20-20-20 Rule of Thumb
The 20-20-20 rule was developed by our founder, Ron Harrris, as a way to educate at risk communities on common signs of tsunamies. The rule states that if you feel the ground shake for at least 20 seconds, then a tsunami could arrive in the next 20 minutes so you need to get to an elevation of at least 20 meters.
This rule of thumb is taught to those in at risk communities. Although it is simple and easy to remember and understand, it still clearly communicates when to expect tsunamies and how to stay safe.
It is also important to note that tsunamis have multiple waves. Although the first is often the most destructive, the waves that follow still have a lot of energy and destructive power. Not all tsunamis are preceded by a recession of the shore line. (see page on tsunamis)
If you feel the ground shake for 20 seconds then it is safe to assume that a tsunami has been triggered and is on the way
A tsunami will most likely arrive in the next 20 minutes
20 meters or 66 feet (about 8 flights of stairs)
Get to ground that is at least 20 meters high to avoid tsunami waves.