Unconsolidated Quaternary sediments are widely distributed on the Earth surface. As active faults usually disturb the Quaternary sediments, the study of the deformation styles of these sediments is therefore of great significance to the assessment of fault activity and property. Oriented samples of unconsolidated Quaternary sediments deformed by faulting have been collected from some typical active fault profiles. They were solidified in lab by filling epoxy resin diluted by acetone with solidified agent. Oriented thin sections were cut according to the primitive orientations of the samples in the field. Deformation features of the samples were observed carefully under optical microscope. An attempt has been made to identify the deformation microstructures of the samples, which may reflect the features of faulting. The observations show that the deformation in unconsolidated Quaternary sediments can be classified into two styles: fracturing and flow. The fracturing deformation is represented by parallel slip bands, straight slip planes, broken mineral grains etc, while the flow deformation is characterized by flow structures, mineral grain rotation, drag structure of clay minerals and others. The deformation style and property of unconsolidated Quaternary sediments depend to a large extent on the characteristics of the sediments themselves. Unconsolidated Quaternary sediments are composed mainly of clastic grains and clays. They can be considered as a visco-elastic body, and may behave as elastic-plastic materials. The duration of applied force has a great effect on the deformation behavior of unconsolidated Quaternary sediments. It means that strain rate plays an important role in the deformation behavior of unconsolidated Quaternary sediments. It is suggested that the fracturing deformation is generated by high strain rate event such as earthquake, while the flow deformation is generated by low strain rate event such as creep slip. The detailed observation of deformation styles of unconsolidated Quaternary sediments,therefore, may provide important information on the kinetic process of faulting.

The Zhongwei-Tongxin fault zone is one of the arcuate active fault zones in northeastern margin of Tibetan plateau. An earthquake of M =7 1/2 occurred on the middle segment of the fault zone in 1709 A.D. The structures of the fault zone are complicated and composed of a series of secondary faults. The fault zone can be divided into three segments according to the differences in the style of movement, strength and time of activity of the secondary faults. The study of the behavior of paleo-seismicity on the fault zone, therefore, is of great significance to better understanding of the segmented rupturing and the assessment of future seismic risk. The western segment of the fault zone is nearly E-W-trending with a total length of about 60km, most of which is covered by wind carried sand. The recent activity of the faults on this segment is displayed most distinctly at Xiaohongshan area. The middle segment trends NWW with a length of 55km. This segment is the most active one among the three segments of the fault zone. A series of streams, terraces, ridges and alluvial fans were sinistrally offset along the fault. The average left lateral-strike slip rate since Holocene is 3.58mm/a. The eastern segment changes from NW-trending to NNW-and S-N-trending, having a length of about 40km. This segment is located in the compressional area of Zhongwei-Tongxin left-lateral strike slip fault zone, where folding deformation is predominant and the fault is activated weakly. Seven trenches were excavated recently along the fault zone. Five of them are located on the middle segment and the rest on the western segment. Combining new data from the seven trenches and results obtained before, we discuss in this paper the recurrence behavior of paleoearthquakes on Zhongwei-Tongxin fault zone. The seven trenches have revealed six paleoearthquake events of the past 14 000 years along Zhongwei-Tongxin fault zone. One of them occurred in late Pleistocene and had ruptured the whole fault zone, while the others all occurred in Holocene and had ruptured only the middle or western segment. The 1709 Zhongwei earthquake of M =7 1/2 had ruptured only the middle segment of the fault zone. We postulate, therefore, that the magnitude of paleoearthquake that ruptured the middle or western segment of the fault zone should be about 7 1/2,while that of the event ruptured the whole fault zone should be about 8. In addition, we find that the temporal distribution of paleoearthquakes on the Zhongwei-Tongxin fault zone was neither uniform nor evidently clustered.

Invisible faults often developed in Quaternary unconsolidated sediments including concealed faults and die-out faults, which lead to complexity and multi-solution for paleoearthquake research. In this paper, original-state directional samples related to invisible or die-out faults are collected from some typical paleoearthquake profiles and solidified in laboratory. Microstructures have been observed after grinding slides in three-dimension coordinate system. Some indicators of invisible faults have been found in micrscopic field. The mechanisms of die-out faults have also been studied. It is suggested that according to microstructural observation, to confirm or negate the existence of concealed faults or to trace the terminated levels of die-out faults, can help us determine the age and periods of paleoearthquake events more accurately combining with macroscopic observation and age dating.

