Creep events slip less than ordinary earthquakes

We find that slow seismic events have smaller fault slips compared to ordinary earthquakes with similar dimensions. For ordinary earthquakes, the ratio of slip to fault length is largely consistent, yet the physical controls on this ratio are unknown. Recently discovered slow slip or creep events in which faults move quasi-statically over periods of days to years shed new light on this old conundrum. For example, large slow events that extend over 100 km have slips of centimeters, while ordinary earthquakes that rupture a comparable length of fault typically slip meters. The small slips of quasi-static events compared to the large slips of earthquakes show that dynamic processes significantly control the rupture growth of ordinary earthquakes. We propose a model where slip on a heterogeneous fault accounts for the difference. Inertial overshoot may result in larger final slips for earthquakes than comparable creep events.