Sanwei Shan Fault is located in the north of Tibet, which is a branch of eastern segment of Altyn Tagn fault zone. This fault is distributed along the boundary of fault facet and the Quaternary, with the total length of almost 150km. The fault is a straight-line structure read from the satellite image. Based on the spatial distribution of the fault, three segments are divided, namely, Xishuigou-Dongshuigou segment, Dongshuigou-West Shigongkouzi segment and West Shigongkouzi-Suangta segment, these three segments are distributed by left or right step.Though field microgeomorphology investigation along Sanwei Shan Fault, it has been found that two periods of alluvial-pluvial fans are distributed in front of Sanwei Shan Mountain, most of which are overstepped. Comparing the distribution of alluvial-pluvial fans with their formation age in the surrounding regions, and meanwhile, taking the results of optical stimulated luminescence(OSL) dating, it's considered that the formation age of the older alluvial-pluvial fans, which are distributed in northern Qilian Shan, inside of Hexi Corridor and western Hexi Corridor(including the Sanwei Shan piedmont fans), is between later period of late Quaternary and earlier period of Holocene. The gullies on the older fan and ridges have been cut synchronously. The maximum and minimum sinistral displacement is 5.5m and 1.7m, but majority of the values is between 3.0~4.5m. Taking the results from the OSL dating, we conclude that the minimum sinistral strike-slip rate is(0.33±0.04) mm/a since 14 ka BP and(0.28±0.03) mm/a since 20 ka BP.

The co-seismic rupture is one of the important contents in active tectonic mapping.As the late Quaternary landform is a basic recording medium for the recent deformation of active fault,such as the co-seismic rupture,it is quite useful to acquire the activity information of the active fault from various landforms.We implemented a field work along the southeastern segment of the Xianshuihe Fault,mapped the rupture and excavated some trenches.The preservation characteristics of the surface rupture of the 1786 Moxi earthquake were discussed for the glacial area of the Tibetan plateau,the fluvial and flooding area and seriously eroded area at the margin of the Tibetan plateau,respectively.The cracks and offsets were preserved continuously in the glacial landforms such as the moraines and glacial outwashes along Kangding to Yajiageng segment.As the landforms in the fluvial and flooding area were unstable under strong erosion and rapid deposition,the surface rupture can be discovered in the trenches excavated in Yuejinping village and Ertaizi village with gaps for some previous earthquakes.There was no deposition from the erosion landform to record the surface rupture.We can only infer the earthquake effected area and the ruptured fault from the indirect relationship between landslides and the earthquake strong motion or the fault rupturing.Based on the integrated analysis with the geometry and tectonic setting of the southeastern segment of the Xianshuihe Fault,the Kangding-Tianwan segment of the Xianshuihe Fault was taken as the seismogenic fault of the 1786 Moxi earthquake,and the total length of the rupture is about 80 kilometers.

To carry out the project "Study on paleo-tsunami in east and southeast seashore area of China" supported by China Ministry of Science and Technology,we made a study tour to Japan in April,2007.In this visit,we investigated roughly the tsunami deposits in Ishinomaki Plain,Miyaki County,Japan,where a huge earthquake of M_W 9.0 occurred at March 11,2011.This earthquake caused a great tsunami along the northeast coast of Honsyu Island,Japan,bringing lots of death and huge economic loss.To understand the tsunami history in this area and the methods of investigating tsunami deposits,it is necessary to introduce briefly our investigation in Ishinomaki Plain,Miyaki County,Japan.Our investigation results demonstrated three tsunami events occurred in this area. The latest one occurred before 915 AD,when the Towada volcano erupted and the tephra from this eruption covered almost all of the Northeast Japan,corresponding to the 869 AD Jogan earthquake tsunami.

The eastern piedmont fault of Helanshan Mountains is an important tectonic controlling the west boundary of Yinchuan graben.The south segment of the fault locates right in the west of Yinchuan city,which has a length of about 13.2km,strikes NNE-NE and dips south-east at an angle of 50°～80°.The main part of the fault lies between the Ordovician and Quaternary systems,forming the borderline between the hills and diluvium.Parts of the segment of the fault appear in alluvial fans and are displayed as geomorphic scarps.The paper selects the region on the two banks of Dashitou channel to excavate two trenches along the fault based on 1:10,000 geological mapping of the fault area.The result reveals three events since 14ka BP with the ages of 13.8,7.9 and 3.0ka BP and the recurrence intervals of 6 and 5ka,respectively.

