High Rates of Deep Earthquake Dynamic Triggering in the Thermal Halos of Subducting Slabs

Observations of remote dynamic triggering of intermediate and deep (I&D) earthquakes can potentially clarify the faulting process but have not been systematically compiled. We relocate earthquakes following the two largest recent deep earthquakes with a multiple-event location algorithm and compile a comprehensive catalog of dynamically triggered I&D earthquakes from 1964 to 2015. We find 119 large I&D earthquakes that likely dynamically triggered aftershocks at distances between two mainshock fault lengths and 400 km during the first 4 days following these mainshocks. Dynamic triggering is more common for deep than for intermediate depth earthquakes and is overrepresented in areas with low seismicity that are adjacent to slabs, which suggest that subducting slabs in the transition zone are surrounded by material that is critically stressed but warm enough to inhibit rupture initiation. The passage of seismic waves may initiate runaway ductile shear failure, which nucleates over a period of minutes to days.