Ice Stream Slip Triggered by Distant Earthquakes

Abstract:

Large distant earthquakes sometimes trigger tectonic earthquakes, tectonic and volcanic tremor, and other geological phenomena. Triggering is widely believed to occur in systems close to failure, and many recent studies have shown that ice sheets can be modulated by subtle stress perturbations from distant earthquakes, though, interaction between tectonic and cryospheric events is difficult to document, in part due to the paucity of polar observations. The exceptional existence of multi-year GPS measurements at the Whillans Ice Plain allows us to determine whether the quasi-regular stick-slip events were expedited by passing seismic waves from distant large earthquakes. We find evidence for triggering that is manifested as events that occur shortly after the arrival of surface waves from 4 significant earthquakes, including the 2010 magnitude 8.8 Maule and 2011 magnitude 9.1 Tohoku-Oki earthquakes. Triggering, in our observed cases, occurs during passage of surface waves with a threshold of ~2 kPa dynamic stress and with sensitivity to the time passed since the previous slip event (recharge time). Investigating triggering may lead to better understanding of frictional failure processes on glacial basal interfaces and on other natural faults in general.