03/000 phil r. cummins march 2005 the indian ocean tsunamis – science and seismics australian...
TRANSCRIPT
03/000
Phil R. CumminsMarch 2005
The Indian Ocean Tsunamis – Science and Seismics
Australian Government
Geoscience Australia
Outline
• The physics of tsunami generation.• Why the occurrence of large, Indian
Ocean-wide tsunami should have been foreseen prior to 26 Dec. 2005.
• The 2004 Boxing Day Earthquake & Tsunami.
• Comparison with 2005 Easter Earthquake and ‘non-tsunami’.
• Suggestions for future research.
26 Dec Sumatra Earthquake
Fault movement occurred over a 1300 km length, but seismic and tsunami waves were generated over a more limited region
Free Oscillations – Mw=9.3!
Stein et al.’s analysis of free oscillation data shows that the Sumatra-Andaman earthquake had an Mw=9.3, making it the 2nd largest earthquake ever recorded.
Effects in Sumatra
The first effects of the tsunami were felt in Sumatra, where villages along the coast were razed completely by waves of 10-30 metres in height.
(Results of survey by lead by Prof.
Tsuji of Tokyo’s Earthquake Res. Inst.)
2004 & 2005 SumatraEarthquakes2004 2005
Fau
lt S
lip
Ver
tica
l S
eafl
oo
r M
ove
men
t
(Slip models from
Chen Ji, Caltech)
Conclusions• Evidence existed prior to 26/12/2005 that Indian Ocean-
wide tsunami were generated by M≥9 earthquakes offshore
Sumatra.
• The Great Sumatra-Andaman Earthquake of 2004 ruptured
a 1300 km section of the Sumatran subduction zone,
making it the 2nd largest earthquake ever recorded.
• Comparison with the Great Sumatran Earthquake of 2005
suggests that the latter generated a small tsunami because
of the concentration of fault slip at depth.
Geoscience Australia
Geoscience Australia
Mar 2005 – NAF
Suggestions for Future Research on Indian Ocean
Tsunami• Collection & analysis of historical and paleotsunami data to characterize the hazard.
• Modeling & analysis to quantify tsunami risk.• Geodetic monitoring of strain accumulation in
subduction zones.• Further work on tectonic history of the Indian Ocean.• The above should take into account the Makran
subduction zone offshore Iran-Pakistan border, as well as Indonesia.
• Better collaboration among Indian Ocean & Pacific countries, and among earthquake & tsunami researchers.