Indian Ocean Tsunami 2004-Karan Gupta 07617, Vikas Singh 07612,

8/7/2019 Indian Ocean Tsunami 2004-Karan Gupta 07617, Vikas Singh 07612,

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Indian Ocean

Tsunami of 2004Submitted By :

07612 - Vikas Singh

07617 - Karan Gupta


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The Tsunami

Also called seismic sea wave

Generated by an undersea geologic event, such as a

great earthquake, volcanic explosion, or underwaterlandslide

Tsunami in Japanese means harbor wave

Tsunamis are not tidal waves


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Subduction Zone Earthquake

Oceanic crust collides with continental crust andis forced downward

Compression forces build until rock fracturesand an earthquake occurs

Graphic Strahler/Wiley 2005


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Generation of the Tsunami

During the earthquake, the seafloor movesupward, creating a water wave that spreads

outward.Graphic Gerard Fryer 2003


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Undersea Landslideor Slump

Body of sediment slumpsdownward along acontinental shelf

Can be triggered by anearthquake

Water drops at head ofslump, rises at toe to

create a wave Wave moves outward as

a tsunami

Graphic Gerard Fryer 2003


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Volcanic Explosion

The explosive eruption of Krakatau in August1883 created a tsunami that claimed more than36,000 lives


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The Tsunami Wave

The tsunami wave has a wavelength of 100200 kmwith a deep water height of 1 m or less

Travels as fast as 200 m/s (440 mi/hr) in open ocean

As it approaches the shore, it slows, steepens, andrises in height

Deep ocean

Shoaling


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The Wave Keeps Coming

The wave acts like a temporary rise in sea level,

pushing water far inland before it retreats


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Indian Ocean Tsunami ofDecember 26, 2004

Caused by 9.0 earthquake beneath Java Trench,west of Sumatra, Indonesia

Fourth largest earthquake since 1900

1000 km of fault ruptured and sea floor movedupward by about 5 m (16 ft)

Sumatra

Java Trench


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Earth's outer shell made up of ~15 major rigid plates ~ 100 km thick

Plates move relative to each other at speeds of a few cm/ yr (about

the speed at which fingernails grow)

Plates are rigid in the sense that little (ideally no) deformation occurs

within them,

Most (ideally all) deformation occurs at their boundaries, giving rise to

earthquakes, mountain building, volcanism, and other spectacular

phenomena.

Style of boundary and intraplate deformation depends on direction &rate of motion, together with thermo-mechanical structure

BASIC CONCEPTS: RIGID PLATES


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BASICCONCEPTS:

THERMAL

EVOLUTION OFOCEANIC

LITHOSPHERE

Warm mantle material upwells at spreading centers and then cools

Because rock strength decreases with temperature, cooling material

forms strong plates of lithosphere

Cooling oceanic lithosphere moves away from the ridges, eventuallyreaches subduction zones and descends in downgoing slabs back into

the mantle, reheating as it goes

Lithosphere is cold outer boundary layer of thermal convection system

involving mantle and core that removes heat from Earth's interior,

controlling its evolution

Stein &Wysession2003


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Gordon & Stein, 1992

INDIAN PLATE MOVES NORTHCOLLIDING WITH EURASIA


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COMPLEX

PLATEBOUNDARYZONE IN

SOUTHEASTASIA

Northward motion ofIndia deforms all of

the region

Many small plates

(microplates) andblocks

Molnar & Tapponier, 1977


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India subductsbeneath Burma

microplateat about 50 mm/yr

Earthquakes occurat plate interface

along the Sumatraarc (Sunda trench)

These are

spectacular &destructive resultsof many years of

accumulated motion


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INTERSEISMIC:

India subducts beneathBurma microplate

at about 50 mm/yr(precise rate hard toinfer given complexgeometry)

Fault interface is locked

EARTHQUAKE(COSEISMIC):

Fault interface slips,overriding plate

rebounds, releasingaccumulated motion

HOW OFTEN:

Fault slipped ~ 10 m = 10000 mm / 50 mm/yr

10000 mm / 50 mm/yr = 200 yrLonger if some slip is aseismic

Faults arent exactly periodic for reasons we dont understand

Stein & Wysession, 2003


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MODELINGSEISMOGRAMSshows how slip varied

on fault planeMaximum slip area~400 km long

Maximum slip ~ 20 mStein & Wysession


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TWO VIEWS OF THE PART OF THE SUMATRASUBDUCTION ZONE THAT SLIPPED

Seismogram analysis showsmost slip in southern 400 km

Aftershocks show slipextended almost 1200 km

C. Ji

ERI


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Earthquakes rupture a patchalong fault's surface.

Generally speaking, the

larger the rupture patch, thelarger the earthquakemagnitude.

Initial estimates from theaftershock distribution showthe magnitude 9.3 Sumatra-Andaman Islands Earthquakeruptured a patch of faultroughly the size of California

For comparison, a magnitude5 earthquake would rupture

a patch roughly the size ofNew York City's Central Park.


