GPS観測による2000年7月14日三宅島火山噴火に伴う地殻変動

概要

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Based on GPS data at adjacent 15 stations, a process of the 2000 eruption at Miyakejima volcano is analyzed for the period before the first phreatic eruption on July 14. Consequently the following results are obtained: 1) Deflation was remarkable up to around a caldera collapse with a small eruption on July 8. The observed data are explained by a deflation source of -1.2×10^8m^3 in volume, which was located 3km south west of the center of the summit (i.e, the formerly highest peak of Oyama) at 6km in depth. The location was close to the first deflation source detected by the kinematic GPS data on June 27, suggesting that the deflation started on June 27 at around 6km in depth (Meilano et al., 2003). 2) After then the volcano inflated slightly at a shallower depth, and resulted in a phreatic eruption on July 14. In this period, however, the deflation at 6km in depth is assumed to have continued with a rate suggested by an exponential curve fitted to the data during June 29 and July 8. The inflation during July 8 and 12 was considered to be 1.3×10^7m^3 in volume, which was located 2km south-southwest of the center of the summit at 3.5km in depth. The shallow inflation source was just below the source of low frequency tremors (Kikuchi et al., 2001). It suggests a close correlation between the inflation source and occurrence of the tremors.
特定非営利活動法人日本火山学会の論文
2005-06-30