Running across the Zhenjiang and Nanjing area, the Mufushan-Jiaoshan Fault is an important near EW-trending fault in Nanjing and Zhenjiang area. It extends from Mufu Mountain through Yanziji, Qixia Mountain, and Longtan to Jiao Mountain of Zhenjiang, with a total length of about 75km. The overall trend of the Mufushan-Jiaoshan Fault is nearly east-west, dipping to the north, the southern side of the fault is Ningzhen Mountain, the north side is the hollow land along the river and the Yangzhou low hilly plain. The fault is divided into the western and eastern sections by the NW-trending fault near Xiashu Town in Jurong, namely the Mufushan-Qixiashan section and the Zhenjiang section.
Due to the long-term activity of the Mufushan-Jiaoshan Fault, the northern part of the Mufu Mountain, Qixia Mountain and other complex anticlines suffered large-scale fault depression, forming the Yizheng Sag in the north and the Ningzhen Uplift in the south of the Yangtze River. There is a significant differential up-and-down movement of the fault block along the fault. In the Yizheng Sag, there are huge deposits of the Upper Cretaceous, as well as the thicker Paleogene and Neogene, indicating that the Mufushan-Jiaoshan Fault is a long-term active normal fault. On the Bouguer gravity anomaly map and aeromagnetic anomaly map, the expressions of the Mufushan-Jiaoshan Fault are very obvious, indicating that the fault has a large cutting depth and is a large-scale fault.
There have been many destructive earthquakes in the Nanjing-Zhenjiang area, most of which occurred at the intersection of NW-trending faults and near-EW-trending Mufushan-Jiaoshan Fault. In particular, the Yangzhou M6 earthquake in 1624 had a great impact, and the Mufushan-Jiaoshan Fault is possibly the seismogenic structure of this earthquake. With the planning and construction of a series of Yangtze River crossing passages across the fault in Nanjing and Zhenjiang, whether the Mufushan-Jiaoshan Fault is an active fault and whether it has a greater earthquake risk also becomes the focus of attention in this area.
It is of great significance to study the nature, characteristics and the latest active times of the Mufushan-Jiaoshan Fault for the prevention and reduction of earthquake disaster in Zhenjiang city and Nanjing city. Previous work mainly focused on the Nanjing section, and judged that its latest activity age is late Middle Pleistocene; there has not been a systematic study on the fault in the Zhenjiang section, and its latest activity age is still unclear. Based on the project of “Urban active fault exploration and seismic risk assessment in Zhenjiang City”, we carried out a series of shallow seismic explorations along the Mufushan-Jiaoshan Fault in the Zhenjiang section, and on this basis, representative points were selected to carry out drilling joint profiling to study the Quaternary activity characteristics of the Mufushan-Jiaoshan Fault. The results are of great significance for urban earthquake disaster reduction, urban planning and land use.
The results of shallow seismic exploration show that the Zhengjiang section of the Mufushan-Jiaoshan Fault is dominated by normal faulting, and the trend is NEE, dipping to the north, with a dip angle of about 50°~60° and a displacement of 3~7m on the bedrock surface. All breakpoints of Mufushan-Jiaoshan Fault show that only the bedrock surface was dislocated rather than the interior stratum of Quaternary.
On the Qiaotou village site, there is no sign of dislocation in the stratum above the Middle Pleistocene, the lower part of Middle Pleistocene Xiashu formation has been dislocated, the displacement of the bottom boundary of the Middle Pleistocene on both sides of the fault is 3.2m. According to the characteristics of dislocated stratum, the latest active age of Mufushan-Jiaoshan Fault is late Middle Pleistocene. There is no evidence of activity since late Pleistocene. The fault activity is dominated by normal faulting on the Jinshan site, and there is no evidence of faulting in the Holocene. Based on the comprehensive analysis, the latest active age of the Zhenjiang section of the Mufushan-Jiaoshan Fault is the late Middle Pleistocene, and there is no evidence of activity since the late Pleistocene. According to the dating results, the latest activity time is after(222±22)ka and before the late Pleistocene.
Affected by the erosion of the Yangtze River, the Quaternary in the study area is dominated by the Holocene, the Lower Pleistocene is absent, and the Middle Pleistocene is absent or thin. Therefore, the stratum displacement identified by drilling is mainly developed in the bedrock and the bottom of the Quaternary, resulting in the uncertainty of identifying the latest displacement of the fault, and it is difficult to identify the precise magnitude of the displacement. This is the shortcoming of this work.
Mufushan-Jiaoshan Fault is a major fault with strong seismic risk in the Nanjing-Zhenjiang area, especially at the intersection between the fault and the NW-trending fault, which has the seismogenic environment of destructive earthquake. It is necessary to attach great importance to the prevention of earthquake damage in the relevant area.

