U04: The Indian Ocean Tsunami 2004: Two Years On

Union Special Session at Fall 2006 AGU Meeting

U04: The Indian Ocean Tsunami 2004: Two Years On

Almost two years after the Great Earthquake and tsunami of 26th
December 2004 along the Andaman-Sumatra subduction zone, research
based on seismology, geodesy, satellite imagery, tsunami modelling,
and marine geophysical surveying has improved our understanding of
the catastrophic event as well as the subsequent great earthquake of
March 2005. The earthquake of December 26th was the one of the
largest since 1900, and the tsunami the most destructive ever
recorded. It was the first to be recorded by modern broadband
seismometry, and dynamic displacements were also measured at GPS
sites. The tsunami was observed directly by satellite altimetry and
tide gauges, and other observations from tsunami deposits have been
made across the affected area. There have been numerous marine
expeditions exploring the southern section of the earthquake rupture
zone, acquiring multibeam swath bathymetry, reflection- and
refraction seismic data and aftershock activity with ocean-bottom-
seismometer networks, as well as seabed visual imagery. Numerous
inverse and forward models have investigated the rupture evolution
and slip distribution in this event. Tsunami wave models have been
based on various rupture mechanisms, and these in turn have been
derived from combinations of seismology, GPS geodesy, inverse models
of the tsunami, and coral reef geodesy. A better understanding of the
Andaman-Sumatra subduction zone is being applied to hazard assessment
in other areas such as Cascadia and Japan, even as efforts to
reconcile these models continue. New tsunami warning systems are
being installed in the Indian Ocean Basin, both in deep and coastal
waters. Notwithstanding the new work, and mainly due to uncertainties
attributable to data limitations, our understanding of the earthquake
and tsunami is incomplete. Studies on spatial and temporal evolution
of fault slip indicate interesting - even perplexing - fault rupture
behaviour. Specific questions include; what are the commonalities and
differences between proposed rupture models; how well can the
earthquake source description and resulting seafloor deformation be
related to genesis of the destructive tsunami; is current theory
adequate to explain the various seismic, geodetic, tsunami and other
observations (for example, can afterslip be clearly distinguished
from asthenosphere relaxation in explaining post seismic
displacements); is excitation of the tsunami clearly understood; and
how does the slip evolution and tsunami excitation in this case
compare with other great subduction earthquakes? Based on the
enormous amount of new work on the Andaman-Sumatra earthquakes and
tsunamis, the objective of the session is to bring together
scientists from all disciplines to present their research in the
region and to foster and encourage multidisciplinary collaboration.
Applications of the research in the Indian Ocean to other areas are
also encouraged.

David R Tappin
British Geological Survey
Kingsley Dunham Centre
Keyworth
Nottingham, GBR NG12 5GG
44 115 9363449
drta@bgs.ac.uk

Stefan Ladage
Federal Institute for Geosciences and Natural Resources (BGR)
Stilleweg 2
Hannover, DEU D-30655
+49 (0)511 643 3737
s.ladage@bgr.de

Chris Goldfinger
Oregon State University,
104 Ocean Admin Bldg
Corvallis, OR, 97331-5
USA
(541) 737-5214
gold@coas.oregonstate.edu

Kenneth Hudnut
U. S. Geological Survey
USA
hudnut@usgs.gov

Hiroo Kanamori
California Institute of Technology
USA
hiroo@gps.caltech.edu

Jeffrey Freymueller
University of Alaska, Fairbanks
USA
907-474-7286
jeff@giseis.alaska.edu