An earthquake of M6½ occurred near Fushan County in the 9th year of Dading Period of the Jin Dynasty(in 1209), which caused a large number of casualties and property losses. Many experts and scholars speculated that the Fushan Fault might be its seismogenic structure, but no in-depth research has been conducted, which greatly hinders the development of earthquake prevention and disaster reduction in the region. The Fushan Fault is located on the east side of the Linfen fault basin in the Shanxi fault depression zone. It is a boundary fault between the Linfen fault basin and the uplift area of the Taihangshan block. Predecessors have done little research on the Fushan Fault. This paper carries out a quantitative study on the late Quaternary activity and displacement rate of the Fushan Fault. First, we carried out remote sensing interpretation, fault surface excavation, collection and testing of fault geomorphological samples in the area of Qianjiao village of Fushan Fault. It is determined that the Fushan Fault starts from Hanzhuang village, Beihan Town in the north, extends to the southwest through Yushipo village, Fenghuangling village, Baozishang village, Zhaojiapo village in Beiwang town, Nanwang village, Zhuge village, Qianjiao village, Guojiapo village, Qiaojiapo village in Tiantan town, Dongguopo village and Zhaishang village in Zhangzhuang town, Lijiatu village and Zhujiashan village in Xiangshuihe town, and terminates in Chejiazhuang village in Xiangshuihe town, with a total length of 24km. The formation age of geomorphological bodies was obtained. It is determined that the latest stratum dislocation event of the fault is later than 7ka, and the fault is a Holocene active fault and has the ability to generate earthquakes of magnitude 7 and above. A total of two phases of stratum dislocation events have occurred on the Fushan Fault since 17ka BP(Late Quaternary): The first-phase event E1 occurred between 17ka and 7ka BP, producing a displacement of 2.04m, the average displacement rate of the Fushan Fault is 0.20mm/a; the second-phase event E2 occurred since 7ka BP, producing a displacement of 3.93m, and the average displacement rate of the Fushan Fault is 0.56mm/a. The displacement rate of the fault has been increasing since the Late Pleistocene. The future seismic hazard of this fault is worthy of attention. This paper also uses land-based LiDAR scanning to obtain the topographic data of the fault plane on the Qiaojiapo village bedrock section of the Fushan Fault(4.5km away from the Qianjiao village section). The isotropic variogram method was used to calculate the fractal dimensions of the fault surface morphology, and the morphological weathering zone was divided, and two phases of ancient seismic events of the Fushan Fault since the Late Quaternary were determined, which are, from old to new, the first-phase event E1 which caused a co-seismic displacement of 3.18m, and the second-phase event E2 which caused a co-seismic displacement of 2.51m. Studies have shown that the bedrock fault plane fractal method is an effective method for studying ancient seismic events in the bedrock area, and its ancient seismic period division is consistent with that of the sedimentary coverage area. Finally, this paper discusses the seismogenic structure of the 1209 Fushan earthquake with magnitude of 6½, and believes that the seismogenic structure of the Fushan earthquake is most likely to be the Fushan Fault. However, due to the lack of a lower age limit and that the only upper limit age is far away from the historical earthquake time, it is necessary to conduct a more detailed investigation and research on the fault to determine whether there can be a revelation of ancient earthquake events with a younger age and comparable magnitude.
This study has greatly improved Fushan County’s risk prevention and control, and territorial planning capabilities.

