The influence of sea water velocity variation on seismic traveltimes,ray paths,and amplitude

海水速度变化对地震波走时、射线路径及振幅的影响(英文)

The main factors affecting seismic exploration is the propagation velocity of seismic waves in the medium. In the past, during marine seismic data processing, the propagation velocity of sea water was generally taken as a constant 1500 m/s. However, for deep water exploration, the sound velocity varies with the season, time, location, water depth, ocean currents, and etc.. It also results in a layered velocity distribution, so there is a difference of seismic traveltime, ray paths, and amplitude, which affect the migration imaging results if sea water propagation velocity is still taken as constant for the propagation wavefield. In this paper, we will start from an empirical equation of seismic wave velocity in seawater with changes of temperature, salinity, and depth, consider the variation of their values, build a seawater velocity model, and quantitatively analyze the impact of seawater velocity variation on seismic traveltime, ray paths, and amplitude in the seawater velocity model.

影响地震勘探的主要因素是地震波在介质中的传播速度,在以往海洋地震勘探数据处理中,都是将海水的传播速度取为常速1500m/s。但对于深水勘探,由于海水中的声速随季节、时间、地理位置、水深、洋流等的变化而不同会造成海水速度的分层结构,因此再将海水速度取为常数进行波场传播计算必然造成地震波传播当中的走时、射线路径和振幅的差异,最终影响偏移剖面的成像结果。本文从影响海水速度变化的主要因素(海水温度、盐度和深度)的经验公式出发,综合考虑其情况建立海水速度模型,并在所建立的模型上定量分析讨论了海水速度变化对地震波走时、射线路径及振幅的影响。