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

Submergence of coast: Coastal Change Inferred from Satellite Synthetic Aperture Radar Images (ERS-1 and ERS-2) in Great Nicobar Island and Little Nicobar Island

The image is derived from a comparison of intensity of reflected microwave observed by European ERS-1/2 satellites between December 27, 1992 (before Earthquake) and January 12, 2005 (after Earthquake). An area colored in red is a region where the reflective intensity is decreased.
The red areas are distributed especially along the west coast of Great Nicobar and Little Nicobar islands, India. The image indicates Tsunami inundation area, coastal erosion and a subsidence caused by a crustal deformation due to the M9 earthquake.

This image was generated by manual coastline detection and compilation from the original radar images below.


Original Change Image

The reflection intensity in the ocean depends on incidence angle of the radar, polarization of the microwave, and ocean wave (i.e., roughness).
Due to low incidence angle and VV polarization of ERS satellites, it is not good for coastline change detection that intensity in the ocean is very large. Red and cyan areas in the ocean are mainly due to difference in ocean wave distribution.

About Radar Images

Radar (SAR) images used for this study were acquired by ERS-1/2.
SAR image processing from the raw data to SLC, single-look-complex, image has been done by GSI using GAMMA software.

satellite ERS-1 ERS-2
observation time 1992/12/27 04:08UTC 2005/01/12 04:06UTC
orbit Descending
incidence angle ~ 23 degree
microwave frequency 5.30GHz(C band)
wave length of microwave 5.6564615cm
polarization VV
satellite altitude ~ 786km
data Signal Data (raw)
tide level @ Great Nicobar 24cm 32cm

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