On 21 May 2021, a great earthquake of M6.4 struck Southwest China. This catastrophic event caused extensive casualties, a large number of houses collapsed, traffic disrupted, and large bridges damaged in Yunnan Province. The epicentre of the Yunnan Yangbi earthquake is located near the NW trending Weixi-Qiaohou-Weishan Fault. After this earthquake, the Institute of Geophysics of China Earthquake Administration calculated the focal mechanism solution using the global network data, the result shows that the earthquake is a strike-slip faulting event with normal component. The result of the focal mechanism solution is consistent with the strike of the Weixi-Qiaohou Fault and the distribution of aftershocks. Therefore, the strike of seismogenic structure of this earthquake was determined to be NW. Based on the strong motion observation data of 21 strong motion seismographs and 304 seismic intensity meters, the earthquake ground motion intensity map of the 21 May, 2021 Yangbi, Yunnan earthquake was obtained using the deviation correction method of magnitude shift, considering the geological tectonic background of the seismogenic fault, the focal mechanism solution and the precise location of aftershocks of this event. A commonly used proxy V_S30, the time-averaged shear wave velocity to 30m depth, was used to account for the local site effect of ground motion in the calculation of ground motion intensity map. We used V_S30-based amplification terms, which depends on the amplitude and frequency of ground motion, to account for site amplification. The V_S30 data of the macroscopic site classification was estimated using the correlation between topographic gradient and V_S30. Ground motion prediction equations(GMPEs) was used to supplement sparse data in its interpolation and estimation of ground motions. The selection of GMPEs for ground motion estimation were the attenuation relation of peak acceleration in western China in the fourth generation seismic zoning map. The observations of the ground motion for this event show that the maximum horizontal peak ground acceleration is 720.3cm/s² on the Yangbi station, 7.9km from the epicentre. Horizontal peak ground acceleration at 14 seismic stations is greater than 45cm/s². A large number of remote observation records with small values of ground motion also revealed the attenuation characteristics of ground motion for this earthquake. Using strong motion observation data available, we computed an event bias that effectively removed the inter-event uncertainty from the selected GMPE. The deviation correction method of magnitude shift minimizes the systematic deviation between the observed and estimated data produced by ground motion prediction equation, and reduces the uncertainties of the ground motion estimation in the area without stations. After the ground motion observations were corrected(de-amplified) to “rock”, we flagged any data that exceed three times the sigma of the GMPE at the observation point as abnormal data. The bias was then recalculated using different earthquake magnitudes and the flagging was repeated until systematic deviation between the observed and estimated data produced by GMPE was minimal. The results of the earthquake ground motion intensity map show that the highest seismic intensity caused by Yangbi earthquake is Ⅷ. Cangshanxi Town in Yangbi County and Taiping Town are located in the seismic intensity Ⅷ area. The area of seismic intensity Ⅵ and above covers an area of about 6 500km², spreading northwest in general. Many roads including Expressway G56 and national highway G215, pass through the estimated seismic intensity Ⅶ area, which may cause road damage and traffic disruption following this earthquake. On the other hand, the reliability of small amplitude observations recorded by far-field simple intensity meters need to be evaluated further. Finally, the seismogenic tectonic setting, the focal mechanism solution and the aftershock distribution of the earthquake also play a macro-control role in the distribution of the earthquake ground motion intensity. The results of this paper can provide theoretical basis and reference for earthquake emergency response decision-making and provide input for earthquake disaster emergency assessment.

