Ice Stream C, Antarctica, sticky spots detected by microearthquake monitoring

Microearthquakes at the base of slow-moving Ice Stream C occur many times more frequently than at the base of fast-moving Ice Stream B. We suggest that the microearthquake source sites are so-called "sticky spots', defined as limited zones of stronger subglacial material interspersed within a weaker matrix. The fault-plane area of the microearthquakes (O(10²m²)) is therefore a measure of the size of the sticky spots. The spatial density of the microearthquakes (O(10km^-2)) is a measure of the distribution of sticky spots. The average stress drop associated with these microearthquakes is consistent with an ice-stream bed model of weak subglacial till interspersed with stronger zones that support much or all of the basal shear stress. -from Authors