Tsunami

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Tsunami
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What Is It?

• Causes
• Earthquakes-(most common)
• Eruption of coastal and island volcanoes
• Submarine landslides
• Ocean impacts of large meteorites (rare)

• Series of traveling shallow water waves
• Hit coast in intervals
• Majority of tsunami occur in Pacific Ocean
• subduction zones

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• wind generated waves
• period 5 - 20 seconds
• wavelength 100-200 meters

• shallow water waves
• ratio between water depth and wavelength is small
• period of 10 minutes to 2 hours
• wavelength in excess 480 km
• 2-3 meters high in deep seas

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• In shallow water it loses speed and increases in
  height
• contour of the ocean floor and coast can change
  speed direction
• Wave height can reach 30 to 50 meters
• Rate of energy loss of waves is inversely
  proportional to its wavelength
• Areas most at risk are less than 50 feet above
  sea level and within a mile of the coast.

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Recent Tsunamis in Japan
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1960 Chile Earthquake

• Magnitude 9.5
• South American plate moved over the subducting
  Nazca plate
• Tsunami hit Chile then reversed 17,000 miles
  across the Pacific Ocean and hit Japan
• water level 4.5 meters
• 122 fatalities
• animation

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1993 Hokkaido tsunami

• Earthquake-magnitude 7.8 in Sea of Japan
• misbeleif that a tsunami would not occur in the
  Sea of Japan
• late issue of warning
• water levels up to 9 meters
• 200 fatalities

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Japans management

• seawalls
• breakwaters
• buoys linked to Global Positioning Systems
• forcasting centers work with Tsunami Warning
  System in the Pacific

• conduct drills once a year
• some villages move to higher ground
• Education
• videos
• Karakuwa tsunami simulation hall

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Tips for survival

• head to higher ground after strong earthquakes
• Do not go to the shore to watch a tsunami
• cooperate with warnings and evacuation procedures

• abandon belongings
• realize roads may not be accessible
• do not return until the all clear is given