Spatiotemporal evolution of tremors. (a) Map view of tremor epicentres with colours corresponding to days of the study period. The grey line represents the trench. (b) Temporal evolution of tremors projected along the X–Y profile [red line in (a)]. The colour notation corresponds to that in (a). The orange inclined lines delineate trench-parallel migration of tremors. Note that only the first 50 d are shown because this study detected few tremors after this period.