The Daqingshan Mountains and its adjacent Huhehot fault basin, Nei Monggol, are the ideal area to study denudation and uplift. By means of morphomeric analysis and field observation, this paper provides evidence for arching deformation of four accordant summit levels aged in Oligcene, Miocene, Plicene, and Quaternary stream terrace flights. On the basis of the result of seismic surveying for the Huhehot basin, the average Cenozoic denudation and crustal isostatic uplift amounts are estimated to be 3 310m and 2 910m, respectively, for the Daqingshan Mountains. It is thus evident that the resulting relief lowering due to denudation after crustal isostatic uplift is really slight, only 400m. For the denudation of the Daqingshan Mountains, obviously strenthening with time resulted from the long term climatic change during the Cenozoic era. The crustal isostatic uplift is a principal regional deformation mechanism for the Daqingshan Mountains. First, the crustal isostatic uplift controls the Cenozoic landscape evolution history. Second, the rate of the crustal isostatic uplift of late Quaternary has been quicker from the western part to the eastern of the Daqingshan Mountains. And third, the amount of the Quaternary crustal isostatic uplift of the Daqingshan Mountains is greater than the Ordos'tectonic uplift by one order. A close coupling relation between denudation to lose gravity equilibrium and crustal isostatic uplift to restore gravity equilibrium runs through the Cenozoic land evolution history of the Daqingshan Mountains. The faulting has a different position before and after the establishment of the coupling relation. And the flexural isostatic has accommodated long term local differential movement on the fault zone.

A detailed study of paleoearthquakes in Yanhuai basin and along Haiyuan fault of China shows that recurrence behavior of large earthquakes is of variery. Characteristic earthquake is common behavior of fault activity and there is grading of characteristic earthquakes. Besides, there is phasing of recurrence behavior of large earthquakes and the interaction between segments and (or) faults. These must influence the recurrence behavior of large earthquakes. Then, when the phasing of recurrence behavior appears and when the characteristic earthquakes of different intensity cause different interval time of recurrence, we must take trend average value of recurrence interval for assessing hazard of large earthquakes using either definite method or probability method. For example, the different average value is taken as fault behavior is during long-interval between event clusters and as it is during short-interval in a cluster. Characteristic earthquakes occurred on a master segment have different average value of recurrence interval from those occurred on a secondary segment so the different average value should be taken.

The reverse fault fold zones in the foreland basin of northern Tianshan is a typical active compression area in interior of continents. The research of the surface and deep structure,and its relationship in the active compression tectonic region is extremely important for the understanding its seismogenic structure and dividing its potential earthquake sources. On the basis of detailed research on the major active tectonics and synthetical studies in northern Tianshan,the deformation of the structure,earthquakes and active tectonics,and the relationship between surface and deep structures have been discussed in this paper. Finally,a few questions have been put forward in the process of potential earthquake source dividing in the active compression tectonic belt. Based on the research of the 1906 Manas earthquake (M7.7) and paleoearthquakes on the active reverse faults,we can know that the blind active crust ramp under the piedmont in the northern Tianshan area is the place of large earthquake occurring,and divided the blind ramp into two segments at the Jinguohe area. The active blind crust ramp may have two large potential earthquake (M8.0) sources. There are eight active anticlines in the northern Tianshan,west Urumqi. We can also compare these active anticlines with the active folds in the west region of the United States of America,and conclude that these active anticlines can only produce some middle earthquakes (M6.0). All the active anticlines in the northern Tianshan,west Urumqi,may have eight potential earthquake sources.

The recognizable segment boundaries of the Rukuu reverse fault system are obtained through study of coseismic surface ruptures for the 1896 Rikuu earthquake, long-term faulting behaviour and offset geomorphology. They are the transition areas for permanent change of fault scarps, watershed altitudes most nearby the faults and geometrical structures of active reverse faults in cross section, and buried tranverse bedrock ridges. The stepovers and fault trace gaps in kilometers' order can not stop or slow down effectively coseismic-surface-rupture propagation along the reverse fault strike, thus, can not serve as segment boundaries for reverse faults. The seismic risk on the Senya and Yokote segments of the Rikuu reverse fault system along the eastern margin of the Yokote basin is also assessed briefly.

