中文摘要：

深度域地震波速度模型是地震勘探中最重要的参数之一，是获得精确深度域偏移剖面的基础．本文基于成像射线的概念，阐述了时间偏移域和深度域之间的关系，明确了时间偏移后的像点是通过成像射线与深度域的散射点联系起来的．在有横向变速的情况下，时间偏移剖面需要经过时深转换才能真实反映深度域层位，同样，从时间偏移剖面上提取的速度也需要经过时深转换才能得到深度域的速度．与前者不同的是，在速度的时深转换中，不仅速度的位置需要改变，且其数值也需要进行校正．该校正因子有几种等价的描述形式：度规量、速度扩散因子和几何扩散因子．

英文摘要：

The seismic velocity model in the depth domain is one of the most important parameters in seismic exploration and the basis to obtain precise migration sections in the depth domain. Based on image ray, we elaborate the relationship between the time-migration domain and depth domain, and define that the image point in the timemigration domain is related to the scattering point in depth domain by image ray. If the velocity varies laterally, in order to show the real subsurface structure, time-migration section and velocity both need a time-to-depth conversion. Different from time-to-depth conversion of migration sections, we need to correct both positions and values of the velocity in time-to depth conversion of velocity. The correction factor can be expressed in several equivalent forms： matrix tensor, velocily spreading factor and geometrical spreading factor.