Search for Direct Stress Correlation Signatures of the Critical Earthquake Model

TL;DR

This study tests the critical earthquake model by analyzing stress correlation signatures before large quakes, using a physically-based stress accumulation approach, but finds no clear acceleration or correlation length increase.

Contribution

It introduces a new physically-based stress accumulation function using a visco-elastic Green function to analyze earthquake precursors and stress correlations.

Findings

No observed acceleration in cumulative stress before main shocks.

No increase in stress correlation length as predicted by the model.

Suggests earthquakes may reflect tectonic organization rather than stress buildup.

Abstract

We propose a new test of the critical earthquake model based on the hypothesis that precursory earthquakes are ``actors'' that create fluctuations in the stress field which exhibit an increasing correlation length as the critical large event becomes imminent. Our approach constitutes an attempt to build a more physically-based cumulative function in the spirit of but improving on the cumulative Benioff strain used in previous works documenting the phenomenon of accelerated seismicity. Using a space and time dependent visco-elastic Green function in a two-layer model of the Earth lithosphere, we compute the spatio-temporal stress fluctuations induced by every earthquake precursor and estimate, through an appropriate wavelet transform, the contribution of each event to the correlation properties of the stress field around the location of the main shock at different scales. Our physically-based definition of the cumulative stress function adding up the contribution of stress loads by all earthquakes preceding a main shock seems to be unable to reproduce an acceleration of the cumulative stress nor an increase of the stress correlation length similar to those observed previously for the cumulative Benioff strain. Either earthquakes are ``witnesses'' of large scale tectonic organization and/or the triggering Green function requires much more than just visco-elastic stress transfers.