The Anqiu-Juxian Fault is the latest active fault in Tanlu fault zone, which is also the seismogenic fault of Tancheng M8.5 earthquake in 1668. In order to probe the shallow structure and the characteristics of faults in the eastern graben of Tanlu fault zone, we applied the high-resolution shallow seismic reflection method with multifold overlaying and stacking. In addition, we laid out two shallow seismic reflection lines across the Anqiu-Juxian Fault and the eastern graben of Tanlu fault zone. The shallow seismic profiles clearly reveal the stratigraphic interface morphology and shallow fault characteristics. The results show that the eastern graben of Tanlu fault zone is a graben basin consisting of multiple faults, and the thickness of Quaternary strata and graben structure characteristics are obviously affected and controlled by Changyi-Dadian Fault F₁ and Baifenzi-Fulaishan Fault F₂. Also, the eastern and western sides of the graben are the basement uplift areas, and the sediment thickness of the Quaternary strata in uplift areas is less than 30m. There are thick Cenozoic strata deposited in the barben, the stratigraphic morphology changes greatly laterally, showing an inclined form which is shallow in the west and deep in the east, and the Cenozoic strata are in angular unconformity contact with the overlying strata. The deepest part of Quaternary strata in the graben is located near the horizontal distance of 7400m, and its depth is about 190m. The Anqiu-Juxian Fault revealed by the shallow seismic reflection profile is composed of two branch faults dipping in opposite direction, which merge into one fault in the deep section. According to the discernible buried depth of the upper breakpoints of these faults and the characteristics of the Quaternary activity, the activity of Baifenzi-Fulaishan Fault on the western boundary of the eastern graben of Tanlu fault zone is relatively weak and the discernible depth of the upper breakpoint is 53m, we infer that the Baifenzi-Fulaishan Fault is a pre-Quaternary fault. The Changyi-Dadian Fault on the eastern boundary of the eastern graben of Tanlu fault zone not only cut the bedrock’s top interface, but also revealed signs of dislocation since Quaternary. The discernible depth of the upper breakpoint of Changyi-Dadian Fault is about 26~33m. The Anqiu-Juxian Fault is the latest active fault in the study area, which possess the characteristics of large scale and large penetration depth. The fault controls the deposition of the Cenozoic strata in the graben and plays an important role in the formation of the the eastern graben of Tanlu fault zone. The discernible depth of the upper breakpoint of Anqiu-Juxian Fault is about 17~22m. Therefore, we infer that the active ages of Changyi-Dadian Fault and Anqiu-Juxian Fault are the late Pleistocene and Holocene, respectively. The research results can provide seismological evidence for further understanding of activity mode and activity age of the seismogenic fault of the 1668 Tancheng M$8\frac{1}{2}$ earthquake, as well as the near-surface characteristics and activity of the Banquan segment of the Tanlu fault zone.

