Coastal Changes in Andaman Islands, caused by 2004 Indian Ocean Earthquake
Emergence of coast: Coastal Change Inferred from Satellite Synthetic Aperture Radar Images (ENVISAT)
CommentsThese images are derived from a comparison of intensity of reflected microwave observed by ENVISAT ASAR between June 3, 2004 (before Earthquake) and December 30, 2004 (after Earthquake).
The intensity depends on the roughness of earth surface. The intensity images are represented in black-to-white (high intensity) greyscale. Ocean with no wave is usually represented in black or dark grey in intensity images. The color of the greyscale intensity image before the earthquake was converted to black-to-red redscale. The color after the earthquake to black-to-cyan cyanscale. An additive color process of these two images in redscale and cyanscale produces an change map. Area, where there is no roughness change, is represented in greyscale, because the additive process between red and cyan results in white. Red means decreasing of intensity (i.e., roughness) in the change map. Cyan corresponds to increasing of intensity (i.e., roughness). Cyan ribbons in northern, western, and southern Andaman Islands are due to uplift by the coseismic fault slip. Up to 1.6km wide emergence of reef is seen in North Sentinel island. The reflection intensity in the ocean depends on incidence angle of the radar, polarization of the microwave and ocean wave (i.e., roughness). Red and cyan areas in the ocean are due to difference in these three factors. There are two red and cyan bands each in the Andaman Islands image. These correspond to seams between scenes. Because there are sometimes gaps between scenes in raw data files of ENVISAT ASAR data, intensity loss in synthetic aperture processing results in these red an cyan bands. Satellite and Sensor Specification and Tide LevelRadar data used here are acquired by ENVISAT ASAR (ESA).
Processed by GSI, Japan using GAMMA software.
ASTER images in West island and Cape Price (northern tip of North Andaman island)Details of North Sentinel IslandClick here for details of North Sentinel Island!
North Sentinel island increased in size by about 100 to 1600 m. Uplifted Region in Little Andaman Island |