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NORMAL MODES(ULTRA-LONG

PERIOD WAVES)SHOW SEISMICMOMENT 3 TIMESTHAT INFERREDFROM SURFACE

WAVESIMPLIES SLIP ONAREA 3 TIMESLARGER

Entire 1200-kmlong aftershockzone likely slipped


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0S2 YIELDS SEISMICMOMENT Mo =

1 x 1030 dyn-cm

2.5 TIMES BIGGER THANINFERRED FROM 300-sSURFACE WAVES

CORRESPONDING MOMENTMAGNITUDE Mw IS 9.3,COMPARED TO 9.0 FROMSURFACE WAVES

Comparison of fault areas,moments, magnitudes,amount of slip shows this wasa gigantic earthquake

the big one


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IF ENTIRE ZONESLIPPED, STRAINBUILT UP HASBEEN RELEASED,LEAVING LITTLEDANGER OFCOMPARABLE

TSUNAMI

Risk of local tsunamifrom large aftershocks

or oceanwide tsunamifrom boundarysegments to southremains


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EARTHQUAKE MAGNITUDE9.3

One of the largest earthquakes since seismometer

invented ~ 1900

Stein & Wysession afterIRIS


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SUCH GREATEARTHQUAKES

ARE RARE

Stein & Wysession,


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SOME MAJOR DAMAGE DONE BY EARTHQUAKE SHAKING ITSELF,BUT STRONG GROUND MOTION DECAYS RAPIDLY WITH DISTANCE

0.2 g

Stein & Wysession,2003


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0.2 g

Damage

onset for

modern

buildings

DAMAGE DEPENDS ON BUILDING TYPERESISTANT CONSTRUCTION REDUCES EARTHQUAKE RISKS

Earthquakes don't kill people; buildings kill"

Coburn &Spence 1992


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TSUNAMI - water wave generated by earthquake

NY Times


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TSUNAMI GENERATED ALONG FAULT, WHERE SEAFLOOR DISPLACED, AND SPREADS OUTWARD

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

Red - up motion, blue downHyndeman and Wang, 1993

Qui

Ti

TI

Z

i

i

ure.


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WAVE PATH GIVEN BY SNELLS LAW

Going from material with speed v1 to speed v2

Angle of incidence I changes by

sin i1 / v1 = sin i2 / v2

SLOW

FAST

Tsunami wave bends as water depth & thus speed

Stein & Wysession


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TRACE RAYPATHSUSINGSNELLS LAW

RAYS BENDAS WATERDEPTHCHANGES

FIND WHENWAVESARRIVE ATDIFFERENTPLACES

DENSITY OFWAVESSHOWSFOCUSING &DEFOCUSING

Woods & Okal, 1987

1 hour


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NOAA


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IN DEEP OCEAN tsunami has long wavelength, travels fast,small amplitude - doesnt affect ships

AS IT APPROACHES SHORE, it slows. Since energy is

conserved, amplitude builds up - very damaging


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Because seismic waves travel muchfaster (km/s) than tsunamis, rapidanalysis of seismograms can identifyearthquakes likely to cause majortsunamis and predict when waves

will arrive

TSUNAMI WARNING

Deep ocean buoys can measurewave heights, verify tsunamiand reduce false alarms


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HOWEVER, HARD TO PREDICT EARTHQUAKESrecurrence is highly variable

M>7 mean 132 yr W 105 yr

Estimated probability in 30 yrs 7-

Sieh et al.,1989Extend earthquake history

with geologic records -

paleoseismology


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EARTHQUAKE RECURRENCEAT SUBDUCTION ZONES IS

COM PLICATED

In many subduction zones, thrustearthquakes have patterns inspace and time. Largeearthquakes occurred in theNankai trough area of Japanapproximately every 125 years

since 1498 with similar fault areas

In some cases entire regionseems to have slipped at once; inothers slip was divided intoseveral events over a few years.

Repeatability suggests that asegment that has not slipped forsome time is a gap due for anearthquake, but its hard to usethis concept well because of

variability

GAP?

NOTHING YET Ando, 1975


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EARTHQUAKE PREDICTION?

Because little is known about the fundamental physics of faulting, manyattempts to predict earthquakes searched for precursors, observablebehavior that precedes earthquakes. To date, search has provedgenerally unsuccessful

In one hypothesis, all earthquakes start off as tiny earthquakes, whichhappen frequently, but only a few cascade via random failure processinto large earthquakes

This hypothesis draws on ideas from nonlinear dynamics or chaos theory,in which small perturbations can grow to have unpredictable largeconsequences. These ideas were posed in terms of the possibility thatthe flap of a butterfly's wings in Brazil might set off a tornado in Texas, orin general that minuscule disturbances do not affect the overall

frequency of storms but can modify when they occur

If so, there is nothing special about those tiny earthquakes that happentogrow into large ones, the interval between large earthquakes is highlyvariable and no observable precursors should occur before them. Thus

earthquake prediction is either impossible or nearly so.