The Anqiu-Juxian Fault is a major branch fault and an active prominent fault of the Yishu Fault belt. The spatial distribution, geometric features and the latest activities of the Anqiu-Juxian Fault are studied by field survey and mapping in this study. The northern segment of the Anqiu-Juxian Fault between Juxian and Changyi can be divided into four segments, namely from north to south, the Changyi-Nanliu segment, the Anqiu-Mengtuan segment, the Qingfengling segment and the Mengyan segment. These segments are left-step en echelon arranged, and each of the fault segments consists of right-step en echelon arranged sub-segments. The Changyi-Nanliu segment is about 31km long and composed of 4 sub-segments in right-step en-echelon arrangement, namely, Wenshan sub-segment, Zhuli sub-segment, Shuangguan-Meicun sub-segment and Nanliu sub-segment, from north to south. The length of these sub-segments is 5km, 7km, 10km and 9km, respectively. The width of the stepover between them is about 2～3km. The Changyi-Nanliu segment generally strikes～15°, and the fault plane dips both west and east with dip angle 70°～80°. This segment offsets the widely distributed eolian yellow or orange fine sand and silt that were formed in the latest late Pleistocene, and it also offsets the mid-Holocene grey-yellow clay. The latest active age of the Changyi-Nanliu segment is the middle and late Holocene. This segment is characterized by right-lateral strike-slip motion with thrust and normal fault component, and the normal faulting activity is usually younger than the reverse faulting activity. The Anqiu-Mengtuan segment is about 50km long and exposes～21km. It strikes 15°～20°with the major fault plane dipping NWW with dip angle 70°～80°. This fault segment is characterized by right-lateral strike-slip motion with west-to-east thrust component. The segment can also be divided into two sub-segments, namely, the 13km long Anqiu-Guangong sub-segment and the 8km long Anshang-Mengtuan sub-segment, as in right-step en echelon arrangement, with a stepover of about 3km in width. The youngest offset stratum along the Anqiu-Mengtuan segment is the late Pleistocene, so, its latest active age is the late Paleocene and early Holocene. The Qingfengling segment is about 32km long, striking 15°～20°, dipping mainly southeast and partly west with dip angles more than 60° generally. This segment is characterized by right-lateral strike-slip motion with minor thrust component. It is composed of 4 sub-segments, which are the Xiaodianzi-Henhushan sub-segment, Kushan-Chezhuang, Maobu and Wangtaizi sub-segment, respectively from north to south. The length of these sub-segments is 6km, 8km, 14km and 4km, respectively. The former three sub-segments are aligned right-laterally. The Qingfengling segment offsets the upper late Pleistocene and the early Holocene strata; its latest active age is the early Holocene. The Mengyan segment exposes about 20km, striking 20° and dipping northwest with dip angle ～70°. It is also characterized by right-lateral strike-slip motion with thrust component, and its latest active age is the early Holocene.
The only historical earthquake that occurred on the north segment of the Anqiu-Juxian Fault between Juxian and Changyi is the 70BC Anqiu M7 earthquake. However, paleo-earthquake researches show that several strong earthquakes occurred along the Qingfengling segment and the Mengyan segment between the latest late Pleistocene to early Holocene. The time of the latest strong earthquake is ～3 500a BP, 2 084a BP (-70BC), ～10 000a BP, ～10 000a BP on the Changyi-Nanliu segment, Anqiu-Mengtan segment, Qingfengling segment, and Mengyan segment, respectively. Since the strong earthquake recurrence interval is still not known for each segment, the exact time for the next strong earthquake can't be predicted. However, according to the geometric features, latest active age, latest activity features, historic earthquake data and paleoearthquake documents of this active fault, the 4 segments do have seismotectonic conditions for generating M≥7 earthquake, and the potential earthquake risk does exist and may be rather high and imperative. Thus, the fault activities and the potential earthquake hazard should be considered during future earthquake hazard prevention and prediction.

The Qi-Chu earthquake,occurring in 179 BC(the first year of Hanwen Emperor,Han Dynasty),is a contentious historical earthquake event. Its basic parameters have not been determined. According to former researches on administrative division in Han Dynasty and analysis on historical earthquake records,the paper presents a discussion on the basic parameters of this earthquake event. A comprehensive method is developed to determine the epicenter,focusing on the border area between Qi and Chu States and the direct line of their capitals,and also considering other conditions from historical data. Moreover,based on results of seismic and geological investigation,the paper verifies the rationality of location of the epicenter from the seismotectonic point of view.Firstly,considering the frequent regime changes in Han Dynasty,the paper tries to recover the then administrative divisions and the boundary between Qi State and Chu State around the first year of Hanwen Emperor. Secondly,we analyzed carefully the range of the region indicated by historical earthquake records as "29 mountains collapsed and water burst during the Qi-Chu earthquake",and compared the spatial distribution and intensity of damage caused by other historical earthquakes to obtain important constraints for determining the location and magnitude of this event. It is suggested by textual analysis that the Qi-Chu earthquake ought to be the magnitude 7 earthquake occurring in the southern area of Pingyi County(N35.2?,E117.6?)on June 6,179 BC.Thirdly,geological structures and active faults around the epicenter area of Qi-Chu earthquake are studied by analyzing satellite image and geological data. As the earthquake was ruled out from the Tanlu Fault zone,it is considered that the Cangni active fault probably is the seismogenic structure of the Qi-Chu earthquake. Nearby the epicenter,the Cangni active fault with clear landforms and greatest displacement has controlled the development of the Baiyan Basin and offset the late Quaternary sediments.

