Fig. 4

(a) Stacked cross-correlation functions of different tremor events. (b) Cross-correlation coefficients of intra-slab earthquakes shown in Fig. 1(b). (c) Relations between S-P time and the source depth calculated using the 1D velocity structure (Table 1) for different epicentral distances. The distributions of tremor events and intra-slab earthquakes are shown by pink and blue crosses, respectively, with error bars calculated as the half-value width of cross-correlation functions for tremors, and visual reading errors for intra-slab earthquakes.