The 4 paleoearthquake events that have occurred on seismogenic fault of 1679 Sanhe Pinggu M8 Earthquake since 20ka B.P. are exposed through the analysis of trenches and fault scarp profiles. The earlier two events are marked by liquefaction and the later two events are shown by direct fault offset,including the 1679 event. The 1679 event and pre 1679 event are two characteristic earthquakes of which the maximum displacement is about 1.75m and 1.41m,respectively and the intensity of two events is very close. The occurrence time of 4 events was about 20000,13000,7500 and 317a B.P.,respectively. Average interval of recurrence is (6561?691)a. It indicates the characteristics of quasi- periodic occurrence of earthquakes.

The 240km long Haiyuan fracture zone is a typical active fault in the inland of China. The 1920 Haiyuan earthquake (M_S8.6) has made the whole fault offset sinistrally. Our recent research on the large scale geological-geomorphological mapping and 3-D trench excavation at Gaowanzi,Haiyuan fault has revealed that at least 7 paleoearthquakes have been occurred since Holocene. And we have also studied the time intensity distribution of these events. Except the earthquake of 1920,these events have their ages about (10004±3196),(6689±169),(6120±505),(4208±577),(2763±372),(1005±465) and 30a,respectively,and the recurrence interval between two adjacent events is (3315±3200),(561±532),(1920±766),(1425±686),(1578±595) and (980±465)a,respectively. It shows that recurrence of these events is not uniform. At least 4 events comply with the Quasi periodic occurrence model and their average recurrence interval is (1641±207)a while the former 3 events and the later 2 events have the possibility of complying with the nonquasi-periodic occurrence model. This implies that the fault activity has the stage feature in the time distribution,that is,it complies with different occurrence models in different period. We have obtained the horizontal displacements of events Ⅲ,Ⅳ,Ⅴ,Ⅵ,Ⅶ. They are (5.6±2.3),(1.5±1.1),(1.5±1.1),(2±1) and (7±0.5)m,respectively. It indicates that the intensity distribution is also not uniform. The intensity of event Ⅲ is nearly the same as that of event Ⅶ while that of other events is much smaller. This suggests that the characteristic slip of the Haiyuan fault is graded,that is,large characteristic earthquakes occurred on the master segments while relatively small ones occurred on the secondary segments. The recurrence interval of the large earthquakes which have nearly the same intensity as that of 1920 earthquake is about 6000a since middle Holocene while that of small earthquakes with 1～2m horizontal displacement is 1000～2000a. There are 3 events whose displacement is 1～2m occurred between these two large earthquakes. So we estimate that the next earthquake is a relatively small one with a horizontal displacement of 1～2m.

Three basic geomorphic units, which were developed in response to the climate changes during the last glaciation, are recongnized along the northern piedmont of the ENE-trending Liulengshan range from airphoto interpretations and field observations.These three units are the inter-stadial fluvial fan (S₃) about 23～53 ka old, the maximum-glacial fluvial fan(S₂) about 10～23 ka old and the post-glacial fluvial fan(S₁) about 1～10 ka old, respectively.Five fluvial terraces(T₀～T₄) were also developed owing to the climatic temperature fluctuations on thousandyear scale.These geomorphic units(S₁～S₃) and fluvial terraces(T₀～T₄) are chronometrically dated by thermoluminescence.Stripped geomorphic mapping shows a natural segmentation in offset-geomorphology along the norhern piedmont fault of Liulengshan range.Six segments can be divided in the mapping areas and they are the Xifutou, Donghouzikou-Dawangcun, Xitunpu-Qiulin, Huoshilin-Qiuchangcheng, Huajialing-Xiejiayao and Longmazhuang-Xinpu segments from the west to the east, respectively.A set of quantitative data (faulting ages, vertical displacements and slip rates) are obtained from long-distance topographic profiles across the offset geomorphic units or fuvial terraces.The average Holocene vertical slip rates are 0.43～0.48mm/a for the Donghouzikou-Dawangcun segment, a bout 0.45 mm /a for t he Xitunpn-Qiulin segment, and 0.53～0.55mm/a for the Longmazhuang-Xinpu segment.The faulting irregularity is demonstrated by temproal and spatial flucturation in vertical slip rates during the Late Quaternary.The period of 15.6～7.6ha B P is the main phase of intensely verical faulting along the northern piedmont of Liulengshan range.

Excavation of trenches revealed three palaeoseismic events along the southern boundary fault of Xianhua basin. They occurred in 8.54 ka,7.08 ka,and 5. 31 ka B.P.,respectivly,The average reccurence interval is1 615±360a. The displacement of three events are 0.55～0.74m,0.52～0.7m and 1.63～2.2m,respectivly.However,the event displacing the surface has not occurred since 5.31 ka B.P.,suggesting that reccurrence interval of palaeoearthquakes is not simply quasi-periodic.

