Figure 9
A model showing the raypath between source and station (Minakami et al.1970). H1, elevation at the caldera margin; H2, station elevation; S1 + S2, distance along the Earth's surface to the station; h1, caldera depth; h2, hypocentral depth measured from the caldera floor; a, radius of the spherical hypocenter domain (in this paper, a = 0, h2 = 0, under the assumption that the infrasonic signal is excited at the floor of the caldera); r, horizontal distance from the caldera margin to the source; Δ, epicentral or horizontal distance from the hypocentral domain to the station. The corrected distance S1 + S2 − R is calculated for each station.