Running across the east of Zhenjiang city, the Wufengshan-Xilaiqiao Fault and Dantu-Jianshan Fault are two important NW-trending faults in Zhenjiang area. They controlled the Cretaceous stratigraphic deposition and Mesozoic volcanic activities, and also have obvious control effects on modern geomorphology and Quaternary stratigraphic distribution.
There have been many destructive earthquakes in Zhenjiang area, most of which occurred at the intersection of NW-trending faults and near EW faults. It is of great significance to study the nature, characteristics and the latest active age of the NW-trending faults in Zhenjiang area for the prevention and reduction of earthquake disaster in Zhenjiang City, but the past targeted research work and the knowledge of activity of the faults are very limited. Based on the project of “Urban active fault exploration and seismic risk assessment in Zhenjiang City”, a series of shallow seismic exploration work has been carried out on the two major NW-trending faults in Zhenjiang area, and representative points were selected to carry out drilling joint profiling to study the Quaternary activity characteristics of these two faults. The results are of great significance for urban earthquake disaster reduction, urban planning and land use.
The results of shallow seismic exploration show that the Wufengshan-Xilaiqiao Fault is dominated by normal faulting, dipping to the northeast, with a dip angle of about 60° and a displacement of 5~9m on the bedrock surface. The Dantu-Jianshan Fault is dominated by normal faulting, dipping to the southwest, with a dip angle of about 50°~55° and a displacement of 2~7m on the bedrock surface. All breakpoints of Wufengshan-Xilaiqiao Fault and Dantu-Jianshan Fault reveal that only the bedrock surface was dislocated, not the interior stratum of Quaternary.
On the Dalu site, there is no sign of dislocation in the stratum above the Middle Pleistocene, and the bottom boundary of the Middle Pleistocene has been dislocated, with a displacement of 2m. The dislocation of the bottom boundary of the lower Pleistocene is 3.2m on both sides of the fault, and the maximum displacement of the bedrock surface is 9.1m. The characteristics of the fault surface developed in the drill cores indicate that the latest activity of the fault is of sinistral normal faulting. According to the characteristics of dislocated stratum, the latest active age of Wufengshan-Xilaiqiao Fault is early Middle Pleistocene. On the Fangxian site, there is no sign of fault in the stratum above the Middle Pleistocene, and the bottom of the Middle Pleistocene may be affected by the fault. The displacement of the bottom boundary of Baishan Formation on both sides of the fault is 2m, and the maximum displacement of the bedrock surface is 6.7m. Due to the insufficient evidence of dislocation of Baishan Formation, the latest active age of Dantu-Jianshan Fault is estimated to be between early Pleistocene and early Middle Pleistocene.
The NW-trending Su-Xi-Chang Fault is an important regional fault in the Yangtze River Delta region. Its latest active age is the early Middle Pleistocene, and the displacement in the Quaternary is about 3m. The Wufengshan-Xilaiqiao Fault and the Dantu-Jianshan Fault can be regarded as spatial extension of the Su-Xi-Chang Fault to the northwest, and their activities are also consistent. This study shows that the two NW-trending faults in the Zhenjiang area have significant activity since the Quaternary, and are the main faults with relatively high earthquake risk in this area. Therefore, the intersection of these two faults with EW-trending faults and NE-trending faults should be the focus of attention for earthquake damage prevention in the Zhenjiang area.
The bedrock depth in the Zhenjiang area is relatively shallow, and the stratification difference within the cover layer is small, resulting in an unsatisfactory effect by the geophysical exploration methods. The Lower Pleistocene of the Quaternary system is basically missing, and the boundaries of the Middle and Upper Pleistocene are difficult to distinguish. Developed mainly in the bedrock and the bottom of the Quaternary, the stratum displacement is difficult to judge whether it was caused by sedimentary difference or fault activity. Therefore, the quantitative study of fault activity in this paper is still insufficient.

In southern mountainous area of Lanzhou city, there are 4 large-scale regional fault zones, which have been active since Late Pleistocene. They include the active Northern marginal fault zone of Maxianshan Mountains(F₁), the active Southern marginal fault zone of Maxianshan Mountains(F₂), the active Southern marginal fault zone of Xinglongshan Mountains(F₃)and the active Northern marginal fault zone of Xinglongshan Mountains(F₄). They are assigned to the Maxianshan Xinglongshan Mountains active fault system. Among the 4 fault zones, the Northern marginal fault zone of Maxianshan Mountains has the strongest activity. The fault initiates from Neiguan~ying faulted basin in the east, passing through Miaowan, Yangzhai, Yinshan, and after converging with the Southern marginal fault zone of Xinglongshan Mountains at Moyunguan it runs along Tianjiagou, Hutan, Guanshan, Xianshuigou, and terminates at Bapanxia Gorge of the Yellow River in the west. The fault is generally striking N60°W, having a total length of about 115 5km.The nearest distance from Lanzhou city to the fault is only about 4km, so that the recent activity and the seismic potential of the fault zone play an important role in the seismic design and the safety measures for the Lanzhou City. The geometric feature of the Northern marginal fault zone of Maxianshan Mountains is relatively simple, and it can be divided into 4 subsidiary segments according to the branching, bending, and discontinuous step over of the fault, as well as the difference of recent activity. These subsidiary fault segments are called the Neiguanying(F_1-1), Maxianshan(F_1-2), Qidaoliang(F_1-3)and Wusushan(F_1-4)segments, respectively. The results of geological mapping of the active faults on the scale of 1/50000 indicate that the Northern marginal fault zone of Maxianshan Mountains is a long standing, south dipping thrust fault, which has become a left lateral strike slip fault with dip slip component since Middle Pleistocene. Apart from this segment, the other segments are Holocene active fault zones. Among them, the Wusushan segment is also dominated by thrust movement but is dipping to the north. It is only the Maxianshan segment that displays obvious left lateral strike slip movement with normal component, resulting in a series of offset landforms, such as offset ridge, hills, valley and terrace. The largest offset may reach up to several hundred meters, while the smallest only about several meters. The amounts of horizontal displacements along the fault are concentrated mainly at 10～ 30m, 95～ 105m and 140～ 160m, reflecting that the faults are dominated mainly by stick-slip movement. At the same time, a series of fault scarps are developed along the fault zone, and the height of the scarp at the first level terrace is about 1～1.5m. The standard offset of the second level terrace is observed at Quanshenmiao gully as about 49m, and that of the first level terrace is observed at the eastern branch of Shitougou gully as about 25m. According to the ages of the terraces, it is estimated that the average horizontal slip rate of the fault since Late Pleistocene is about 3.73mm/a.

