Discovery Lecture, Dept. of Earth and Atmospheric Sciences, Purdue University February 28, 2005

Prof. Larry Braile, braile@purdue.edu, www.eas.purdue.edu/~braile

(Despite the popularity of this image, tsunami waves do not normally look like this.)

The M9.0 Andaman Islands-Sumatra Earthquake and

Tsunami of 26 December 2004

Tectonic Setting

USGS

Schematic plate tectonic setting for tsunami

generation

NOAACommonly, in mega-thrust earthquakes, a

very large area of the ocean floor is uplifted

TRENCH

Historical Seismicity

(Indonesia is one of the most seismically active areas in the world, has a long subduction zone plate boundary, and many 7+ earthquakes have occurred there in the past, so it should be no surprise that an M9+ tsunami-generating event would occur there.)

Question: What other great (M > 8) earthquakes have occurred in the region?

Answer: Since 1900 and prior to the December 26 earthquake, the largest earthquake along the subduction zone from southern Sumatra to the Andaman Islands occurred in 2000 and had a magnitude of 7.9.  A magnitude 8.4 earthquake occurred in 1797, a magnitude 8.5 in 1861 and a magnitude 8.7 in 1833 . All three ruptured sections of the subduction zone to the south of the recent earthquake.  Interestingly, the 1797 and 1833 quakes are believed to have ruptured roughly the same area with only 36 years separating the events. Paleoseismic evidence shows that great earthquakes or earthquake couplets occur about every 230 years (http://www.gps.caltech.edu/~sieh/publications/a10.html).

USGS

Sumatra earthquakes FAQs

Show earthquake activity in Indonesia and aftershocks of the 26 December earthquake using the Seismic Eruption program (written by Alan Jones, SUNY-Binghamton)

http://www.geol.binghamton.edu/faculty/jones/

USGS

Main shock and aftershocks

~1200 km of the plate boundary moved, max. displacement ~ 15 m (?, preliminary est.)

24-hour seismograph record

~135 degrees distance

Seismogram

Surface waves around the world

Descriptor Magnitude Average Annually

Great 8 and higher 1 ¹

Major 7 - 7.9 17 ²

Strong 6 - 6.9 134 ²

Moderate 5 - 5.9 1319 ²

Light 4 - 4.9 13,000 (est.)

Minor 3 - 3.9 130,000 (est.)

Very Minor 2 - 2.9 1,300,000 (est.)

¹ Based on observations since 1900. ² Based on observations since 1990.

Worldwide earthquakes per year (from USGS):

Worldwide earthquakes per year:

Frequency-magnitude relationship suggests that magnitude 9+ events will occur about once per decade; statistically, since 1900, the actual number is ~once per 20 years.

Magnitude versus Fault Length

10

100

1000

10000

6 7 8 9 10

Magnitude

Fa

ult

Le

ng

th (

km

)Magnitude of earthquake is controlled by fault length that ruptures (data for diagram generated

using Seismic/Eruption program)

Magnitude versus fault length (determined from aftershock zonelength) for various earthquakes (Alaska, 1964; Denali, 2002; Landers, 1992; Loma Prieta, 1989; Northridge, 1994, etc.). Results were quickly obtained using Seismic/Eruption views.