The Longmenshan Fault zone is an important thrust belt on the eastern margin of the Qinghai-Tibet Plateau,consisting of the back-range,the central and the front-range faults,which differ from each other in size and activity.The rupture zone of the Wenchuan earthquake of 12 May 2008 occurred over a length of～270km along the Yingxiu-Beichuan Fault(a segment of the Central Fault)and a length of～70km along the Guanxian-Anxian Fault(a segment of the Front-Range Fault).The northern end of the fracture zone is at the Nanba region in Central Fault.In this work,we make a detailed field investigation on the northeast segment of the Longmenshan Fault zone.Qingchuan Fault is the northeast segment of the Longmenshan Back-range Fault,and the Chaba-Lin'ansi Fault is the northeast segment of the Longmenshan Central Fault.Along the above two faults,we make geological and geomorphologic mapping of Tuguanpu,Da'an and Hujiaba regions,where the Qingchuan Fault runs through the Tuguanpu and Da'an area,and Chaba-Lin'ansi Fault runs through the Hujiaba area.Based on the field investigation,there are five terraces in the northeast Longmenshan area along the major rivers.The height above the river of T1 terrace is about 3～5m,and the formation time is Holocene.The heights of T2 and T3 terraces are 10m and 30～35m above the river,and the deposition time of alluvium and diluvium is Late Pleistocence.The remnant of T4 terrace's sediment covers on some hills,with the height above the river of about 60～70m.In the remnant,granite cobble and sandstone cobbles have been air slaked,these gravels have the shapes only.T5 terrace's height is about 90m,the sediment on it has been eroded.Qingchuan Fault and Chaba-Lin'ansi Fault were strongly active faults in the times before T3 and after T4 formed.Some fault grooves were formed on T4 or T5 terrace,they have 30～180m in width,and 8～20m in depth.The vertical displacement of T4 terrace's gravels is 10～15m.Fault groove didn't form on T3 terrace,or the terrace height on a fault wall is consistent with other fault wall.At some places,T3 terrace's gravels overlie the fault zone.

In the eastern mainland of China there are few cross sections of faults where dislocation of Quaternary strata can be observed. However,recently we found such a profile about 2km away from the Nanling county,Anhui Province(30°55'456″N,118°177'74″E),west to the highway from Nanling to Fanchang. This fault has been identified on the satellite image,but its trace is confined to the southern side of the Nanling Basin. Our field investigation indicates that the northwestern end of this fault lies at the Xiaodanyang-Fangshan Fault. It is only 20km long,striking in NW,dipping to southwest. From observations on the profile,it consists of two small fractures and has two periods of activity at least. The first active period is before middle Pleistocene time,or probably in early Pleistocene. And the second active period is in or after middle Pleistocene. Its latest motion is of thrust with an amount of dislocation of 40cm. This fault cross section shows that the NW-trending faults in the eastern Mainland of China have new activities,though on small scales in general.

The neotectonic movement and characteristics of fault activity in the Anqing-Ma'anshan section of the Changjiang River valley are analyzed on the basis of data obtained from field investigation,shallow seismic prospecting and drilling. The results show that during neotectonic time this river valley section and its both sides as a whole was dominated by weak and intermittent uplift movement. As a consequence,owing to the effect of the activity of NE-and NNE-trending faults,relatively strong vertical differential movement occurred in Wuwei-Anqing area during Paleogene-Neogene,and had continued to early and middle Pleistocene. The NE-NNE-trending and NW-trending faults were developed in the bed rocks of the valley and its both sides. The former was formed during Indo-Chinese epoch,while the later was formed during Yanshan epoch. The most recent active period of the larger faults controlling the development of Cenozoic Basins is middle Pleistocene,while the newest activity of the relatively small faults developed within pre-Cenozoic group is pre-Quaternary. The Quaternary system in the valley is \{10～\}50m thick,consisting mainly of Pleistocene-Holocene deposits. The isopach of these deposits is smoothly distributed,indicating normal valley deposition. Seismic activity along the valley and its both sides is relatively weak,and historically only 4 destructive earthquakes have been recorded. Among these events,the largest one is the M5(3/4) earthquake occurring at Chaohu in 1585,and the other events including one with M5(1/4) and two with M4(3/4). Since the beginning of instrumental records in 1970,the largest magnitude that has been recorded so far is ML 3.7. All these results may provide better constraints on the assessment of the crustal stability for this river valley section.

According to the results of 1/10,000 stripped geologic mapping of the northwest segment of the Maxianshan north marginal fault and historical accounts of past events,we discuss in this paper the range of the magistoseismic area,seismogenic fault,pattern and combination feature of the surface ruptures of the 1125 A.D.Lanzhou M7 earthquake.The results show that the magistoseismic area of this earthquake is located in Lanzhou City and its southwest,and the epicenter can be located at the Xianshuigou area.The seismogenic fault of this earthquake is the Xianshuigou-Maquangou sub-segment on the northwest segment of the Maxianshan north marginal fault.This earthquake has produced a surface rupture zone of about 7km long and 300～1000m wide,extending along the seismogenic fault.The surface ruptures consist of earthquake fractures,fault scarps,seismic fissures,seismic landslides,and seismic pits.The surface rupture zone can be sub-divided into 2 sub-segments:the Maidiwan-Xianshuigou sub-segment in the southwest and the Damajiatan-Maquangou sub-segment in the northwest.Among them,the Maidiwan-Xianshuigou sub-segment consists of two parallel surface ruptures,while the Damajiatan-Maquangou sub-segment comprises a single surface rupture.Basing on large scale mapping,it is determined that the left-lateral displacement produced by this event is 2.4～2.5m,and the vertical offset is 0.45～0.92m.Regionally,the Maxianshan north marginal fault is located at the junction of the northern margin of the Qinghai-Xizang plateau and the northern segment of the North-south tectonic belt,which have been strongly active since neotectonic period.A rhombic block confined by major faults of different strikes is developed in this region,and we call it the Gansu-Ningxia rhombic block.The 1125 A.D.Lanzhou M7 earthquake just occurred on the western edge of the rhombic block,i.e.the Wuwei-Zhuanlanghe-Maxianshan Fault zone.The strong uplift and northeastward pushing of the active Qinghai-Xizang block may cause the stress relief on the boundary faults of the Gansu-Ningxia rhombic block,and hence the occurrence of several strong earthquakes.

