Joint Base Pearl Harbor-Hickam Logo Commander, Navy Region Hawaii  |  Joint Base Pearl Harbor-Hickam
Commander, Navy Installations Command
  Find Your Region or Installation



A tsunami (pronounced "soo-nahm'ee) is a series of waves generated by an undersea disturbance such as an earthquake.  From the area of the disturbance, the waves will travel outward in all directions, much like the ripples caused by throwing a rock into a pond.  The time between wave crests may be from 5 to 90 minutes, and the wave speed in the open ocean will average 450 miles per hour.

Questions and answers:

1) What's a tsunami?

Tsunami is Japanese for "great harbor wave," now the common term for any seismic sea wave.  Sometimes wrongly called "tidal waves."  Tidal waves occur every day during changes in tide.  A tsunami is a SERIES of ocean waves generated by a shock of some kind, a volcanic eruption, a submarine landslide, or explosion, but usually a sea floor rupture associated with an earthquake.  These waves many continue to arrive for several hours and are capable of causing destruction in coastal areas.  Ocean-going tsunamis arrive as a SERIES of coastal waves, perhaps 7 to 10 in all, with the largest somewhere in the middle of the set.  Tsunamis are most common in the Pacific Ocean and are fairly rare in the Atlantic and Mediterranean Oceans.

2) What areas are vulnerable to tsunami?

All coastal areas of the Hawaiian Islands are vulnerable.  For specific areas, see the Civil Defense pages in the front of telephone books for maps or visit the Hawaii State Civil Defense website for maps depicting the Tsunami Evacuation Zones. Scroll down the page on the site to the Tsunami Evacuation Zone Mapping Tool. For JBPHH, inder the the Island Area, use the Oahu-Ewa Beach to Airport.

The red zones that cover land areas (Reef Runway, Alpha Docks, Iroquois Point - all must be evacuated). All ofthe shorelines in JBPHH inner harbor, Ford Island, Pearl City Peninsula, etc. are outlined. While a wave will NOT reach Ford Island or Pearl City Peninsula or other parts ofthe inner harbor, strong rip currents will exist, so ensure you stay out of and away from the water.

Remember during an emergency is the wrong time to look for this information! You need to know if your home or workplace is in a Tsunami Evacuation Zone BEFORE the sirens sound. If the sirens sound move to high ground!!!!!

3) How will I know that a tsunami is expected?

A local Earthquake: A local earthquake that causes you to fall or hold on to something to keep from falling is a natural tsunami warning.  There may be no time for an official warning.  An Earthquake in Hawaiian Waters: If a significant earth-quake occurs in the vicinity of the Hawaiian Islands, the Pacific Tsunami Warning Center (PTWC) will issue an URGENT TSUNAMI WARNING for those islands which could be affected by tsunami.  The warning will be announced over radio and television stations in conjunction with the sounding of outdoor warning sirens.

A Distant Earthquake: In the event of a significant earthquake in distant areas of the Pacific Basin, i.e., the Aleutians, Alaska, South America, etc., the PTWC will issue a Tsunami Watch until a tsunami can be confired or discounted.  A Tsunami Warning will be issued by the PTWC when a tsunami is confirmed.  The warning will be announced over radio and television stations in conjunction with the sounding of outdoor warning sirens.

4) What is a Tsunami Watch?

An alert issued by the PTWC that a tsunami MAY have been generated.

5) What is a Tsunami Warning?

An alert that a tsunami HAS been generated.

6) What should I do when a Tsunami Watch or Warning is issued?

Tsunami Watch: All the watch advisories are your signal to prepare.  Monitor radio or television stations for Watch upgrade to Warning status or Watch cancellation.  Tsunami Warning: Listen to radio or television stations for official instructions.  If you are within a tsunami evacuation zone, evacuate immediately.  If you are in a multiple story building of six (6) floors or more and is constructed of heavy concrete and steel construction, you should be safe if you move to the third floor or above.  Remain in safe areas until the "All Clear" is announced over a radio or television station.

7) How can I get to a safe area or a shelter if I have no transportation?

Preferably walk, or request the assistance of nearby friends, or neighbors to relocate to an area immediately outside of the tsunami evacuation zone.

8) Will entry into tsunami evacuation zones be permitted?

Prior to wave arrival, roadblocks will be established by Police to restrict traffic into the tsunami evacuation zones to people requiring emergency entry.  Roads into tsunami evacuatio zones will be sealed off at the key locations 45 minutes prior to arrival of the first wave.  Anyone still in the evacuation zones will be directed by police patrols to move immediately to safe locations.

9) What if a Tsunami Warning is issued while my child is in school?

Schools and day care centers located within evacuation zones will evacuate according to their plans.  Public schools and certain private schools and day care centers outside the evacuation zones will remain open and care centers outside they can be safely picked up or released.  Parents should be familiar with their school's or day care center's emergency plans.

10) What should I do if I am outside the tsunami evacuation zone when a Tsunami Watch or Warning is issued?

If you are outside the tsunami evacuation zones, you are not in danger.  However, to avoid traffic gridlock, you should curtail non-essential travel, avoid roadways in or near the evacuation zone, and not interfere with evacuation.


(Last Updated: 9/4/14)

Share This Page