TSUNAMIS

A TSUNAMI (JAPANESE FOR “HARBOR WAVE”) IS A CATASTROPHIC

OCEAN WAVE THAT’S USUALLY CAUSED BY AN EARTHQUAKE, VOLCANO ERUPTION, OR A COASTAL LANDSLIDE.

HOW IT’S GENERATED

A TSUNAMI IS GENERATED BY A DISTURBANCE THAT DISPLACES A LARGE WATER MASS FROM IT’S EQUILIBRIUM POSITION.

IN EARTHQUAKE GENERATED TSUNAMIS, THE WATER COLUMN IS DISTURBED BY THE UPLIFT OR SUBSIDENCE OF THE SEA FLOOR.

SUBMARINE LANDSLIDES AS WELL AS VOLCANIC ERUPTIONS MAY ALSO GENERATE TSUNAMIS AS ROCKS AND SEDIMENTS FROM THESE

EVENTS ARE REDISTRIBUTED ACROSS THE OCEAN FLOOR.

TSUNAMIS MAY TRAVEL HUNDREDS OF KILOMETERS HAVING WAVE LENGTHS (DISTANCE BETWEEN SUCCESSIVE CRESTS OF A WAVE) OF 100 TO 200 KM WITH WITH SPEEDS UP TO 800 KPH IN DEEP WATER. WAVE AMPLITUDES OF TSUNAMIS (HEIGHT OF WAVES) IN DEEP WATER ON THE OTHER HAND ARE ONLY 1 TO 2

FEET HIGH.

AS TSUNAMIS NEAR COASTAL WATERS, FRICTION WITH THE RISING SEA FLOOR DECREASES THE VELOCITY OF THE WAVES AND SHORTENS THE WAVELENGTHS BUT ALSO INCREASES THE

WAVE AMPLITUDES AS HIGH AS 30 METERS OF 100 FT.

AFTER THE RISE IN SEA LEVEL, THE CONTINENTAL SHELF WATER BEGINS TO MOVE BACK AND FORTH FROM THE WAVES

CREATING AN OSCILLATION EFFECT OR “RUN-UPS” WHICH INCLUDE THE RIDGE OR THE FORWARD MOVEMENT OF THE WAVE AND THE TROUGH OR THE DRAWBACK OF THE WAVE

WHICH EXPOSES NORMALLY SUBMERGED AREAS.

THE SCALE USED TO MEASURE TSUNAMIS IS SIEBERG-AMBRASEYS SCALE AND THE IMAMURA-IIDA SCALE USED FOR TSUNAMIS IN THE MEDITERRANEAN SEA AND PACIFIC OCEAN, RESPECTIVELY. THE MAGNITUDE OF TSUNAMIS IS MEASURED

BY THE ML (MURTY AND LOOMIS).

PREVALENCE

ACCORDING TO THE INTERNATIONAL TSUNAMI SOCIETY, TSUNAMIS ARE MOST PREVALENT IN THE PACIFIC OCEAN DUE TO THE HIGH SEISMIC ACTIVITY WITHIN THE “GREAT

RING OF FIRE” WHERE 90% OF THE WORLD’S EARTHQUAKES OCCUR. THIS IS WHERE 80% OF THE

WORLD’S TSUNAMIS HAPPEN.

WAVE EFFECT

TSUNAMIS CAN CAUSE EXTENSIVE DAMAGE THAT CAN DESTROY CITIES, KNOCK OUT POWER GRIDS AND CAUSE BROWN OUTS, PRODUCE HIGH FLOODS, AND

TAKE MANY LIVES.

ON MARCH 11, 2011 AN EARTHQUAKE MEASURING A MAGNITUDE OF 9.0 ON THE RICHTER SCALE PRODUCED A GIANT TSUNAMI

DEVASTATING JAPAN’S EASTERN COAST ISLAND OF HONSHU. THE WAVES REACHED AS HIGH AS 33 FT AND STRUCK THE CITY OF

SENDAI AND OTHER LOW LYING COASTAL REGIONS OF JAPAN’S EASTERN ISLANDS. THE WAVES TRAVELED AS FAR AS 3 KM INLAND

AND FLOODED AN ESTIMATED AREA OF 550 SQUARE KM. THE TSUNAMI ALSO CREATED A MAJOR NUCLEAR ACCIDENT AT A POWER

STATION ALONG THE COAST IN WHICH MORE THAN 300 TONS OF RADIOACTIVE MATERIAL LEAKED INTO THE PACIFIC OCEAN

AFFECTING FISH AND OTHER MARINE LIFE.

