Migration properties of non‐volcanic tremor in Shikoku, southwest Japan

Abstract

Based on the precise locations of deep non‐volcanic tremor in southwest Japan, which show a depth‐dependent behavior, we clarified characteristic properties of tremor migration. Major tremor swarms are mainly initiated at deep levels of the tremor zone, corresponding to areas of frequent minor tremor, and migrate up‐dip along the subduction interface. In central and eastern Shikoku, tremor occurs in two clusters, separated by a small gap, with the timing of tremor activity in the clusters differing by 1 or 2 days. The time evolution of tremor activity in western Shikoku reveals that the migration front of tremor propagates continuously and radially, even in the case of a tremor gap. These findings indicate that the rupture front of slow slip events propagates continuously and radially from the deep levels through the area without tremor activity. The occurrence of tremor may depend on the existence of inhomogeneous patches upon the plate interface.