Figure 2

Examples of slant stack vespagrams for selected events. (Top) EV9 (Table 1) recorded at the Hi-net. Seismograms are phase-weight stacked with n=1 (Schimmel and Paulssen [1997]), and the color shows the stacked intensity (the strongest signals are red). The horizontal axis is the delay time (Δ t) in seconds after the first peak of the direct P wave. The vertical axis is the slowness relative to the direct P wave (Δ p) in seconds per degree. Arrival of the X phase (s-to-P reflected wave at horizontal interface above the foci) is seen near 8 s after P (s641P, Table 1). The predictions of s-to-P based on ak135 are marked with blue dots for every 5 km of interface depth. The stack outputs between 3 to 10.5 s after P are magnified 20 times, while those after 10.5 s are magnified 40 times. (Bottom) Same as the top panel, for EV8, showing the arrival of s639P (Table 1). The outputs after 4.5 s after P are magnified 30 times.