Alaska, 1964

Denali, 2002

Landers, 1992

Sumatra, 2004

Largest earthquakes, 1900 - 2004

USGS

  Location Date UTC Magnitude Coordinates

1. Chile 1960 05 22 9.5 38.24 S 73.05 W

2.Prince William Sound, Alaska

1964 03 28 9.2 61.02 N 147.65 W

3.Andreanof Islands, Alaska

1957 03 09 9.1 51.56 N 175.39 W

4. Kamchatka 1952 11 04 9.0 52.76 N 160.06 E

5.Off the West Coast of Northern Sumatra

2004 12 26 9.0 3.30 N 95.78 E

6. Off the Coast of Ecuador

1906 01 31 8.8 1.0 N 81.5 W

7. Rat Islands, Alaska 1965 02 04 8.7 51.21 N 178.50 E

8. Assam - Tibet 1950 08 15 8.6 28.5 N 96.5 E

9. Kamchatka 1923 02 03 8.5 54.0 N 161.0 E

10. Banda Sea, Indonesia 1938 02 01 8.5 5.05 S 131.62 E

11. Kuril Islands 1963 10 13 8.5 44.9 N 149.6 E

Largest earthquakes, 1900 - 2004

USGS

Date Magn. Max Ht Killed Location Comments

9-2-92 7.2 10 m 170 Nicaragua Measured Pacific-wide

12-12-92 7.5 26 m 1000Flores Island

7-12-93 7.6 30 m 200 Hokkaido

6-2-94 7.2 14 m 220 Java

10-4-94 8.1 11 m 11Kuril Islands

Measured Pacific-wide

11-14-94 7.1 7 m 70 Mindoro

02-21-96 7.5 5 m 12 Peru

07-17-98 7.0 15 m 2000 New Guinea

06-23-01 8.3 5 m 50 Peru Measured Pacific-wide

Some recent Tsunamis

NOAA

Date Magn.Max. Ht.

Killed Location Comments

5-22-1782 7.0 10 m 40000 Taiwan

11-22-1815 7.0 ? 10253 Indonesia

8-27-1883 - 35 m 36000 Indonesia Krakatau Eruption

1-21-1917 6.5 ? 15000 Indonesia

4-1-1946 7.9 35 m 173 AleutiansMany deaths in Hilo, Hawaii

5-22-1960 9.5 25 m 534 ChileLargest historical earthquake

3-28-1964 9.2 67 m 115 Alaska

2-4-1976 7.5 ? 22778 Guatemala

12-26-2004 9.0 15 m ~217,000 (4/8/05 est.)

N. Sumatra

Greatest number of fatalities

Some Notable Tsunamis

Question: What other significant tsunamis have occurred in the region?

Answer: The following destructive tsunamis are listed on a data base maintained by the Tsunami Laboratory, Institute of Computational Mathematics and Mathematical Geophysics (http://tsun.sscc.ru/tsulab/20041226tsun.htm)

1. 1797/02/10 Central part of the western Sumatra. The quake was most felt near Padang and in the area within +/-2 deg of equator. Padang was flooded by powerful waves. More then 300 fatalities. 2. 1833/11/24 South coast of the western Sumatra, estimated rupture from 1 S to 6 S latitude. Huge tidal wave flooded all southern part of the western Sumatra. Numerous victims. 3. 1843/01/05 Strong earthquake west of the central Sumatra. Terrible wave came from the south-east and flooded all the coast of the Nias Island. Many fatalities. 4.  1861/02/16 Exceptionally strong earthquake affected all the western coast of Sumatra. Several thousand fatalities. 5. 1883 Krakatau explosion 36,000 fatalities

USGS

Tsunami travel time (hours; simulation)

NOAA

Tsunami wave height (cm; simulation)

NOAA

Tsunami wave height (2 hours after earthquake) measured from satellite radar altimetry

NOAA

Satellite radar altimetry

Satellite radar altimetry

Gower, J., EOS, v. 86, no. 4, 25 January, 2005

Tsunami wave propagation characteristics – note that as water depth becomes smaller, waves slow down, become shorter wavelength, and have larger amplitude

When the water is 10 m deep, what is the separation of the waves in minutes?

NOAA

Animation courtesy of Dr. Dan Russell, Kettering University

http://www.gmi.edu/~drussell/demos.html

Water waves animation

Direction of propagation

Tsunami simulation

http://staff.aist.go.jp/kenji.satake/animation.gif

Tsunami simulations Open Quick Time simulations

(see these websites)http://www.pmel.noaa.gov/tsunami/

http://www.pmel.noaa.gov/tsunami/Mov/TITOV-INDO2004.mov

http://es.ucsc.edu/~ward/indo.mov

Note distance of propagation and reflection of waves

Double click on the file: TITOV-INDO2004[1].movTo view Quick Time movie of Tsunami simulation from NOAAhttp://www.pmel.noaa.gov/tsunami/Mov/TITOV-INDO2004.mov

Also, simulation from S. Ward, UCSC: indo[1].movhttp://es.ucsc.edu/~ward/indo.mov

Show video segments of tsunami waves and damage

Source: http://www.asiantsunamivideos.com/

Chedi Resort, Phuket, Thailand, Wave height ~4+ m (?, from estimates of water level from beach umbrellas on grassy area above the beach)

Damage in Banda Aceh

Earthquake and Tsunami Damage, Banda Aceh, Sumatra

Earthquake and Tsunami Damage,

Sri Lanka

Tsunami wave trough, Sri Lanka coast

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 or gather fish or shells at that time.

