球坐标系下多震相走时三参数同时反演成像  

Simultaneous inversion of three model parameters with multiple phases of arrival times in spherical coordinates

作　　者：黄国娇[1] 白超英[2] 钱卫[1] 

机构地区：[1]河海大学地球科学与工程学院地质科学与工程系,南京211100 [2]长安大学地质工程与测绘学院地球物理系,西安710054

出　　处：《地球物理学报》2015年第10期3627-3638,共12页Chinese Journal of Geophysics

基　　金：江苏省自然科学基金项目(BK20150799);国家自然科学基金项目(41504038);河海大学中央高校基本科研业务费项目(2014B13814);教育部博士学科专项基金项目(20110205110010)资助

摘　　要：球坐标系下多震相走时三参数(速度、震源位置和反射界面)同时反演需要解决两个关键问题:(1)球坐标系下3D速度模型中多次透射、反射(折射)及转换波精确、快速的射线追踪;(2)同时反演时三种不同参数间的强耦合问题.为此,我们将直角坐标系下分区多步不规则最短路径算法推广至球坐标系中,进行区域或者全球尺度的多震相射线追踪.然后将其与适合多参数同时反演的子空间算法相结合,形成一种球坐标系下联合多震相走时三参数同时反演的方法技术.与双参数(速度和反射界面或速度和震源位置)同时反演的数值模拟对比分析显示:三参数与双参数的同时反演结果大体接近,并且它们对到时数据中可容许的随机噪声不太敏感.结果说明本文中的同时反演成像为一种提高成像分辨率,同时反演速度、震源位置和反射界面的有效方法.To guarantee computational precision and improve the resolution of seismic traveltime tomography at a regional or global scale,we conduct a 3D simultaneous inversion of three different parameters（velocity,hypocenter location and reflector geometry）in spherical coordinates with multi-phase travel times.For this task,there are two key issues：（1）It needs an efficient and accurate arrival tracking algorithm for multiply transmitted,reflected（or refracted）and converted waves in a 3D variable velocity model with embedded velocity discontinuities（or subsurface interfaces）,and（2）A subdimensional inversion solver is required which can easily search for different types of model parameters to balance the tradeoff between the different types of model parameter updated in the simultaneous inversion process.For these purposes,we first extend a popular grid/cell-based wavefront expanding ray tracing algorithm（the multistage irregular shortest-path ray tracing method,shorted as ISPM）,which previously worked only in Cartesian coordinates at a local scale,to spherical coordinatesappropriate to a regional or global scale.In 3Dspherical coordinates a trapezoidal prism cell is used to divide the spherical earth model,except for the global and other irregular subsurface interfaces,where a trapezoidal cone is used.And in one previous paper we have discussed the computational accuracy of the multistage ISPM algorithm against the analytic solution of AK135 Travel Time Table for 49 kinds of global phases and concluded that the computational accuracy can be tuned to within the 0.1sabsolute time error when it works in the spherical coordinates.We then incorporate the subspace method to formulate a simultaneous inversion algorithm,in which the multiple classes of arrivals（including direct and reflected arrivals from different velocity discontinuities）can be used to simultaneously update the velocity fields,hypocenter location and reflector geometries.In order to illustrate the performance of inversion for three

关 键 词：球坐标系 分区多步不规则最短路径算法 多震相走时 三参数同时反演 子空间法 

分 类 号：P315[天文地球—地震学]