The mechanisms of spatial and temporal earthquake clustering

TL;DR

This paper introduces a modified spring-block model with structural relaxation that successfully reproduces realistic spatial and temporal earthquake clustering, providing a microscopic basis for rate-and-state friction laws.

Contribution

It demonstrates that adding a structural relaxation mechanism to spring-block models captures earthquake clustering without needing velocity weakening friction laws.

Findings

Realistic earthquake patterns emerge with the relaxational mechanism.

The model reproduces clustering features not seen in traditional models.

Provides a microscopic basis for rate-and-state friction equations.

Abstract

The number of earthquakes as a function of magnitude decays as a power law. This trend is usually justified using spring-block models, where slips with the appropriate global statistics have been numerically observed. However, prominent spatial and temporal clustering features of earthquakes are not reproduced by this kind of modeling. We show that when a spring-block model is complemented with a mechanism allowing for structural relaxation, realistic earthquake patterns are obtained. The proposed model does not need to include a phenomenological velocity weakening friction law, as traditional spring-block models do, since this behavior is effectively induced by the relaxational mechanism as well. In this way, the model provides also a simple microscopic basis for the widely used phenomenological rate-and-state equations of rock friction.