The quantitative analysis of morphologic characteristics of bedrock fault surface is a useful approach to study faulting history and identify paleo-earthquake. It is an effective complement to trenching technique, specially to identifying paleo-earthquakes in a bedrock area where the trenching technique cannot be applied. This paper focuses on the Luoyunshan piedmont fault, which is an active normal fault extending along the eastern boundary of the Shanxi Graben, China. There are a lot of fault scarps along the fault zone, which supply plentiful samples to be selected to our research, that is, to study faulting history and identify paleo-earthquakes in bedrock area by the quantitative analysis of morphologic characteristics of fault surfaces. In this paper, we calculate the 2D fractal dimension of two bedrock fault surfaces on the Luoyunshan piedmont fault in the Shanxi Graben, China using the isotropic empirical variance function, which is a popular method in fractal geometry. Results indicate that the fractal dimension varies systematically with height above the base of the fault surface exposures, indicating segmentation of the fault surface morphology. The 2D fractal dimension on a fault surface shows a ‘stair-like’ vertical segmentation, which is consistent with the weathering band and suggests that those fault surfaces are outcropped due to periodic faulting earthquakes. However, compared to the results of gneiss obtained by the former researchers, the characteristic fractal value of limestone shows an opposite evolution trend. 1)The paleo-earthquake study of the bedrock fault surface can be used as a supplementary method to study the activity history of faults in specific geomorphological regions. It can be used to fill the gaps in the exploration of the paleo-earthquake method in the bedrock area, and then broaden the study of active faults in space and scope. The quantitative analysis of bedrock fault surface morphology is an effective method to study faulting history and identify paleo-earthquake. The quantitative feature analysis method of the bedrock fault surface is a cost-effective method for the study of paleo-earthquakes in the bedrock fault surface. The number of weathered bands and band height can be identified by the segment number and segment height of the characteristic fractal dimension, and then the paleoearthquake events and the co-seismic displacement can be determined; 2)The exposure of the fault surface of the Luoyunshan bedrock is affected and controlled by both fault activity and erosion. A strong fault activity(ruptured earthquake)forms a segment of fault surface which is equivalent to the vertical co-seismic displacement of the earthquake. After the segment is cropped out, it suffers from the same effect of weathering and erosion, and thus this segment has approximately the same fractal dimension. Multiple severe fault activities(ruptured earthquake)form multiple fault surface topography. The long-term erosion under weak hydrodynamic conditions at the base of the fault cliff between two adjacent fault activities(intermittent period)will form a gradual slow-connect region where the fractal dimension gradually changes with the height of the fault surface. Based on the segmentation of quantitative morphology of the two fault surfaces on the Luoyunshan piedmont fault, we identified four earthquake events. Two sets of co-seismic displacement of about 3m and 1m on the fault are obtained; 3)The relationship between the fault surface morphology parameters and the time is described as follows:The fractal dimension of the limestone area decreases with the increase of the exposure time, which reflects the gradual smoothing characteristics after exposed. The phenomenon is opposite to the evolution of the geological features of gneiss faults acquired by the predecessors on the Huoshan piedmont fault; 4)Lithology plays an important role in morphology evolution of fault surface and the two opposite evolution trends of the characteristic fractal value on limestone and gneiss show that the weathering mechanism of limestone is different from that of the gneiss.

A magnitude 7(3/4) earthquake happened in Linfen, Shanxi, on May 18, 1965(the 34th year of Qing Emperor Kangxi). In the Catalogue of Chinese Historical Strong Earthquakes, the epicenter of this earthquake is located at the northwest of Zhangli Village of Xiangfen County and Dongkang Village of Yaodu District, Linfen City(36.0°N, 111.5°E), and the epicentral intensity is Ⅹ. It was inferred by previous studies that Guojiazhuang Fault is the seismogenic structure of the earthquake. In this paper, in cooperation with the Archives of Linfen City and Earthquake Administration of Linfen, the author looked up in details the first-hand materials of the earthquake damage to the ancient town of Linfen and its surrounding areas, and based on this, drew the isoseismals of the earthquake. Through discussions with relevant experts, we consider that it would be more appropriate that the location of the macroscopic epicenter of this earthquake is in Donguan area of the ancient town of Linfen, the epicentral intensity is Ⅺ, and the major axis of the isoseismals is in NWW. Later, in the implementation of "Linfen city active fault detection and seismic risk evaluation", we found two earthquake fault outcrops near the macroscopic epicentral area of the 1695 Linfen earthquake. Shallow seismic exploration lines and drill rows perpendicular to the strike of the fault outcrops were arranged to implement the exploration. The results demonstrate that the right-lateral stepover composed of Guojiazhuang Fault and Liucun Fault, together with the Luoyunshan Fault(Longci segment), were involved in the 1695 Linfen earthquake, the intersection of the faults is the microscopic epicenter of the earthquake, and the above-mentioned three faults are the seismogenic structure of the earthquake. In addition, the seismic geological remains in this region(landslides, earthquake ground cracks, sand emitting channels, etc.) are mainly distributed on the hanging wall of the Guojiazhuang Fault, this proves from another perspective that the earthquake remains is the product of activity of Guojiazhuang Fault in 1695.

