Slip-rate-dependent friction as a universal mechanism for slow slip events

Abstract

A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events and their wide range of depths, slip rates, durations, stress drops, and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening frictional sliding at low slip rates toward rate-neutral or rate-strengthening behavior at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-dependent transition quantitatively explains experimental data for natural fault rocks representative of materials in the source regions of slow slip events. With a standard constant-parameter rate-and-state friction law, slow slip events arise only near the threshold for slip instability. The inclusion of velocity dependent friction parameters significantly broadens the range of conditions for slow slip

Slow slip events are regular earthquakes

“…Here, I test this hypothesis and realise such a continuum of rupture speeds (Figure S1A) in numerical simulations controlled by a rate-and-state friction law with rate-weakening behaviour at low slip rates and rate-strengthening behaviour at high slip rates, as observed in laboratory experiments [18][19][20][21][22][23][24][25][26][27][28] (Methods A1). The numerical simulations show that the steady rupture speed (v r /v s ) is primarily controlled by two parameters (Figure 2a): the stress drop (∆τ /σ) and the critical slip rate (V c µ/σv s ) above which the fault friction transitions from rate-weakening to rate-strengthening.…”

“…Equation 18 shows that the peak slip rate V p of steady ruptures can be uniquely determined from the energy balance condition of V-shape rate-and-state friction. I find that equation 18 well predicts the relations among V p , ∆τ , G 0 , and G c in all the simulated steady ruptures (Figure 2c…”

“…Earthquake ruptures on elongated faults can steadily propagate at speeds from slower than S-wave up to P-wave speed, depending on the balance between dissipated and potential energies 14 . SSE ruptures can also steadily propagate on elongated faults [15][16][17] , facilitated by a frictional transition from rate-weakening at slow slip rates to rate-strengthening at high slip rates that has been observed experimentally [18][19][20][21][22][23][24][25][26][27][28] . It has been reported that rupture speeds, on a continuum from SSE speeds up to earthquake speeds, is controlled by shear stress drop in laboratory experiments 21,29,30 and in a one-dimensional (1D) continuous Burridge-Knopoff model 31 , but the mechanical relationship between SSE and earthquake ruptures on elongated faults is not completely understood.…”

Melting by numbers: Assessing the effective melt fertility of crustal rocks

“…The alternating jumps in amount of fluid are similar to stick-slip motion during friction (Burridge and Knopoff, 1967), suggesting instability development dues to the contrasted rheology of the fluid in its matrix. The liberated fluids alter the local pore fluid (Dobson et al, 2002;Tarling et al, 2019), with the possibility of inducing earthquakes, and even so-called silent earthquakes (Im et al, 2020).…”

Megathrust Modeling Workshop Report

“…Their values and thus the stability of slip depends on lithology, pressure, and temperature, which provides a first-order framework for aseismic to seismic slip transition at a megathrust (e.g., Scholz, 1998;Rice et al, 2001;Saffer & Marone, 2003). Frictional dynamics also depends on the effective normal stress (e.g., Liu & Rice, 2007) and elastic properties, and the rate-state parameters may also themselves depend on slip velocity (Im et al, 2020). Of course, that dependence might be more naturally captured in alternative friction formulations, such as those based on micromechanical models (e.g., Den Hartog & Spiers, 2014;Ikari et al, 2016;Van den Ende et al, 2018).…”