THE 2004 GIANT SUMATRA EARTHQUAKE AND TSUNAMI

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THE 2004 GIANT SUMATRA EARTHQUAKE AND TSUNAMI
Barbara ROMANOWICZ Univ. of California at Berkeley
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Alaska 1964 M 9.2
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Aleutians 1946 (M7.8) (Hilo)
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Lisbon (1755)
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12/26/04 Sumatra eq. Mw 9.0
1300 km rupture zone 15-20m of slip shaking
lasted -8 mn
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WORLDWIDE EARTHQUAKES PER YEAR
Frequency-magnitude relationship suggests that
magnitude 9 events will occur about once per
decade since 1900, the actual number is once
per 20 years.
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LARGEST EARTHQUAKES, 1900 - 2004
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LARGEST EARTHQUAKES, 1900 - 2004
9.3
USGS
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Mo rigidity x slip x rupture area (N-m)
Harvard CMT group
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Some recent Tsunami
NOAA
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The Geophysical Context
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COMPLEX PLATE BOUNDARY ZONE IN SOUTHEAST
ASIA Northward motion of India deforms all of
the region Many small plates (microplates) and
blocks
Molnar Tapponnier, 1977
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INTERSEISMIC India subducts beneath Burma
microplateat about 5 cm/yr, of which 3 cm/yr is
convergence Fault interface is
locked EARTHQUAKE (COSEISMIC) Fault interface
slips, overriding plate rebounds, releasing
accumulated motion
Stein Wysession, 2003
HOW OFTEN Fault slipped 12 m 1200 cm 1200
cm / 3 cm/yr 400 yr Longer if some slip is
aseismic
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Generic subduction zone cross section
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Earthquake generated tsunamis
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Tsunami wave propagation characteristics
NOAA
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Commonly, the water recedes (a wave trough)
significantly for a few minutes before the first
wave crest arrives. People often go out to
explore the beach at that time.
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TSUNAMI TRAVEL TIME (HOURS SIMULATION)
NOAA
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TSUNAMI WARNING

• Earthquake waves travel 10 times faster than
  tsunami
• seismic velocities 6-8 km/s
• tsunami (deep sea) 600 km/h 0.6 km/s
• Seismology rapid earthquake location, size and
  mechanism
• deep sea buoys verify tsunami and provide alert

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Timeline
Origin Time 12/26/05 0058 UTC
PTWC Alarm
10 min
USGS SP Alarm
Initial USGS Loc (mb6.2) PTWC Bulletin (Mwp8.1)
20 min
USGS Released Auto Loc (mb6.3, n132) USGS Auto
MT (Mw8.2)
30 min
Time since OT
40 min
USGS Reviewed MT (Mw8.2)
50 min
PTWC Bulletin M8.5
60 min
70 min
USGS Reviewed Loc (Ms8.5, n157) Sent 25,000
emails, calls to White House, State Dept.,
Embassies, etc.
80 min
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TSUNAMI WARNING
Because seismic waves travel much faster (km/s)
than tsunamis, rapid analysis of seismograms can
identify earthquakes likely to cause major
tsunamis and predict when waves will arrive
Deep ocean buoys can measure wave heights, verify
tsunami and reduce false alarms
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Historical Seismicityandfuture earthquakes
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COMPARISON WITH PREVIOUS RUPTURES
BILHAM, 2005
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Stress change after the 12/26/04 Sumatra
earthquake
McCoskey et al.,2005
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Current and future seismological investigations
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Stein Wysession after IRIS
One of the largest earthquakes since seismic
recording The largest since the deployment of
modern broadband instrumentation
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STS-1 seismometers
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Ni et al., Nature, 2005
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MODELING SEISMOGRAMS shows how slip varied on
fault plane Maximum slip area 400 km
long Maximum slip 20 m
Stein Wysession
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After Park et al, 2005
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(0.8 to 2.2 mHz)
Sumatra 12/26/04
CAN
1S5
3S2
1S4
UNM
0S12
0S9
0S8
0S7
0S10
0S11
0S0
0S5
1S3 /3S1
0S6
200 hours starting 10 hours before origin time
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Mode 23S5
Bolivia 06/09/94
Ritzwoller et al., 1988
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oS2
oSo
oS3
After Park et al, 2005
(53.9 min) (25.7 min) (20.5
min)
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Sumatra-Andaman earthquake 26 December 2004 CAN
G station (STS1)
20.9 dr0.05mm
25.7
0S2
53.9
0S3
0S0
3S1 2S2 1S3
0S4
44.2
0S5
1S2
0T2
2S1
0T3
0T4
Courtesy of G. Roult, IPGP
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0S3
2S1
0T2
0S2
Courtesy of G. Roult
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mode 0S2 5 singlets
Courtesy of G. Roult, IPGP
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mode 0S3 7 singlets
Courtesy of G. Roult, IPGP
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0S2
0S3
Preared by A.Cao, BSL
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Mo 1030 dyne-cm Mw 9.3
0S2
Stein and Okal, Nature, 2005
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Stein and Okal, 2005
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ARU
RPN
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ARU Distance 6705 km Azimuth 337o
Dec. 04 event
March05 event
R1
R2
R3
Source Directivity effect
J. Rhie, BSL
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RPN Distance 16360 km Azimuth 137o
Dec.04 event
March05 event
R1
R2
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COULD IT HAVE HAPPENED HERE?TSUNAMIS IN SAN
FRANCISCO BAY

