DOC

2 - Extramarks

By Michael King,2014-11-14 07:35
16 views 0
2 - Extramarks

     Disaster Management

2. Tsunami The killer sea

    wave

    Do you know what Tsunamis are? How they can be predicted and how you can save yourself from

    the deadly Tsunami? Read the section below and you will know more about it. Follow the instructions

    if you reside in any of the coastal states of the country.

    The term ‗Tsunami‘ has been coined from the Japanese term Tsu meaning ‗harbour‘ and nami

    meaning ‗waves‘. Tsunamis are waves generated by earthquakes, volcanic eruptions, or underwater

    landslides and can reach 15m or more in height devastating coastal communities. In recorded history,

    tsunamis worldwide have killed hundreds of thousands of people. Tsunamis caused by nearby

    earthquakes may reach the coast within minutes. When the waves enter shallow water, they may rise

    to several feet or, in rare cases, tens of feet, striking the coast with devastating force. The Tsunami

    danger period can continue for many hours after a major earthquake. A killer Tsunami hit 11 South

    Eastern Countries of Asia on

    the 26th of December 2004

    killing more than 1,50,000

    precious lives. The count

    hasn’t stopped.... At the end

    of the day statistics only

    remain. The emotional,

    economical and ecological toll

    of the disaster can’t be

    calculated. Many villages

    have lost an entire

    generation. This was the

    biggest earthquake to hit the

    world in 40 years and no one

    could have thought that its

    effects would ripple worldwide

    overnight.

    Tsunami wave train

    formation 2

    Submarine fault movement, landslide, or volcanic activity

1

    As waves approach shore they slow down, the waves lengths shorten and become higher

    3

    Possible bore

    formation on shore 4

    8

    Important Facts About Tsunamis

    ? Some tsunamis can be very large. In

    coastal areas their height can be as great as 10m or more (30m in extreme cases), and they can move inland

    several hundred meters.

    ? All low-lying coastal areas can be

    struck by tsunamis.

    ? A tsunami consists of a series of

    waves. Often the first wave may

    not be the largest. The danger from

    subsequent tsunami waves can last

    for several hours after the arrival of the first wave.

    ? Tsunamis can move even 50 km per

    hour on coastal plain, faster than a person can run.

    ? Sometimes a tsunami causes the

    water near the shore to recede,

    exposing the ocean floor. This is

    nature‘s Tsunami warning and should

    be heeded.

    ? The force of some tsunamis is

    enormous. Large rocks weighing

    several tons along with boats and

    other debris can be moved inland

    several meters by tsunami wave activity. Homes Tsunamis may also be generated by very large earthquakes far away in other areas of the Ocean. Waves caused by these travel at hundreds of kilometers per hour, reaching the coast several hours after the earthquake. Unlike ordinary tides, which are short, frequent and surface level, tsunami, are barely noticeable in their deep-sea formation stage. At this point despite a wavelength up to 100 km, they are shallow in depth and move at hundreds of kilometer per hour. If a quake hits Los Angeles, a Tsunami can reach Tokyo in a time less than a Jet would take to traverse the same distance. In 1883, the violent explosion of the famous volcano, Krakatoa in Indonesia, produced tsunamis measuring 40 meters which

    crashed upon Java and Sumatra. Over

36,000 people lost their lives as a result of

    tsunamis that are capable of crossing

    oceans. Tsunamis are nearly always created

    by movement of the sea floor associated

    with earthquakes which occur beneath the

    sea floor or near the ocean.

    Tsunami wave train formation: Seen in the figure is the rupture in the seafloor shunted in the vertical direction. This movement displaces hundreds of cubic kilometres of the overlaying water, generating a massive tsunami, or sea surge.

    and other buildings are destroyed. All floating material and water move with great force

    and can

    kill or injure people.

    ? Tsunamis can occur at any time of day or night.

    ? Tsunamis can travel up rivers and streams that lead to the ocean. Rupture in seafloor pushes water upwards starting the wave

    1

    Wave moves rapidly in deep ocean reaching speed of upto 500 km./h

    2

    As the wave nears land its slows to about 45 km/h but squeezed upwards, increasing in height

    3 Wave heads inland

    destroying all in its path

    4

    9

    What to do BEFORE a Tsunami

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

    ? Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters. ? Plan evacuation routes from your home, school, workplace or any other place you

    could be where

    tsunamis present a risk.

    ? Practice your evacuation routes

    ? Have disaster supplies on hand.

    ? Discuss tsunamis with your family

    ? Develop an emergency communication plan. In case family members are separated

    from one

    another during a tsunami have a plan for getting back together. Ask an out-of-state

    relative or

    friend to serve as the family contact (After a disaster, it is often easier to call long

    distance).

    If you are at risk from tsunamis, you should:

    ? Avoid building or living in buildings within several hundred feet of the coastline.

    ? Make a list of items to bring inside in the event of a tsunami. ? Elevate coastal homes. Most tsunami waves

    are less than 10 feet (3 meters). Elevating your

house will help reduce damage to your property

    from most tsunamis.

