Synchronization of megathrust earthquakes to periodic slow slip events in a single-degree-of-freedom spring-slider model

Makiko Ohtani,Masao Nakatani,Nobuki Kame

doi:10.1038/s41598-019-44684-4

Abstract

Recently recognized slow slip events (SSEs) recurring in the deeper extensions of seismogenic zones along plate boundaries are drawing attention to their potential for triggering megathrust earthquakes that rupture the entire seismogenic zone. We describe how earthquakes simulated in a single-degree-of-freedom model are synchronized to the rhythm of imposed periodic SSEs. The time lag tQ from the one most recent SSE to a seismic event varies with system parameters and may take a broad range of eligible values between 0 and TSSE (SSE recurrence period). Earthquakes were found to synchronize with SSEs in various patterns depending on the proportion of SSE-driven loading within an SSE cycle, the recurrence period of the SSEs, and the duration of the SSEs, although synchronization itself remained a prevalent feature. Asynchrony was found only for long SSE durations.

Highlights

Global Navigation Satellite System (GNSS) networks, being deployed recently, have revealed the presence of slow slip events (SSEs) in the deeper extensions of seismogenic zones[1,2,3,4]
We conduct a quantitative study of dependence of the system behavior on the proportion r of the loading driven by SSEs within an SSE cycle, their recurrence period TSSE and their duration dSSE
The Vload is set at rVplTSSE/dSSE when an SSE is going on and at (1 − r)VplTSSE/(TSSE − dSSE) during the rest of the time so the long-term pulling velocity remains at Vpl, where Vpl = 5 cm/yr and r = 0–1

Summary

Introduction

Global Navigation Satellite System (GNSS) networks, being deployed recently, have revealed the presence of slow slip events (SSEs) in the deeper extensions of seismogenic zones[1,2,3,4]. In the Guerrero region of Mexico, where SSEs recur every 3–4 years, an earthquake occurred in an area adjacent to the location of an ongoing SSE in 2014 (Papanoa earthquake) It is believed the seismic event was triggered by the SSE10. A variety of models have so far been used to study how an earthquake fault responds to stress perturbations from nearby events[11,12,13] Those models used the steady increase of fault stress to represent tectonic loading, and a stress perturbation was imposed at an arbitrary magnitude and timing. These studies consider only one-time stress perturbation event, so the impact of the history of SSEs recurring throughout a seismic cycle cannot be evaluated. Synchronization occurred even by the repetition of very small SSEs, and we could not reach a physiological understanding such as a characteristic www.nature.com/scientificreports/

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Conclusion