Correlations between Earthquake Properties and Characteristics of Possible ULF Geomagnetic Precursor over Multiple Earthquakes

Khairul Adib Yusof,Suaidi Ahadi,Mardina Abdullah,Nurul Shazana Abdul Hamid,Akimasa Yoshikawa

doi:10.3390/universe7010020

Abstract

In this study, we improved and adapted existing signal processing methods on vast geomagnetic field data to investigate the correlations between various earthquake properties and characteristics of possible geomagnetic precursors. The data from 10 magnetometer stations were utilized to detect precursory ultra-low frequency emission and estimate the source direction for 34 earthquakes occurring between the year 2007–2016 in Southeast Asia, East Asia, and South America regions. As a result, possible precursors of 20 earthquakes were identified (58.82% detection rate). Weak correlations were obtained when all precursors were considered. However, statistically significant and strong linear correlations (r ≥ 0.60, p < 0.05) were found when the precursors from two closely located stations in Japan (Onagawa (ONW) and Tohno (TNO)) were exclusively investigated. For these stations, it was found that the lead time of the precursor is strongly (or very strongly) correlated with the earthquake magnitude, the local seismicity index, and the hypocentral depth. In addition, the error percentage of the estimated direction showed a strong correlation with the hypocentral depth. It is concluded that, when the study area is restricted to a specific location, the earthquake properties are more likely to have correlations with several characteristics of the possible precursors.

Highlights

A useful earthquake prediction must comprise three elements: (i) precursor detection,(ii) estimation of epicenter location, and (iii) determination of earthquake properties
It is to be noted that some data gaps existed during the period of observation for several earthquakes; these gaps are shown by disconnections of line, for example on 17th January 2012
This observation aligns with the premise of the polarization ratio analysis (PRA) method which assumes that seismo-EM emission is more dominant in the vertical component

Summary

Introduction

A useful earthquake prediction must comprise three elements: (i) precursor detection,(ii) estimation of epicenter location, and (iii) determination of earthquake properties (e.g., hypocentral depth, epicentral distance, and magnitude). One of the most popular approaches is by studying anomalous lowfrequency seismo-electromagnetic (seismo-EM) phenomena, i.e., direct lithospheric [1,2], seismo-ionospheric and seismo-atmospheric emissions [3]. In these phenomena, preearthquake seismo-EM emission is assumed to either directly or indirectly originate from the epicenter and is generated by one of these suggested mechanisms: (i) microfracture electrification [4], (ii) electrokinetic effect [5], (iii) electric current induction due to conductivity variation [6], and (iv) piezomagnetic effect [7]. This observation was reported by prior studies [14,15,16]

Methods

Results

Conclusion