A 240km-long co-seismic surface rupture was produced along the Beichuan-Yingxiu Fault during the 2008 Wenchuan earthquake.We made a detailed survey at representative sites along the surface rupture and analyzed the data based on the geometry between the benchmark and deformation.The co-seismic vertical slip,horizontal dip-slip shortening,strike slip and moving direction of the hanging-wall were calculated based on the survey data of these sites.Results show that the spatial distribution of the co-seismic deformation of the fault varies a lot along the fault.The maximal horizontal slip,as we got till now,is located in the Shenxigou site of Hongkou with a value of 4.98m,and the maximal strike slip is also located in the same site with a value of 4.5m.The maximal vertical displacement is located to the northeast of Shenxigou with a value of 5.7～6.7m.The average horizontal slip for the NE trending fault is 1～2m,and the average vertical slip is 3m.But horizontal and vertical slip for the NW-trending branch from Xiaoyudong to Caoba is only 0.5～1.5m.The data from Leigu town show that the gravity deformation resulting from the fault-related landslide was perhaps superimposed on the tectonic one.The dip angles of the fault at the surveyed sites calculated from the horizontal shortening and vertical displacement indicate that the Beichuan-Yingxiu Fault is a steep dipping reverse fault with some strike-slip.From the comparison between field results and geophysical inversion,we believe that the spatial distribution of co-seismic fault-slip is related to the barriers and rupture process along the fault plane.

Field investigations show that the M_S8.0 Wenchuan earthquake of 12^th May 2008 ruptured two NW-dipping imbricate reverse faults along the Longmenshan Fault zone at the eastern margin of the Tibetan Plateau.This earthquake generated a 240km long surface rupture along the Beichuan-Yingxiu Fault characterized by right-lateral oblique faulting and a 90km long surface rupture along the Guanxian-Jiangyou Fault characterized by dip-slip reverse faulting.Maximum vertical and horizontal dispacements of 6.2m and 4.9m,respectively,were observed along the Beichuan-Yingxiu Fault,whereas a maximum vertical displacement of 3.5m occurred along the Guanxian-jiangyou Fault.This co-seismic surface rupture pattern,involving multiple structures,is among the most complicated of recent great earthquakes.Its surface rupture length is the longest among the co-seismic surface rupture zones for reverse faulting events ever reported.Aftershocks recorded by local network clearly outline the hanging wall of the Beichuan-Yingxiu Fault and indicate that the fault dips about 47? to the west.Industry seismic lines,in addition to surface ruptures and aftershocks,allow us to build a 3D model for the rupture geometry that shows crustal shortening is the dominant process along the Longmen Shan to accommodate long-term deformation.Oblique thrusting accomplished by the earthquake indicates that the east-southeastward extrusion of Tibet Plateau accommodates,in part,the continuing penetration of the Indian plate into the Eurasian plate,and this extrusion is transformed at the eastern margin of the Tibetan Plateau into crustal thickening and shortening along the Longmenshan Fault zone that is responsible for the growth of high topography in the region.

It is the first time that several profiles of acoustic survey have been conducted across the Qianliyan Fault in the northern part of the South Yellow Sea. According to the difference of the late Quaternary fault activities revealed by the acoustic survey,the Qianliyan Fault may be divided by the Chaoliandao Fault into two segments. The southern segment is not active since the late Pleistocene,no offset in late Pleistocene strata has been observed on the acoustic profiles to the southeast of Rizhao. The northern segment is active in the late Pleistocene,normal faults are observed on the acoustic profiles west of Qianliyan island and offset the middle and upper part of the late Pleistocene layers,but no offset has been found in the latest Pleistocene and Holocene strata. In addition,it is found that the Qianliyan Fault offsets the late Pleistocene strata in the sea region 15km east of Shidao,Rongcheng County. In summary,the northern segment of the Qianliyan Fault is active in the latest Pleistocene in the sea region from the west of Qianliyan Island to the east of Shidao. Besides the Qianliyan Fault,other faults develop in the region to the southeast of the Qianliyan Island,which show obvious late Pleistocene active evidence. Therefore,the relative uplift status of the block where the Qianliyan Island lies on may be related to the late Pleistocene tectonic activities including that of the Qianliyan Fault. Both modern and history seismicity are relatively week in the region along the Qianliyan Fault. Since the establishment of the seismograph network in this region,no earthquake with magnitude equal or larger than 5and no small earthquake clusters have occurred along the Qianliyan Fault and in the surrounding area. The only historic earthquake is the 1932 M6(1/2) southern Yellow Sea earthquake which occurred in the sea region 28km southeast of the Qianliyan Fault. It is obviously that the seismicity is not concordant with the late Pleistocene active features of the Qianliyan Fault. Above all,the Qianliyan Fault is over 100km long from the Qianliyan Island to the offshore near Shidao and it is obviously active in the latest Pleistocene,the probability of the occurrence of a some M6.5 earthquake along the Qianliyan Fault should be considered in the practice of earthquake prediction and seismic hazard analysis.

