Lessons from the 2004 Sumatra earthquake and the Asian tsunami

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Lessons from the 2004 Sumatra earthquake and the
Asian tsunami

• Kenji Satake
• Geological Survey of Japan
• National Institute of Advanced Industrial Science
  and Technology

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The Sumatra earthquake and tsunami
Worst tsunami disaster in history
Casualties from tsunami
India 16,000
Thailand 8,300
Sri Lanka 35,000
Somalia 300
Indonesia 160,000
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Outline

• The largest earthquake in the last 40 years
• Tsunami generation and propagation
• Past and future earthquakes
• Tsunami warning and hazard reduction systems

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Only four M9 events in 20th century
Cumulative seismic moment Harvard CMT
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A Flying Start, Then a Slow Slip
Slow slip only
Fast and slow slips
Tsunami source
Fast slip only
May 20 issue of Science
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Northward rupture propagation
1,300 km 2.8 km/s 8 minutes
Ishii et al., 2005
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Three slip distribution models
3 x 1022 Nm
6.5 x 1022 Nm
6.5 x 1022 Nm
surface waves
SH waves
regional surface waves
telseismic body regional surface waves
SH waves
regional surface waves
telseismic body regional surface waves
Ammon et al. (2005, Science)
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Crustal deformation near the source
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Tsunami surveys around Bengal Bay
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Outline

• The largest earthquake in the last 40 years
• Tsunami generation and propagation
• Past and future earthquakes
• Tsunami warning and hazard reduction systems

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Seafloor deformation
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Real-time simulation
http//staff.aist.go.jp/kenji.satake/Sumatra-E.htm
l
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Forward and inverse problems
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Tsunami source estimated from arrival times
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Jason-1 altimeter on NASAs satellite
Observed Sea Surface Heights (SSH)
120 min
Estimated tsunami source
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Outline

• The largest earthquake in the last 40 years
• Tsunami generation and propagation
• Past and future earthquakes
• Tsunami warning and hazard reduction systems

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Next earthquake?
McCloskey et al., 2005 Nalbant et al., 2005
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Past earthquakes along Sumatran trench
http//www.gps.caltech.edu/sieh/home.html
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Past earthquakes along Sumatran trench
Seih et al. (2004, AGU fall meeting) No giant
earthquakes have struck the outer-arc islands of
western Sumatra since the sequence of 1797, 1833
and 1861. Paleoseismic studies of coral
microatolls reveal that failure of the subduction
interface occurs in clusters of such earthquakes
about every 230 years. Thus, the next such
sequence may well be no more than a few decades
away.
1833 Mw 9.0 slip 10 m uplift 2m
http//www.gps.caltech.edu/sieh/home.html
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Outline

• The largest earthquake in the last 40 years
• Tsunami generation and propagation
• Past and future earthquakes
• Tsunami warning and hazard reduction systems

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1960 Chilean earthquake

• Largest eq. in 20th century (Mw 9.5)
• The tsunami arrived
• Hawaii 15 hrs 60 casualties
• Japan 23 hrs 150 casualties
• Intl Tsunami Warning System
• Very few knowledge
• No plate tectonics
• No global seismic network
• Ms 8.5

Onagawa, Japan
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Tsunami Warning System
Global seismic network
Sea level network
DART buoys
GLOSS Global Sea Level Observing System
NOAA
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Tsunami Information Bulletins from PTWC

• December 26, 2004
• 059 GMT Earthquake
• 114 GMT ( 1st bulletin 15 min after the eq.)
• LOCATION - OFF W COAST OF NORTHERN SUMATERA
• MAGNITUDE - 8.0
• 2 08 GMT ( 2nd bulletin 69 min after the eq.)
• LOCATION    -  OFF W COAST OF NORTHERN SUMATERA
• MAGNITUDE   -  8.5
• EVALUATION
• REVISED MAGNITUDE
• THERE IS THE POSSIBILITY OF A TSUNAMI NEAR THE
  EPICENTER.    

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Tsunami Warning and Hazard Reduction
Tsunami Warning System
Education and Awareness
Hazard Mitigation
Tsunami Warning Message e.g., JMA, PTWC
Coastal Communities Residents
Evacuation
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Conclusions

• The 2004 Sumatra-Andaman earthquake was the
  largest event in the last 40 years and caused
  gt200,000 tsunami casualties.
• The tsunami was recorded by tide gauges,
  satellite altimetry and field surveys, and the
  data are used in real time to study the tsunami
  source.
• Past tsunamis can be studied by historic and
  geologic data. Data from such paleoseismological
  studies can be used for probabilistic estimates
  of future earthquakes and tsunamis.
• To prevent future disaster, tsunami warning
  systems, hazard assessment and preparation, and
  education are all necessary.