Research on characteristics of growth faults in the southern East China Sea Shelf Basin

The growth fault is an important and widely distributed structure in extensional and strike-slip basins. 18 growth faults have been identified by the authors with seismic data in the south East China Sea Shelf Basin (ECSSB). According to their roles in controlling tectonic units development and the vertical sequence they cut through, the faults may be divided into several orders, i.e. the 1^st order basin-controlling faults, the 2^nd order concave controlling faults, the 3^rd order band controlling faults and cap faults. As to the distribution pattern, the majority of the growth faults of the study area are distributed in NE and NNE directions with a few in NEE direction. Various types of faults combinations are identified in seismic profiles, such as the steplike faults, the "Y" type faults, the domino-type faults, and the combination of graben and horst faults. According to the kinematics characteristics of faults such as growth index and fault throw, it is found that the growth faulting movement of Paleogene was in a decreasing trend from west to east, and thus the faults became younger to the east. The intensity of growth faulting in the whole study area reached a peak in Paleocene and became stable after Miocene, resulted from the joint effects of the extension dynamics background, that is the retrogradation of the subduction slab of the west Pacific margin and the eastern vermiculation of the ECSSB due to the subduction and collision between the India plate and Eurasian plate. Further study on growth fault and associated structures as well as the steplike fault zone in gentle slope belts is suggested to push forward the explorationin ECSSB basins.