Abstract: We conduct the wave field separation of the gravity field for northern Henan Province and adjacent areas by the wavelet multi-scale decomposition method, and obtain multi-order gravity wavelet details and regional gravity field information. Then the Parker density surface inversion is used to invert the Moho interface. Based on the analysis of wavelet details in different orders and results of three seismic sounding profiles available in this area, we attempt to reveal the deep crustal structure of the study area. Research results show that the crustal structure is dominated by uneven density distribution accompanied by uplifts and depressions in the region with obvious heterogeneities of the density in horizontal and vertical directions. The gravity field characteristics in the middle-upper crust correspond to the surface topography, the lower crust is dominated by the large-scale high-low gravity anomalies, and several major depression basins show the characteristics of low velocity and low density. At the same time, the depth of the Moho interface changes greatly, which forms the block structure pattern of the regional crustal thickness. Among these features, the area with relatively large variations of the Moho is located in the transition zone of the basin to the Taihang Mountains, or exactly the Moho mutation belt. The Moho interface of the basin area as a whole is dominated by the uplift intertwined with local variations, of which the least and largest depths are 31km and 37km, respectively. Due to the gravity isostasy, the crustal thickness is larger(about 41km)in the northwest of the Taihang Mountains, with less average crustal density. In the study area, earthquakes tend to occur around the transition zone with density changes where the Moho is locally convex. The seismogenic mechanism may be associated with upwelling of upper mantle materials, low-velocity and low-density structures in the middle-lower crust and connection of deep large faults. Moreover, the deep large faults play a controlling role in the distribution of regional earthquakes.

Key words: Multi-scale wavelet decomposition, Bouguer gravity anomaly, Crust-mantle structure, Northern Henan and adjacent areas

摘要： 文中利用小波多尺度分解方法对豫北及邻区重力场进行了波场分离，得到多阶重力小波细节及区域重力场信息。随后利用Parker法密度界面反演对该区Moho界面进行了反演分析。通过对不同阶次小波细节的分析研究，并结合该区内已有3条地震测深剖面资料，对该区地壳深部结构进行了深入研究。结果表明，研究区壳内结构以隆坳相伴的密度非均匀分布为主，其密度在横向和纵向上均存在明显的非均匀性。其中，中上地壳重力场特征与地表地形地貌特征具有对应关系，中下地壳以大尺度的高、低重力异常为主，几个主要的凹陷盆地表现出低速低密的特征。同时Moho面埋深起伏变化较大，形成了区域地壳厚度的分块构造格局。其中，研究区内Moho面起伏比较大的区域位于盆地向太行山过渡地带，为Moho面陡变带。盆地区Moho面整体以上隆为主，但存在局部起伏变化，地壳厚度最小约31km，最大约37km；由于重力均衡作用，西北部太行山区地壳厚度较大，约41km，但地壳平均密度较低。研究区的地震多发生在局部存在Moho面上凸区附近密度变化的过渡带周缘，孕震机制可能与上地幔物质上涌底侵、中下地壳存在低速低密结构以及深大断裂的贯通有一定关系。同时深大断裂也对区域地震分布起到了控制性作用。

关键词: 小波多尺度分解, 布格重力异常, 壳幔结构, 豫北及邻区