Tsunamis can happen on any U.S. coast, according to the government's Ready Campaign. The Pacific and Caribbean coastlines, however, are at the greatest risk.
So what's the difference between a watch and a warning, and what's the best way to stay safe before and after? Here are some tips from the Ready Campaign.
1. BUILD AN EMERGENCY KIT
Have an emergency kit ready to go before a tsunami hits. Here are things to include in a basic emergency kit, according to the Ready Campaign.
Water - one gallon of water per person per day for at least three days, for drinking and sanitation
Food - at least a three-day supply of non-perishable food
Battery - powered or hand crank radio and a NOAA Weather Radio with tone alert
First aid kit
Whistle to signal for help
Dust mask to help filter contaminated air and plastic sheeting and duct tape to shelter-in-place
Moist towelettes, garbage bags and plastic ties for personal sanitation
Wrench or pliers to turn off utilities
Manual can opener for food
Cell phone with chargers and a backup battery
2. KNOW THE ALERT TERMS
As happened on Tuesday, the National Weather Service will use terms to keep you informed about potential tsunamis. What's the difference between a watch and a warning? Here's a look at each type of alert.
Warning A warning means that "a tsunami with the potential to generate widespread inundation is imminent or expected." Warnings may be cause for evacuations. As with all types of alerts, keep in mind that warnings can be updated, so you should always check tsunami.gov for the latest information.
Advisory An advisory means that significant inundation isn't expected, but there is still potential for strong waves and currents to pose danger to people near the water. An advisory may cause beaches to close or harbors to be evacuated.
Watch Watches are issued to alert those in a specific area that they should be prepared to take action if necessary. They may be upgraded or cancelled.
3. BE READY TO ACT
It's not enough to know what the terms mean. You should know what to do when you hear them.
Have a plan: Know your evacuation routes and shelters. Know how you will get in touch with your family and keep up-to-date on alerts. Know specific information your family might need, such as which evacuation centers accept pets, which medications your family members need and who is responsible for helping whom.
Make sure everyone in your family knows what to do by practicing your family plan.
4. GET SOMEWHERE SAFE HOWEVER YOU CAN
If you are asked to evacuate, you should do so immediately. Do not go to watch the tsunami and do not be fooled by receding water. It is not safe; it is "nature's tsunami warning."
If you are in an evacuation area but don't think you'll have time to get somewhere safe, ask emergency officials if there are nearby buildings that are tall or sturdy enough to provide protection.
5. STAY UNTIL IT'S SAFE
Once you get to a safe place, stay there until officials give the all-clear. A wave passing does not necessarily mean the danger is over, as a larger wave might be behind it.
6. CHECK FOR INJURIES
If you were in an affected area during the tsunami, check yourself and others for injuries before leaving the safe area. Contact emergency officials if needed.
7. BE CAREFUL RETURNING
After leaving the safe area, use caution. Do not go into a disaster area, as it could interfere with emergency response efforts. Be alert as you enter buildings, checking for damage. Don't go into a building that has water around it, as the floors may be damaged.