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.
Bibliographical noteFunding Information:
Seongjun Park is grateful to Kiwamu Nishida for valuable discussion on microseisms. The authors thank Allison Bent (Editor-in-Chief), Pieter Smets, and an anonymous reviewer for fruitful review comments. This work was supported by the Korea Meteorological Administration Research and Development Program under Grant KMI2018-02910. In addition, this research was partly supported by National Research Foundation of Korea (NRF-2017R1A6A1 A07015374 and NRF-2018R1D1A1A09083446).
© 2020 Seismological Society of America.
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