Glacial Earthquakes



Glacial earthquakes are earthquakes of (surface-wave) magnitude ~ 5 that occur in glaciated regions (primarily Greenland). They were first detected in 2003. Since the initial detections, we have characterized them in much more detail. In particular, we now know that glacial earthquakes are intimately related to ice motion. They occur only in regions with very high ice flow speeds (in excess of a few km/year); the mechanisms are consistent with acceleration of massive chunks of ice in the downstream direction; and they occur more often during the summer months, when the most melt is generated.

Plotted at right (red dots) are the locations of the Greenland glacial earthquakes that occurred between 1993 and 2005. The background colors denote the balance velocity field (from Bamber et al. 2001) in m/yr. Note that the events occur only in regions where the ice speed is greater than 1 km/yr.

Update: We now think we understand the physical process relatively well. Very large icebergs likely calve off into the fjord and push against the glacier face, creating a large force that is transmitted to the solid Earth. See plots below for schematics of this, and see publications section for more details.