Topographic Change of the Summit Crater of Asama Volcano during the 2004 Eruption Derived from Airborne Synthetic Aperture Radar (SAR) Measurements

Bokuro URABE, Nobuyuki WATANABE, and Makoto MURAKAMI


An active volcano, Mt. Asama, located in the central part of the Honshu island of Japan, erupted on September 1, 2004. Since then, thick volcanic fumes have prevented monitoring of the topography on the summit crater floor by standard optical methods. To detect geomorphic changes of the volcano, GSI repeatedly carried out Airborne Synthetic Aperture Radar (AirSAR) measurements including interferometry between September 2004 and March 2005. The comparison of AirSAR results with a digital elevation model (DEM) by Airborne Laser Scanning measurements in October 2003 revealed that a pancake shape lava mound had formed on the crater floor, and the volume of the lava mound amounted to 2.1×106 m3. From this, AirSAR measurement is recognized as an effective method for monitoring the topographic change of active volcano craters, and for foreseeing crises.


1. Topographic Observation using AirSAR
2. Observation of the Summit Crater of Asama Volcano using AirSAR
  2.1 Outline of measurement
  2.2 Interpretation of SAR images
  2.3 Analysis of interpretation results
  2.4 Calculation of height change of the crater bottom and erupted lava amount
3. Summary