Unexpected departure from seismic laws with largest labquakes on model granular materials

Abstract

In an effort to understand the most devastating natural earthquakes, we present a series of largest laboratory quakes on model granular materials under triaxial compression in fully drained and quasi-static shearing conditions. These largest labquakes can lead to a complete loss of normal and tangential stresses and even a destruction of the granular structure. The repeated spontaneous stick–slip frictional failures under uncontrolled triggering stress reproduce the traditional statistical seismic relations (Gutenberg–Richter, Omori–Utsu, inter-event times and productivity) with unexpected deviations created by biggest detected stick–slip motions in laboratory. A surprising long quiescent period results from these lab-quakes, contrasting the presence of numerous aftershocks following the majority of natural earthquakes. We also identify the appearance conditions of these unexpected granular instabilities. This work would have practical implications in improving qualitatively our understanding of the potentially highest magnitude earthquakes.