1984 年 4 巻 4 号 p. 367-372_2
The earthquake 'Nagano - ken Seibu Jisin' which struck at about 8 : 48 a.m. on 14 September 1984, triggered landslides on the hillside of Mt. Ontake. This report dercribes a method to make a montage photograph expressing the landslide condition in the early age.
A cloud free Landsat MSS data obtained before the landslides is chosen as a base image for the montage photograph. Also, an early information about the location of the landslides is collected by means of aerial photography and ground observation carried out by the reporters of the Japan Broadcasting Corporation.
Above two kinds of landslide information are superimposed digitally into the above Landsat image to manufacuture a montage photograph of the landslide condition. This montage imagery is further transformed to a 3D expression using the high resolution digital terrain model of the area.
Compared with the Landsat MSS image taken after the earthquake, these montage photographs have following advantages;
(1) Whole view of the landslides in the montage is almost same as the actual condition, though uncertain information about the landslides could be involved in it.
(2) Accuracy of landslide location indicated on the montage depends upon the accuracy of the early information by aerial or ground observation. A landslide shown at upper - left side of the montage did not occure in actual.
The other landslides in the area are likely same as the actual ones seen on the Landsat MSS image obtained after the earthquake on 23 September 1984.
(3) 3D expression of the montage image may inform us more effectively the landslide condition with the aspect of the topography. Montage image manufactured by this method will be usefull when we meet some cases like this, in which the whole image of the disaster needs to be known in the early age.