The NS-trending Minshan mountain in Northwestern Sichuan is an active Quatemay uplift.Its western and eastern boundaries are controlled by the active Minshan and Huya faults, respectively. The northern segment of Minshan fault has been active since 2 Ma ago. It is a reverse fault with left－lateral strike-slip component. The strike-slip displacement is about 2.4 km with a 1mm/a slip rate since 2 Ma, determined by matching offset placer gold mine with its mother lode. The Minshan and Huya faults are the major seismogenic structures in the region.

The NE-trending central segment of the Longmenshan thrust belt is composed of 3 major thrust or reverse faults. Geomorphic evidence and earthquake activity indicate that Quaternary activity is stronger on the southwest and weaker on the northeast along the central segment of the Longmenshan thrust belt. The segmentation of faulting is probably produced by the activity on the NS-trending Minshan uplift on the north of the Longmenshan thrust belt. Because deformation is dispersed on 3 faults, only moderate(M≤6)earthquakes have occurred along the central segment of the Longmenshan thrust belt.

The western Sichuan foreland basin initiated in T₃³ by continuous compression of the Long-menshan thrust-nappe belt,and its depositional centers were gradually transposed from NW to SE. The evolutionary history of the middle Longmenshan thrust-nappe belt and associated tectonics can be divided into three major stages:taphrogenic stage (D～T₃²),tectonic inversion stage (T₃³),and continuous thrusting stage (J～Kz).

The Longmenshan region inches the Longmenshan thrust belt,the western Sichuan foreland basin, the Longquanshan tectonic belt, and the Minshan uplift. The NE-trending Longmenshan thrust belt is composed of 4 major thusts and related napes, which form an extensive-compressive belt. The thrusting, mainly in a forward propagation style, started in the middle tolater part of Late Triassic and propagated from northwest to southeast. The Quaternary activity of the central and southern parts of the Longmenshan belt is stronger than the northern part.The western Sichuan foreland basin began to develop in the Late Triassic. The basin gradually retreated toward southwest since the late stage of Late Triassic, and the Quaternary deposition is limited on the Chengdu plain. The Longquanshan tectonic belt forms the eastern boundary of the foreland basin. It is a fault-propagation fold controlled by a master fault on its western margin.The NS-trending Minshan uplift northwest of the Longmenshan thrust belt is active since 2 Ma ago. The uplift is controlled by the Minjing and Huya faults, both with late Quaternary activities, on its western and eastern margins, respectively. The left-lateral slip rate of the Minjiang fault is about 1 mm/a. The Longmenshan thrust belt coincides with a steep gravity and magnetic gradient zone.The velocity structure and crustal thickness are very different on its northwestern and southeastern sides. There is a low velocity and high conductivity layer at a depth of 20 km on the west ofthe Longmenshan belt. The layer may be a detachment. Therefore, the Longmenshan belt maybe formed by a series of listric thrusts, and the wedges cut by the thrusts are thicker on the westand thinner on the east. The southern and central Longmenshan thrust belt and the Minshan uplift apparently control the seismicity in the region. This NE- to NS-trending seismic belt may be the active east-central margin of the Tibatan Plateau. Focal rnechanism solutions suggest that the principal compressive stress axis in the region trends NWW.The formation of the Longmenshan belt may be caused by the NW-SE directed compressionon the Songpan-Garze fold belt on the west. From Eocene to present, collision of the Indian and Eurasian plates caused southeastward movement of the western Sichuan block. This movementproduced a continuous compression on the Longmenshan belt. The movement of the westernSichuan block produced reverse faulting with left-lateral component on the boundary faults of the NS-trending Minshan uplift. The Quaternary activity in the northern part of Longmenshan beltis relatively weak due to the existence of the Minshan uplift.

