江苏沿海地区小波多尺度重力场特征与构造活动性分析

Characteristics of Wavelet Multi-Scale Gravity Field and Analysisof Tectonic Activity in Jiangsu Coastal Area

利用小波多尺度分析方法对江苏沿海地区重力场进行波场分离,得到多阶小波细节信息。通过对不同阶次小波细节进行分析研究,获得不同深度凹陷及隆起的空间展布情况,并推断研究区内7条深大断裂的走向及倾向,发现以兴化-大丰一带为界,北部断裂大部分走向为NNE向,倾向NW,且坡度较陡;南部断裂大部分走向NEE向,倾向SE,且坡度较缓,这种南北差异可能是下扬子对冲构造格局的反映。结合地震资料分析认为,地震分布与NE向和NEE向、NW向、近EW向(活动)断裂关系密切,东海-赣榆西北部和大丰港沿海一带断裂的活动性较强,应力场相对不稳定,发生地震的风险较高。

We use wavelet multi-scale analysis method to separate the gravity field in Jiangsu coastal area,and obtain the details of multi-order gravity wavelet.We obtain the spatial distribution of depressions and uplifts in different depths by analyzing the details of different order wavelets,and then provide constraints on the orientation and tendency of seven deep faults in the study area.We find that the orientation and tendency of most of the faults in the north of Xinghua-Dafeng line tend to be NNE and NW,respectively,with steep slopes;while in the south of the Xinghua-Dafeng line,the orientation and tendency of most of the faults are NEE and SE,respectively,and with relatively small slopes.We suggest that the difference patterns between these faults may be a reflection of the ramp structure of the lower Yangtze.After a combination with seismic observations,we find that the distribution of earthquakes is closely related with faults with NE-NEE,NW and nearly EW orientations.Therefore,the faults in the northwest of Donghai-Ganyu and Dafeng harbor exhibit strong activities and unstable stress field,and we speculate there is a higher risk of earthquakes in this area.