a coupled teleseismic ocean-general-circulation- model ......model system for global tsunami warning...

A Coupled Teleseismic OceanA Coupled Teleseismic Ocean--GeneralGeneral--CirculationCirculation--Model System for Global Tsunami WarningModel System for Global Tsunami Warning

Y. Tony Song

Jet Propulsion Laboratory, California Institute of Technology

Contents:

1. Tsunami formation theory

2. Methodology of seismic prediction

3. 26 Dec 2004 & 28 Mar 2005 Tsunamis

4. Summary

Contributors:

L.-L. Fu & Victor Zlotnicki (NASA JPL)

Chen Ji & Vala Hjorleifsdottir (SeismoLab, Caltech)

C.K. Shum & Y. Yi (Ohio State University)

Tony Song, January 2006

Facts: Too Many False AlarmsFacts: Too Many False Alarms

•• A strong earthquake does not necessarily results in a A strong earthquake does not necessarily results in a proportionally strong tsunami.proportionally strong tsunami.

July 1998 New Guinea M7.5; 15m runJuly 1998 New Guinea M7.5; 15m run--up and 2,000 fatalitiesup and 2,000 fatalities

March 2005 N. Sumatra M8.7; 2m runMarch 2005 N. Sumatra M8.7; 2m run--up and 100 fatalities, due to evacuationup and 100 fatalities, due to evacuation

June 2005 Northern California M7.1; triggered a tsunami alert; nJune 2005 Northern California M7.1; triggered a tsunami alert; no tsunamio tsunami

•• Without knowing Without knowing how tsunamis form from earthquakeshow tsunamis form from earthquakes, it , it would be impossible to predict a tsunami precisely.would be impossible to predict a tsunami precisely.

• For a long time, it has been believed that the under earthquakes that involve a significant vertical motion are more effective in generating tsunamis than those that primarily horizontal motion (Pond & Pichard 1983; Satake 1995). The old theory is wrong!


Earthquake Fault & Topography

−4

−3

−2

−1

90E 92E 94E 96E 98E Eq

5N

10N

15N(a) Topography

92E 93E 94E 95E 96E−5

−4

−3

−2

−1

0

Dep

th (

km)

Longitude

(b) Section 5oN

Slip

4 km

3 km

2 km 1 km

Vertical motions

Lateral motion

Mega tsunamis are caused by horizontal motions of continental slopes!


Ocean Bottom Pressure

TOPEX/Poseidon

Sea Surface Height

Ocean

Data used in this studyData used in this study

(1)(1) The Global Seismographic The Global Seismographic Network gives the seismic Network gives the seismic waves generated by the waves generated by the undersea earthquake.undersea earthquake.

(2)(2) Satellite radar altimeters Satellite radar altimeters measure the seameasure the sea--surface surface waveswaves——tsunami, caused by tsunami, caused by the seafloor motionsthe seafloor motions

(3)(3) Tide gauges record shallow Tide gauges record shallow waves or runwaves or run--up to up to beachesbeaches

∫−=ζ

ρhb dzgP

Tude gauges


Method 1Method 1: Seismic Waveform Inversion: Seismic Waveform Inversion

[ ] )(),()sin(),()cos()( 21

1 1

tStVYtVYDtu jkjkjkjkjkjkjk

n

j

n

kjk λλ += ∑∑

= =

Dynamical seafloor deformationDynamical seafloor deformation

90E 92E 94E 96E 98E

2N

4N

6N

8N

10N

12N

14N(a) Displacement

20 m

−2 −1 0 1 2

90E 92E 94E 96E 98E

2N

4N

6N

8N

10N

12N

14N(b) Topography

−5 −4 −3 −2 −1

meter km

•GPS measurements from C. Vigny (Nature 2005)•Fault area survey by British Navy (K. Moran)


Method 2Method 2: Deriving tsunami source energy: Deriving tsunami source energy

Seismic data inverted 3D seafloor motions: (u, n, e)—upward, northward and eastward fault displacement

Vertical uplift: Horizontal displacement:

yx nhehu ++=∆η ))(,)((),( nzezvu yxbb δδ=at sea-surface within the bottom layer of z < LHhx

Tsunami kinetic energy:

KE=2.1 x 1015 Joule

Amp=70%

Tsunami potential energy:

