Observation of Teleseismic S Wave Microseisms Generated by Typhoons in the Western Pacific Ocean

• Published in: Geophysical research letters Vol. 47; no. 19
• Main Authors: Liu, Qiaoxia, Ni, Sidao, Qiu, Yong, Zeng, Xiangfang, Zhang, Baolong, Wang, Fuyun, Duan, Yonghong, Xu, Zhiping
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.10.2020
• Subjects: Apertures; backprojection; ChinArray; Earthquake damage; Elastic waves; Excitation; Hurricanes; Microseisms; Ocean floor; Oceans; P waves; Property damage; Regions; S wave; S waves; Sedimentary structures; Seismic activity; Seismic arrays; Seismic waves; Storm damage; Storms; Surface waves; typhoon; Typhoons; Wave energy; Wave power; Waveforms; Western Pacific; China; Pacific Ocean
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL089031

Microseisms generated by storms primarily propagate as surface and P waves. However, there has been only one report of S wave microseisms excited by strong storms in the North Atlantic, not from typhoons in the Pacific. In this paper, we present the first observations for S wave microseisms caused by typhoons in Western Pacific, via analyzing ambient seismic waveform recorded by a large‐aperture seismic array in China. The results show that three super typhoons clearly generated S wave microseisms at periods of 5–10 s. The strength of S wave microseism is found to be correlated with P wave. The excitation mechanism for S wave microseism observed in regions with flat seafloor may be related to the interaction between P waves and sub‐ocean sedimentary structure. Plain Language Summary Besides causing property damages and life losses, ocean storms can also generate seismic waves named as microseisms, which could also be used as signals for studying interior of the Earth. Microseisms mostly propagate as surface waves and P waves. Yet S waves from storms are only detected in the North Atlantic Ocean shown by previous studies. However, there are no reports of S wave microseism by storms in the Pacific Ocean, though the typhoons there are strong and frequent. In this study, we observe and locate S wave microseisms generated by three super typhoons in Western Pacific by processing continuous ambient seismic waveforms recorded in China. The source regions of P and S waves are located very close to each other in the deep ocean near typhoons. Our results show that observability of S wave microseisms depends on P wave energy, which is controlled by strength of typhoons. It is demonstrated that S wave microseisms not only can be generated in the regions with steep topography but also can be excited in the flat seafloor regions. This work is helpful for understanding the excitation mechanism of the S waves. Key Points We observed body‐wave (P, SV, and probable SH) microseisms from typhoons in the Western Pacific We found that S wave strength is related to P wave power, which in turn relies on typhoon intensity S wave microseisms could be generated in the regions with flat seafloor or bathymetric gradients