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1 Centre for Earth Science
Studies
Akkulam, Trivandrum, India 695031
(C.P.R., K.R., R.A., A.E.,
T.M.)
2 Centre for Ocean and Island
Studies
Port Blair, India 744 101
(P.M.M.)
3 Geophysical Institute
University
of Alaska
Fairbanks, Alaska 99775
(J.F.)
* Present address: CSIR Centre for Mathematical Modelling and Computer Simulation, Bangalore, India 560037.
The Indian Ocean earthquake of 26 December 2004 led to significant
ground deformation in the Andaman and Nicobar region, accounting for
800 km
of the rupture. Part of this article deals with coseismic changes along these
islands,
observable from coastal morphology, biological indicators, and Global
Positioning
System (GPS) data. Our studies indicate that the islands south of
10° N latitude
coseismically subsided by 11.5 m, both on their eastern and western
margins,
whereas those to the north showed a mixed response. The western margin of the
Middle Andaman emerged by >1 m, and the eastern margin submerged by the same
amount. In the North Andaman, both western and eastern margins emerged by
>1 m.
We also assess the pattern of long-term deformation (uplift/subsidence) and
attempt
to reconstruct earthquake/tsunami history, with the available data. Geological
evidence
for past submergence includes dead mangrove vegetation dating to 740 ±
100 yr B.P., near Port Blair and peat layers at 24 m and
1015 m depths observed
in core samples from nearby locations. Preliminary paleoseismological/tsunami
evidence
from the Andaman and Nicobar region and from the east coast of India, suggest
at least one predecessor for the 2004 earthquake 9001000 years ago. The
history of
earthquakes, although incomplete at this stage, seems to imply that the
2004-type
earthquakes are infrequent and follow variable intervals.
This article has been cited by other articles:
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S. L. Bilek, K. Satake, and K. Sieh Introduction to the Special Issue on the 2004 Sumatra-Andaman Earthquake and the Indian Ocean Tsunami Bulletin of the Seismological Society of America, January 1, 2007; 97(1A): S1 - S5. [Full Text] [PDF] |
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