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.

Developed along the coast of South China have been three sets of active fault zones,in whichthe NE～NNE trending faults are of the largest scale,with their surficial manifestation most evident and with the ENE～EW trending faults cutting most deeply and the developing historylongest,as well as with their growth and activity most evident for the NW～WNW trendingfaults.The resuhlt indicates that the characteristics of all faults mentioned above are in evidence inmacro～microtectonics,suggesting that the faults are of similar formations and developing history and controled by similar sources of tectonic forces.Their characteristics are to some extentrepresentative of the evolutions of the crustal motion.

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.

In the coastal area of Southern Fujian,the late Pleistocene sediments have a wide distribution (Fig.1).The late Pleistocene strata are mainly composed of following sediments in ascending order:Dgrey medium-fine sand,2)black mud or peat,and 3)yellow sand and sandy clay.The other possible late Pleistocene deposits,so-called "Old Red Sand",are the semi-cemented,well-sorted,and red quartz silt-fine sand.These deposits are distributed over the bays and gullies of mainland and the islands,and constitute the second terrace,tiebar and other littoral accumulation landforms.In this paper,a number of natural outcrop sections of late Pleistocene strata have been described and drown in Fig.2.Based on the sedimentologic and geomorphologic investigation in the field and the data of ¹⁴C dating (Table 1),analyses of foraminifers and ostracods (Table 2) and pollen analysis (Table 3),the following conclusions can be obtained:1.The grey and yellow sand and sandy clay intercalated with black mud or peat belong to the late Late Pleistocene,i.e.the middle and late pleni-glacial substages of the last Glacial Stage,between about 40,000 and 16,000 years B.P..2.The grey and yellow sand and sandy clay,especially the black mud or peat,of the late Late Pleistocene are mainly the deposits of marine-land transitional facies,in part the littoral,and in part lake and swamp facies.3.On the whole,the climate of the late Late Pleistocene was warm and humid,but sometime cooler and drier.4.The "Old Red Sand" is the littoral sediments which were deposited under the heat and humid climate.It might be deposited during the late stage of Late Pleistocene,but the possibility of forming in the earlier period can not be ruled out.

The application of the tectonic landforms in the study of seismogeology in the Guangdong province mainly consists of the two aspects:study of the neotectonic movement for the zoning of the potential risk;the recognization of the activities of the faults,both of them are complementary to one another.This paper has an introduction to the efforts in this regard.

Along the Fujian-Guangdong region there are in general 3 sets of tectonic lines. The most striking ones, belonging to the NE-trending Neocathaysian system, represent the principal ranges and valleys. The Ew-trending lines are lesser in number. The Nw-trending ones, poorly known and represented often by fractures, will be briefly discussed in this paper.The NW-trending fractures are numerous in Southeast China, particularly in the coastal areas of Fujian, Guangdong and Guangxi provinces. They are equidistantly apart in a regular pattern, many of them are followed by rivers; some may measure be comparable in size with the Neocathaysian fracture; most of them are vigorously active in recent geological periods.A thorough investigation into the NW-trending fractures may be significant in solving (l)some geological problems not yet resolved theoretically, as well as those frequently met in Southeast China and (2)some practival problems regarding ore searching, delta conservancy and earthquake predition.