    ? Take precautions to prevent flooding.

    ? Have an engineer check your home and advise

    about ways to make it more resistant to tsunami

    water.

    ? Use a local radio or television station for updated

    emergency information.

    ? Follow instructions issued by local authorities.

    What to do DURING a Tsunami

    ? If you are at home and hear there is a tsunami warning, you should make sure your entire family is aware of the warning. Your family should evacuate the house if you live in a tsunami prone area. Evacuate to a safe elevated area and move in an orderly, calm and safe manner to the evacuation site.

    Detecting Tsunamis

    With the use of satellite technology it is possible to provide nearly immediate warning of potentially tsuna-migenic earthquakes. Warning time depends upon the distance of the epicenter

    from the coast line. The warning includes predicted times at selected coastal communities

    where the tsunami could travel in a few hours.

    Coastal tidal gauges can stop tsunamis close to the shore, but they are useless in deep oceans.

    Tsunami detectors, linked to land by submarine cables, are deployed 50 odd kms. out at sea.

    ‗Tsunameters‘ transmit warnings of buoys on the sea surface, which relay it to satellites.

    Myth…

    Tsunamis are caused by

    moon‘s pull.

    Design Solution to Tsunami effect

    10

    ? Take your Disaster Supplies Kit. Having supplies will make you more comfortable during the evacuation.

    ? If you evacuate, take your animals with you.

    ? If you are at the beach or near the ocean and you feel the earth shake, move immediately to higher ground. Do not wait for Tsunami warning to be announced. Stay away from rivers and streams that lead to the oceans.

    ? High multi-storey, reinforced concrete buildings (like hotels etc.) are located in many low-lying coastal areas. The upper floors of these buildings can provide a safe place.

    ? Offshore reefs and shallow areas may help break the forces of tsunami waves, but large and dangerous waves can still be a threat to coastal residents in these areas. Staying

    away from low-lying coastal areas is the safest advice when there is a tsunami warning. ? Update yourself on emergency information or warning announced on radio and television from time

    to time.

    If you are on a boat or ship

    ? Since tsunami wave activity is imperceptible in the open ocean, do not return to port if you are at sea

    and a tsunami warning has been issued for your area. Tsunami can cause rapid changes in water

    level and unpredictable dangerous currents in harbors and ports.

    ? If there is time to move your boat or ship from port to deep water (after you know a tsunami warning

    has been issued), you should weigh the following considerations:

    ? Most large harbors and ports are under the control of a harbor/port authority. These authorities

    direct operations during periods of increased readiness. Keep in contact with the authorities

    should a forced movement of vessels is directed.

    ? Smaller ports may not be under the control of a port authority. If you are aware there is a tsunami

    warning and you have time to move your vessel to deep water, then you may do so in an orderly

    manner. Owners of small boats may find it safest to leave their boat at the pier and physically

    move to higher grounds.

    Damaging wave activity and unpredictable currents can affect harbors for a period of time following the

    initial tsunami impact on the coast. Contact the harbor authority before returning to port. What to do AFTER a Tsunami

    After a tsunami, you should:

    ? Continue using a radio or television for updated emergency information. The tsunami may have

    damaged roads, bridges, or other places that may be unsafe.

    ? Check yourself for injuries and get first aid if necessary before helping injured or trapped persons.

    If someone needs to be rescued, call professionals with the right equipment to help. Many people

    might get killed or injured while trying to rescue others in flooded areas. ? Help people who require special assistance-infants, elderly people, those without transportation, large families who may need additional help in an emergency situation, people with disabilities, and the people who care for them.

    ? Avoid disaster areas. Your presence might hamper rescue and other

    emergency operations and put you at further risk from the residual effects Eyewitness…

    I saw the water

    disappearing and the

    water went back so far

    away and everyone

    wondered what it was a

    full moon or what? Then

    we saw the waves come,

    and we ran,‖ said Katri

    Seppanen a tourist from

    Finland

    11

    of floods, such as contaminated water, crumbled roads, landslides, mudflows, and other hazards.

    ? Use the telephone only for emergency calls. Telephone lines are frequently overwhelmed in disaster

    situations. They need to be cleared for emergency calls to get through. ? Stay out of a building if water remains around it. Tsunami water, like floodwater, can undermine

    foundations, causing buildings to sink, floors to crack, or walls to collapse. ? When re-entering buildings or homes, be very careful ! Tsunami-driven floodwater may have damaged

    buildings where you least expect it. Carefully watch every step you take. ? Wear long pants, a long-sleeved shirt, and sturdy shoes. The most common injury following a

    disaster is cut feet.

    ? Use battery-powered lanterns or flashlights when examining buildings. Battery powered lighting is

    the safest and easiest to use and it does not present a fire hazard for the user, occupants, or

    building. DO NOT USE CANDLES.

    ? Examine walls, floors, doors, staircases, and windows to make sure that the building is not in danger

    of collapsing.

    ? Inspect foundations for cracks or other damage. Cracks and damage to a foundation can render a