GSI HOME > Research & Development > Geography and Crustal Dynamics Research Center > Sumatra Earthquake and Indian Ocean Tsunami in 2004 > Coastal Changes in Andaman Islands, caused by 2004 Indian Ocean Earthquake Last Updated : May 30, 2005

Coastal Changes in Andaman Islands, caused by 2004 Indian Ocean Earthquake

Emergence of coast: Coastal Change Inferred from Satellite Synthetic Aperture Radar Images (ENVISAT)

Landfall Is.,
West Is.,
Cape Price
Andaman Islands
Interview Is.
N. Sentinel Is.
Little Andaman Is.
Click on each image for larger view! Areas colored in cyan denote emergence of reefs due to uplift caused by a crustal deformation due to the 2004 Indian Ocean, M9 earthquake.


These 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 Level

Radar data used here are acquired by ENVISAT ASAR (ESA).
Processed by GSI, Japan using GAMMA software.
observation time 2004/06/03 03:45UTC 2004/12/30 03:45UTC
orbit Descending
beam IS2
incidence angle ~ 23 degree
microwave frequency 5.33GHz (C band)
wave length of microwave 5.6235 cm
polarization VV HH
satellite altitude ~ 786km
data Signal Data (raw)
tide level @ Port Blair 88 cm 25 cm

ASTER images in West island and Cape Price (northern tip of North Andaman island)

Details of North Sentinel Island

Click here for details!
North Sentinel island increased in size by about 100 to 1600 m.

Uplifted Region in Little Andaman Island

Go to top