The Kalpintag nappe is located at the southwestern foot of the Tianshan Mountains,consisting of several rows of NE-to EW-trending fold-reverse fault zones.This paper demonstrates the activities and slip rate of the frontal faults of the first to third row fold-reverse fault zones located to the west of the Piqiang-Bachu phosphorite mine.The newly-found evidence shows that the front of each fold-reverse fault zone is composed of several faults of typical reverse fault type.The faults with newest activity are located at the forefront of the fold-reverse fault zones,and the active period of the faults is late Pleistocene-Holocene.They dissect the T₀,T₁,T₂ and T₃ terraces,resulting in fault scarps of different heights.According to the in-situ measurement of the fault scarps and the dating data of the relevant samples,it is estimated that the amount and rate of vertical displacement along the faults since the formation of the T₀ terrace are 0.9～1.1m and 0.53～0.65mm/a,respectively,while the amount and rate of the corresponding crustal shortening are 1.93～2.56m and 1.14～1.52mm/a,respectively.Similarly,it is estimated that the amount and rate of vertical displacement since the formation of the T₁ terrace are 1.4～1.8m,and 0.36～0.46mm/a,with the corresponding crustal shortening of 3.00～3.86m,and shortening rate of 0.77～0.99mm/a.The vertical displacement amount and rate since the formation of the T₂ terrace are about 2.1～3.0m and 0.31～0.45mm/a,respectively,and the amount and rate of the corresponding crustal shortening are 4.50～6.98m and 0.67～1.04mm/a.The amount and rate of vertical displacement since the formation of the T₃ terrace are 3.4～4.2m and 0.28～0.35mm/a,and the amount and rate of the corresponding crustal shortening are 7.29～9.22m and 0.61～0.77mm/a,respectively.Based on the obtained amount and rate of crustal shortening since the formation of T₀ terrace,the total amount and rate of crustal shortening of the Kalpintag nappe since 1.7ka can be estimated to be 9.65～12.80m and 5.68～7.53mm,respectively.

The Maxianshan north marginal fault belongs tectonically to the Kunlun-Qilian-Qinling Caledo～nian-Variscan orogenic belt.The northwest segment of the fault locates within the Mesozoic Lanzhou basin,consisting of Xianshuigou-Maquangou,Xinchenggou and Qingshizui sub-segments.The Xianshuigou-Maquangou sub-segment is 7km in length,and comprises two sub-parallel faults,having a general strike of 290°～300°,dipping NE or SW at an angle of 60° or more.The faults dissect mainly the Cretaceous system,and locally act as the boundary of the Cretaceous system with the Ordovician and Jurassic systems.Upwards,the faults cut through the late Pleistocene loess or the gravel bed of gully terrace,appearing as fault scarp or fault escarpment.This sub-segment was the active segment of the whole fault during late Pleistocene to Holocene periods.The faulting of this sub-segment was dominated by left-lateral strike-slipping.The left-lateral displacement along this sub-segment since late Holocene is 5～8m,and the displacement rate is 0.5～1.72mm/yr.The Xinchenggou sub-segment is about 1.6km long,striking 325°and dipping southwest at the angle of greater than 60°.This sub-segment can be assigned to reverse fault,dissecting the Cretaceous system,and is covered with the gravel bed of the third level terrace of the Yellow River and the late Pleistocene loess.This sub-segment,therefore,has no longer been active since late Pleistocene.The Qingshizui sub-segment is about 2.5km long,striking 280°～310°and dipping northeast at angles of 58°～80°,and can be assigned to normal fault.The fault dissects mainly the Cretaceous system,and locally becomes the boundary between the Cretaceous and Ordovician systems.The fault is also covered with the gravel bed of the third level terrace of the Yellow River and the late Pleistocene loess.This may indicate that this sub-segment has ceased its activity since late Pleistocene.Macroscopically,the middle and eastern segments of the Maxianshan north marginal fault,together with the Zhuanglanghe Fault have made up a right-stepped en echelon zone.The faulting process of the former during late Pleistocene-Holocene was dominated by left-lateral strike-slipping,while that of the later by right-lateral strike-slipping,so a compressional step-over was formed between the two faults.Therefore,the Xianshuigou-Maquangou sub-segment can be assigned to shear fault within the compressional step-over,and hence the latest activity of this sub-segment is later than that of the middle and eastern segments of the Maxianshan north marginal fault.

