Low-velocity layers in the northwestern margin of the South China Sea: Evidence from receiver functions of ocean-bottom seismometer data

Abstract Microseisms in frequencies of 0.05–0.5 Hz are a presentation of solid earth response to the ocean waves that are developed by atmospheric pressure change. The South China Sea provides a natural laboratory with a closed ocean environment to examine the influence of regional factors on microseism development as well as the nature of microseisms. The microseisms induced by typhoons crossing over the South China Sea are investigated. Typhoons are typical transient sources of varying strengths and locations. Primary microseisms develop nearly stationary in the northeastern South China Sea for most typhoons, suggesting effective environment for excitation of primary microseisms. Typhoon-induced secondary microseisms develop around the typhoon paths with time delays varying up to one day. Typhoon-induced microseism amplitudes are proportional to the ocean-wave amplitudes in the source regions, decaying with distance. Ocean waves develop following the typhoons for days. The dominant frequency of typhoon-induced microseisms increases with time due to the influence of dispersive ocean waves. The microseisms are affected by regional factors including crustal structures, coastal geometry, ocean depth, and ocean-bottom topography.

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Crustal structure and extension mode in the northwestern margin of the South China Sea

Geochemistry Geophysics Geosystems ◽

10.1002/2016gc006247 ◽

2016 ◽

Vol 17 (6) ◽

pp. 2143-2167 ◽

Cited By ~ 20

Author(s):

Jinwei Gao ◽

Shiguo Wu ◽

Kirk McIntosh ◽

Lijun Mi ◽

Zheng Liu ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Crustal Structure ◽

The South China Sea ◽

The South ◽

China Sea ◽

Northwestern Margin

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Spatial variability of diapycnal mixing in the South China Sea inferred from density overturn analysis

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0241.1 ◽

2021 ◽

Author(s):

Yuan-Zheng Lu ◽

Xian-Rong Cen ◽

Shuang-Xi Guo ◽

Ling Qu ◽

Peng-Qi Huang ◽

...

Keyword(s):

South China Sea ◽

Continental Slope ◽

South China ◽

The South China Sea ◽

Central Basin ◽

Ocean Bottom ◽

The South ◽

Diapycnal Mixing ◽

China Sea ◽

Diapycnal Diffusivity

AbstractThe nominal spatial distribution of diapycnal mixing in the South China Sea (SCS) is obtained with Thorpe-scale analysis from 2004 to 2020. The inferred dissipation rate ε and diapycnal diffusivity Kz between 100 and 1500 m indicated that the strongest mixing occurred in the Luzon Strait and Dongsha Plateau regions, with ε ~ 3.0 × 10-8 W/kg (εmax = 5.3 × 10-6 W/kg) and Kz ~ 3.5 × 10-4 m2/s (Kz max = 4.2 = 10-2 m2/s). The weakest mixing occurred in the thermocline of the central basin, with ε ~ 6.2 × 10-10 W/kg and Kz ~ 3.7 × 10-6 m2/s. The ε and Kz in the continental slope indicated that the mixing in the northern part [O(10-8) W/kg, O(10-4) m2/s] was comparatively stronger than that in the Xisha and Nansha regions [O(10-9) W/kg, O(10-5) m2/s]. The Kz in the continental slope region (200–2000 m) decayed at a closed rate from the ocean bottom to the main thermocline when the measured depth D was normalized by the ocean depth H as D/H, whether in the shallow or deep oceans. The diapycnal diffusivity was parameterized as Kz = 3.3 × 10−4 (1 + )−2 − 6.0 × 10−6 m2/s. The vertically integrated energy dissipation was nominally as 15.8 mW/m2 for all data and 25.6 mW/m2 for data at stations H < 2000 m. This was about one order higher than that in the open oceans (3.0–3.3 mW/m2), which confirmed the active mixing state in the SCS.

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