Abstract
Based on the optimum P-wave model, the S-wave velocity structure of a wide angle seismic profile (OBS2006-1), across the northwestern sub-basin (NWSB) and the Macclesfield, is simulated by a 2-D ray-tracing method. The results indicate the S-wave velocities in the upper and lower crust of the NWSB are 3.2–3.6 km/s and 3.6–4.0 km/s, with Vp/Vs ratios of 1.82–1.88 and 1.74–1.82, respectively, which reflect typical oceanic crust characteristics. The S-wave velocity in the upper crust of the NWSB is a little higher in the NNW segment than that in the SSE segment, while the lateral variation of Vp/Vs ratio is in the opposite. We suggest that the NWSB might have experienced asymmetrical magma flows during sea floor spreading, which may have blurred the magnetic anomaly lineation. The comparison of S-wave velocities along the northern margin of the SCS shows that the west section is different from the east section, and the northwestern margin has a non-volcanic crust structure. The S-wave structures and P-wave velocity models along the northern margin, Macclesfield and Reed Bank show that the Macclesfield might have a conjugate relationship with the Reed Bank.
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Acknowledgments
We are grateful to the scientists who joined cruise and the crew of the R/V “Fendou 7”. The seismic experiment and research were supported by the National Natural Science Foundation of China (Grants 41406052, 41176046, 91228205 and 41576037), the National Basic Research program of China (Grant 2012CB417301), the National Program on Global Change and Air-Sea Interaction, SOA (No. GASI-GEOGE-01), MOST of China (No. 2016YFC0600402) and Scientific Research Fund of the Second Institute of Oceanography, State Oceanic Administration (JG1413, JG1410). We used the RayInvr code (Zelt and Smith 1992) for seismic inversion. Some figures were plotted using GMT (Wessel and Smith 1995). We would also like to thank two anonymous reviewers for their constructive comments.
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Wei, X., Ruan, A., Li, J. et al. S-wave velocity structure and tectonic implications of the northwestern sub-basin and Macclesfield of the South China Sea. Mar Geophys Res 38, 125–136 (2017). https://doi.org/10.1007/s11001-016-9288-x
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DOI: https://doi.org/10.1007/s11001-016-9288-x