Figure 2

Locations of detected tremors and example waveforms. (a) The close-up map for tremor region with detected tremor candidate signals (gray dots) and signals we regard as tremors (red dots). Blue dots represent the epicenters of intra-slab earthquakes located both by this study and by GeoNet. Plate contours (green lines, Ansell and Bannister [1996]) and SSE distributions (green regions, Wallace and Beavan [2010]) are also shown. Crosses represent the station distribution. The locations of stations whose names are indicated are represented by thicker crosses. Two cross sections show the depth distribution of tremors and intra-slab earthquakes projected to vertical and horizontal axis. In the right bottom panel, timing of tremor events in box T is shown against TT′ axis. Green background represents the SSE period (Wallace and Beavan [2010]; Wallace et al. [2012]; Wallace and Eberhart-Phillips [2013]). Tremor candidates in box V are considered to be volcanic ones. (b) Representative (typical) tectonic tremor waveforms detected in this study. East–west components are shown. The station location is shown in Figure 2a (date: Jan. 24, 2009, 54,800 to 55,600 s).