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Identifying the approach of a major earthquake

Panayiotis A. Varotsos, Nicholas V. Sarlis, Toshiyasu Nagao

TL;DR

The paper investigates identifying approaching major earthquakes by analyzing seismicity in natural time and its fluctuations under time reversal, introducing the precursor metric $\Lambda_i$ computed at scales $i = 2000, 3000, 4000$ events. The method relies on the entropy in natural time $S$ and its reverse $S_-$, with $ΔS = S - S_-$ and precursor signal $Λ_i = σ(ΔS_i)/σ(ΔS_{100})$, showing that a minimum in $ΔS$ coupled with rising $Λ_i$ can indicate an impending large event. In the 2011 Tohoku case, scale overlap between $i=4000$ and $i=3000$ began around mid-2008, and $Λ_i$ followed a Lifshitz–Slyozov–Wagner scaling $A (t - t_0)^{1/3}$ with $A \propto i$, yielding an approximate three-year lead time to the $M = 9$ quake. The 2024 Noto event exhibits a shorter lead time, with overlap from late 2022 to mid-2023, suggesting variability in precursory timing; overall, the results indicate potential for $Λ_i$-based precursors but require further validation with ongoing seismic data.

Abstract

By analyzing the seismicity in natural time and studying the evolution of the fluctuations of the entropy change of seismicity under time reversal for various scales of different length i (number of events), we can identify the approach of a major earthquake (EQ) occurrence. The current investigation is extended from 1984 until now for the seismicity in Japan.

Identifying the approach of a major earthquake

TL;DR

The paper investigates identifying approaching major earthquakes by analyzing seismicity in natural time and its fluctuations under time reversal, introducing the precursor metric computed at scales events. The method relies on the entropy in natural time and its reverse , with and precursor signal , showing that a minimum in coupled with rising can indicate an impending large event. In the 2011 Tohoku case, scale overlap between and began around mid-2008, and followed a Lifshitz–Slyozov–Wagner scaling with , yielding an approximate three-year lead time to the quake. The 2024 Noto event exhibits a shorter lead time, with overlap from late 2022 to mid-2023, suggesting variability in precursory timing; overall, the results indicate potential for -based precursors but require further validation with ongoing seismic data.

Abstract

By analyzing the seismicity in natural time and studying the evolution of the fluctuations of the entropy change of seismicity under time reversal for various scales of different length i (number of events), we can identify the approach of a major earthquake (EQ) occurrence. The current investigation is extended from 1984 until now for the seismicity in Japan.
Paper Structure (4 sections, 3 equations, 3 figures)

This paper contains 4 sections, 3 equations, 3 figures.

Table of Contents

  1. Introduction
  2. The $M$9 Tohoku EQ on 11 March 2011
  3. The $M$7.6 Noto EQ on 1 January 2024
  4. Main conclusion

Figures (3)

  • Figure 1: The complexity measure $\Lambda_i$ versus the conventional time for the scales $i$ = 2000 (red), 3000 (blue) and 4000 (green) events since 1 January 1984 until the $M$9 Tohoku EQ on 11 March 2011 for appropriate vertical scales in each panel. The black solid circles show the magnitudes ($M \geq7$) of EQs, which are read in the right scale. Taken from Ref. ENTROPY18. In panel (d), the scale 3000 events exhibits a maximum in the range from 1 July 2002 to 1 January 2003 while the other two scales 2000 and 4000 events gradually decrease. Some months later, i.e., on 26 September 2003 the Tokachi-Oki EQ of magnitude $M$8.0 occurred.
  • Figure 2: The measure $\Lambda_i$ versus the conventional time for the scales $i=$2000 (red), 3000 (blue), and 4000 (green) events from 1 July 2008 until 10 April 2025.
  • Figure 3: The measure $\Lambda_i$ versus the conventional time for the scales $i=$2000 (red), 3000 (blue), and 4000 (green) events from 1 January 2025 until 20 December 2025.