跨南海西南次海盆OBS、多道地震与重力联合调查

doi:10.11978/2018108

Abstract

Abstract:

A 1050-km long comprehensive geophysical profile (CFT) was acquired across the conjugate margins of the southwestern sub-basin of the South China Sea, which includes 49 OBSs, 6- or 8-km long streamer, gravimeter, and magnetometer. Various refined processing procedures were applied to the aforementioned geophysical data; and a joint reflection and refraction seismic travel time inversion was performed to derive a 2-D velocity model of the crustal structure and upper mantle. Based on this new tomographic model and shipboard gravity data, a comprehensive crustal structure model was created. Finally, some interesting issues including High Velocity Layer (HVL) in the base of crust, an anomalous low density seamount (long-men seamount) along the CFT profile are discussed in this paper. HVL are widely distributed under the northern slope, southwestern sub-basin and Nansha block along the CFT profile, with the velocity varying from 7.0 to 7.5 km·s ^-1, and thickness between 0 and 4 km. HVL in the marginal lower crust might be derived from melting and mixing of lower crust material and mantle material, and HVL in the oceanic crust might have originated from serpentinization by tectonically dominated seafloor spreading.

Key words: southwestern sub-basin, wide-angle refraction seismic, long streamer multi-channel seismic, seismic tomography, high velocity layer of lower crust, Longmen Seamount

Jun WANG,Yan QIU,Pin YAN,M DELESCLUSE,Yanlin WANG,M PUBELLIER,Xin NIE. A joint investigation using OBS, multi-channel seismic and gravity data across the southwestern sub-basin of the South China Sea[J].Journal of Tropical Oceanography, 2019, 38(4): 81-90.

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层位	速度范围/(km·s^-1)
水体	1.5
沉积地层	1.7~3.5
基底以下壳内	4.0~7.5
地幔	8.0

参数名称	参数值
横向相关长度/km	10~30
纵向相关长度/km	0~24
速度平滑参数	1.7~3.5
迭代次数	10~20

A joint investigation using OBS, multi-channel seismic and gravity data across the southwestern sub-basin of the South China Sea

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