| 氏名 |
岩下 里詩 |
| 論文題目 |
ＧＰＳによる北海道駒ケ岳の地殻変動
Crustal Deformation around Komagatake Volcano in Hokkaido detected by GPS |
| 論文要旨 |
Komagatake in southwestern Hokkaido is one of
the most active volcanoes in Japan. After 54 years volcanic rest since
the 1942 event, a small phreatic eruption occurred on March 5 th, 1996
and on October 25 th, 1998. Those eruptions were followed by other 4 phreatic
ones in 2000. These activities imply the increasing magma accumulation and
possible magmatic eruption in near future. In this study, I established a
GPS monitoring network estimated the deformation source to investigate
the characteristics associated with the volcanic activity.
It was difficult to operate continuous GPS observations in around the
volcano due to luck of electric power and the severe winter conditions
(5-7m snow).To overcome these problems and make it possible to operate
continuous GPS observation around the summit of the mountain, we installed
low-power-consumption single frequency receivers connected to solar power.
To correct the ionosphere-induced error on single frequency data,
I applied the estimated ionospheric model by dual frequency data to analyze
the single frequency data. I found this capable of eliminating the seasonal
variation and estimate the baseline vectors with high accuracy.
The calculated deformation pattern clearly shows inflation of the volcano.
The deformation source was calculated assuming the point source model.
Estimated pressure source by grid-search procedure is located at the 2.
4km depth beneath the main crater with 486000[m3/yr] volume change.
The results are good agreement with other independent observation result.
The most probable implication is that the inflation due to magma accumulation
has increased almost constantly during the observation.
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