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Coastal Changes in Simeulue island, caused by the 2004 Earthquake

Emergence of Reefs: Coastal Change Inferred from Satellite Synthetic Aperture Radar Images (Canadian RADARSAT)

Larger View[PNG:4,762KB]

Magnified Image of Northwestern Simeulue Island

The image is derived from a comparison of intensity of reflected microwave observed by Canadian RADARSAT satellite between July 22, 2003 (before Earthquake) and February 17, 2005 (after Earthquake). An area colored in cyan is a region where the reflective intensity is increased. The ribbons of cyan are distributed along the west coast of northwestern part of Simeulue Island, Indonesia. The image indicates emergence of reefs due to uplift caused by a crustal deformation due to the 2004 Indian Ocean, M9 earthquake.

The width of the cyan ribbon is about 300m at maximum.

The emergence had increased the size of small islets and even produced some new small islets.



Tide level at the northwestern Simeulue
 -14.5cm and -1.5cm for the first and second image acquisition, respectively.

About Radar Images

Radar (SAR) images used for this study were acquired by Canadian RADARSAT. GSI requested to take the second, February 17, 2005, image. SAR image processing from the raw data to SLC, single-look-complex, image has been done by GSI with GAMMA software.
track angle -11.90 degree
orbit Ascending
beam Standard 7
incidence angle ~ 47 degree
microwave frequency 5.30GHz(C band)
wave length of microwave 5.6564614cm
polarization HH
satellite altitude ~ 795km
data Signal Data (raw)

Region of Emergence Coast in Simeulue Island Seen in Satellite Radar Images


Whole Image of Simeulue Island

Whole high resolution image[PNG:12,453KB]
Dark, red or cyan region on the southeast land are due to wrong AGC, auto-gain-control, onboard. In spite of the problem, coastal change can be checked in southeast region. No coastal changes are seen in the southeast region from this image.

Comparison with the Field Observation by Caltech Tectonics Observatory


Photos by Kerry Sieh
Tectonics Observatory
Caltech

Upper-Right Photo:
Girls standing on a dead Porites microatoll uplifted about 95 cm during the earthquake.

Bottom-Left Photo:
Uplifted reef due to the earthquake. Height and width of the uplift are about 150cm from measurement by Prof. Sieh and about 300m from the radar imagery, respectively.

Acknowledgements:
We thank Professor Kerry Sieh, Tectonics Observatory, Caltech for permitting us to use his valuable photos and data.
The map below is made from impressive field observation by people in Tectonics Observatory, Caltech.
The cyan ribbons in the above radar images correspond well with the uplift plot in cyan below. Generally, wider ribbon corresponds to larger uplift.

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