The Kalpintag Fault locates at the most forefront of Kalpintag nappe tectonics, and can be separated into eastern and western segments by Piqiang Fault. Six large trenches are excavated along the western segment and four paleoearthquakes can be distinguished in the three trenches of them. The first paleoevent occurred about 12ka BP, the second event occurred about 8.6ka BP, the third event occurred about 5ka BP,and the last event occurred after (1.73±0.15) ka BP, which probably is the Xike'er M6.8 earthquake in 1961 AD. The four paleoevents are characterized by 3～4ka quasi-periodic recurrence interval. The Kalpintag nappe structure are composed of 5～6 rows of fold-reverse fault zones. The faults with the latest activity are located at the forefront of the fold-reverse fault zones with 10km spacing between each fault. The north-dipping and listric style fault surfaces merged into the detachment surface in the deep along the bottom of Cambrian at 6～10km depth. The field investigation discovered that earthquake ruptures and paleoearthquake traces can be found not only along Kalpintag Fault but also along other faults, but the rupture length and seismic slip are smaller than that formed by an M≥7 earthquake. Although five paleoearthquakes since 14ka BP are obtained along western segment of Kalpintag Fault, some events are probably missed because of less trenches and dating samples. Many problems such as magnitude of these events, seismogenic fault and their rupture zones formed by one or several events await study in the future.

The Kalpintag fold nappe is located at the northwestern foot of the Tianshan Mountains. Since Cenozoic, owing to the Indian-Eurasian collision, the Mesozoic fold structures of Tianshan have been rejuvenated, uplifted and pushed northward and westward. As a result, several rows of fold-reverse fault zones have been progressively formed within the foreland basins. This paper describes in detail the Cenozoic deformation features and propagation of the fold-reverse fault zone on the west of the nearly south-north-trending Piqiang fault zone. The results show that the Cenozoic deformation of the nappe was characterized by wavy differential uplift, and this has caused the successive formation of the fold-reverse fault zone from the southern side of the Tianshan Mountains to the Tarim Basin. Among them, the early-formed folds are close to the Tianshan Mountains, while the latter-formed folds are close to the Tarim Basin, indicating the general tendency of northward propagation of the fold-reverse fault zone during their formation process. The distance of propagation may reach up to 76km. Moreover, the front of individual fold-reverse fault zone consists of several fault strands, which are associated with folds and have different ages of formation and time of recent activity. The early-formed faults are close to the Mountain side and the latter-formed close to the basin, indicating the northward propagation of the frontal faults of the individual fold. The distance of propagation is about 100～500m. The mechanism of the propagation of the fold-reverse fault zone is discussed in this paper as well.

Kalpin thrust tectonic is an active reverse fault fold zone at the southwestern Tianshan front piedmont, it consists of five to six rows of arc fold zones which are formed by Cambrian-Quaternary sedimentary rocks. The major morphology of the anticline is multiple box-shaped or asymmetry inclined, mostly, and it is similar to that of fault-bend fold and fault-propagation fold. Depending on the seismic reflection surveys data, the reverse faults on the front of the nappe in Kalpin thrust tectonic zone form an integrate detachment surface in the deep along the gypsum stratum in Cambrian. The depth of the detachment is shallower in the southeast and deeper in the northwest. The depth of the detachment fault is deeper in the west part (about 9km deep) and shallower in the east part (about 5km deep) of the Piqiang fault. In the middle part of the Kalpin reverse fault-fold zone, we have made two balanced cross-sections at the two sides of Piqiang fault. On the two geological cross-sections, we construct the structure mode at depth using fault-bend fold or fault-propagation fold model. The length of the two sections is 73km and 78km, respectively. The restored sections yield a crustal shortening of 40km to 45km, the shortening rate is 33% and 37%, respectively. Calculating the long-term shortening rate from these two across-sections is difficult, because the time of initiation of deformation is poorly known. Geological evidence suggests that most of the shortening began in the beginning of the deposition of the thick conglomerate unit in lower Quaternary. If the initiation time is about 2.5Ma, the shortening rate of Kalpin thrust tectonic zone is 15.4～17.3mm/a.

Owing to strong and permanent Cenozoic re-orogenic processing, a lot of EW-striking active thrusts and folds have been developed in Tian Shan, resulting in crustal shortening in NS direction. There also exist NW-striking transform-like strike-slip faults that cut the Tian Shan and accommodate uneven crustal shortening larger in the west and smaller in the east. The seismogenic structures in and around the Tian Shan mainly include EW-striking thrust ramps or blind thrusts and NW-striking transform-like strike-slip faults. The 2003 AD Bachu-Jiashi earthquake is located at south of the Kalpintag nappe. A NE-trending deep seismic reflection profile about 50km long across the epicenter has been conducted after the earthquake. From this reflection profile four blind faults are identified. Together with earthquake relocation, these identified blind faults are used in the paper to interpret the seismogenic structures of the 1997 AD Jiashi strong earthquake swarm and 2003 AD Bachu-Jiashi earthquake. The 1997 AD Jiashi strong earthquakes were generated mainly by a NW-striking buried transform-like strike-slip fault, while the 2003 AD Bachu-jiashi earthquake by blind thrusts in front of the Kalpintag nappe.