Based on the 1︰50000 geological and geomorphologic mapping of active fault, the structural geomorphic features and activity of Hancheng Fault are investigated in detail. In the study, we divide the fault into three sections from north to south: the section between Xiweikou and Panhe River, the section between Panhe River and Xingjiabao and the section between Xingjiabao and Yijing, the three sections show different characters of tectonic landform. The section between Xiweikou and Panhe River is a kind of typical basin-mountain landform, where diluvial fans spread widely. In the north of Yumenkou, the fault deforms the diluvial fans, forming scarps, along which the fault extends. In the south of Yumenkou, the fault extends along the rear edge of the diluvial fans. In the section between Panhe River and Xingjiabao the fault extends along the front of the loess mesa. In the section between Xingjiabao and Yijing the fault forms scarp in the loess and extends as an arc shaped zone, and the landform is formed by the accumulative deformation of the fault. The activity of the fault becomes weak gradually from northeast to southwest. The fault activity of the section between Xiweikou and Panhe River is the strongest, and the latest age of activity is Holocene. The slip rate since the mid-Holocene is bigger than 0.8mm/a at Yumenkou. The fault activity of the section between Panhe River and Xingjiabao is weaker than the north part, the fault's latest active age is identified as the later period of Late Pleistocene and the activity becomes weak gradually from northeast to southwest. At the estuary of the Jushui River the slip rate of the fault is about 0.49mm/a since late Late Pleistocene. The fault activity of the section between Xingjiabao and Yijing is the weakest. There is no evidence of paleosol S1 deformed in fault profiles, and only some phenomena of fracture and sand liquefaction in the earlier Late Pleistocene loess. The activity of the fault is in line with the fault landform feature. At macro level, the relationship between the uplifted side and the thrown side of the fault switches gradually from the Ordos uplifting region and the rifted basin to the interior blocks of the rifted basin, which maybe is the regional reason why the activity of the Hancheng Fault becomes weak from the northeast to the southwest.

On the basis of consulting historical records about the positions of Hukou waterfall at different times,we conduct a field geological survey along the Yellow River and ultimately determine the specific locations of the Hukou waterfall in the different periods.Based on this,the retrogressive erosion rates in different periods are calculated as about 1.66m/year during the Xia Dynasty to the Tang Dynasty period,about 1.01m/year in the Tang Dynasty to the Yuan Dynasty,about 0.97m/year in the Yuan Dynasty to the Ming Dynasty,about 1.28m/year in the Ming Dynasty to the Republican period,and 0.6m/year from the Republican period to the present.Considering the complex geological conditions along the Yellow River,the average retrogressive erosion rate of Hukou waterfall on the Yellow River is obtained to be 1.51m/year since the historical records (early Qin Dynasty to the present).Lithology surrounding the Hukou waterfall includes mainly the Triassic gray,gray-green thick-layered mid-grained feldspar sandstone and dark purple,yellow-green mudstone,this hardness and softness combination feature is the unique geological condition of the Yellow River.After abrasing the softer shale driven by water cyclotron at this position,water washes off the debris,causing the overlying feldspar sandstone suspended for a long period.Feldspar greywacke block collapses under accumulative water erosion in long years,and then retrogressive erosion occurs in Hukou waterfall.In the process of 1 ︰ 50 000 active fault mapping of Hancheng Fault,we excavated a trench at Shaojialing,and the trench profile shows that:in the early and middle period of late Pleistocene,there are obvious surface ruptures produced by the fault.Cumulative offset near the trench is more than 20 meters in height difference.Yellow River terraces survey at Yumenkou also confirms that a fault slip of about 20 meters occurred during the early and middle period of the late Pleistocene.Assuming the retrogressive erosion rate is constant,the author thinks the Hancheng Fault was activated at early and middle age of the Late Pleistocene,forming a 20~30m high scarp (knick point),and today's position of Hukou waterfall may be the position of this knick point after the retrogressive erosion of about 40 to 50ka.

Knowledge about regional stress field is a significant basis for better understanding the tectonic activity of faults. This study reports the magnetic fabric investigation performed at sites along the northeastern section of the Hancheng Fault zone after we finished the 1 : 50,000 field mapping of active fualts in this region. Samples were collected at selected sites at Shaojialing, Zhubeizhuang and Shangyukou. Our results show that magnetic fabric, derived from anisotropy of magnetic susceptibility, reveals oblate susceptibility ellipsoids that are slightly modified compared to the inferred original depositional fabric. A dominant distribution of K_max along the NW-SE direction indicates that the northeastern section of the Hancheng Fault zone is subjected to horizontal extensional stress along this direction. A weakly NW-SE directional distribution of K_min is interpreted to reflect the action of horizontal compressive stress. This NW-SE compressive stress at the Shaojialing site appears to be somewhat stronger than that at the Shangyukou and Zhubeizhuang sites. Nevertheless, magnetic fabric properties are located in the oblate area in the P_J-T and Flinn diagrams. This may reflect inhomogeneous distributions of tectonic stresses along the Hancheng Fault zone, indicating that even within a strongly extensional stress-field, prolate magnetic fabric may be difficult to develop. This work may provide basic evidence for further studies on the activity of the Hancheng Fault zone.

