Spatial spreading characteristics and Quaternary activities of the northern extension of the Maoshan fracture zone based on multilevel soundings

This paper describes a three-dimensional and comprehensive method for completing the northern extension of the Maoshan fracture zone from deep to shallow. Gravity field data interpretation and geomagnetic survey were used to initially locate the rupture, followed by shallow seismic survey for precise positioning, and finally the upper rupture point was captured and its Quaternary activities were investigated according to the method of joint geologic profile exploration with small spaced drill holes across the rupture point. Research has found: ① The Maoshan fracture zone continues to extend northward into the urban area of Zhenjiang, and the northern extension of the Maoshan fracture zone cuts at least to the mid-crustal region. ② The shallow part of the northern extension of the Maoshan fracture zone shows normal faulting characteristics, with an inclination to the east and a strike to the north-east, an apparent dip of about 60°, and an apparent break distance of about 3～5 m. ③ The results of the joint geologic profile of the boreholes show that the bedrock surface on both sides of the fracture point has a small difference, and the overlying Quaternary strata do not have any large undulation and do not have any obvious signs of Quaternary activity, so it is comprehensively judged that the northern extension of the Maoshan fracture zone is a pre-Quaternary fracture. This study preliminarily suggests that the Maoshan fault may be geospatially linked to two significant seismic events in the history of the Jiangsu landmass. This finding provides a new perspective for further research on the seismogenic tectonic features and seismic activity patterns in the region, and may inspire future related studies.