南海东北部大陆坡地震反射异常体的属性分析与岩性识别*

doi:10.11978/2021028

Abstract

Abstract:

The northern margin of the South China Sea (SCS) is often regarded as a magma-poor passive continental margin. Many high amplitude anomalies were observed in previous studies on seismic profiles at the northern part of the Continent-Ocean Transition (COT) in the northern SCS, and were interpreted as sills and volcanos. However, further investigation on the properties of these high amplitude anomalies was lacking. In this study, we observed a large anomaly with a thickness of ~1.2 km in two multi-channel seismic profiles (SO1E and SOY) on the northeastern continental slope of the SCS. This provides an opportunity to determine the presence of magmatic activities north of the COT. Velocity analysis and AVO (amplitude variation with offset) analysis were performed for the large-amplitude anomaly. Results show that the high-amplitude anomaly has a higher P wave velocity and Poisson’s ratio than the host strata above. Considering the regional geologic background, the internal reflection characteristics, spatial size and shape of this high-amplitude anomaly, we suggest that the high-amplitude anomaly can be characterized as an igneous rock and further classified as a laccolith. This also indicates that multi-phase magmatism occurred north of the COT since the Miocene.

Key words: northeastern South China Sea, laccolith, velocity analysis, AVO analysis

CLC Number:

P738.4

LI Bo’an, HU Shanzheng, YAN Pin, YU Junhui, WANG Xiao, TANG Qunshu. Property analysis and lithology identification of seismic reflection anomalies on the continental slope of northeastern South China Sea[J].Journal of Tropical Oceanography, 2022, 41(1): 204-214.

Figures/Tables 8

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CDP	点号	时间/ms	叠加速度/(m•s^-1)	层速度/(m•s^-1)
1#	①	1915	1502	1874
	②	2370	1581	2387
	③	3195	1845	2977
	④	3485	1960	3207
2#	①	1924	1503	1828
	②	2419	1577	2381
	③	3264	1820	3270
	④	3586	1996	3282
3#	①	2173	1504	1890
	②	2725	1590	2546
	③	3305	1798	3692
	④	3773	2128	3370
4#	①	2188	1503	1850
	②	2763	1586	2404
	③	3310	1747	3601
	④	3883	2120	3322
5#	①	2413	1502	1932
	②	2920	1586	2252
	③	3470	1708	3584
	④	3865	1944	3362

Property analysis and lithology identification of seismic reflection anomalies on the continental slope of northeastern South China Sea

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