Tsunami (soo-NAH-mee): a Japanese word that means harbor wave; a sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine slides, or exploding volcanic islands. Typically generated by seismic or volcanic activity or by underwater landslides, a tsunami consists of a series of high-energy waves that radiate outward like pond ripples from the area in which the generating event occurred.
Seiche (saysh): a series of standing waves (sloshing action) of an enclosed body or partially enclosed body of water caused by earthquake shaking. Seiche action can affect harbors, bays, lakes, rivers, and canals.
While tsunami and seiche events occur infrequently in Puget Sound, it is important to be aware of their very real and dangerous potential, an awful reality illustrated by the March 2011 earthquake and tsunami in Japan and the December 2004 earthquake and tsunami in Southeast Asia.
Early warning signs of the arrival of tsunami waves is usually typified by a sudden and unexpected recession of water; the first wave will be followed by additional waves a few minutes or even a few hours later. Tsunami waves can resonate in bays and harbors for several days after arrival of the first wave as was witnessed in Crescent City, California following the March 2011 Great East Japan earthquake and tsunami.
The National Tsunami Warning Center (NTWC) is responsible for tsunami warnings for California, Oregon, Washington, British Columbia and Alaska. The Pacific Tsunami Warning Center (PTWC) provides warnings to international authorities, Hawaii, and U.S. Territories within the Pacific Basin. The NTWC may issue the following bulletins:
- Information: A message with information about an earthquake that is not expected to generate a tsunami or additional analysis is underway to confirm whether a tsunami was generated.
- Advisory: An earthquake has occurred in the Pacific Basin, which might generate a tsunami.
- Watch: A tsunami was or may have been generated, but is at least two hours travel time to the area in Watch status.
- Warning: A tsunami was, or may have been generated, which could cause damage; therefore, people in the warned area are strongly advised to evacuate.
- Information Statement: In most cases, statements are issued to indicate there is no threat from an earthquake and to prevent unnecessary evacuations.
- Watch: An earthquake has occurred in the Pacific basin, which might trigger a tsunami. The danger level is not yet known; stay alert for further information. The National Tsunami Warning Center may expand, upgrade or cancel watches depending on changing conditions.
- Advisory: The threat of a tsunami exists. Strong currents are likely; stay away from the shore, out of ports & harbors. The National Tsunami Warning Center may expand, upgrade, or cancel advisories depending on changing conditions.
- Warning: A tsunami was, or may be generated, which could cause significant widespread damage .If you are within the warned area, you may be advised to evacuate. Familiarize yourself in advance with the evacuation routes.
In partnership with:
What to do to prepare for a tsunami:
- Learn about the tsunami risk in your community.
- Learn about established tsunami evacuation routes and pick the safest route from your home, school, workplace, or any other place you’ll be where tsunamis present a risk. Try to go to an area at least 100 feet above sea level or up higher and two miles inland, away from the coastline. Determine routes you would take by car, and also by foot.
- Make arrangements for housing in the event you need to evacuate your home, and always have your kit ready to go.
- Follow flood preparedness precautions. Tsunamis are large amounts of water that crash onto the coastline, creating floods.
- Establish meeting places and phone numbers in case family members are separated.
When you’re away from home:
- Learn if the area you are visiting is at risk from tsunami.
- Check with the hotel, motel, campground operators, or local officials for tsunami evacuation information and how you would be warned. It is important to know designated escape routes before a warning is issued.
- Find out if your NOAA weather radio will work where you are visiting. If so, set it so it can receive information about that area.
What to do during a tsunami:
- If you feel the ground shake, you should take precaution and move to high ground immediately as a local tsunami may have been generated.
- When an alert is issued by the National Tsunami Warning Center for a distant tsunami, listen to a NOAA weather radio, Coast Guard emergency frequency station, or radio/television for emergency information.
- Stay away from the beach. Watching a tsunami from the beach or cliffs could put you in grave danger. If you can see the wave, you are too close to escape it.
- Follow instructions issued by local authorities. Recommended evacuation routes may be different from the one you use, or you may be advised to go to even higher ground.
- Take your disaster supplies with you.
- Get to higher ground and as far inland as possible.
- 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.
What to do after a tsunami:
- Continue listening to your NOAA weather radio and monitoring the television and radio for emergency news. The tsunami may have damaged roads, bridges, or other places that may be unsafe.
- Helped inured or trapped persons. Give first aid where appropriate. Do not move seriously injured persons unless they are in immediate danger of further injury.
- Use the telephone only for emergency calls.
- Stay away from flooded and damaged areas until officials say it is safe to return.
- Never drive through flooded areas – cars can be carried away by just two feet of water.
- Stay away from debris in the water; it may pose a safety hazard to boats and people.
- Return home only after authorities advise it is safe to do so.
- Stay out of the building if waters remain around it. Tsunami waters, like flood waters, can undermine foundations, causing buildings to sink, floors to crack, or walls to collapse.
- When re-entering buildings or homes, use extreme caution:
- Wear sturdy shoes.
- Use battery-powered lanterns or flashlights instead of candles, lighters, matches or other ignition devices that could create a hazardous fire situation.
- Examine walls, floors, doors, staircases, and windows to make sure the building is not in danger of collapsing.
- Inspect foundations for cracks or other damage.
- Look for fire hazards. There may be broken or leaking gas lines, flooded electrical circuits, submerged electrical equipment. Fire is the most frequent hazard following floods.
- Check for gas leaks. If you smell gas or hear a blowing or hissing noise, open a window and quickly leave the building. Turn off the gas if you can and contact the utility company.
- Look for electrical system damage. If you see sparks or broken or frayed wires, or smell burning insulation, turn off the electricity at the main electrical panel. Note: stepping into water, or water damage to the electrical panel may present an electrical hazard as you try to turn it off – if this is the case, contact an electrician first for advice.
- Do not use any appliances or lights until an electrician has checked the electrical system.
- Check for sewage and water line damage. If you suspect damage, avoid using the toilets and contact a plumber. Contact the utility company for any damage to water pipes.
- Use a stick to poke through debris in flooded areas.
- Watch for loose plaster, drywall and ceilings that could fall.
- Open doors and windows to help dry the building.
- Shovel mud while it is still moist to give walls and floors an opportunity to dry.
- Only use tap water if local health officials advise it is safe.
- Check food supplies. Any food that has come in contact with flood waters may be contaminated and should be thrown out.
- Take photographs to document damage for insurance purposes.