The Science behind the Earthquake and Tsunami of Dec. 26, 2004

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The Science behind the Earthquake and Tsunami of

Dec. 26, 2004

Rob McCaffrey

Rensselaer Polytechnic Institute

STANYS Conference Nov. 7, 2005

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Largest Known Quakes

2005 Nias

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Singapore

Jakarta

Kuala Lumpur2004 (9.3)

1892 (7.6)

1833 (9)

1866 (8.5)

2005 (8.7)Sumatra

Aceh

Bock et al., AGU, 2005.

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How much did the ground move?

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The Island of Jawi-jawi off thecoast of Sumatra

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1989

2005

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Mw 9.23 Dec 26, 2004

Mw 8.7 Mar 28, 2005

Velocities from 1991-2004

Bock et al., AGU, 2005.

10Bock et al., AGU, 2005.

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Bock et al., AGU, 2005.

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Bock et al., AGU, 2005.

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from surface displacements (40 days later)

Slip distribution of Dec 2004 quake from seismic waves

Data from Subarya et al., Nature, in press, 2005.

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Survey mode GPS coseismic displacements – December 26 earthquake

Data from Subarya et al., Nature, in press, 2005.

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All of northernSumatra moved by about 3 meters or more!

Data from Subarya et al., Nature, in press, 2005.

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At southern end of slip region, lifting and extreme tilting of the island indicates the edge of the slip area is abrupt.

Data from Subarya et al., Nature, in press, 2005.

17NIAS

NIASSimeulue

Simeulue2005 quake mostly deeper and beneath land (Nias)

Data from Subarya et al., Nature, in press, 2005.

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Singapore

Jakarta

Kuala Lumpur2004 (9.2)

1833 (9)

1866 (8.5)2005 (8.7)

Sumatra

Aceh

?

Bock et al., AGU, 2005.

19Sieh and Natawidjaja, 2000

India Plate

Australia Plate

Mechanical Barriers to Seismic Rupture

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Tsunami = “harbor wave”

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Wave speed proportional to ( g h )1/2

(g = gravity, h = wave height)By conservation of energy, wave height

proportional to h-1/4

The top of the wave outruns the bottom!

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Tsunami Animation

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Pacific Warning System

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Normal tide gauge record

Record with passing tsunami

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Kashmir earthquake of Oct 8 2005

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US Pacific Northwest

Offshore Oregon and Washington there sits a loaded subduction zone similar to the Sumatra subduction zone.

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Sumatra fault area superimposed on US Pacific Northwest

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Lose the seat, move your feet!