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Difference in nighttime-light intensity before
and after an earthquake can be used to estimate earthquake damaged areas,
because it may bring about power outage, evacuation, the slow-down of the
economic activities, etc. in earthquake-affected areas. The areas where
the nighttime-light intensity became weaker after the earthquake are colored
in red and yellow in the map above. The nighttime-light images used here
were observed by the DMSP (Defense Meteorological Satellite Program)/OLS
(Operational Linescan System).
The gray spots in the map show the areas
where the brightness after the earthquake exceeds the measure range of
the OLS sensor, and the light intensity difference cannot be figured out
in the areas. The pale purple areas in the map show cloud existence where
the city lights were influenced and the light intensity difference cannot
be figured out in the areas, either.
Also
see Nighttime lights satellite imagery