Typhoon-Induced Microseisms around the South China Sea

2020 ◽  
Vol 91 (6) ◽  
pp. 3454-3468
Author(s):  
Seongjun Park ◽  
Tae-Kyung Hong
Keyword(s):  
South China Sea ◽  
South China ◽  
Bottom Topography ◽  
Pressure Change ◽  
Ocean Waves ◽  
The South China Sea ◽  
Ocean Bottom ◽  
The South ◽  
China Sea ◽  
Regional Factors

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.

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

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.

scholarly journals The South China sea continental slope morphology and its relation to the anomalous gravitational field

2019 ◽  
pp. 67-76
Author(s):  
T. D. Leonova ◽  
M. G. Valitov ◽  
O. V. Belous
Keyword(s):  
Gravitational Field ◽  
South China Sea ◽  
Continental Slope ◽  
South China ◽  
Deep Water ◽  
Bottom Topography ◽  
Complex Structure ◽  
The South China Sea ◽  
The South ◽  
China Sea

The bottom topography of the studied area of the South China Sea is characterized by an uneven distribution of depths, their sharp variations and the presence of a large number of seamounts. As a result of the research conducted, bathymetric profiles, a bathymetric map and a scheme of Faye anomalies were compiled. Geomorphological zoning was conducted. Sections of bottom distinguished by morphology were identified: 1) weakly dissected slope, steep (angles up to 15) in the upper part and more gentle (57) to the bottom of the deep-water step, 2) slope eroded by fluvial processes, 3) stepped slope, 4) chains of mountains and flat-topped hills, 5) accumulative bottom of the deep-water plain. It was established that the gravitational field as a whole reflects the complex structure of the bottom, and the local forms of the underwater relief are expressed in Faye anomalies. For elevations, zones of positive anomalies of Faye are marked, and sections of canyon-like valleys were mapped by an intense negative anomaly of the gravitational field to -60 mGal. In the process of endogenous evolution of the region, the relief became more complex. The primary endogenous continental slope was almost everywhere transformed by exogenous processes. Within the shelf, the filling of the basin led to the unification of all its projections into a single raised base. A significant role in the formation of the modern relief was played by large-scale repeated sea regressions, as a result of which the formation of the sedimentary cover was interrupted by periods of its erosion with the formation of planation surfaces. The Late Pleistocene peak of the regression (1618 thousand years BP), which caused the complete drainage of the shelf areas of the region, caused the erosion of the shelf and the movement of coarse clastic material through submarine canyons and valleys.

A Wide Angle Ocean Bottom Seismometer Experiment Across Liyue Bank, the Southern Margin of the South China Sea

2011 ◽  
Vol 54 (6) ◽  
pp. 1033-1044 ◽  
Author(s):  
Ai-Guo RUAN ◽  
Xiong-Wei NIU ◽  
Xue-Lin QIU ◽  
Jia-Biao LI ◽  
Zhen-Li WU ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Wide Angle ◽  
The South ◽  
China Sea ◽  
Southern Margin

Simulation of meridional overturning in the upper layer of the South China Sea with an idealized bottom topography

2004 ◽  
Vol 49 (7) ◽  
pp. 740-746 ◽  
Author(s):  
Dongxiao Wang ◽  
Xiongbin Liu ◽  
Wenzhi Wang ◽  
Yan Du ◽  
Weidong Zhou
Keyword(s):  
South China Sea ◽  
South China ◽  
Bottom Topography ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Meridional Overturning
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