中文摘要：

改进集中的能力预先叠时间移植允许想象的节反映结构的特征，深度，和接口形状，它是为起始的深度迁居速度模型的准备的关键步。传统的对称的旅行时间方程基于一个分层的模型的假设被导出。完成与强壮的侧面的变化集中在媒介的需要的效果是困难的。非对称的旅行时间方程基于谎言代数学和一个伪 differential 操作符包含能甚至在强烈侧面的可变媒介并且也改进集中的能力的侧面的速度衍生物为相对振幅保藏的重量系数的计算精确。与对称的方法相比，非对称的方法是更有效的。在这篇论文，我们描述几关键步非对称预先叠旅行时间计算和现在的一些测试用合成、真实的数据结果。

英文摘要：

Improving the focusing capability of pre-stack time migration allows the imaged section to reflect structural characteristics, depth, and interface shape and it is a key step for the preparation of the initial depth migration velocity model. The traditional symmetrical travel time equation is derived based on the assumption of a layered model. It is difficult to achieve the desired effect of focusing in media with strong lateral variation. The nonsymmetrical travel time equation based on Lie algebra and a pseudo-differential operator contains a lateral velocity derivative which can improve the focusing capability even in strongly lateral variable media and also the computation precision of the weight coefficients for relative amplitude preservation. Compared with the symmetrical methods, the nonsymmetrical method is more effective. In this paper, we describe several key steps of nonsymmetric pre-stack travel time calculation and present some test results using synthetic and real data.