Understanding Tsunamis In Hawaii

“We shouldn’t rest because…tsunami threat in Hawaii, from a Civil Defense point of view, is a 24/7, 365 day potential.”  State Civil Defense Vice Director Ed Teixeira

The Island of Hawaii breathed a sigh of relief yesterday after the Pacific Tsunami Warning Center canceled the Tsunami Warning that had been in effect for the Hawaii for several hours after the 8.8 earthquake that struck Chile Friday night (Hawaii time).

Events like this serve as reminders of the realities that come with life on an island in the Pacific.  Reminders to double-check our emergency preparedness kits and to be sure our families understand what to do when the sirens sound in coastal areas.

But science and history teach us that we cannot rely solely on sirens or Civil Defense warnings.  Understanding the two types of tsunamis that can impact our state is important for anyone who spends time on Hawaii’s shores.

Tsunamis generated from a distant seismic event, usually from Alaska’s Aleutian Island chain or from the west coast of South America, allow time for tsunami warnings to be communicated to residents and visitors.  In these events, if a tsunami wave is generated, the emergency sirens tell residents to tune in to local news or radio broadcasts for updates from Hawaii Civil Defense to determine whether an evacuation is necessary.

Locally-generated tsunamis, however, can happen in a matter of minutes after an earthquake and there may be no time for warnings to be broadcast.  The warning signs to look for in these events are 1) the ground shakes and 2) the ocean recedes in an unusual way.  The Pacific Tsunami Warning Center website says this:

Because Hawaiʻi is seismically active, a shallow undersea earthquake can reach sufficient size to generate a local tsunami. While destructive local tsunamis are less frequent, there is little time to react to such an event.

Waves from the tsunami caused by the 1975 Kalapana earthquake killed two campers in the Halape area about a minute after they experienced the strong shaking. Therefore, if you feel strong shaking and are near the water, you should immediately move to higher ground.

For example, a tsunami generated from the southeast coast of the Big Island will only take 5-10 minutes to reach Hilo or Kona, so you should act fast. Residents of Maui have about 15-20 minutes, and Oʻahu has about 30-40 minutes warning.

Preparation is the key.  This list of resources have information that can help you and your family be as prepared as possible in the event of a tsunami, earthquake or other natural disaster:

Hawaii State Civil Defense
(Use the Tsunami Evacuation Zone Mapping Tool to see if your location is in an evacuation zone.)

Hawaii County Civil Defense

American Red Cross Emergency Kit Checklist (PDF)
(Note:  The Red Cross recommends a 5-7 day kit for Hawaii.)

Sign up for Hawaii County Civil Defense Text Messages


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