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Fig. 9 | Earth, Planets and Space

Fig. 9

From: Phreatic eruptions and deformation of Ioto Island (Iwo-jima), Japan, triggered by deep magma injection

Fig. 9

(Reproduced with permission from Ossaka et al. 1985)

The one-dimensional velocity structure of the S wave estimated using microtremor observation at the seismic array for 3 h from 0:00 to 3:00 on December 6 (dotted line) and 12 (broken line), 2014, and their average (solid line). The results of the analysis show that there is a low-velocity surface layer up to a depth of 100 m, a high-velocity layer of 1.2–1.3 km/s at a depth of 100–180 m, a low-velocity layer of 1.1 km/s at a depth of 180–480 m, and a high-velocity layer of 1.7 km at a depth of 480 m or more. The dark gray and light gray layers show lava and tuff layers obtained by the borehole survey of a depth of 150 m.

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