贺兰山—银川地堑重力异常小波多尺度 特征及构造含义  

Multi-scale Wavelet Features and Tectonic Implications of the Gravity Anomaly in the Helanshan-Yinchuan Graben

作　　者：何辛 姬计法[1] 李勇江[1] 冯建林[1] HE Xin;JI Jifa;LI Yongjiang;FENG Jianlin(Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,Henan,China)

机构地区：[1]中国地震局地球物理勘探中心,河南郑州450002

出　　处：《地震研究》2025年第4期594-601,共8页Journal of Seismological Research

基　　金：中国地震局地球物理勘探中心青年基金资助项目(YFGEC2023005).

摘　　要：基于流动地球物理场观测项目获得的相对重力数据,对贺兰山—银川地堑及邻区深部构造进行讨论。计算获得研究区布格重力异常,采用小波多尺度分解方法对布格重力异常进行2~5阶小波细节分解,结合区域地质、地球物理资料,对重力场结果进行分析。结果表明:贺兰山—银川地堑布格重力异常与邻区有较大差异,小波细节特征显示在横向上同邻区也有较大差异,贺兰山—银川地堑构造更为复杂,以独立的小地块形式存在于阿拉善微陆块、华北陆块以及祁连早古生代造山带之间。贺兰山—银川地堑及邻区断裂主要为浅源和壳内断裂,主要分布在牛首山、贺兰山东麓、银川地堑东缘周围。这些断裂带也是重力异常突变带、梯度带,是孕育地震的理想环境。此外研究区中上地壳重力异常明显,可能是导致该地区地震以浅源地震居多的主要原因。Using the relative gravity data obtained from the mobile gravimetric network of the geophysical field observation project,we calculated the Bouguer gravity anomaly in the Helanshan-Yinchuan Graben and its adjacent areas.We used the multi-scale wavelet decomposition method to perform a detailed 2nd-to-5th order wavelet decomposition of the Bouguer gravity anomaly,and we further estimated the approximate source depth of the detailed 2nd-to-5th order wavelet field by the radial logarithmic power spectrum method.We analyzed these results by the help of the regional geological and geophysical data in the study area.We found that the Bouguer gravity anomaly in the Helanshan-Yinchuan Graben is significantly different from that in the adjacent areas,and the detailed wavelet features show significant differences in the horizontal direction.The Helanshan-Yinchuan Graben has more complex structures;these structures exist in the form of independent small blocks between the Alxa micro-landmass,the North China landmass,and the Qilian Early Paleozoic orogenic belt.The faults in the Helanshan-Yinchuan Graben and the adjacent areas are mainly shallow-sourced and intercrustal faults,mainly distributed around the Niushoushan Mountain fault,the East Helanshan Mountain fault,and the Yellow River fault zone on the eastern edge of the Yinchuan Graben.These fault zones are also zones of abrupt changes in gravity anomaly and gradient zones,the earthquake-prone environment.In addition,the gravity anomaly in the upper and middle Crust in the study area is obvious,which may be the main reason for the predominance of shallow earthquakes in the study area.

关 键 词：贺兰山—银川地堑 布格重力异常 小波多尺度分解 

分 类 号：P315.726[天文地球—地震学]