Spatiotemporal correlations of aftershock sequences

TL;DR

This paper investigates the spatiotemporal correlations in aftershock sequences from California, revealing similarities between sequences and limitations of current models in capturing small-scale seismic structures.

Contribution

It introduces the analysis of spatiotemporal correlations using the concept of recurrent events and evaluates the ETAS model's effectiveness in representing these correlations.

Findings

Sequences share similar properties

ETAS model captures large-scale correlations

Model fails at small spatial scales

Abstract

Aftershock sequences are of particular interest in seismic research since they may condition seismic activity in a given region over long time spans. While they are typically identified with periods of enhanced seismic activity after a large earthquake as characterized by the Omori law, our knowledge of the spatiotemporal correlations between events in an aftershock sequence is limited. Here, we study the spatiotemporal correlations of two aftershock sequences form California (Parkfield and Hector Mine) using the recently introduced concept of "recurrent" events. We find that both sequences have very similar properties and that most of them are captured by the space-time epidemic-type aftershock sequence (ETAS) model if one takes into account catalog incompleteness. However, the stochastic model does not capture the spatiotemporal correlations leading to the observed structure of seismicity on small spatial scales.