Chaotic Slow Slip Events in New Zealand from two coupled slip patches: a proof of concept

TL;DR

This paper presents a physics-based coupled oscillator model that reproduces chaotic slow slip events in New Zealand's Hikurangi subduction zone, demonstrating the influence of shear zone response on SSE behavior.

Contribution

It introduces a novel coupled oscillator model capturing chaotic SSEs, highlighting the role of shear zone physics in slip event variability.

Findings

Model reproduces chaotic SSE patterns observed in Gisborne

Shear zone response significantly influences SSE behavior

Simplified physics-based approach offers predictive insights

Abstract

Recent studies showed that seemingly random Slow Slip Events (SSEs) can display chaotic patterns within the largest source of seismic hazards in New Zealand, the Hikurangi subduction zone. Some irregular SSE occurrences are therefore not arbitrary but behave with short-term predictability. However, the forecasting challenge persists as observations remain too short and noisy to constrain purely data-driven solutions, calling for a physics-based modelling approach. Here we propose a physical model of two coupled oscillators, each capturing the behaviour of a single slow-slip patch, for the deep Kaimanawa and the shallow East Coast SSEs respectively. The simplified model successfully reproduces the type of chaotic behaviour observed at the Global Navigational Satellite System station in Gisborne, yielding SSEs of appropriately varying amplitude and duration. Those results reveal that the multi-physics response of the shear zone strongly controls the underlying system, even before accounting for any geometrical complexity or distribution of material properties.