重电联合反演解析苏北地区印支面及其展布特征

Interpretation of the Indosinian surface and its distribution characteristics in Northern Jiangsu Province by gravity-magnetotelluric joint inversion

印支面作为江苏乃至下扬子地区的一个重要构造界面和侵蚀面,对于分析和指示古生界泥页岩层系的展布、研究构造保存条件均有十分重要的意义。在综合分析研究区物性特征的基础上,结合钻井资料和以往地质认识,给定不同地层和岩石的物性参数,建立初始地质-地球物理模型,利用高精度重力和大地电磁测深数据进行重电联合反演和模型修正,最终得到满足拟合精度的地质模型,并以此绘制断裂与构造单元分布图和印支面深度图。结果显示,苏北地区印支面深度起伏较大、构造复杂,断裂主要以北东向为主,可划分为3个一级构造单元和16个二级构造单元。结果证明,在具有相同物性界面的条件下,重电联合反演方法克服了单一物探方法的局限性,提高了解释精度和可靠性,对类似地区解析深部构造面具有参考价值。

As an important tectonic interface and erosion surface in Jiangsu Province and even in the Lower Yangtze region,the Indosinian surface is of great significance for analyzing and indicating the distribution of the Paleozoic shale strata and studying structural preservation conditions.Based on the comprehensive analysis of the physical characteristics,combined with drilling data and previous geological understanding,this work established an initial geological-geophysical model after setting up physical parameters of different strata and rocks.Gravity-magnetotelluric joint inversion was conducted with high-precision gravity and magnetotelluric exploration data,and a geological model that satisfies the fitting accuracy was obtained.Based on this,the distribution map of fractures and structural units and the Indosinian surface depth map were also drawn.It is inferred that the Indosinian surface in the study area has a large fluctuation and its structure is complex.The faults in the study area are mainly in the northeast direction,and can be divided into three first-order structural units and 16 second-order structural units.It is shown that the gravity-magnetotelluric joint inversion method overcomes the limitations of the single geophysical method and improves the interpretation accuracy and reliability under the condition of the same physical interface,which provides an important reference for the analysis of deep structural planes in similar areas.