The Xiaodianzi-Maobu segment is part of the Anqiu-Juzian Fault in the Tancheng-Lujiang Fault zone. It starts from northeast of Xiaodianzi village, Juxian County in the north and terminates at Maobu, Juxian County in the south. The fault segment has a general strike of 10°～20°, dipping northwest or southeast at an angle of 60°, and has a length of about 30km. The segment can further be divided into 5 sub-segments: the Xiaodianzi-Qijiazhuang, Yuanhe, Kushan-Xilianci, Qingfengling and Sanzhuang-Zhaike sub-segments from north to south successively. These 5 sub-segments are aligned in right or left-step en-echelon, appearing as a brush structure converging to the north and diverging to the south. The fault segment appears as distinct lineation on satellite image or aerial photo, and geomorphically, as distinct bedrock scarp. According to field observation on natural exposures or trench logs, as well as dating results of samples collected from the fault segment, it can be deduced that the latest faulting event occurred in early Holocene and was dominated by right-lateral strike-slip with compressional reverse faulting component. The distinct horizontal fault striate is well developed along the fault plane and the drainage system crossing the fault segment is right-laterally distorted. This corroborates the right-lateral strike-slip of the fault segment. Field measurement of displacement and dating of the relevant samples have indicated that the displacement amount of the fault is 64～73m, and the displacement rate is 0.91～1.04mm/a in the past 70ka, while in the past 11ka, the displacement is 5.5～7.8m and displacement rate is 0.46～0.65mm/a. The reverse faulting along the fault segment can also be recognized in exposures or trench logs. It can be observed that the Cretaceous or Paleocene system is thrusted over the Quaternary system, making a distinct fault scarp landform. Field measurement of fault scarp and laboratory dating of relevant samples have revealed that in the past 11ka the vertical displacement along the fault segment is 2.3～3.8m and the displacement rate is 0.17～0.32mm/a. In the same period, the right-lateral displacement is 2～3 times as large as the vertical displacement.

Tanlu Fault zone is one of the most important active faults in east China. Yishu Fault,the middle section of the Tanlu Fault zone,presents a graben system consisting of two grabens and four main boundary faults. The eastern graben between Weifang and Jiashan is the most active segment of the Tanlu fault zone,along which developed a 360km long Holocene active fault zone (F₅). The F₅ fault zone has been defined as what consists of all Holocene faults in the eastern graben. The Anqiu earthquake of AD 70 and the Tancheng earthquake of 1668 occurred along the northern and middle segments of the Holocene active fault,respectively. We found a 7km long surface rupture between the main boundary faults of the eastern graben in Juxian County,when we made an investigation on the Yishu Fault in 2003. As an active fault,it should belong to the F₅ fault zone. The carbon date of the un-faulted deposit covering the newly-found surface rupture shows that no earthquake has occurred along this rupture since 2 140?190 yr BP. Therefore,we infer that this newly-found surface rupture is independent of the surface rupture of 1668 Tancheng earthquake,although it is necessary to make a further research to verify this inference.

The Youjiang Fault zone is located in the Guixi (Western Guangxi) fault block region. Since the beginning of seismic records,22 earthquakes of magnitude 4.0～6 occurred in this region,among which the largest one is the magnitude 6/2 earthquake occurred in the area between Leye,Guangxi Autonomous Region and Luodian,Guizhou Province in 1875. Of these events,15 earthquakes of magnitude 4.0～5.0 occurred on the Youjiang Fault zone. The Tianlin Bagui M5.0 earthquake of 1962 and the Pingguo M5.0 earthquake of 1977 had caused certain damages of basic installations in the regions. Obviously,the Guixi region is an active region of moderate earthquake,and the Youjiang Fault zone is an active belt of moderate earthquake,which plays an important role in the seismicity in Guixi fault block region and in the territory of the Guangxi Autonomous Region. Based on the interpretation and analysis of satellite images,aerophotos,and large-scale topographic maps,as well as field investigation,a line of geologic geomorphic evidence of late Pleistocene activity of the Youjiang Fault zone have been obtained,and the left-lateral displacements on the fault zone have been measured. This paper presents all these results and provides the horizontal and vertical slip rates of the fault zone since mid-late Pleistocene. The Youjiang Fault zone can be divided into 3 segments. They are the west of Bose,Bose-Silin and Silin-Tanluo segments,each of which can be subdivided into several sub-segments. The offset of late Pleistocene terrace deposit and talus can be observed along each segment of the fault zone. The ages of the deposits have been dated to be (3.28±0.25)×10⁴a BP～(10.16±0.79)×10⁴a BP. Geomorphically,the fault zone controlled the development of the Bose-Tiandong late Quaternary basin. A series of fault valleys,troughs,and scarps were developed along the fault strand,while the drainage system crossing the fault zone was left-laterally offset. According to the comparison of the amplitudes of vertical and horizontal displacements on the fault zone,it is inferred that the activity since late Pleistocene of the fault zone has been dominated by left-lateral strike-slipping accompanied by extensional differential motion. The horizontal displacement rate since late Pleistocene on the fault zone has been determined to be 1.47～1.98 mm/a,the vertical displacement rate since middle Pleistocene is 0.74～0.76 mm/a,and the vertical displacement rate since late Pleistoce is 0.1～0.35mm/a. All these values are significantly lower than those on the fault zones surrounding or within the Chuandian fault block. The recent results of GPS observation support also this conclusion.