Tsunami wave, Sri Lanka; note strong current

Banda Aceh, Sumatra, before tsunamihttp://geo-world.org/tsunami/

Banda Aceh, Sumatra, after tsunamiAlso: http://www.digitalglobe.com/

Factors that increased loss of life and damage

1. Magnitude of earthquake – largest event in 40 years; and location near highly populated coastlines.2. Approximately north-south orientation of the plate boundary that focused energy to the west and east.

3. Location off the coast of Sumatra (?)N. Sumatra west coast S. Am.

4. the lack of a tsunami warning system and adequate rapid communication systems

DART tsunami warning system

NOAADART: Deep ocean Assessment and Reporting of

Tsunamis

5. the lack of adequate public awareness of tsunamis and tsunami hazards

(Although the 26 December 2004 earthquake and tsunami was a tragic event, two benefits are: that countries are now committed to installing effective tsunami warning systems worldwide, and, there is greatly increased public awareness of tsunamis and tsunami hazards.)

Many people watched the waves approach and did not take action until too late, or went out to explore the beach during a wave trough

6. the common building construction characteristics in developing countries

Some significant observations and occurrences

• Tsunami warning system could have saved many lives (many deaths occurred as tsunami hit over two hours after the earthquake).

• In Sumatra, experiencing the strong earthquake caused some people to move to higher ground; however, many did not.

• Apparently, many animals sensed the seismic waves, the sound of the tsunami waves approaching, or the vibration of the ground caused by crashing ocean waves, and moved to higher ground.

• Many people watched the waves approach or went out to explore the beach during a wave trough (receding water).

• A 10-year old girl is credited with saving about 100 people on a beach in Thailand when she noticed the water receding suddenly and told her mother that it looked like a Tsunami was approaching – a lesson that she had recently learned in school.

Earthquake and Tsunami Safety• Earthquake safety – “Duck and cover”.

• Tsunami safety (when in a coastal, near-sea-level area; two situations, local EQ or distant EQ):

• If you feel strong shaking for 15+ seconds, after shaking, move to higher ground.

• If there is a tsunami warning, or if you observe unusual waves (appear to be large and rapid tidal changes, or water recedes), move to higher ground.

• Do not return until event is over; a tsunami includes multiple waves sometimes separated

by 10-30 minutes and may last for hours.

L. Braile, Purdue Universitybraile@purdue.edu, www.eas.purdue.edu/~braile

Seismic/Eruption Program (Windows; FREE): http://www.geol.binghamton.edu/faculty/jones/

Tsunami Videos:http://www.asiantsunamivideos.com/

Digital Globe images:http://www.digitalglobe.com/

Animations: http://staff.aist.go.jp/kenji.satake/animation.gifhttp://www.pmel.noaa.gov/tsunami/Mov/TITOV-INDO2004.movhttp://es.ucsc.edu/~ward/indo.mov

Tsunami database search:http://tsun.sscc.ru/HTDBPacNew/page.asp

7. the growth of population and building in hazardous, low-elevation coastal areas

Global population map

Close-up of Global population map

Global seismic hazard map

Close-up of Global seismic hazard map

Files needed:

• NOAA animation:

TITOV-INDO2004[1].mov

• S. Ward Animation:

indo[1]Ward.mov

• Videos:

See: http://www.asiantsunamivideos.com/

December 26, 2004

Great subductionthrust

fault earthquake

Largest historical natural disasters

The same geologic processes that make our planet habitable

also make it dangerousSeth Stein, Northwestern Univ.