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.

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.