The Longmenshan Fault zone is an important thrust fault on the eastern margin of the Qinghai-Tibet Plateau.The Cenozoic activity of the fault zone has attracted great attention of many scientists at home and abroad.The Longmenshan Fault zone consists of the Back-range,the Central and the Front-range Faults,which differ from each other in size and activity.Meanwhile,the activity of the whole fault zone is characterized by segmentation.Previous studies on the middle and southern segments of the fault zone showed that these two segments have been active since late Pleistocene.However,little work had been done on the activity of the northern segment of the fault zone so far.In this study,we made a detailed field investigation on the northern segment of the fault Fault and collected many samples from the strata covering the fault or from fault zone materials for TL and ESR dating.According to the observation of the northern segment of the Longmenshan Fault zone and dating results,it can be concluded that the Back-range Fault had once been active in early-mid Quaternary,but has been inactive since late Pleistocene,the Central Fault was active during early Quaternary or pre-Quaternary,and the Front-range Fault was active during pre-Quaternary.They all have been inactive since late Pleistocene.However,the middle and southern segments of the Longmenshan Fault zone have been active since late Quaternary,controlling the development of late-Quaternary basin,and many strong earthquakes occurred in history along these two segments.What has caused the different activities of the different segments of the Longmenshan fault? The main reason might be the change of the construction of the block boundaries due to the variation of the regional stress field in this region.Since mid-Pleistocene,affected by the southeastward moving of the Tibet Plateau,the stress field of the region where the Longmenshan fault zone is located was changed,causing the change of the boundary faults that bound the active blocks.At present,the northern segment of the Longmenshan Fault zone is no longer the boundary fault of the active block,while the uplifting of the Minshan Mountains acts as a protective wall hampering the movement of the Longmenshan fault zone.All these factors have caused the weakening of the activity of the northern segment of the Longmenshan Fault zone.However,the southern and middle segments of the Longmenshan Fault zone,together with the Minshan uplift tectonic zone constitute the eastern border of the compressional system,controlling the development of present topography and strong earthquakes in this region.This recognition may provide useful information for the study of the geodynamics of the Qinghai-Tibet Plateau.

Fault structures are well developed in the Zhujiang Delta area. They can be classified into NW-, NE- and E-W-trending groups, most of which display distinct features of vertical differential movement. Since most of the faults are buried and their activities are relatively weak, the evidence of vertical dislocation are difficult to be identified directly in the field, and hence the amount of displacement along the faults can not be measured. Fortunately, a large number of drill holes have been drilled during the construction of the Zhujiang Delta, and a lot of data concerning the present altitudes above sea level of late Quaternary deposits and their ages have been measured and determined. Basing on the analysis of the formation and evolution of the Zhujiang Delta, we have selected a pair or some pairs of bore holes, which are close in position and may reveal the deposition time and environment of the same strata for comparative analysis. Then the vertical displacements along the faults can be determined according to the differences between the present altitudes above sea level of the same strata on both sides of the faults, and hence the dislocation rates can be calculated based upon the age data. We have calculated the late Quaternary vertical dislocation rates for 5 faults. The results show that the dislocation rates are within the range of 0.14～0.47mm/a. Among them, the vertical dislocation rate of the Xijiang Fault in the past 29,400 years is 0.44mm/a. The vertical dislocation rate of the Baini-Shawan Fault in the past 15,000 years is 0.39mm/a, while that in the past 11,400 years is 0.38mm/a. The vertical dislocation rate of the Gulao-Conghua Fault in the past 29,530 years is 0.47mm/a. The vertical dislocation rate of the Wuguishan north piedmont fault in the past 6,390 years is 0.19mm/a. The vertical dislocation rate of the Shougouling Fault in the past 29,800 years is 0.14mm/a, and that in the past 17,480 years is 0.19～0.21mm/a. All these results are of great importance to the project of detecting the active faults in major cities that will be carried out in the near future.

The inner part of the Sichuan-Yunnan rhombic block is dissected by the Lijiang-Xiaojinhe Fault, and hence can be subdivided into Northwest Sichuan sub-block in the north and Central Yunnan sub-block in the south. The eastern boundary faults of these two sub-blocks are regularly characterized by left-lateral strike-slip, while the western boundary faults are characterized by right-lateral strike-slip. The slip rate of both the eastern and western boundary faults are significantly different. All these phenomena may indicate the composite movement of these sub-blocks characterized by southeastward horizontal slipping associated with clockwise rotation around a vertical axis during the Cenozoic time. Among them, the horizontal slip rate of the Southwest Sichuan sub-block is 5mm/a, and the angular velocity of clockwise rotation is about 1 4°/Ma, while those of the Central Yunnan sub-block are 3.5mm/a and 1 5°/Ma, respectively. About 90 oriented samples have been collected from Paleogene strata in Yaoan, Dayao, Yongren and Beimajie of Kunming within the Central Yunnan sub-block. The vectors of remanent magnetism of each sample (measured magnetic declination and inclination) have been obtained through alternating field demagnetization and thermal demagnetization. The comparison between the measured magnetic declination and the expected value shows that the accumulated clockwise rotation of the Central Yunnan sub-block of the Sichuan-Yunnan rhombic block since early Miocene has reached up to 30°～48°. The feature represented by the entire rotation of the sub-blocks accompanied by left-lateral slipping along the boundary active faults is consistent with the kinetic model of clockwise rotation of the block in left-lateral strike-slip faulting region.