THE AFTERMATH

An estimated of more than 18,000 civilians lost their lives to the destruction of the tsunami most of which died in drowning.

Japan has stated that it will cost as much as 309 billion dollars ro rebuild damages caused by the earthquake and typhoon.

Two years after the quake, about 300,000 people who lost their homes were still living in temporary housing, the Japanese government said.

RED CROSSTSUNAMI PREPAREDNESS

Red Cross Tsunami Preparedness

PREVENTION/MITIGATION

Find out if your home, school, workplace or other frequently visited locations are in tsunami hazard areas.

Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters. Evacuation orders may be based on these numbers.

Plan evacuation routes from your home, school, workplace and other places you could be where tsunamis present a risk. If possible, pick areas 100 feet (30 meters) above sea level or go as far as 2 miles (3 kilometers) inland, away from the coastline. If you cannot get this high or far, go as high or far as you can. Every foot inland or upward may make a difference. You should be able to reach your safe location on foot within 15 minutes.

PREVENTION/MITIGATION

Find out what the school evacuation plan is. Find out if the plan requires you to pick your children up from school or from another location. Telephone lines during a tsunami watch or warning may be overloaded, and routes to and from schools may be jammed.

Practice your evacuation routes. Familiarity may save your life. Be able to follow your escape route at night and during inclement weather. Practicing your tsunami survival plan makes the appropriate response more of a reaction, requiring less thinking during an actual emergency.

If you are a tourist, familiarize yourself with local tsunami evacuation protocols. You may be able to safely evacuate to the third floor and higher in reinforced concrete hotel structures.

HOW TO RESPOND DURING A TSUNAMI

If you are in a coastal area and feel an earthquake that lasts 20 seconds or longer:

Drop, cover and hold on. You should first protect yourself from the earthquake.

When the shaking stops, gather members of your household and move quickly to higher ground away from the coast. A tsunami may be coming within minutes.

Avoid downed power lines and stay away from buildings and bridges from which heavy objects might fall during an aftershock.

HOW TO RESPOND DURING A TSUNAMI

What to do during a tsunami watch:

Use a Disaster weather radio or tune to a an emergency frequency station or a local radio or television station for updated emergency information.

Locate household members and review evacuation plans. Be ready to move quickly if a tsunami warning is issued.

HOW TO RESPOND DURING A TSUNAMI

What to do during a tsunami warning:

If you hear an official tsunami warning or detect signs of a tsunami, evacuate at once.

Take your emergency preparedness kit. Having supplies will make you more comfortable during the evacuation.

Take your pets with you. If it is not safe for you, it’s not safe for them.

Get to higher ground as far inland as possible. Watching a tsunami could put you in grave danger. If you can see the wave, you are too close to escape it.

WHAT TO DO AFTER A TSUNAMI

Continue using a Weather Radio or tuning to a Coast Guard station or a local radio or television station for the latest updates.

Return home only after local officials tell you it is safe. A tsunami is a series of waves that may continue for hours. Do not assume that after one wave the danger is over. The next wave may be larger than the first one.

Check yourself for injuries and get first aid as needed before helping injured or trapped persons.

If someone needs to be rescued, call professionals with the right equipment to help. Many people have been killed or injured trying to rescue others.

WHAT TO DO AFTER A TSUNAMI

Help people who require special assistance—infants, elderly people, those without transportation, people with disabilities and large families who may need additional help in an emergency situation.

Avoid disaster areas. Your presence might interfere with emergency response operations and put you at further risk from the residual effects of floods.

Use the telephone only for emergency calls.

Stay out of any building that has water around it. Tsunami water can cause floors to crack or walls to collapse.

WHAT TO DO AFTER A TSUNAMI

Use caution when re-entering buildings or homes. Tsunami-driven floodwater may have damaged buildings where you least expect it. Carefully watch every step you take.

To avoid injury, wear protective clothing and be cautious when cleaning up.

Watch animals closely and keep them under your direct control.

NDRRMC PLAN