Multi-phase seismic source imprint of tropical cyclones

Lise Retailleau,Lucia Gualtieri

doi:10.1038/s41467-021-22231-y

Abstract

The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide. The 2–10 s period band, known as secondary microseism, represents the largest background seismic wavefield. While moving over the ocean, tropical cyclones generate particularly strong and localized sources of secondary microseisms that are detected remotely by seismic arrays. We assess and compare the seismic sources of P, SV, and SH waves associated with typhoon Ioke (2006) during its extra-tropical transition. To understand their generation mechanisms, we compare the observed multi-phase sources with theoretical sources computed with a numerical ocean wave model, and we assess the influence of the ocean resonance (or ocean site effect) and coastal reflection of ocean waves. We show how the location and lateral extent of the associated seismic source is period- and phase-dependent. This information is crucial for the use of body waves for ambient noise imaging and gives insights about the sea state, complementary to satellite data.

Highlights

The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide
While Retailleau and Gualtieri[15] focused on retrieving the track of the event by locating P-wave sources, here we focus on the latest part of the event, during which the typhoon made the tropical–extratropical transition, from September 2 to 6 2006, before becoming an extratropical storm
In order to study the lateral extent of the source and better understanding the source mechanisms, we focus our analysis on two periods of time, before and after the tropical–extratropical transition

Summary

Introduction

The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide. We show how the location and lateral extent of the associated seismic source is period- and phase-dependent This information is crucial for the use of body waves for ambient noise imaging and gives insights about the sea state, complementary to satellite data. The period of the resulting seismic waves—between 2 and 10 s—is half the period of the involved ocean waves Extreme events, such as tropical cyclones, are among the most efficient storms to generate secondary microseisms[4], whose sources are well-localized. We use the Southern California seismic data[29] (Fig. 1a, b) to identify and locate the seismic sources of typhoon Ioke using the back-projection method[10] developed by Retailleau et al.[30,31]. This method was adapted to study P-wave sources of typhoon Ioke by Retailleau and Gualtieri[15]

Methods

Results

Conclusion