On the basis of 1/10,000 active fault mapping in Fuzhou Basin, interpretation of aerial photos and detailed field investigation, 11 sites on six faults in the basin were selected for exploratory trenching. The main results of trenching are as follows:(1)Two trenches were dug across the Hutou-Miaopu Fault. One of the trenches reveals a fault plane, which is developed in lava bed and covered by Quaternary strata with an age of 75?6ka B.P. The other trench reveals that a series of joints are developed in tuff bed, but they do not offset the overlying strata of 119?10ka in age. These facts may indicate that the fault had ceased moving since late Pleistocene.(2)Two trenches were excavated across the Gushan Fault. No fault plane can be identified in one of the trenches, but the second trench reveals a minor fault plane, which is developed in granite and does not offset the overlying strata of 100?9ka in age. It can be concluded, therefore,that the fault had also ceased moving since late Pleistocene.(3)Two trenches were excavated across the Wuhushan Fault. In both trenches, the relationships between the volcanic rocks and Quaternary deposits, as well as the fault planes in volcanic rocks and overlying Quaternary deposits are well exposed. A series of minor fault planes developed in granitic rocks are well exposed in one trench, and these minor faults do not offset the overlying strata of 98?8.3ka in age. It is postulated, therefore,that the fault might have ceased moving since the early stage of late Pleistocene.(4)The micro-gemorphological expression of the Minhou-Nanyu Fault can be distinctly traced along the fault strand. A fault trough is observed at Heshangsi Temple, where two trenches were excavated to identify the two faults on the eastern and western sides of the trough. The trench logs show that the fault planes that are developed in granitic rocks do not offset the overlying Quaternary deposits of 29?2ka in age. Obviously, the Minhou-Nanyu Fault had ceased moving since the late stage of late Pleistocene.(5)One trench was excavated across the Tongkou-Hongshanqiao Fault. The trench log reveals two fault planes, which dislocate the same bed of Quaternary strata and are covered by the younger bed. The age of offset bed is dated to be 193?16ka B.P, and that of the overlying bed is 100?9ka. It is suggested, therefore, that the fault had also ceased moving since late Pleistocene.(6)A 4-5 meters deep trench was excavated across the Bayishuiku-Shanggan buried fault. Geophysical prospecting data suggested that the fault probably passes the trenching site. However, no fault is found in the trench, and the Quaternary deposits here are nearly horizontal. The age of bottom deposits is dated to be 39?3ka B.P. It seems that the Bayishuiku-Shanggan Fault had ceased its activity since the late stage of late Pleistocene. The afore-mentioned conclusions are merely drawn from the results of trenching, and more detailed study is needed in the future.

Four prospecting trenches were excavated along 4 subsidiary faults of the Daliangshan fault zone, and 9 paleo-seismic events were revealed by these trenches. West of Doukanzi village, the Tc-1 trench is located on the northern segment of the Shimian-Haitang-Yuexi subsidiary fault. The occurrence time of 2 paleo-earthquakes revealed by this trench is 35ka and 3.5ka, respectively. In the north of Keqilada village, the Tc-2 trench is located on the middle-northern segment of the Puxiong-Zhuhe subsidiary fault. The occurrence time of 2 paleo-seismic events revealed by this trench is 28～30ka and 24ka, respectively. The trench Tc-3 in the south of Tuodu village is located on the middle-northern segment of the Tuodu-Butuo subsidiary fault. The occurrence time of 3 paleo-earthquakes revealed by this trench is 25ka, 10ka and 7.5ka, respectively. The trench TC-4 at Cizijiao village is located on the northern segment of the Jifulada-Jiaojihe subsidiary fault, and the occurrence time of 2 paleo-seismic events revealed by this trench is 15ka and 4.5ka. Among the 9 events, 4 events occurred in Holocene time. The occurrence of the 9 events indicates that the Daliangshan fault zone has been active since late Pleistocene. The vertical displacements produced by these 9 earthquakes are 0.5～1.5m. In comparison to the displacement produced by the historical earthquakes along the Xianshuihe-Xiaojiang fault zone, it can be postulated that the maximum magnitude of these 9 events is M≥7. The study of fault segmentation has shown that a major fault zone can be divided into several segments with independent rupturing history. The segments are separated from each other by relatively large scale bending, turning, crossing and step-over, which may effectively inhibit the propagation of the rupture. The four subsidiary faults of the Daliangshan fault zone are 60～90km in length, and the width of the step-over zone between two subsidiary faults is 5～15km, which is wide enough to inhibit the propagation of rupture on the adjacent faults. That is why the subsidiary faults become an independent rupturing unit. It is concluded, therefore, that the paleo-seismic events revealed by the 4 trenches were independent rupturing events.

