6-8jVolcano
Research Center
The Volcano Research Center (VRC) is
promoting a wide range of scientific research, with a view to elucidating the
elementary processes and fundamental principles of various phenomena going on
in and beneath volcanoes, and thereby forming a basis for the prediction of
volcanic eruptions. Our research subjects include the formation processes of
volcanoes, eruption mechanisms, movement of magma, and physicochemical
phenomena related to magma migration and accumulation, while our approaches
range from measurements and surveys, through theoretical and numerical
simulations, to laboratory experiments.
Fig.1 Permanent stations and hypocenter distribution at Fuji
volcano. Solid
circles show hypocenters of low-frequency earthquakes.
Fig.2 Permanent
stations and hypocenter distribution at Kusatsu-Shirane volcano. Open
circles represent hypocenters for earthquakes while others for volcanic
tremor.
Volcano observatories at Asama,
Kirishima and Izu-Oshima are permanent facilities attached to VRC, while we
also dispose permanent observation networks at Fuji, Kusatsu-Shirane and
Miyakejima. At these volcanoes, data on seismic activity (at all volcanoes),
ground deformation (at Asama, Kirishima, Izu-Oshima, Fuji and Miyakejima) and
electromagnetic phenomena (at Kirishima, Izu-Oshima, Miyakejima and Fuji) are registered on a permanent basis. In
addition to permanent measurements, we carry out special sessions of seismic,
ground deformation, gravity, geomagnetic and geothermal measurements and
volcanic ejecta surveys, according to our research subjects and the level of
volcanic activity. For the recent eruptions of Miyakejima volcano in 2000, see
5-6 Eruption of Miyakejima volcano. These observations provide basic data for
volcanological research in and out of the Earthquake Research Institute(ERI),
and they are also made full use of in the evaluation of individual volcanoes by
the Coordinating Committee for the Prediction of Volcanic Eruptions(CCPVE) and other
organs. We are also promoting joint experiments including volcanic structure
explorations and intensive observations at selected volcanoes, which are
defined as key subjects for basic research in the National Program for the
Prediction of Volcanic Eruptions.
To
achieve further progress on several problems in the basic research on the
volcanic activity and eruption prediction, we have promoted scientific drilling
projects: a 1km-deep observation well within the caldera of Izu-Oshima volcano,
the international scientific drilling project at Unzen volcano and scientific
drilling at Fuji volcano (see, 5-2 Prediction of Volcanic Eruptions).
Progress
was also made in theoretical study on the mechanisms governing magma ascent as
well as volcanic eruptions. We proposed a model of magma plumbing mechanism,
comprising an elastically responding magma chamber and a vent opening and
closing with viscosity, to account for ground deformation data obtained during
periodic recurrence of eruptions (Fig.3).
Fig.3 Observed (above) and theoretical
(below) deformations associated with cyclic magma effusions.
We
have been operating, with a view to exchanging opinions and information on
eruptions home and abroad, an electronic mailing list "funka'' consisting
of volcanologists all over the nation, and also publishing a prompt report
"Current Volcanic Eruptions in Japan'' in English in our official
homepage. This Web site is providing valuable information on Japan's volcanic
eruptions for the worldwide eruption database "Global Volcanism Network''
operated by the U.S. National Museum of Natural History, Smithsonian Institution.
Fig.4 The
1973 eruption of Asama volcano.
Fig.5 Permanent
stations and typical hypocenter distribution at Asama volcano.
Fig.6 A small eruption in 1991 at
Shinmoe-dake, Kirishima volcano.
Fig.7 Geomagnetic changes at Shinmoe-dake,
Kirishima volcano, showing underground temperature elevation.
Fig.8 Fissure eruption on November 21,
1986 at Izu-Oshima volcano.
Fig.9 Distribution of seismic-wave scattering
intensity in the east-west cross-section across the central caldera area of
Izu-Oshima volcano.
