Based on the tectonic-geomorphic features,comparison of Quaternary system with isochron-ic geomorphic surface on both sides of the fault as well as the micro-and macro-structural indica-tions of the fault trace,the activity since late Pleistocene along the southern segment ofWuchuan-Sihui fault zone is discussed.It is suggested that this segment of the fault is relativelystable during this period.

The tectonic motion in South China is characteristic of vertical uplifting and subsiding of the blocks.Based on the data for such 58 Holocene carbonaceous samples from the study region as shells,beach rock,puddle,peat and coral reef,the authors estimated and compared the rate of the vertical tectonic motion for various fault block regions,which have been confirmed by the rate of the present crust deformation.The results indicate that the motion of the active fault has a rate of 1.5mm per year while the inactive,only about 0.5mm per year.The former is of a value 3 or 4 times the latter and forms the part of main seismic zones in the study region such as the Quanzhou-Santou seismic zone and those in the northern Hainan Island.And the inactive fault blocks make up the nonseismic zones or the microseismic region such as the southern Hainan Island and the Zhujiang Delta.The value in point corresponds with the strength of the seismicity.In this paper the authors discuss the relationship between the differential velocity for the moving blocks and the neotectonic stress field along the coastal area of South China and indicate that because the crust of southern Fujian and the eastern Guangdong are in the process of being deformed between Pacific plate and Phillippine Sea plate,the strength of the tectonic motion is more intensive than the central Guangdong and may act as a seismic barrier to the latter.In the coastal area of western Guangdong the crust is in the presense of the tension of South China Sea basin,the strength of tectonic motion being also larger than the central Guangdong.The velocity of vertical tectonic motion in the coastal area of South China gradually increases from the central Guangdong to the southern Fujian and eastern Guangdong and from the central Guangdong to the eastern Guangxi and western Guangdong.The vertical differential movement of the blocks is only a main model in the coastal area of South China and its adjacent area.