The Xiaojiang fault is the southern portion of the Kangding fault zone, which is a noticeable active fault in southwest China and plays an important role in the left-lateral extrusion of the Tibetan Plateau. We determined average slip rates of the Xiaojiang fault, on the basis of offset landforms that were precisely mapped and dated by radiocarbon or thermoluminescence methods. The Xiaojiang fault consists of two subparallel fault strands in its middle segment; the average left-lateral slip rates on the west and east strands were determined to be 7.0～9.0mm/yr and 6.0～7.5mm/yr, respectively. Thus, the total slip rate on the Xiaojiang fault amounts to 13.0～16.5mm/yr. This value is approximately equal to that on the Xianshuihe fault, the northern part of the Kangding fault zone, and about twice as high as that on the Anninghe and Zemuhe faults, the middle part of the Kangding fault zone. Our results suggest that there must be other active faults that accommodate the missing slip in the middle of the Kangding fault zone; the most probable candidate may be the Puxionghe-Butou fault zone located several ten kilometers to the east of the middle segment.

Interpretation of aerophotoes and field investigation make authors find that a series of fault scarps are distributed in the .unconsolidated Quaternary sediments on the northern piedmont of Qinling Mts. Further geological,geomorphological and chronological studies of the fault scarps in combination with the analysis of levelled morphological sections of the scarps and excavated trenches led us to reveal the spatial distribution,geometric features,ages and offsets of the fault scarps and the activity of the northern piedmont fault of Qinling Mountain in late Quatery. It is indicated that the fault scarps occurred and were preserved on special tectonic and geomorphic parts of the zone. The heights of the scarps range from 1.1m to 7.7m,but the scarps on elder morphological surfaces are higher than those on younger morphological surfaces. The average slip rate along the middle segment of the northern piedmont fault in late Holocene is about 1mm/a,while that along the western segment of the fault is about 0.5mm/a. Three or four large paleoseismic events probably occurred on the northern piedmont fault since late Pleistocene.

Based on the measurements of the positions of knickpoints in the gullies passing throngh pluvial fans,this paper deals with the factors that influence the headward migra tion rate of knickpoints in the gullies dissecting the east piedmont fans of Helanshan Mt. The relation between the position and age of knickpoint hasbeen established. The result shows that at least 3 prehistoric events of magnitude,as large as that of 1739 Pingluo earthquake have occured along the eastern Piedmont fault of Helan Mountain since Holocene. The recurrence interval of great earthquakes in this area is determined to be 2500-3500 years.

Haiyuan active fault zone is a main active fault in the northeast boundary of Qing-hai-Xizang plateau. Geologically, mapping of 1:50,000 has been made along the fault zone. The results show that Haiyuan active fault zone, 237km long, striking WNW in its west segment and striking NW in the east segment, has been a strike-slip fault sense since middle-late early Pleistoncene. The horizontal offset is 12-14.5km from middle-late early Pleistocene, with the slip rate of 11.7-19.2mm/a. The strong activity has been going on since the begining of the Holocene, with the sinistral strike slip rate of 6-10mm/a.Haiyuan strike slip fault zone consists of 11 secondary shear faults, mostly left stepping pinnate, partly right stepping pinnate. 8 pull-apart basins and 2 pushed-up blocks were formed along the fault zone. Pull-apart basins showing 2 types of romb and elongated, big ones began to develop in middle Pleistocene, small ones in late Pleistocene. The largest thickness of sediments is greater than 750m. A tensile-shear fault with the sinistral strike-slip was formed in some pull-apart basins.The tensile-shear fault links up two secondary shear faults which control pull-apart basin, intersecting them with low angle. After the formation of this kind fault, pull-apart process of the basin decreased and pull-apart basin gradually became feeble and die. The thrust faults intersecting the secondary shear faults with high angle was formed in the pushing area, appeared as an uplift in topography.A great earthquake of magnitude 8.6 occurred in Haiyuan, in December 16, 1920. The surface ruptures of earthquake can be divided as 15 fracture segments, which developed along secondary shear faults, tensile shear faults on pull-apart basin and boundary normal fault at both ends of pull-apart basin. The horizonal dislocation of 268 values have been measured. The maximum displacement of left-lateral strike-slip is 10-11m.At the southeast end of Haiyuan strike slip fault, a rare end compressional area, which consists of thrust fault zone of east pediment of Liupan Mountain, Madong Mountain fold zone and Xiaoguan Mountain thrust fault zone, striking nearly NS, was formed. The detail mapping and studying have been made on the deformation features of these compressional structure belts and calculation on the amount of crust shortening have been made, and the value is about 12.4-16.7km, which is about equal to the sinistral offset amount of Haiyuan active fault zone.

On the basis of field tectonic mapping and measurement of the water setting displacement, we concluded in this paper that the Xiangshan-Tianjingshan arc fracture zone experienced two different active stages in the Cretaceous, i. e. strongly compression in the beginning and left-lateral strike-slip with compression at the end. The time boundary and cause of transition were analyzed and discussed. The appearance and range of the seismic deformation zone of the 1709 south of Zhongwei M = 7¹/₂ earthquake is also described.