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.

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.

Hydrogen is recognized as one of the most useful gases to detect fault activities. Based on long-term high-accuracy soil hydrogen observation data in fault zones, the paper evaluates the reliability of data according to the distribution of measurements. Through the evaluation of earthquake-reflecting ability of hydrogen concentration, we consider that there is a certain corresponding relationship between hydrogen concentration and seismic activity and we present the judging index for this anomaly. Hydrogen concentration characteristics with the earthquakes within the range of 350km around the station were analyzed, especially the two earthquakes, which occurred on October 24, 2010 and March 8, 2011 in Taikang, Henan Province, with magnitude M_S4.6 and M_S4.1 respectively. The observation station is located at Xiaxian in Shanxi Province, 300km away from the epicenter. In a week before the two earthquakes, high-accuracy soil hydrogen concentration measurements showed similar anomaly variation, which was increasing abruptly, then decreasing, and after the earthquakes it returned to background level. Overall, the changing scope was more than 20 times of the background value. We concluded that the anomaly was affected by tectonic setting of the earthquakes. The similar hydrogen distribution pattern recorded at the same station is attributed to the same tectonic position and focal mechanism solution. The hydrogen could be an effective tool for short-term and imminent earthquake prediction, which provides reference for short-term and imminent earthquake prediction in areas with high earthquake risk.

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.

Nowadays,as the information is highly advanced,the visualization in scientific computing(VISC)is developing rapidly and the three-dimensional Geographic Information System(3D GIS)also becomes one of the hot topics of GIS research. The 3D geological modeling,which is closely related to the VISC and 3D GIS,has drawn more and more attention of domestic and foreign experts and scholars; it has been highly desirable to resolve the complex geological problems in a 3D space.In view of the above research topic and combining the project of Taiyuan Active fault Survey and Seismic Risk Assessment,the 3D space database of shallow seismic survey is established based on the detailed analysis and sorting of a large amount of exploration data in this paper. The algorithm of the 3D geological model is also designed by use of ArcGIS's powerful 3D displaying function,and then the program is developed using the AOVAB.Based on the 3D geological modeling technology which combines the VISC and 3D GIS,the 3D geological visualization model is developed for the Quaternary stratigraphic sections and fault profiles within the Taiyuan active fault survey area,and the 3D buffer model is also tried to be established under the ArcGIS environment in view of the 3D fault model. The statistical analysis of active fault data and seismic data is carried out,and the relationship between active faults and spatial distribution of earthquakes is studied.This study accomplished the 3D geological model for the Quaternary stratigraphic sections,fault profiles and 3D space buffer within the Taiyuan active fault survey area,and carried out the analysis of the relationship between faults and spatial distribution of historic earthquakes based on this model. These results have significance for theoretical and scientific studies,and can provide reference to active faults survey in other cities in the future.

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.

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.

Xizhang trench is located at 10 kilometers northwest of the Taiyuan City,Shanxi Province,and it was excavated at the front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng Fault zone.The dimensions of the trench are 108m in length,8m in width,and 10m in depth.There are 18 strata revealed in the trench.The upper stratum is sandy loam;the upper stratum of the downthrown block of the fault is gravel,the lower stratum is interbed of brown loam and sandy loam.The strata on the upthrown block of the fault are sandy loam containing gravel.The trench shows 3 fault planes,and the upper fault point on the fault plane is 1.5m deep from the ground surface,the newest dislocated stratum is(3.74±0.06)ka BP.The trench reveals a lot of deformation traces,such as fault plane,dislocated strata,colluvial wedge and the dipping of formation.The relation between the strata and the faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng Fault zone since Early Holocene,they are about(3.74±0.06)～(3.06±0.26)ka BP,(8.35±0.09)～(3.74±0.06)ka BP,and(10.66±0.85)～(8.35±0.09)ka BP,respectively.The average interval of the events is2.6～3.6ka.The minimum coseismic vertical displacements of the 3 events are 3.0m,2.5m,and 3.2m,respectively.The significance of Xizhang trench is that the Jiaocheng Fault used to be active thousands years ago,though there wasn't M≥7 earthquake recorded in historical words.The evidence of newest activities of the Jiaocheng Fault zone during Holocene is important for earthquake safety assessment of Taiyuan City in the future.