high velocity belt extending along the NW-SE direction exists beneath the region southwest of the Dabie mountain region. Another high velocity area exists evidently beneath the Sulu ultrahigh-pressure metamorphosed (UHPM) belt and the region east of the UHPM belt. It looks that the two high velocity areas exist separately in each deep place. The low velocity area extending along NW-SE direction exists beneath the link region between the southern end of Sulu UHPM belt and the northeastern end of the Dabie mountain region, crossing the middle segment of the Tan-Lu fault. The velocity gradient variations along the NE-SW direction reveal beneath the Dabie UHPM belt. The velocity gradient belt strikes along about the NW-SE direction. Such velocity gradient variation belt striking nearly N-S direction also reveals beneath the eastern boundary of the Dabie mountain region. A velocity boundary zone exists beneath the northern segment of the Tanlu fault. The velocity variation is discontinuity as crossing the western boundary of the Sulu UHPM belt. The velocity structures beneath the both sides of the northern segment of the Tanlu fault are usually different from each other. The velocity structure beneath the northern segment of the Tanlu fault is usually different from that beneath each side.