• Local
• Possible tsunamis in 1854, 1856, 1868, 1887
• 1898 Mare Island Earthquake (M 6-6.5)
• 1906 San Francisco Earthquake (M 7.8)
• Tele-tsunamis
• 1960 Chilean (M9.5)
• 1964 Good Friday Alaska (M9.2)

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California Integrated Seismic Network subset o
f Berkeley and Caltech broadband stations
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Courtesy of D.Dreger, UCB
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2003 San Simeon earthquake

• Finite-source models show a shallow rupture
  extending 25 km SE of the epicenter.
• The finite-source parameters were used to update
  ShakeMap the day of the earthquake greatly
  improving strong shaking estimates in the most
  heavily impacted areas.

Dreger, 2004
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Mode attenuation
mode 0S0
Q 5300
30
10
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mode 0S2 singlet m2
Q 500
Station CRZF, Crozet, Indian Ocean
Courtesy of G. Roult, IPGP
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Anomalous splitting of core modes
With inner core anisotropy
Durek and Romanowicz, 1999
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Mantle mode
CMB
ICB
Core mode
CMB
ICB
Ritzwoller et al. database
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THE END
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EPS 20 Earthquakes
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Interesting Effects of Earthquake Change in
length of day -2.68?sec Change in oblateness
10E-9 Shift of North Pole 2.5 cm 145E (As
calculated by Chao and Gross of NASA Goddard and
JPL)
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mode 0S0, decay of amplitude with time
period
period
CRZF
PAF
f 0.81465203 1/Q 0.1813
f 0.81465942 1/Q 0.1805
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Chen Jis Modeled Surface Displacements
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Stein and Okal, 2005
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Source ??
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High frequency
Low frequency
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With inner core anisotropy
Durek and Romanowicz, 1999
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11/03/02 Denali Earthquake Dreger et al, 2003
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Chile earthquake, 1960 May 22th, recorded at
Paris (IPGP) with an inclinometer
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Kinematic Modeling of the Denali Earthquake

• Regional distance seismic and GPS data were
  inverted for kinematic slip parameters (e.g.
  Dreger et al., 2004 Oglesby et al., 2005).
• Slip is mostly shallow with 4 primary asperities.
• Rupture velocity is fast on average.
• Simulated PGV correlates with the occurrence of
  liquefaction features (e.g. Kayen et al., 2004)
• Continuing efforts include updating the kinematic
  model using the recently released GPS data set,
  and examining implications for using finite
  source parameters in ShakeMap.

Dreger 2004
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AFFECTED COUNTRIES
BBC
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Bolivia 06/09/94 Mw8.2 h647 km station BKS
Kuril 10/04/94 Mw8.3 h58 km station BKS
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Most recent large event 7.9 - 2000 Previous
events gtM8 1861- 8.5 1833 - 8.7 1797 -
8.4 Tsunamis 1797 1833 1843 1861 1881 1883
- Krakatau! 1907 1941 2004