Episodic tremor and slip on a frictional interface with critical zero weakening in elastic solid

Non-Volcanic Tremor (NVT) and related relatively weak and slow slip events termed Episodic Tremor and Slip (ETS) are observed below the seismogenic sections of numerous subduction zones and several major strike-slip faults. These events have various characteristics that distinguish them from regular tectonic earthquakes. Here we show that a frictional fault in elastic solid with a region below the seismogenic zone having on average a critical (near-)zero weakening during slip provides a simple unified explanation for the diverse observed phenomenology of NVT–ETS. The results imply that NVT–ETS have little predictive power on the occurrence of large events in the overriding seismogenic zone. Additional model predictions that may be tested with future high-resolution observations are fractal slip distributions and failure areas, discrete power-law frequency-moment statistics with exponent 3/2 and exponential tapering, overall scale-invariant potency/moment/magnitude time histories, triggered periodic NVT with evolving size and rate correlated with the stressing rate of the periodic triggering mechanisms, and parabolic (or exponential) source time functions for event sizes measured by duration (or moment/potency).