A possible space-based tsunami early warning system using observations of the tsunami ionospheric hole.

Masashi Kamogawa,Yoshiaki Orihara,Yoshihiro Kakinami,Aditya Riadi Gusman,Tatsuya Kanaya,Chiaki Tsurudome,Daiki Ikeda,Yuto Tomida,Atsushi Toyoda,Jann-Yenq Liu

doi:10.1038/srep37989

Abstract

Ionospheric plasma disturbances after a large tsunami can be detected by measurement of the total electron content (TEC) between a Global Positioning System (GPS) satellite and its ground-based receivers. TEC depression lasting for a few minutes to tens of minutes termed as tsunami ionospheric hole (TIH) is formed above the tsunami source area. Here we describe the quantitative relationship between initial tsunami height and the TEC depression rate caused by a TIH from seven tsunamigenic earthquakes in Japan and Chile. We found that the percentage of TEC depression and initial tsunami height are correlated and the largest TEC depressions appear 10 to 20 minutes after the main shocks. Our findings imply that Ionospheric TEC measurement using the existing ground receiver networks could be used in an early warning system for near-field tsunamis that take more than 20 minutes to arrive in coastal areas.

Highlights

The intensity of southward propagation of the TEC disturbance was clearly visible in the northern hemisphere, while that of northward propagation was not clearly observed, because the asymmetrical intensity of northward and southward propagation is caused by the different plasma motion forced to the direction of magnetic field lines[11]
For the Tohoku EQ, the TEC disturbance began above the tsunami source area and the TEC disturbance originating from acoustic waves subsequently propagated radially
We investigate large EQs with accompanying tsunamis in Japan and Chile because the dense and intermediate-dense networks of global positioning system (GPS) receiving stations enables us to obtain TEC data above the tsunami source area in magnetic latitudes ranging from 20°N to 35°N in Japan and from 20°S to 35°S in Chile, and the inclination of the magnetic field can be regarded as approximately constant

Summary

Introduction

The intensity of southward (northward) propagation of the TEC disturbance was clearly visible in the northern (southern) hemisphere, while that of northward (southward) propagation was not clearly observed, because the asymmetrical intensity of northward and southward propagation is caused by the different plasma motion forced to the direction of magnetic field lines[11]. In addition to the origin of these disturbances, a TEC depression with a radius of a few hundred kilometres, which remained stationary for approximately 1 hour, was observed[14] This was termed as the tsunami ionospheric hole (TIH). In the decompression phase of the acoustic waves, the downward plasma caused dissociative recombination and suppressed ion production, creating a TEC depression, i.e. TIH. Astafyeva et al.[15] reported a correlation between initial tsunami height and initial TEC enhancement amplitude, and between initial tsunami height and TIH duration for 11 large global EQs. the quantitative relationship between the initial tsunami height and amplitude of the TEC disturbance immediately above the tsunami source area is required to assess the possibility of using GPS-TEC ionospheric monitoring for a practical early warning system. We discuss the possibility of constructing an early warning system using only the existing GPS network

Methods

Results

Conclusion