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PLATE TECTONICS ISDESTRUCTIVE TO HUMAN

SOCIETY

Mt SaintHelens1980 eruption

USGS

1989LomaPrietaearthquake


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Plate boundary volcanism producesatmospheric gases (carbon dioxideCO2 ; water H2O) needed to support

life and keep planet warm enoughfor life ("greenhouse" )

May explain howlife evolved onearth (at midocean ridge hotsprings)

Plate tectonics raises continentsabove sea level

Plate tectonics produces mineralresources including fossil fuels

BUT PLATE TECTONICSIS ALSO CRUCIAL FOR

HUMAN LIFE

Press & Siever


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CIVILIZATIONEXISTS BY

GEOLOGICALCONSENT

The same geologicprocesses that make our

planet habitable also make

it dangerous


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Banda Aceh, Sumatra, Indonesia

Courtesy of DigitalGlobe June 23, 2004


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Courtesy of DigitalGlobe

Banda Aceh, Sumatra, Indonesia

Dec 28, 2004


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Kalutara Beach, Sri Lanka

Courtesy of DigitalGlobe Jan 1, 2004


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Courtesy of DigitalGlobe Dec 26, 2004


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The Tsunamis Toll

Deaths: >210,000 Indonesia: 166,000

Thailand: 5,000

Sri Lanka: 30,000

India: 10,000 Damage: >$7 billion

Indonesia: $4.4 billion

India: $1.5 billion

Sri Lanka: $900 million Aid Donations: >$6.5 billion

Government pledges: $5.3 billion

Private donors: $12 billion


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Southeast Asia Tsunami 2004

The worst tsunami in recorded history wascreated at 7:58 am on December 26, 2004

Magnitude 9.3 (second strongest earthquakeever recorded on a seismograph)

Lasted 10 minutes (longest lasting earthquakein history)


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229,866 confirmed dead, which includes42,883 missing and never accounted for

More than $7 billion dollars damage


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This earthquake was unusually large ingeographical extent

An estimated ~1,600 km (~1,000 mi) of fault lineslipped up to 15 m (50 ft) along the subduction

zone where geologist believed that the Indo-Australian plate dives under the Eurasian plate

However, researchinto this tsunamilead to thediscovery of theBurma microplate


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Scientist now understand that the very largeIndia and Australian plates are being subductedunder the very small Burma microplate

The massivelybigger Indiaand Australianplates easilyshove the

smaller Burmamicroplatearound


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Seismographic data revealed that the first phaseinvolved a rupture about 400 kilometers (250 miles)long and 100 kilometers (60 miles) wide, located30 kilometers (19 miles) beneath the sea bed,which is the longest rupture ever known to have

been caused by an earthquake


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The rupture proceeded at a speed of about10,000 km/h (6,300 mph), beginning off the coastof Aceh and proceeding north-westerly over aperiod of about 100 seconds


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Then a pause of about 100 seconds took placebefore the rupture continued northwardstowards the Andaman and Nicobar Islands

There was a vertical change along the rupture

that ranged from a few meters up to 50 meters


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The sea bed isestimated to haverisen by severalmeters, displacingan estimated30 cubic kilometers(7 cubic miles) ofocean water and

triggeringdevastating tsunamiwaves


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The tsunami waves did not originate from apoint source, but rather radiated outwardsalong the entire 1,600 kilometer (1,000 mile)length of the rupture


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The common perception is that the tsunami wasjust one great wave that swept in from the sea


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Actually, there were four tsunami waves thatcame ashore over a 90 minute time period

The resultingtsunamis

devastated theshores ofIndonesia, SriLanka, India,Thailand and othercountries withwaves as high as30 meters(100 feet)


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Second tsunami wave starting toretreat at Kata Noi Beach, Thailand,10:17 am


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Receding waters after the secondtsunami at 10:20 am


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3rd tsunami wave arriving at 11:00am


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4th tsunami wave just arriving at 11:22 am


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These tsunamis caused serious damage and deathsas far as the east coast of Africa, with the farthestrecorded deaths due to the tsunami occurring inStruisbaai , South Africa, 8,000 kilometers(5,000 miles) away from the epicenter, where a

1.5 meter (5 foot) wave surged on shore during hightide about 12 hours after the earthquake


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In addition to the staggering death toll, thedamage to cities and villages was estimatedto be seven billion dollars


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TheU

S military provided the first foreign aid, butit took a week before help reached all of thestricken


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A plot showing all of theaftershocks of magnitude4.0 and greater thatoccurred over a 15 dayperiod betweenDecember 26, 2004 and

January 10, 2005


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The tsunami-lashed Andaman and Nicobar Islandssuffered 9,500 aftershocks between December 26and February 19


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Meanwhile, thetectonic platesremain extremelyactive in Southeast

Asia

There have beenmany majorearthquakes in the

past and manymore will occur inthe future

Documents

Indian Ocean Tsunami 2004-Karan Gupta 07617, Vikas Singh 07612,