【摘要】 地震波走时是克希霍夫叠前深度偏移的重要参数。三维克希霍夫偏移成像由于需频繁读取大数据量的走时表文件,所以计算效率不高。这里提出一种通过压缩三维射线追踪走时表,来提高克希霍夫偏移计算效率的方法:首先规划一个具有规则网格控制点并覆盖所有走时表点集的最小长方体区域,然后以三维三次B样条函数为插值基函数进行最小二乘法曲面体拟合,求出规则网格控制点的数值并以数组形式存储入内存,采用稀疏化存储进一步节省了内存空间。在偏移成像时,再由这些规则网格控制点的数值,使用线性插值公式解编出走时表。实际资料算例验证了该走时表压缩方法不仅近似精度高,计算稳定度高,计算效率高,而且由于省去了频繁进行大数据量走时表文件的读写操作,所以克希霍夫偏移的计算效率提高了二倍以上。更多还原

【Abstract】 Travel time of seismic waves is an important parameter of Kirchhoff migration. In process of 3-D Kirchhoff migration, the enormous travel time table file is frequently read, which leads to a fairly low calculation efficiency. A method is proposed to improve the computing efficiency of 3-D Kirchhoff migration by compressing the ray tracing traveltime table: At first,a smallest rectangle region in 3-D space with regular grids is constructed, where all the travel time data points are included. Then, the 3-D cubic B-spline function is used to fit a cuboidal surface which covers all the 3-D scattered travel time data, and the values of the finite regular grids can be calculated using least square method and are stored into memory in terms of an array. Compressed sparse column method is used to save more space. When the scattered travel time data are needed by migration, they can be decompressed by liner interpolation of 3-D B-spline function. Application to real seismic data shows that the traveltime compression method can not only compress travel time data with high approximate accuracy, stable calculation result, high calculation efficiency, but also improve the numerical efficiency of Kirchboff migration by twice because the enormous travel time table file neednt be frequently read any more.更多还原