Topographic Change of the Summit Crater of the Asama

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    Topographic Change of the Summit Crater of the Asama Volcano during ,**. Eruption
      Derived from Repeated Airborne Synthetic Aperture Radar (SAR) Measurements

                         Shoichi OKI , Makoto MURAKAMI                 , Nobuyuki WATANABE           ,
                                    Bokuro URABE             and Masanori MIYAWAKI

         The Asama volcano (elevation ,/02 m), central Japan, erupted on September +, ,**.. Since then thick
    volcanic fumes prevented monitoring of the topography on the summit crater floor by standard optical methods.
    To detect geomorphic changes of the volcano, Airborne Synthetic Aperture Radar (AirSAR) measurements
    including interferometry were repeatedly carried out on September +0, October ,,, December +/, ,**. and March
    +*, ,**/. The comparison of AirSAR result in September with a digital elevation model (DEM) by laser
    profiling measurements in October ,**- revealed that a pancake shape lava mound (volume *.3 +*0 m-) was
    formed on the floor. The subsequent AirSAR measurement on October ,, indicated that the pancake shape
    mound had disappeared and a small pit hole was formed. The volume of ejecta amounted to ,.+ +*0 m-. The
    AirSAR results in December ,**. and March ,**/ suggested that the shape of the crater floor stayed generally
    unchanged during that time window. From these, we infer that lava extrusion during the ,**. Asama eruption
    occurred within a short period around September and October.
    Key words : Asama volcano, SAR, DEM, topography, volume of lava


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      +** 23+2 QQQQQQQ                 , + -                             Topographic Department, The Geographical Survey
    QQQQQQQ             QQQQ                                             Institute, +-Kitasato, Tsukuba, Ibaraki -*/ *2++,
    Engineering A#airs Division, Minister’s Secretariat,                 Japan.
    Ministry of Land, Infrastructure and Transport, ,                      +2- 2/*+ QQQ QQ QQ + +*
    + - Kasumigaseki, Chiyoda, Tokyo +** 23+2, Japan.                         Q QQ Q                            QQ
      -*/ *2++    QQ          Q Q+                                       QQ
    QQQ        Q Q           QQ                                          NEC Aerospace Systems, Ltd., Defense and Aero-
    Geography and Geodynamics Research Center, The                       nautic Systems Division, +st Engineering Department,
    Geographical Survey Institute, + Kitasato, Tsukuba,                  + +* Nisshin-cho, Fuchu, Tokyo +2- 2/*+, Japan.
    Ibaraki -*/ *2++, Japan.
      -*/ *2++    QQ         Q Q+                                        Corresponding author : Makoto Murakami
    QQQ        QQ                                                        e-mail : mccopy@gsi.go.jp