Aseismic slow slip on an inland active fault triggered by a nearby shallow event, the 2008 Iwate-Miyagi Nairiku earthquake (Mw6.8)

Using GPS observations, we have detected an aseismic slip event on the intraplate Dedana Fault that was triggered by the Iwate-Miyagi Nairiku earthquake (Mw6.8, 13 Jun 2008 UTC) on a nearby but separate fault. The observations cannot be satisfactorily explained in terms of either viscoelastic relaxation or poroelastic rebound, and we cannot explain the observed displacement time series without presuming that aseismic slip occurred on the Dedana Fault. This slip was likely triggered by the mainshock stress change. The detection of future such aseismic slip events on intraplate faults is likely to require denser geodetic networks than are currently in operation, but is important for fully characterizing the seismic hazard associated with intraplate earthquakes.