The urban area in the eastern China region is mostly covered by the relatively thick loose Quaternary deposits,below which,in many cities,there exist many considerably large buried faults.In these thick-Quaternary-covering areas,does the date of the upper layers dislocated by the buried faults represent the latest faulting? In this paper,based on the integrated analysis on the data of geology,geophysics and earthquakes of cities in the east of China,including Xingtai and Tangshan,we discussed the relation between the upper offset point and the latest activity times of the buried faults in these areas covered by thick Quaternary.Our study shows,in the area with very thick recent deposits in East China,one should not determine the latest faulting of one fault fully according to the younger layers displaced by the fault.To a fault running through the area covered with thick young deposits,its latest active period should be determined comprehensively by the tectonic settings,the controlling of the fault to the young strata,the youngest layer displaced by the fault,the thickness of the young deposits,seismicity and modern tectonic stress field,etc.

The western Qinling Fault zone is one of the main left-lateral strike-slip active faults in northeastern Tibet. At site of Huangxianggou, the behavior of the fault zone shows typical strike-slip movement. Detailed analysis on the amounts of the offset of the late Quaternary landforms and geologic bodies along the fault shows that at Huangxianggou the maximum horizontal displacement since the late of late-Pleistocene is about 40～60m, and the minimum is 6～8m which is possibly the amount of one principal slip associated with one large earthquake event. And it is also inferred that the amounts of the displacement along the fault can be grouped, and between the groups there is a stable increment of 6～8m. The grouping and the increment of amounts of the offsets suggest that this fault segment displays an activity associated with characteristic earthquakes, and the 7 groups of the displacement values represent 7 characteristic events on the fault. Analysis on the microgeomorphology related to the faulting, such as periodic sag-ponding and deformed pluvial fans, also suggests the corresponding events. Thus it can be inferred, the activity of the fault zone has been dominated by several strong movements since late Late-Pleistocene.

The Yishu Fault zone is a part of the Tanlu Fault zone that passes through Shandong Province and the northern area of Jiangsu. It is composed of 5 nearly parallel faults among which the Anqiu-Juxian Fault is the most important and prominent active fault since late Pleistocene and is usually considered to be the seismogenic fault of the 70 BC M 7 Anqiu earthquake and the 1668 AD M 8¹/₂ Tancheng earthquake. By detailed research in recent years, e.g. the active fault mapping implemented during the “Eighth Five-Year Plan” period, we have gained thorough knowledge of the middle segment of the Anqiu-Juxian Fault to the south of Juxian, while the knowledge of the segment to the north of Juxian has been poor, even no active fault profiles have ever been found. Recent discoveries about the geometry and activity of the Anqiu-Zhuli segment of the Anqiu-Juxian Fault are introduced in this paper. The segment consists of the Nanliu sub-segment, the Shuangguan-Meicun sub-segment and the Zhuli sub-segment. All these sub-segments are distributed along the linear boundary line between hilly area and plain, or locate in the eastern slope of the NNE-trending hills. These fault segments are featured with right-lateral strike-slip movement combined with dip component, and their latest activity age is late Pleistocene to early Holocene. In conclusion, The Anqiu-Juxian Fault is the predominant active structure between Juxian and Changyi in the north of Shandong, and it should have some connections with the occurrence of the 70 BC M 7 Anqiu earthquake. Since the elapsed time is nearly 2100 years, the future earthquake risk in this area shall be emphasized.

