HR: 0830h
AN: V51J-0413    [PDF]
TI: Was Miyakejima undergoing subsidence before the 2000 caldera collapse? JERS1 InSAR results: 1992-1998
AU: * Furuya, M
EM: furuya@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AB: Miyakejima volcano is a basaltic strato volcano island on the eastern edge of the Philippine Sea Plate, and was undergoing a number of eruption activities over the past centuries. In July-August 2000, the Miyakejima volcano underwent a caldera collapse, prompting many modern geodetic and geophysical measurements (e.g., Geshi {\it et al}. 2002; Furuya {\it et al}. 2003). The observation results on the pre-caldera-collapse stages are, however, limitted. Were there any precursory secular subsidence before the collapse? Though Miyazaki (1990) reported a secular subsidence at the Miyakejima, using leveling technique, there are no documented reports, to my knowledge, which employed radar interferometry to examine the ground displacements at Miyakejima. Here I will report on the results derived from the radar interferometry at Miyakejima volcano. I chose JERS-1 data (L-band HH) for the analysis, so that I could get rid of the loss of coherence; most of the Miyakejima is covered with vegetation. To remove the topographic fringes as well as to re-estimate the spatial baseline data (Rosen {\it et al}. 1996), I employed 10-meter resolution digital elevation map derived by Geographical Survey Institute, Japan. I could generate 24 differential interferograms at the time of writing this text. However, I do not yet recognize any significant "signals" that can be discriminated with the atmospheric "noise". There appears to be no specific subsidence pattern, which are detected in a number of other volcanos in the world (e.g., Lu {\it et al}. 2002; Yarai {\it et al}. 2002; Okuyama {\it et al}. 2002). I am going to show a stacked interferogram like that in Fujiwara {\it et al}. (1998) and to examine the existence of volcanic signals.
DE: 1294 Instruments and techniques
DE: 8100 TECTONOPHYSICS
DE: 8424 Hydrothermal systems (8135)
DE: 8434 Magma migration
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting