Fast and slow earthquakes emerge due to fault geometrical complexity

TL;DR

This paper demonstrates that simple fault geometrical complexity can produce both slow slip events and fast earthquakes, providing insights into their physical mechanisms and scaling relationships.

Contribution

The study introduces a minimal fault model with geometrical complexity that explains the emergence of both slow and fast earthquakes without complex rheologies.

Findings

Simple geometrical fault complexity can generate SSEs and earthquakes.

The model reproduces observed scaling relationships of slip events.

Physical paradoxes between observations and models are addressed.

Abstract

Active faults release elastic strain energy via a whole continuum of modes of slip, ranging from devastating earthquakes to Slow Slip Events and persistent creep. Understanding the mechanisms controlling the occurrence of rapid, dynamic slip radiating seismic waves (i.e. earthquakes) or slow, silent slip (i.e. SSEs) is a fundamental point in the estimation of seismic hazard along subduction zones. On top of showing slower rupture propagation velocity than earthquakes, SSEs exhibit different scaling relationships, which could reflect either different physical mechanisms or an intriguing lack of observations. Like earthquakes, SSEs are bound to occur along unstable portions of active faults, raising the question of the physical control of the mode of slip (seismic or aseismic) along these sections. Here, we use the numerical implementation of a simple rate-weakening fault model to explain the spontaneous occurrence, the characteristics and the scaling relationship of SSEs and earthquakes. We show that the simplest of fault geometrical complexities with uniform friction properties can reproduce slow and fast earthquakes without appealing to complex rheologies or mechanisms. Our model helps resolve many of the existing paradoxes between observations and physical models of earthquakes and SSEs.