Rupture speed dependence on initial stress profiles: Insights from glacier and laboratory stick-slip

Slow slip events are now well-established in fault and glacier systems, though the processes controlling slow rupture remain poorly understood. The Whillans Ice Plain provides a window into these processes through bi-daily stick-slip seismic events that displace an ice mass over 100 km long with a variety of rupture speeds observed at a single location. We compare the glacier events with laboratory experiments that have analogous loading conditions. Both systems exhibit average rupture velocities that increase systematically with the pre-rupture stresses, with local rupture velocities exhibiting large variability that correlates well with local interfacial stresses. The slip events in both cases are not time-predictable, but clearly slip-predictable. Local pre-stress may control rupture behavior in a range of frictional failure events, including earthquakes.