Weak phases production and heat generation control fault friction during seismic slip

The triggering and magnitude of earthquakes is determined by the friction evolution along faults. Experimental results have revealed a drastic decrease of the friction coefficient for velocities close to the maximum seismic one, independently of the material studied. Due to the extreme loading conditions during seismic slip, many competing physical phenomena occur (like mineral decomposition, nanoparticle lubrication, melting among others) that are typically thermal in origin and are changing the nature of the material. Here we show that a large set of experimental data for different rocks can be described by such thermally-activated mechanisms, combined with the production of weak phases. By taking into account the energy balance of all processes during fault movement, we present a framework that reconciles the data, and is capable of explaining the frictional behavior of faults, across the full range of slip velocities (10(-9) to 10 m/s). Decrease of friction during seismic slip is linked to temperature increase and weak phases production inside the fault core. Here the authors propose a mathematical framework which explains the frictional behaviour of all materials reported in literature and precisely captures material weakening during fault slip.