Comparison of the velocity spectrum between ordinary earthquake, tectonic tremor and noise. (a) Synthetic velocity power spectrum of the omega-square model (Brune ). Arrows show the corner frequency, corresponding to the peak of spectra. (b) Comparison of velocity power spectra between an ordinary intra-slab earthquake and a distant earthquake at station TUVZ (Figure 2a). (c) Comparison of velocity power spectra between an ordinary intra-slab earthquake and two examples of tectonic tremors, all of which occurred with similar epicenter. Black arrow represents the peak of spectrum (approximate corner frequency) of the ordinary earthquake. Orange arrow represents the peak of tectonic tremor spectrum. Date, time, and location of events: ordinary earthquake for (b) and (c): May. 2, 2009, 52,230 to 52,270 s (39.46°S, 175.83°E, 54 km in GeoNet catalog); distant earthquake for (b): Sep. 8, 2010, 42,130 to 42,160 s (20.52°S, 170.06°N, 14.1 km in Global CMT catalog; Dziewonski et al. ; Ekström et al. ); tectonic tremor 1 for (c): Jan. 24, 2009, 53,350 to 53,450 s (39.36°S, 175.93°E, 23.9 km in this study); tectonic tremor 2 for (c): May. 12, 2009, 26,200 to 26,300 s (39.39°S, 176.00°E, 33.4 km in this study).