Terrestrial phenomena disasters/Volcanoes/Pyroclastic flows. Slope disasters/Volcanoes (Pyroclastic flow, etc.)
Disaster name
Eruption of Fugendake, Mt. Unzen, in Nagasaki Prefecture in June 1991 (pyroclastic flow montage)
Author of WEB conversion
Nakayama Yasunori

Case Study

No. 18

1. Analysis objective

Create a "montage image of the Mt. Unzen pyroclastic flow" from SPOT data.

2. Analysis procedure Analysis flow chart

This aims to understand the topographical extent, scale, point of origin and other characteristics of the pyroclastic flow and contribute to the creation of disaster relief measures and recovery plans, by superimposing and describing detailed pyroclastic flow starting points and resulting damage zones interpreted from aerial photographs and investigations with satellite data obtained prior to the eruption and creating a bird's-eye view by combining this with digital topographic data.

1) Data utilized

1. Satellite data: SPOT/HRV
2. Digital elevation model: 60m mesh, 1m elevation points (newly created)
3. Pyroclastic flow damage area map: created by interpreting aerial photograph exposures following the occurrence of pyroclastic flows

2) Supplemental diagrams

1. Analysis flow chart
2. Analysis images

3. Analysis results

By combining high spatial resolution satellite images with detailed pyroclastic flow damage information from aerial photographs taken immediately after the eruption plus topographic information, we were able to achieve a far more detailed understanding of the downstream pyroclastic flow areas and damage areas according to the layout of topographic features than is possible using two-dimensional information.

The results were useful for projecting the expansion of the damage areas that accompanied subsequent volcanic activity, and as a database for disaster prevention measures against the occurrence of debris flows.

4. Results from using the analysis results

The results were released to newspaper and television reporters by the Ministry of Education, Culture, Sports, Science and Technology (Former Science and Technology Agency). The information was also referred to by the Committee for Volcanic Eruption Prediction (Committee member), and used to understand volcanic activity and investigate the effects of future volcanic activity.

The study clearly demonstrated that when this type of information is released promptly there is a strong likelihood it will be utilized at the actual disaster site.

5. Sources

Nakayama Y., others: Mt. Unzen Pyroclastic Flow Montage Image Created from SPOT data, Journal of the Remote Sensing Society of Japan, Vol. 11, No. 3, pp. 43-47, 1991

Nakayama Y.: Mt. Unzen Pyroclastic Flow Montage Image Created from SPOT Data, Case Studies of Disaster Analysis Based on Global Observation Data, pp. 32-33, 1995