The northern piedmont fault of the Liuleng Mountain in the extentional region of the north-ern end of Shanxi graben system lies along the southern edge of Yangyuan basin and controls theorigin and development of the basin, It is a dip-slip normal fault, NEE-trending and N-dipping.Two moderate and large earthquake swarms (Ms=6.1, Ms=5.8) successively occurried alongthe fault in 1989 and 1991.The fault consists of a marginal faul of the basin (F₁)and a newly formed fault(F₂) cuttingthe late Pleistocene to Holocene alluvial deposits within the basin. The F₁ and F₂ faults form astepped fault zone along the northern piedmont and joint together into the western segment. Thefault activity is characterized by inheritant displacements. It cuts stream terraces of different agesand piedmont loess terraces, causing two basalt eruptions (K-Ar age of the basalt and TL age ofits underlying baked bed is 1.71±0.41Ma, 18.29±1.39～19.7±1.54×10⁴a B.P. respectively). Later activity along the fault offset the basalt to form a 30～50m high scarp. At the middlesegment of the fault, F₁ has been inactive since late Pleistocene,whereas newly formed fault F₂ at 2～3km north of the edge of the basin has offset alluvial fan surface and stream terraces of different ages since late Quaternary. The eastern segment of the fault cuts the third terrace at thejunction of Sanggan and Huliu rivers and formed a 50～60m high scarp.Several topographic profiles across the scarps on different segments and un-coeval geomorphic surface were mapped to obtain vertical offset by using auto-level. Ages of the different geomorphic surfaces were determined by TL and ¹⁴C. Average vertical slip rate is 0.43～0.75mm/aduring the late Pleistocene to the Holocene. The age of the youngest layer cut by the fault is 0.76～0.86×10⁴a B.P..

The 1906 Manas earthquake is an important event in the northern Tianshan of China. TheSeismogenic fault controlling this earthquake has not been well understood. Detailed field investi-gation indicates that the ground ruptures in the epicentral area were caused by gravitational andshaking effects during the earthquake. The fresh fault scarps along the Tugulu-Manas-Houer-goush reverse fault and fold zone are the possible surface ruptures associated with the 1906 Manasearthquake. The displacement is between 0.2 and 0.5m. Total length of the fault scarp is lessthan 10 km which is far more less than a normal rupture length associated with an earthquake of magnitude 7.7.Anticlinal uplifting along this reverse fault and fold zone indicates that the earthquake probably occurred along low-angle reverse fault at depth as a blind reverse faulting event.The surface rupture and deformation took place far away from the epicentral area. Most of thecoseismic deformation was accomodated by folding and uplifting,and only less than 10 km surface rupture was formed.Thus,the 1906 Manas earthquake is probably a“folding earthquake”.

Shanxi graben system is one of the most famous strong earthquake belts on China Continent. In this paper, the problems on recurrence and migration of the historic strong earthquakes (M≥6), the precusory anomalies of the intermediate and strong earthquakes (41/3≤M<7) before M≥7 earthquakes occurring, and linear segmentation of the strain accumulation curves are discussed. The temporary trends of the recent and future seismicities are analysed. Finally the possible seismic risk areas in which intermediate and strong earthquake may occur are also outlined in the graben system.

Gyaring Co fault zone across Xainza and central Tibet had been formed before late Cretaceous period,and has been reactivated with right lateral motion since Quaternary.The fault zone consists of four subparallel faults in an arrangement of right stepping en echelon,and three pull-apart basins,occupied by Zigui Co,Gyaring Co and Waang Co respectively,are formed in righ-step like.Gyaring Co fault zone is one of main seis-mogenic fault in central Tibetean plateau.At least four surface ruptures associated with earthquake have occurred clearly along the fault zone since Holocene,with the segmentation of activity along the fault zone.

Through the mapping on the large scale and measurement in the epicentral area of the Haiyuan earthquake, left-lateral displacements of the gullies of various kinds which cross the earthquake fault are found. The data show that the larger the gullies are, the larger the horizontal displacements. Among these displacements, there are 73 offsets of small gullies and farming banks which were formed in the earthquake of 1920 (M= 8.5) with the maximum of about 10m.Displacements of various gullies are relatively large between the Yanghuzhang valley and the Gudunzi valley.On the basis of displacements of gullies on the second terrace, initial time of offseting as well as the average and maximal displacements associated with a great earthquake, we have calculated the slip rate and seismic recurrence for 8.5 earthquakes along the studied fault.