PE=5.4 x 1014 Joule

Amp=30%


Method 3: Ocean Models with Bottom-Layer Forcing

1. S-coordinate (Song&Haidvogel 1994):

)()()1( sChHshsz cc −+++=ζ

ROMSSCRUM/ (Boussinesq)

2. Sp-coordinate (Song&Hou 2005):

)()()()1( 0' sCppsppspp cbcbs −−+−+=

Ocean-bottom-pressure model (non-Boussinesq)

Three-dimensional seafloor motions are applied


http://marine.rutgers.edu/po/models/roms/index.php

Prediction system: Seismograph to Tsunami Waves

[ ] )(),()sin(),()cos()( 21

1 1

tStVYtVYDtu jkjkjkjkjkjkjk

n

j

n

kjk λλ += ∑∑

= =

Bottom-pressure coupling

1

2

3


Validations by Satellites and Tide-Gauges

Asymmetric “N-Waves”•Leading depression waves toward Thailand•Leading elevation waves toward Sri Lanka

70E 80E 90E 100E 110E20S

10S

Eq

10N

20N

30N

Jason

(a) 2:00 hrs after quake

70E 80E 90E 100E 110E20S

10S

Eq

10N

20N

30N

Envisat

(b) 3:10 hrs after quake

10S 5S Eq 5N 10N 15N 20N−60

−40

−20

0

20

40

60

80(c) Jason track Jason data

Model:

20S 10S Eq. 10N 20N−30

−20

−10

0

10

20

30

40

SS

H (

cm)

(d) Envisat track Envisat data

Model:

26.1 26.2 26.3

Male

Gan

Hanima

Belawan

Sibolga

prop

agat

ing

wes

twar

d

pro

paga

ting

east

war

d

(a) Vertical only

26.1 26.2 26.3

Male

Gan

Hanima

Belawan

Sibolga

(b) Vertical & Horizontal

Dec Dec

2 m

Data

Model

Data

Model

Recedingfirst

Elevatingfirst


Seismic Prediction of 28 March 2005

The horizontal slip has occurred in the shallow and relatively flat region; therefore, it is ineffective for generating long waves.


0.5

1

1.5

2

2.5

3

3.5

4

4.5

95E 97E 99EEQ

1N

2N

3N

4N

T=300 sec

a) Horizontal slip

1m/s−100

−50

0

50

100

95E 97E 99EEQ

1N

2N

3N

4N

T=300 sec

b) Vertical uplift (cm)

−30

−20

−10

0

10

20

30

70E 80E 90E 100E15S

5S

5N

15N

25N

*Male

c) 28 Mar tsunami (slip & uplift)

2h 4h 6h 8h

−20

20−100

0

100

26 Dec04

28 Mar05

Res

idua

l (cm

)

d) Tide at Male

km

Data

Model

Conclusion RemarksConclusion RemarksEvidence from seismometers, satellite altimeters, and tide gaugeEvidence from seismometers, satellite altimeters, and tide gauges suggests that s suggests that

horizontal motionshorizontal motions of faulting are the main cause of the Indian Ocean of faulting are the main cause of the Indian Ocean tsunami. The vertical uplift accounts for only 30% of the tsunamtsunami. The vertical uplift accounts for only 30% of the tsunami height.i height.

Implications:Implications:1.1. Movement of continental marginsMovement of continental margins, rather than the local vertical uplift of , rather than the local vertical uplift of

seafloorseafloor, should be the focus of tsunami observation and prediction., should be the focus of tsunami observation and prediction.

2.2. Many Many remoteremote--sensingsensing technologies (e.g., GPS), combining with the technologies (e.g., GPS), combining with the proposed methodology, become useful for tsunami detection.proposed methodology, become useful for tsunami detection.

3.3. Seismic predictionSeismic prediction of tsunamis is feasible: Based on JPLof tsunamis is feasible: Based on JPL’’s supercomputer, s supercomputer, the coupled earthquakethe coupled earthquake--tsunami modeling system is going to connect to the tsunami modeling system is going to connect to the globalglobal--seismographicseismographic--network. network.

Song et al., Song et al., GRLGRL, , 3232, doi:10.1029/2005GL023683 (2005)., doi:10.1029/2005GL023683 (2005).

Song et al., Horizontal motions of faulting dictate the 26 DecemSong et al., Horizontal motions of faulting dictate the 26 December tsunami (submitted to ber tsunami (submitted to NatureNature).).


a coupled teleseismic ocean-general-circulation- model ......model system for global tsunami warning...

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