基于抛物线密度模型的频率域三维界面反演及其在川滇地区的应用  

3D interface inversion of gravity data in the frequency domain using aparabolic density-depth function and the application in Sichuan-Yunnan region

作　　者：张恩会[1] 石磊[1] 李永华[1] 王谦身[2] 韩长武 

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国石油西部钻探苏里格气田项目经理部,鄂尔多斯乌审旗017300

出　　处：《地球物理学报》2015年第2期556-565,共10页Chinese Journal of Geophysics

基　　金：地震行业专项(201408014);中国地震局地球物理研究所基本业务专项(DQJB12B14);地下信息探测技术与仪器教育部重点实验室(中国地质大学;北京)开放课题项目(GDL1203)联合资助

摘　　要：密度界面反演作为了解地球内部结构的一种重要方法,长期以来都是重力学研究的主要内容.本文结合抛物线密度模型及频率域算法的优点,将抛物线密度函数应用于Parker-Oldenburg算法,经过理论推导得到了抛物线密度模型的频率域公式,从而建立了基于抛物线密度模型的三维密度界面重力异常正反演的算法和流程.理论模型数据试验表明本方法快速、有效,适用于大多数浅部比深部增加更快的实际地壳密度.研究中还利用该方法对川滇地区重力异常进行了反演,获得了该区的莫霍面深度分布,并与接收函数研究结果进行对比分析,进一步验证了本文方法的正确性和有效性.As an important way to reveal the internal structure of the earth,inversion of the density interface is a main subject of gravity research for a long time.Inversion of field data in the frequency domain provides a quick and efficient data analysis method.Combining the advantages of the frequency domain and parabolic density function,this paper presents a processing method for gravity anomaly data of a three-dimensional underground interface using parabolic densitydepth function in the frequency domain. The method we used to make forward modeling of the gravity anomaly is based on the algorithm proposed by Parker and Oldenburg which uses constant density contrast. We substituted the constant density function in gravity forward formula for the parabolic density function.Then the Fast Fourier Transform（FFT）was applied to both sides of the equation.We derived the gravity anomaly formula of 3Ddensity interface with parabolic density contrast after calculating the involved integral.To invert the density interface depth,an iterative algorithm was preformed to adjust the interface depth step by step until the difference between the theoretical anomalies and observations reduced to the threshold value.In addition,in order to avoid the divergence of the algorithm which is difficult to avoid for the calculation in the frequency domain,we also added a low-pass filter to the codes. We applied our method to a theoretical model which has 91×71grid data with 10 km interval in x-axis and y-axis,and a complex 3Dinterface with parabolic density contrast variation in depth.In the synthetic test,we compared the method proposed in this paper with the constant,exponential and binomial functions.Besides the points with acute topography fluctuation,the results show that the inversion using parabolic function provides good and stable estimates of the interface depth of the theoretical model with RMS 0.02 km,and that the constant density function inversion gives the worst estimate of the theoretical model. According to the compariso

关 键 词：抛物线密度模型 频率域 界面反演 川滇地区 

分 类 号：P312[天文地球—固体地球物理学]