TSUNAMI

WHAT IS TSUNAMI

Important points: In deep ocean, tsunami has small amplitude and travels with speed of jet airliner.

When approaching land, speed slows and amplitude increases dramatically.

HOW TSUNAMI IS CAUSED

Tsunami are often generated by large and shallow earthquakes at subduction zones where oceanic plates descend into the deeper mantle. These types of earthquakes can produce the rapid displacements of the ocean floor that generate tsunamis.

Properties of ocean waves & tsunami

Periods LengthsWind-blown short: 5 seconds 39 meters (130 ft)Ocean waves medium: 10 seconds 156 meters (510 ft)

long: 20 seconds 624 meters (2050 ft)Tsunami super long: 3600 seconds >800 kilometers

(60 minutes) (520 miles)

LONG period: Wind waves wash on shore for < 5 seconds. Tsunami can wash on shore for 10 - 15 minutes!

DAMAGE CAUSED BY TSUNAMI

Tsunamis cause damage by

two mechanisms: the smashingforce of a wall of water travelling at high speed, and the destructive power of a largevolume of water draining off the land and carrying a large amount of debris with it,even with waves that do not appear to be large.

Deep-ocean Assessment and Reporting of Tsunami (DART)

Pacific Tsunami Warning System

RECENT TSUNAMIDate Cause Height Location Deaths

1883 Volcanic eruption 35 m Indonesia 36,0001896 Earthquake 29 m Japan 27,0001933 Earthquake 30 m Japan 3,0001946 Earthquake 15 m Alaska 1751960 Earthquake 10 m Chile

>1,2501964 Earthquake 6 m Alaska 1251992 Earthquake 26 m Nicaragua 1701992 Earthquake 26 m Indonesia >1,0001993 Earthquake 31 m Japan 2391994 Earthquake 14 m Indonesia 2381998 Landslide 15 m Papua >2,2002004 Earthquake 30 m Sumatra 245,000

December 26, 2004 TsunamiFacts

The December 26, 2004 Indian Ocean tsunami was caused by an earthquake that is thought to have had the energy of 23,000 Hiroshima-type atomic bombs.

The epicenter of the 9.0 magnitude quake was under the Indian Ocean near the west coast of the Indonesian island of Sumatra. 

The violent movement of sections of the Earth’s crusts known as tectonic plates displaced an enormous amount of water, sending powerful shock waves in every direction.

The tectonic plates in this area had been pushing against each other, building pressure for thousands of years – they continue to do so and will likely cause underwater earthquakes and tsunamis in the future.

A tsunami is a series of waves, and the first wave may not be the most dangerous. A tsunami “wave train” may come as surges five minutes to an hour apart. The cycle may be marked by the repeated retreat and advance of the ocean. The earthquake-induced tsunami resulted in at least 155,000 fatalities, 500,000 injuries, and damages that exceeded $10 billion. Also, it is estimated that 5 million people lost their homes or access to food and water.

SRI HARSHA.G VIIID

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