UNZEN VOLCANO, Western Kyushu (June 1, 1996) Slow deformation of
lava dome after the halt of magma supply was monitored
successfully with GPS and EDM analyses by the Shimabara
Earthquake and Volcano Observatory (SEVO), Kyushu University.
The deformation shows the tendency that endogenous dome is
flattening: the maximum subsidence and lateral movement during
this one year are about 1.5 m and 1 m, respectively; the
averages are 0.5 and 0.4 m, respectively. The temperature
measurement of fumarolic gas at the top of the dome by SEVO
showed that gas had cooled from 500-700 deg. C to 300-500 deg. C
during this one year. Several small block-and-ash flows occurred
on 10, 12 and 13 February 1996, leaving one-year quiescence,
though magma supply had stopped since February 1995. According
to the Shimabara Earthquake and Volcano Observatory (SEVO),
Kyushu University, these flows descended to SE, traveling about
1.0 km from the source; surge-like (ash-dominated) deposits were
associated with the flows. These deposits were