东海莫霍面起伏与地壳减薄特征初步分析

收集、整理大量由地震剖面提供的沉积层厚度资料,得到东海沉积层等厚图。对完全布格重力异常进行沉积层重力效应改正后,得到剩余重力异常,利用地震资料揭示的莫霍面深度值来约束界面反演得到东海莫霍面埋深。结果表明,东海陆架盆地莫霍面深度在25～28 km之间平缓变化,地壳厚度为14～26 km,西厚东薄;冲绳海槽盆地莫霍面深度为16～26 km,地壳厚度为12～22 km,北厚南薄。东海陆架盆地东部与冲绳海槽盆地南部地壳减薄明显,拉张因子分别达到2.6和3。初步分析认为冲绳海槽地壳以过渡壳为主,并未形成洋壳。

Preliminary analyses of the characteristics of Moho undulation and crustal thinning in East China Sea

Numerous sedimentary thickness data provided by seismic profiles were collected and drawn into the sedmimentary isopach in the East China Sea. The residual gravity anomalies were obtained by subtracting the gravity effect generated by the sediments from the complete Bouguer gravity anomalies. Depths to the Moho of the East China Sea were inversed from the residual gravity anomalies with constraint of the seismic penetration depths to the Moho. Our results show that depths to the Moho change between 25 km and 28 km gently and crustal thicknesses change between 14 km and 26 km on the East China Sea Shelf, depths to the Moho change between 16 km and 26 km and crustal thicknesses change between 12 km and 22 km within the Okinawa Trough. Crusts at the east of the East China Sea Shelf Basin and the south of Okinawa Trough are thinned evidently, and their crustal stretching factors are up to 2.6 and 3, respectively. Preliminary analyses suggest that the crust of Okinawa Trough is mainly transition type and there is no obvious evidence to prove the existence of oceanic crust.