Through studies on the historical data of the two historical strong earthquakes in Linfen region,the characteristics of earthquake disaster distribution are summarized,and the actual isoseismal are drawn.By comparison of theoretic isoseismal maps obtained from different attenuation relationship models,the most suitable model and its modification part for different magnitudes in this region are determined.Using the spatial analysis function of GIS techniques,the more visual system of earthquake disaster prediction and evaluation is realized.In addition,the loss situation of earthquake damage in Linfen region under the present economic society is predicted based on the reconstruction data of the two historical strong earthquakes.This work provides reliable basis for practical work of earthquake prevention and disaster reduction in the future.

Elastic anisotropy is an important geophysical property of crustal rocks.Due to the compositional and textural complexity of crustal rocks,the potential factors influencing its elastic anisotropy are various.Microcracks preferred orientation plays an important role on elastic anisotropy in superficial crust.While at deeper crust,lattice preferred orientation(LPO)and shape preferred orientation(SPO)take over and control the elastic anisotropy.Statistic of previous experimental work shows that the content of mica and amphibole is somehow related to the anisotropy of intermediate-acid and basic rocks,respectively.Otherwise,the oriented melt can largely enhance rock's anisotropy,which is a preferable explanation to the observed high anisotropy within the middle to lower crust under Tibetan plateau.

It is commonly agreed that seismic anisotropy,most likely caused by aligned minerals,is a very important indicator of intracrustal deformation.Ultrasonic velocity measurements on the schists,gneisses,migmatites,amphibolites and mylonites from Higher Himalayan Crystallines(HHC) and Honghe strike-slip fault zone in the southwestern China show that the average anisotropic magnitude of them is about 5%,which is much less than that observed by a series of measurements of surface-wave dispersion inversions and waveform inversions of P to S conversions in these regions.Modeled results indicate that seismic anisotropy can be enhanced by alignment of melt.For instance,extra anisotropy of 2%～10% for P-wave velocity and of 2.2%～40% for S-wave velocity would be induced by melt pocket preferred orientation when aspect ratio of melt pockets and melt fraction range from 0.1 to 0.5 and from 5% to 10% respectively.Obviously,the contribution of aligned melt to the anisotropy is likely comparable to or larger than that induced by lattice preferred orientation of major minerals.Geophysical investigations demonstrate that Tibetan and Sichuan-Yunnan crust is characterized by high geothermal gradients and abnormal thickness.Low degree partial melting accounting for low average crustal velocity and low velocity zones is present in the crust pervasively.Hence,we attribute the extremely high anisotropy observed within Tibetan and Sichuan-Yunnan crust to aligned melt pocket induced by localized deformation.It implies that the anisotropy zones within Tibetan and Sichuan-Yunnan crust is one of candidates to cause the upper part of crust(crustal block)to decouple to the other part of lithosphere.

During the post-disaster recovery in Maoxian country,we found that lacustrine sediments are exposed intermittently ～30km north of the present Diexi barrier lake(Xiaohaizi)along the Minjiang River and its tributaries.According to the study on lacustrine sediments around Qiangyang village,we obtained the evidence of activities of the Minjiang Fault in the Holocene.It is concluded that the tectonic deformation of paleo-lacustrine sediments in Qiangyang possibly reflects multi-time ancient seismic activity of Minjiang Fault zone.It is more accepted that the 1st seismic activity resulted in the formation of dammed paleolake in Qiangyang,and accumulation of the 1st set of lacustrine facies deposits;the 2nd seismic activity led to deformation of the lacustrine facies stratum;the 3rd seismic activity caused the deformation of the 1st and 2nd set of lacustrine facies strata;and the 4th seismic activity ruptured the youngest deposit overlying the lacustrine facies stratum.Total Station Instrument measurements indicate that the vertical displacement of the last ancient seismic activity is about 2.6～3.6m.

Advanced Prediction is one of the most effective methods to assure the safety in tunneling.The histories and case experiences show that the TSP203(Tunnel Seismic Prediction203)combined with other techniques can meet the requirements of advanced prediction in tunneling and the prediction implementation costs.This paper firstly introduces the principle of the TSP203,and then compares the prediction result with the excavated conditions of the Dayaoshan railway tunnel.As an example,we introduce the prediction method,explain how to use TSP203 in complicated geological conditions.and analyze the main reason about predication errors according to several years'operation experiences in site as well as seismic theory.The method of TSP203 is a kind of mature technology,it is suitable for planar faults with large intersection angle to the axis of tunnel,but not fit for small intersection angle.However because the karsts terrain has the character of complexity,changeability and uncertainty,the predicting accuracy is a little lower in this kind of place.In addition,groundwater prediction is a technological problem in construction of tunnel that has not been solved both at home and abroad.TSP prediction accuracy is also related with operator's practice levels.Finally,some suggestions are given about how to improve data acquisition accuracy and reliability of explaining the reflected objects.Some important items in predication using TSP203 are summarized.