基于多层次探测研究茅山断裂带北延段空间展布特征及第四纪活动性

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

本文介绍了从深至浅完成对茅山断裂北延立体式综合探测方法。使用重力场资料解译和大地电磁勘探初步定位断裂,随后通过浅层地震勘探进行精确定位,最后根据跨断点的小间距钻孔联合地质剖面探测法捕获了上断点并研判其第四纪活动性。研究发现:①茅山断裂带继续向北延伸入镇江市区,茅山断裂带北延段切割深度至少延伸至中地壳区域;②茅山断裂带北延段浅部区域表现出正断性质,倾向东,走向北东,视倾角约为60°,视断距约为3~5 m;③钻孔联合地质剖面探测结果显示,断点两侧基岩面落差较小,上覆第四纪地层未发现较大的起伏,未见第四纪有明显活动迹象,综合判断茅山断裂带北延段为前第四纪断裂。本项研究初步表明,茅山断裂在地理空间上可能与江苏陆域历史上两次显著的地震事件存在联系。这一发现为进一步研究该地区的发震构造特征和地震活动规律提供了新的视角,并可能对今后的相关研究有所启发。

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:①The 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.②The 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.③The 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.