Based on 166 age data of Quaternary deposits in fossil delta, the rate of the vertical motion of the Zhujiang Delta since late Quaternary has been estimated by eliminating the non-tectonic effects, such as the change of ancient sea level, the compaction of sedimentary layer, and the isostatic crustal subsidence. The estimations have been conducted separately for 11 fault block tectonic regions, which are bounded by NE-trending, E-W-trending and NW-trending faults. The results have indicated that the rate of vertical motion of the Doumen fault block in the south and the Guangzhou-Panyu fault block in the middle parts of the Zhujiang Delta is relatively high. This conclusion has been supported by the results of the studies on the changes of ancient geographic environment, the timing of faulting, and the late Quaternary paleo-seismicity in the Zhujiang Delta area. In contrast to the previous studies, the present study emphasizes the changes of vertical motion rate in different fault blocks and in different time. The result of this study indicates that the secondary fault blocks of the Zhujiang Delta were dominated by elevation motion at a rate of 1～2mm/a during the early Holocene (10～4ka), and were dominated by subsidence at a rate of -3～-4mm/a during the late Holocene (～4ka). The elevation rates of Guangzhou-Panyu, Guanghua Plain, Shunde and Doumen fault blocks were greater than 1mm/a, while the subsidence rates in Guangzhou-Panyu, Shenzhen-Hong Kong, Zhongshan and Doumen fault blocks exceeded -2mm/a.

A number of NE-, NW- and E-W-trending faults are developed within and around the Zhujiang Delta, controlling the formation, evolution and even the seismic activity of the Delta. The previous studies on the Zhujiang Delta focused mainly on the geometry and the nature of recent activity of the Delta. It is a pity, however, that no good surface exposure was found to reveal the cross-cutting relationship between the fault and the Quaternary deposits, so that the recent activities of the faults was deduced indirectly from the interior structures, development features and seismic activity of the Delta. In 1998 and 1999, the authors carried out field investigation in the Zhujiang Delta. During the investigation, we found at the southern foot of Wuguishan mountain 2 good surface exposures showing clearly the cross cutting relationship between the fault and the Quaternary deposits. This is the direct evidence of Quaternary faulting firstly discovered in the Zhujiang Delta area. The Wuguishan Southern Piedmont fault lies in the Zhujiang Delta, extending northeastward from Hutiaomen in the southwest, passing through Dachi, Dutou, and terminating at Yakou, having a total length of 55km. It is striking 60°, dipping southeast or northwest at an angle of over 65°. Geomorphic landform related to faulting, such as terminal facet, fault cliff, and fault valley or nek are well developed along the fault. The newly discovered 2 exposures are located at the southern foot of the Wuguishan mountain, to the west of the newly built Zhuyuan high way to the northeast of Sanxiang. The first exposure is located beside a gully in the vicinity of a stone quarry. At this exposure 3 faults can be recognized with general occurrence of 35°～45°/NW∠65°～85°, the two of which dissect the Quaternary sandy gravel and gravel beds. The second exposure is located to the south of a bedrock hill. At a cross section exposed by quarrying, a 20m wide crushed zone can be recognized between the granite and the Quaternary coarse gravel bed. It seems that the two units are in faulted contact with each other. The fault is composed of a series of compressional planes, striking 65°, and dipping northwest at an angle of 75°～85°. The lower part of the Quaternary deposits that are dissected by the 2 faults consists of yellow gravel bearing coarse grained sands, while the upper part consists of slightly bedded gravel, granule and coarse grained sands. The former is comparable with the regional mid Pleistocene alluvium (sandy gravel and pebble beds), while the latter is comparable with the regional late Pleistocene alluvium (medium fine sands and gravel beds). They are all of terrestrial origin, but span mid-late Pleistocene in ages. According to these 2 exposures, therefore, it is confirmed that the two faults were active during mid-late Pleistocene.

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.