We have investigated the ground rupture zone caused by the M 7.3 earthquake of Jiji,Taiwan in 1999 after occurrence of the event.The results indicate that the seismogenic structure of this event is associated with the Chelongpu fault which is an active fault with dominant reverse-dip-slip and a sinistral strike-slip component.The total length of the ground rupture zone is about 80km.The vertical displacement on the ground along the rupture zone is mostly 1.5～3.5m and the hori-zontal displacement 3.0m.It is suggested that decollement between the basement and the cover of the Taiwan foothills has played an important role to the seismogenic fault.

The effect of earth tide on water level in seven wells of the Ningxia well network is systematically studied.Tide parameters of main tide wave effecting on the water level in seven wells are given after harmonic analysis.From the tide parameters some physico-mechanical parameters of aquifer in seven wells are obtained.The ability of well-aquifer system to reflect the crustal stress and strain and using the effect of tide on well water level to study earthquake prediction are discussed.

The Wuxijiang reservoir area has been considered to be geologically and seismologi-tally stable,but frequent microearthquakes were observed in the middle part of the reservoir area after impounding.On the basis of geologic field-work and seismic data,we have described and analysed the seismogeological background of this area,the geological environment of the reservoir,the geological conditions of the epicentral area and the features of the reservoir-induced seismicity.The conditions which induced earthquakes during impounding of the reservoir were compared with those in the Xinfengjiang reservoir.And the trending reservoir-induced seismicity was appraised by using seismogeological anlogic method.During the flood season in 1983,the water level of the reservoir was first over the normal one and the seimicity did not exceed our appraisals.

This paper illustrated experimental study on the influence of ultrasonic vibration upon microstructure and emanation process of saturated rocks. It was found by scanning electron microscope observation that specimens under ultrasonic vibration, whether on the ultrasonically irradiated sides or on the non-ultrasonically irradiated sides, all show a large number of fissured traces, i. e. microcracks. So it can be inferred that under the ultrasonic vibration the development of microcracks provided an outward-diffusing "passage" for the sealed radon to take part in the emanation process.The results of the ultrasonically vibrating experiments indicate that the ultrasonic vibration made the amount of radon separating-out of rock obviously increased, and the amount would be as much as it was before vibration when the vibration stopped. The increment of separating radon depends on the times of ultrasonic vibration. These results obtained are consistent with the scanning electron microscope observation showing that the primary rock structures were certainly destroyed by ultrasonic vibration. During each vibration, new cracks appeared and the separating amount of radon was also increased correspondingly. For the first vibration, the amount of radon increased by a factor of 4.5 under the temperature-control condition (it will be 4.3 under temperature-uncontroi event). For the fourth vibration, it increased by a factor of 9.1 under temperature-control condition (it will be 11.2 under temperature-uncontroi condition). Among the increment of radon, absorbed radon accounts for 64-76 percent, sealed radon accounts for 24-36 percent. The contribution of the ultrasonic thermal effect to the separating radon accounts merely for 10-30 percent.The experiment results show that the rock emanation process was clearly related to the ultrasonic vibration. Its mechanism is rather complicated. It is reasonably considered that prior to the failure of rock the expensive microcracking produced accoustic emission, i. e. ultrasonic vibration, leading to a constant emanation from rocks in a significant amount which may be probably regarded as a precursory information of radon.