THE FINE VELOCITY STRUCTURE IN THE SHALLOW CRUST ALONG THE HQ?E SEISMIC PROFILE IN SOUTHEASTERN CHINA

This paper discusses the fine velocity structure in the shallow crust on the basis of the wide-angle seismic data collected along the HQ?E profile. The velocity structure depicts the characteristics of formation and development of the South China fold belt. The shallow crust is composed evidently of four strata: sedimentary cover, sediments, Caledonian fold basement and Proterozoic crystalline basement. The velocity structure shows obvious differences laterally along the profile. To the northwest of Wuyi Mountain (near Ningdu), the low velocity depression is correlated to the Mesozoic and Cenozoic basins, with strong relief up to a maximum depth of 10 km at the bottom of the Variscan fold basement. As for the velocity structure to the southeast of Ningdu, the velocity near the surface becomes much higher, and the bottom of the Caledonian fold basement gets thinner, merely 3～5 km in depth. At the end of this paper, the author makes a tentative analysis of several basins according to the fine velocity structure in the shallow crust.