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The 2004 Mw9.3 East Indian Ocean Earthquake and Tsunami: Initial Results
from
the First Multibeam Survey Over the Southern Rupture Zone
Lisa McNeill
Southampton Oceanography Centre, UK
Abstract
The 26 December 2004 Mw 9.3 Sumatra to Andaman Islands subduction zone
earthquake was the second largest earthquake recorded. The tsunami generated by
the earthquake caused the loss of ~300,000 lives and devastation of many Indian
Ocean coastal communities. The Royal Navy's HMS Scott conducted a bathymetric
survey over the rupture zone during early 2005. This is the first time a high
resolution deep-water seafloor survey has been carried out so soon after an
earthquake of this magnitude. Existing geophysical data in the earthquake
rupture zone are rare and therefore the regional subduction zone structure is
poorly known. Data were collected in the southern and intial part of the rupture
zone offshore Sumatra, including the plate boundary and lower accretionary
wedge, the southern termination of the earthquake rupture and probable segment
boundary, and parts of the forearc basin and outer arc high system. The data
reveal the gross morphology of the margin and details of the structural geometry
and ongoing sedimentary processes. Initial results
indicate a number of youthful tectonic and slope failure features within the
lower part of the accretionary wedge. The data collected continue beyond the
2004 rupture zone into part of the 2005 Mw8.7 earthquake rupture zone of the
next segment to the south.
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