Natural Time Analysis of Global Navigation Satellite System Surface Deformation: The Case of the 2016 Kumamoto Earthquakes.

Shih-Sian Yang,Sudipta Sasmal,Stelios M Potirakis,Masashi Hayakawa

doi:10.3390/e22060674

Abstract

In order to have further evidence of the atmospheric oscillation channel of the lithosphere-atmosphere-ionosphere coupling (LAIC), we have studied criticality in global navigation satellite system (GNSS) surface deformation as a possible agent for exciting atmospheric gravity waves (AGWs) in the atmosphere and GNSS fluctuations in the frequency range of AGWs with the use of the natural time (NT) method. The target earthquake (EQ) is the 2016 Kumamoto EQ with its main shock on 15 April 2016 (M = 7.3, universal time). As the result of the application of the NT method to GNSS data, we found that for the one-day sampled GNSS deformation data and its fluctuations in two AGW bands of 20–100 and 100–300 min, we could detect a criticality in the period of 1–14 April, which was one day to two weeks before the EQ. These dates of criticalities are likely to overlap with the time periods of previous results on clear AGW activity in the stratosphere and on the lower ionospheric perturbation. Hence, we suggest that the surface deformation could be a possible candidate for exciting those AGWs in the stratosphere, leading to the lower ionospheric perturbation, which lends further support to the AGW hypothesis of the LAIC process.

Highlights

To successfully predict the occurrence of a major earthquake (EQ) is an issue of mutual concern for human beings, since an EQ is one of the disastrous hazards that we have not been able to prevent for a long time
The aim of this paper is to detect the occurrence of criticality in the lithosphere before the 2016 Kumamoto EQs, which could possibly be connected with our previous findings in the lower ionosphere [23] and stratosphere [24], as further support for the atmospheric gravity waves (AGWs)
The results of the height time series seem to be enough to support our argument of surface deformation on AGW excitation, we investigated the approach to criticality of the other three deformation components and the results are discussed here

Summary

Introduction

To successfully predict the occurrence of a major earthquake (EQ) is an issue of mutual concern for human beings, since an EQ is one of the disastrous hazards that we have not been able to prevent for a long time. It has recently been agreed that precursory phenomena exist around the ground surface and in the lithosphere deservedly. Several kinds of EQ precursors have been found far above the ground surface (e.g., [1,2]). The most important precursor is the perturbations in the ionosphere several days to 1–2 weeks before a forthcoming EQ. The ionospheric perturbations mainly appear in two ways. The other way is the fluctuations in the bottom ionosphere observed using very low-frequency (VLF) and low-frequency (LF) radio wave techniques.

Objectives

Findings

Discussion

Conclusion