14 REPORT OF THE INSTITUTE OF INDUSTRIAL SCIENCE, UNIVERSITY OF TOKYO 
generation. This area is a steep mountainous 
district in cetral Japan and is stratigraphically 
very complicated. The river seen on the photo 
shows a straight-line flow owing to the influence 
of the fault. In the part marked as A on the 
photo is a U-shaped valley. Since there is no 
  
(a) (5) 
Photo. 7 
forest, it can readily be detected on the photo. 
According to the panchromatic photo, this valley comes out all in gray color and it is 
difficult to guess correctly whether it is covered with grass or whether it is a jutting rock. 
However, according to the infrared photo taken simultaneously, the objects come out in 
different shades. So it can readily be surmised that what is seen in the center is a heap of 
sand and gravel, the surroundings represent the part rank with grass and the side beyond 
that represents a forest. 
It is evident from these facts that this small ravine is also a sort of fracture zone which 
was affected by the fault and that it corresponds to the extension of the valley created by a 
fault which stretches from the opposite direction. Fragments of efflorescent bedrocks have 
accumulated in the valley which was fractured by a fault movement and formed this ravine. 
Since these fragments are permeable, no waterway was formed in this ravine. The water 
penetrates into the earth and consequently, unlike other places, the soil was not formed in 
this part alone, thus showing the feature as seen in the photo. 
According to a geological map, the vicinity of this area is mainly formed by amphibole 
granite and amphibole quartz-diorite. In the vicinity of this fractured valley, there are outcrops 
of dikes of felsite, acid tuff and quartz porphyry. It was confirmed from these data that inter- 
pretation by infrared photos is far more reliable than that by panchromatic photos. 
Thus, even the slightest change on a photo must not be overlooked if we are to insure 
the accuracy of photo interpretation required by public works. 
Prompted by the publication of this photo, the need for conducting a boring survey of 
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