ANATOMY OF A TSUNAMIJ. Fernando*, A. Braun**, R. Galapatti***, S.C. Wirasinghe**, J. Ruwanpura**

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OUTLINE

•The Sumatra Andaman Island Earthquake

•The Indian Ocean Tsunami

•Impact on Sri Lanka's Coast and Ecosystems

•Tsunami Warning Systems

•Mitigation Strategies and Better Planning

The Sumatra Andaman Island Earthquake of Dec. 26, 2004

The Sumatra Andaman Island Earthquake of Dec. 26, 2004

– Facts: Sunday, Dec 26 0:58:53 UTC

– >> 6:58:53 local time

– Location: 3.307N 95.947E, depth=30 km

– 250 km SW from Banda Aceh, Indonesia

– Magnitude 9.0-9.3: 2nd, 4th largest EQ since 1900

– Slip of up to 15-20 meters

– 1200 km long fault plane

– Southern fault – fast rupture, northern fault – slow

The Indian Ocean Tsunami

– Travels with the speed of up to 800 km/h

– Speed depends on water depth

– Wavelength 100-250 km

– Waveheight depends on water depth

– Over open ocean waveheight = 20-60 cm

– Wave and height observed by satellite altimetry

Courtesy of K. Satake

The Indian Ocean Tsunami

Courtesy of W. Smith, NOAA

The Indian Ocean Tsunami

Inundation levels based on different wave heights

The Indian Ocean Tsunami

Impact on Sri Lanka's Coast and Ecosystems

•North-south striking fault caused linear wavefront reaching Sri Lanka

•Reached Sri Lanka's east coast frontally at 8:50 AM

•Damage/wave height was a function of local bathymetry

•Sand dunes in the southeast and far northeast coast protected coast

•Man-made and natural gaps in dunes led to wave penetration

•Vegetation protects, coconut trees did not suffer, but palmyrah trees did

•Mangroves protect estuaries, but not found in energetic wave climates

•Displacement of sand and sediments, saltwater intrusion into aquifers

•However, the ecosystem damage was light to moderate

•Internal and external functions are still intact

Impact on Sri Lanka's Coast and Ecosystems

Impact on Sri Lanka's Coast and Ecosystems

Dead Palmyrah Trees in Mullaitivu

Breached spit in Bentota

R/H/42/TEroded face of Hambantota dunes

Tsunami Warning Systems

NOAA Dart – Pacific, new stations in the Atlantic

•GITEWS – Indian Ocean, 2 stations (currently not operational)

•USIOTWS – Indian Ocean, planned

•Detect sea level variations of 1 cm

•Contain 1) detection system, 2) communication system,

•and 3) warning system including social aspects

•How fast can we issue a warning and to whom?

•How reliable must the information be?

Mitigation Strategies and Better Planning

Mitigation Strategies and Better Planning

Detect - Local Seismic NetworkUniform (0,10)

Detect - Global Seismic NetworkUniform (0,10)

TsunamiUniform (0,3)

Process Seismic Info.

Uniform (0,2)

Info. Received by Analyst

Uniform (0,5)

Radio SignalUniform (0,1)

Process Seismic Info.

Uniform (0,2)

Validate with Global NetworkUniform (1,5)

Detected by Tsunami Warning

SystemUniform (5,20)

Detect - Tide Gauge System

Uniform (5,20)

Perform Seismic Analysis

Uniform (2,5)

Info. Received by TWC

Uniform (0,5)

Issue an AlertUniform (1,3)

Issue a Decision on EQ

Uniform (1,3)

Info Received - National

Uniform (0,5)

Issue a Detailed Analysis

Uniform (1,3)

Detect EQ - Human

Uniform (0,10)

Tsunami AnalysisUniform (2,5)

Detect - HumanUniform (5,20)

Info. Received - Local

Uniform (1,10)

Process Info - Human

Uniform (0,20)

Telephone SignalUniform (1,30)

Internet SignalUniform (0,2)

Inform Local Authorities for

PreparationUniform (5,30)

Dummy

Human Info Validated - Local

Uniform (3,10)

Satellite SignalUniform (0,2)

Tsunami Simulation Analysis

Uniform (5,10)

Start

Inform National Centre

Uniform (0,5)

National Office Makes a Decision

Uniform (0,5)

Inform Local Authorities for

InitiationUniform (5,30)

Evacuation Start

FS/FF

FS/FF

FS/FF

FS

FS

FS FS

FS FS FS

FS

FS

FS FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

FS

Conclusions