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为了探明南海中北部陆缘深部地壳结构,使用2D射线追踪正演和反演方法,拟合了一条南海中北部陆缘的OBS广角地震剖面(OBS2006-3).该剖面穿越东沙隆起和潮汕坳陷,长319 km,NNW-SSE走向,共投放海底地震仪14台.速度结构模型表明:潮汕坳陷存在巨厚的中生代沉积,最大厚度达到8 km,速度从顶部的4.4 km/s向下增加到底部的5.3 km/s.莫霍面埋藏深度由陆向海方向减小,其埋深从东沙隆起下方的24～25 km减小到南部隆起带的17 km.东沙隆起下方的上地壳中存在一向上突起的高速异常,速度达到6.9 km/s,可能与地幔物质上涌和岩浆活动有关.在整个剖面的下地壳底部存在厚3～12 km,速度为7.1～7.4 km/s的高速层.根据各个时期岩浆活动特征,推测下地壳高速层是由海底扩张停止之后的岩浆底侵作用形成的.
In order to find out the deep crustal structure of the continental margin in the middle and northern South China Sea, an OBS wide-angle seismic profile (OBS2006-3) of the central and northern continental margin of the South China Sea is fitted using 2D ray tracing forward modeling and inversion methods. Depth of 319 km, NNW-SSE direction, a total of 14 seabed seismographs were put in. The velocity structure model shows that there is a huge Mesozoic sediment in the Chaoshan depression with a maximum thickness of 8 km and a velocity from the top of 4.4 km / s To 5.3 km / s at the bottom of the Mozambique.The burial depth of the Moho decreases from the seaward to the sea, and its burial depth decreases from 24-25 km below the Dongsha uplift to 17 km in the southern uplift.The upper crust beneath the Dongsha uplift There is an uplifted high-speed anomaly at a speed of 6.9 km / s, which may be related to upwelling and magmatic activity of the mantle.At the bottom of the lower crust, there are 3 ~ 12 km thick and 7.1 ~ 7.4 km / s high velocity According to the characteristics of magmatism in each period, it is speculated that the lower crust high-velocity layer is formed by the magmatic underplating after the seafloor expansion ceased.