|
1. Analysis objective
|
The eruption of Mount Usu on March 31, 2000 caused damage such as the collapse of roads and man-made structures, and falling ash caused the withering and death of forest trees. The purpose of this research is to support development of forest maintenance countermeasures for damaged areas, by providing information concerning secondary disasters such as mud flows or debris flows in danger zones or derelict areas following a volcanic eruption.
|
2. Analysis procedure Analysis flow chart
|
Falling ash distribution was estimated using cluster classification from the reflected brightness values of XS images produced by the French satellite SPOT, and the thickness of the fallen ash confirmed from field surveys immediately following the eruption. For forest damage, we completed cluster classifications based on the reflected brightness values in the near-infrared region of the same XS images, then created a forest damage zone map after verifying the damage conditions by referring to the field surveys.
|
3. Analysis results
|
1) Using XS images from the SPOT satellite taken on April 3 and meteorological reports following the eruption, we confirmed the falling ash in an east and east northeast direction over a period from the eruption on March 31 through April 3. From field surveys immediately after the eruption, we estimated the falling ash in a zone within several km from the volcano's crater was 5mm or greater.
2) From field survey results and the satellite images, a uniform correspondence was noted between the classified damage zones and damage conditions at actual sites, and damage such as forest withering and death and breakage of tree trunks from the weight of volcanic ash was verified, centered on the area in the vicinity of the Mount Usu volcanic crater.
The total forest damage area was 84.7ha, including 34.9ha of government-owned forest and 49.8ha of privately-owned forest.
|
4. Results from using the analysis results
|
By using forest GIS or satellite data, it is possible to understand actual forest conditions and estimate damage conditions inside zones that are closed to entry. The forest damage areas calculated from satellite data can be put to good use in field disaster countermeasures. In addition to providing this type of information to disaster prevention authorities and organizations, we released it to the general public by placing it our Internet homepage.
Analysis flow chart including government response
|
|