A earthquake series is referred as the events being successively occurred in a definite time and in the same seismic area. These events are characterized by the common developing process and an unified evolutional history of precursory field. We consider that the seismic precursory field is nothing but a regional field beyond a certain source region.For the North China fault block region can be recognized two earthquake series, Xingtai-Bohai and Haicheng-Tangshan series ever since the occurrence of Xingtai earthquake of 1966 to the year of 1978. The anomalies in the precursory field of this series started in 1972, after 1976 Tangshan earthquake it has been gradually becoming quiet. With regard to the developmental process of this field and its spatial distribution can be distinguished following five anomaly-development periods and relevant six stages.1. The primary period (A), during which the precursory field is developed from the stage in a scattered form (Ⅰ) to a divergent stage on a large scale (Ⅱ).2. Accelerated period (B) before Haicheng earthquake, during which the precursory field migrates northward entering into a convergent stage (Ⅲ) in the extent.3. Developing period (C), during which the precursory field enters into a rediver-gent stage (Ⅳ).4. Transitional or accelerated period before the Tangshan earthquake (D), during which the precursory field enters into a reconvergent stage(Ⅴ).5. Impending period before the Tangshan earthquake (E), during which the precursory field enters into a divergent stage (Ⅴ).It is suggested that the formation and development of the precursory field are closely related to the conjugated shear-rupturing network, and the distribution and development of anomalous points or zones are constrained by slipping of conjugated shear-ruptures and stress concentration at the various tectonic position. Consequently, the precursory phenomena would not be limited in the source area and its neighbouring regions, and the multi-anomalous regions (zone) are formed.Finally, the relationship of the regional precursory field with the earthquake prediction is studied. In general the regional precursory field does not imply only one event, perhaps an earthquake series, and the precursory extent has a certain relation to the magnitude of an event. To discriminate the location of one shock from the earthquake series it is necessary to pay attention to the spatial changes in the precursory field, such as the migration and convergence of anomalies. On the background of regional precursory field, the macroscopic anomalies in a great amount and concentrated form together with some abrupt anomalies can be taken as a precursory signal of a big imminent earthquake.

The earthquake sequence, precursory and geologo-structural background of Haicheng, Tangshan, Songpan-Pingwu earthquakes are discussed in this, article. As we know that all these earthquakes occurred in a seismic zone controlled by the main boundary faults of a intraplate fault block. But the fault plane of a main earthquake is not the same faults rather a related secondary fault. They formed altogether a conjugate shearing rupture zone under the action of regional tectonic stress field. As to the earthquake sequence the foreshocks and aftershocks might be occurred on the conjugate fault planes within an epicentral region rather than limited in the fault plane of a main earthquake, such as the distribution of foreshocks and aftershocks of Haicheng earthquake. The characteristics of the long-, medium- and imminent term earthquake precursory anomalies of the three mentioned earthquakes, especially the character of well-studies anomaly phenomena in the electrical resistivity, radon emission, groundwater and animal behavior, have been investigated. The studies of these earthquake precursors show that they were distributed in an area rather extensive than the epicentral region. Some fault zones in the conjugate fault network appeared usually as distributed belts or concentrated zones of earthquake precursory anomalies, they can be traced in the medium-long term precursory field, but seem more distinct in the short-imminent term precursory anomalous field. These characteristics can be explained by the rupture and sliding originated along the conjugate shear network and the concentration of stress in regional stress field. Moreover, it is worthy to notice the migration of these precursory anomalies along the conjugate rupture zone in the earthquake-brewing process. The macroscopic precursory anomalies of the Songpan-Pingwu and Haicheng earthquakes did not appear first in the epicentral region, but emerged in a set of fault zone conjugated with the fault plane of main earthquake, or in a conjugate fault zone and their intersection region. These phenomena may be originated from the migration of stress-concentrated region and continuous concentration of stress in the earthquake source area. It is also possible that they were progressively initiated at a definite direction along the rupture zone and sliding caused by conjugate faulting.It can be supposed that the effect of conjugate fault on the earthquake brewing and originating process is significant in theoretical studies of seismology and in predicting practice, it should be drawn public attention.

Basing upon the data of geological and seismological observations and crustal deformation this paper deals mainly with the characteristics of the tectonic stress field in China since Late Tertiary. Such a tectonic stress field is characterized first of all by obvious zonations. And it is especially distinct in three broad regions, namely West China, North China-Northeast China and South China-Taiwan. The tectonic stress field in these regions seems to be stable.The mechanical behavior of tectonic belt in S-N direction in Central China varies significantly with different sections, since it should neither be considered as a simple shearing belt nor a tensile fault zone. On the basis of quantitative data obtained it may be suggested that it is predominatly horizontal, but the vertically applied stress also exists in certain regions due to the motion of the Earth's deep-seated materials.It is to be noted also that the tectonic stress field in China is controlled by the joint action of the Indian and the Pacific plates.