Fig. 3
The data recorded at the OSA array (upper panel) for the 1993/12/10 MJMA = 7.1 event. The aperture of the array is approximately 400 m (see Table 1 and Fig. 1). The data are band passed between 0.2 and 0.38 Hz for the semblance analysis (Hatayama et al. 1995). The lower panel shows semblance analysis of time dependence of the apparent slowness vector inferred from the horizontal ground motion for times between 29 and 38 s after the S-wave arrival. For each time point, the stick length means wave propagation slowness, its direction shows the prevailing wave propagation direction in the horizontal plane, and the number corresponds to the propagation velocity. The horizontal axis in both panels is time after the incident S-wave arrival, thick horizontal line in both panels depicts the presence of low-velocity wave, presumably the SL1. The lowest panel is resulting semblance analysis for the same data by Hatayama et al. (1995) showing slowness and polarization directions, see Ibid for further analysis of the data. This experiment serves as a consistency test for the implementation of the semblance technique