Seismological Observations of Ocean Swells Induced by Typhoon Megi Using Dispersive Microseisms Recorded in Coastal Areas

Jianmin Lin,Hong Zheng,Renhao Wu,Sunke Fang,Xiaofeng Li

doi:10.3390/rs10091437

Abstract

Typhoons in the western Pacific Ocean can generate extensive ocean swells, some of which propagate toward Taiwan, Luzon, and the Ryukyu Islands, impacting the coasts and generating double-frequency (DF) microseisms. The dispersion characteristics of DF microseisms relevant to the propagation of ocean swells were analyzed using the fractional Fourier transform (FrFT) to obtain the propagation distance and track the origins of typhoon-induced swells through seismic observations. For the super typhoon Megi in 2010, the origin of the induced ocean swells was tracked and localized accurately using seismic records from stations in eastern Taiwan. The localized source regions and calculated wave periods of the ocean swells are in good agreement with values predicted by ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). However, localized deviations may depend on the effective detection of dispersive DF microseisms, which is tied to both coastline geometry and the geographic locations of seismic stations. This work demonstrates the effectiveness of seismological methods in observing typhoon-induced swells. The dispersion characteristics of DF microseisms recorded by coastal stations could be used as a proxy measure to track and monitor typhoon-induced swells across oceans.

Highlights

Swells induced by a typhoon can be devastating and commonly cause major damage to ships and coastal infrastructure, as they can propagate over long distances with their energy only weakly attenuated [1,2]
The DF microseisms generated by Typhoon Megi were detected effectively on spectrograms w(hFeigreureF2s), wisithtlhitetle scaomntpalminignatiroante
We assumed that the most likely source regions of long-period ocean swells had the highest-amplitude significant wave heights, and we superimposed of the typhoon-induced swells derived from the dispersion characteristics of DF microseisms recorded by station YULB, which is located close to the coastline (~18 km) of eastern Taiwan

Summary

Introduction

Swells induced by a typhoon can be devastating and commonly cause major damage to ships and coastal infrastructure, as they can propagate over long distances with their energy only weakly attenuated [1,2]. We inverted for the origin time and source region of typhoon-induced swells using the dispersion characteristics of DF microseisms, and obtained results that are generally consistent with ERA5 reanalysis of ocean wave data. This demonstrates that seismic monitoring could allow us to track typhoon-induced swells using microseisms recorded at coastal sites. Rχeslfoebpryeenicnet[h4i3s]p, tahpeero,pdtfim/datl, twraansscfoomrmpuatnegdlefroαm χisancucomredriincgaltloy Ereqluataetdionto(9th).e rate of the LFM signal

Results and Discussion

Swell-Generated DF Microseisms

Conclusions