淮北及邻区地壳均衡异常与构造背景

Isostasic anomaly and tectonic background in Huaibei City,Anhui and its adjacent areas

淮北地区位于华北板块东南缘,东侧以郯庐断裂为界与扬子板块相接,研究这一区域的地壳密度结构以及分析其地壳均衡状态对于认识该地区深部构造特征和构造背景具有重要的参考价值.本文基于实测地震数据和重力/GNSS同址观测数据,获取了研究区域重力异常值以及剖面S波速度场,以其为约束反演了剖面地壳密度结构.基于均一和分层地壳模型假设,反演得到了研究区域的莫霍面深度、均衡面深度、均衡异常与均衡附加力,分析了深部构造特征.结果表明,区域内莫霍面深度范围为32~41 km,地壳自西向东逐渐变薄,且上地壳、中地壳和下地壳的变化趋势与莫霍面的变化趋势较为一致,在郯庐断裂带所在区域上地幔物质存在隆起的现象.研究区域整体处于正均衡异常状态,在淮北以东区域,地壳处于较为稳定的状态,均衡面深度范围为30~32km,均衡异常在-2~10 km变化.研究区域内的均衡附加力主要为正值,大小在-20~64 MPa之间变化,整体呈现正均衡异常状态,地壳处于抬升趋势.

Huaibei city,Anhui is located at the southeast edge of the North China plate,and the east side is connected with the Yangtze plate by the Tanlu fault zone.It shows important reference value to understand its deep structural characteristics and tectonic background,while studying the crustal density structure and analyzing the isostatic state in this area.The gravity anomalies and the profile S-wave velocity fields in the study area were calculated based on measured seismic data and gravity/GNSS co-located observation data.These calculations were then used as constraints to invert the crustal density structure along the profiles.Assuming homogeneous and stratified crustal models,we calculated the Moho depth,the isostatic depth,isostatic anomalies and isostatic additional forces in the study area.We also analyzed the deep structural characteristics of the study area.The results show that the Moho depth in this area ranges from 32 km to 41 km,and the crust gradually thins from west to east.The variation trend of upper crust,middle crust and lower crust is consistent with that of Moho surface.In the area where the Tanlu fault zone is located,the upper mantle material is uplifted.The study area is mainly in a positive isostatic state.In the east area of Huaibei,the crust is in a relatively stable state state,with an isostatic depth range of 30~32 km and an isostatic anomalies variation of−2~10 km.The isostatic additional forces in the study area are mainly positive,varying between−20~64 MPa,showing a positive isostatic state overall,and indicating an upward trend in crustal uplift.