台湾海峡西南部深地震探测剖面Pg波走时层析成像

Seismic tomography in deep seismic exploration profile of the southwestern Taiwan strait from Pg wave travel time

采用走时有限差分层析成像方法，利用2014年在台湾海峡西南部区域得到的3条海域测线的Pg波资料，获得了沿探测剖面沉积层上地壳基底的速度结构、基底形态和埋深。3条剖面基底深度为1．5～4．2km。基底埋深虽有一定变化，但仅在局部地区起伏较明显，显示了断裂或凹陷在上部地壳内的结构特征。通过和台湾海峡地质构造区划进行对比，反演得到的基底结构特征与地震剖面穿过区域的地质构造比较吻合，本次走时层析成像结果也为后续深部结构的反演提供了可靠的浅层速度信息。

The Pg travel time picked from three sea area lines, which were completed in southwestern Taiwan Strait in 2014, were used to reconstruct basement velocity structure, topoqraphy and depth of upper crust along the profile by means of finite difference layer imaging of travel time. The minimum and maximum basement depths of three profiles are between 1.Skm and 4.2km. Although there are some changes in basement depth,the fluctuation is obvious only in the local area, which shows the structure of fracture or depression in the upper crust. By comparison with geological structure zonation of the Taiwan Strait, it shows no more difference between the basement structure which is obtained from inversion and the geological structure of the seismic profile across this area. The travel time tomography results also provide reliable shallow layer velocity information for follow-up inversion of the deep structure.