The Kunlunshan M_s 8.1 earthquake of 2001 is a large earthquake produced by a large-scale intraplate strike slip faulting. Field observation shows that the surface rupture of this earthquake is about 426km long,and the maximum sinistral displacement is about 6m. As compared with the other similar intraplate large earthquakes,its rupture length is extraordinarily longer but its horizontal displacement is relatively small. The distribution of horizontal displacement along the surface ruptures is markedly controlled by fault structure. At the section where the horizontal displacement is small,the vertical displacement is also smaller,and no transformation of horizontal and vertical displacements is observed. This feature is also different from that of the other earthquakes. The relationship among rupture length,displacement and seismic magnitude follows a certain empirical equation,in which the ratio between the average displacement amount and rupture length is called "Ultimate linear strain",and is constantly within the range of 10^-5 for the rupture in the earth's crust. This feature can be used as criterion for testing the independency and integrality of the rupture segments. In this paper,we calculated the "ultimate linear strain" of the entire rupture zones and sub-segments of several large earthquakes,including the 1920 Haiyuan earthquake,1951 Bong Co earthquake,1932 Changma earthquake and 2001 Kunlunshan earthquake. The results show that average values of ultimate linear strain of the Haiyuan,Bong Co and Changma earthquakes are approximately close to the statistic value,but the values of ultimate linear strain of their sub-segments are significantly higher. In contrast,the value of ultimate linear strain for the entire surface rupture of the Kunlunshan earthquake is much lower than the statistic value,but the values of ultimate linear strain of its four sub-segments,except the west Taiyanghu segments,are close to the statistic value. Therefore,the Kunlunshan earthquake (M_s 8.1) should be produced by four relatively independent faulting events,instead of a uniform faulting. These characters provide geological evidence supporting the deduction that the Kunlunshan earthquake is successively triggered multiple earthquake events,rather than a single earthquake.

The 14 November,2001 M_S8.1 West Kunlun Pass Earthquake is the largest event associated with the longest surface rupture that has occurred in the Tibetan Plateau since 1951. We made 291 surficial left lateral slip measurements and 111 net vertical slip measurements along the main fault zone. The displacement on the main fault strand is dominated by left lateral strike slip of 2.7m in average,with vertical slip component of mostly less than 1m. The maximum left lateral slip is 6.4m,with as much as 5.1m of vertical slip component. Sinistral surficial slip is quite variable along the main strand of the rupture at distance scales ranging from a few tens of meters to a few hundreds of kilometers,with slip gradient ranging between 10^-1～10^-4. The slip variations over short length scales (tens of meters to a few kilometers) might be caused by variations in thickness of unconsolidated sediments,fault strike and slip of the previous earthquake,distributed non brittle deformation and secondary fractures,complexities in fault geometry,and perhaps by measurement error. Despite this short wavelength variability,there is fairly regular long wavelength (tens to hundreds of kilometers) behavior to the east of the Buka Daban Peak. One notable characteristic of slip distribution along the faults is that very large surficial slips (as large as 5～6 meters) were observed at 5～6 sites located at different surface rupture segments in asymmetry to their left lateral slip functions. Slip on each of these rupture segments diminishes away from the highest slip site to its terminations with different slip gradients. This asymmetric distribution of slips may indicate the propagation direction of the rupture along the faults. This long wavelength variation in slip might be influenced by fault geometry,while the segmentation of the surface rupture zone might play a key role. It should be pointed out that the surficial slip (at both short and long length scales) is only a near field slip measured in the field by using tape measure. Therefore,it should be considered as a minimum value,and may represent the real variations in the amount of brittle slip on visible fractures at the surface,but it potentially underestimates the actual slip produced by the earthquake and slip distribution over the whole surface rupture due to the difficulty in identifying distributed non brittle deformation. This calls for caution in discriminating between one or multiple discrete events and in estimating the size of past and future earthquakes by using displaced deposits in trenches or offset geomorphologic features along strike slip prehistoric fault ruptures.

A series of studies have been carried out to gain an insight into the Quaternary fault activities in Qingdao City and its surrounding area. The spatial distribution, geomorphic features and the features of the structural planes of the faults, as well as the relation between the faults and Quaternary strata have been studied in detail. Moreover, the ages of the relevant fault zone materials and unfaulted overlying Quaternary deposits have been dated by TL and/or ESR methods. This paper summarizes the achievements of these recent studies. It is concluded that the NE trending faults in Qingdao City and its surrounding area share some similarities in their dimension, orientation, age of faulted rocks, mode of motion, and age of the latest faulting. Their latest active period was in the mid late stage of middle Pleistocene. The faults have no longer been active since late Pleistocene. Moreover, in this area no fault of other strikes has been found to be active since late Pleistocene. According to historical earthquakes, the current activity of small earthquakes and Quaternary fault activities in this area, it is suggested that there's no condition for the occurrence of M_S≥6 earthquakes within this area, but it would not be surprising if an M_S≈5 earthquake should occurs in the future.