Hawai‘i’s remote location in the center of the Pacific Ocean makes it particularly vulnerable to tsunamis, often triggered by distant earthquakes, volcanic eruptions, or undersea landslides.
Over the past century, a number of deadly and destructive tsunamis have left a deep impact on the islands—especially in Hilo on the Big Island, which has historically suffered the worst damage.
While the threat of a tsunami is not an everyday or every year thing in Hawai‘i, it is also not that uncommon. For example, between 1837 and 1975, one tsunami hit the Hawaiian Islands every 12 years, on average, and since, there have been several more incidents or major warnings, such as in 1986, 1994, and 2011.
Below are some of the deadliest and most significant strikes in the last century and how they impacted tsunami tracking and response systems:
April 1, 1946 – Warning Systems Needed
One of the deadliest occurred on April 1, 1946, after a massive earthquake near the Aleutian Islands generated a tsunami that struck the Big Island, killing 159 people, including a group of 16 schoolchildren and 4 teachers, and causing extensive damage.
This disaster led to the creation of the Pacific Tsunami Warning Center in 1949. At the time of the April 1, 1946, incident, there was no coordinated tsunami detection or alert system in the Pacific. People were caught off guard, many unaware that an earthquake thousands of miles away could produce deadly waves in Hawai‘i hours later.
The Pacific Tsunami Warning Center is located in Ewa Beach, O‘ahu, today and detects tsunamis generated by large undersea earthquakes and issues warnings to Pacific nations and territories. It detects the tsunamis by using real-time seismic data, ocean buoys, GPS, and satellite monitoring to issue accurate alerts worldwide within minutes.
May 23, 1960 – Multiple Waves and Extended Warnings
Another significant event hit on May 23, 1960, when an earthquake in Chile sent waves across the Pacific. It wasn’t just any earthquake, it was a 9.5 — the strongest earthquake in recorded history. The ensuing tsunami killed 61 people in Hilo, reinforcing the need for better preparedness.
One of the major lessons the public learned was about wave behavior: The first wave was 3 feet tall, the second 9 feet tall, and the third between 14 and 35 feet (increasing to the latter due to the reflective and funneling effect of Hilo Bay’s shape.) The third wave arrived nearly an hour after the first, highlighting the importance of patience and extended warnings.
November 29, 1975 – Tragedy Without Warning
A powerful 7.7 earthquake off the south flank of Kīlauea Volcano triggered a locally generated tsunami that struck the Big Island’s southern coast within just minutes. Waves up to 48 feet high slammed into the Big Island.
Only two people were killed in the entire state during the 1975 tsunami, but tragically, they were teenagers camping with a YMCA youth group in a remote area of Hawai‘i Volcanoes National Park.
The suddenness of the event underscored the danger of local tsunamis, whereas previously, much attention was being given to tsunamis triggered by earthquakes in other areas of the Pacific. Local tsunamis pose significant danger due to their ability to strike before any warning can be issued.
March 11, 2011 – Early Warning System Works
The most recent major tsunami in Hawai‘i was on March 11, 2011, following a magnitude 9.1 earthquake in Japan (the earthquake and ensuing tsunami killed about 16,000 people in Japan).
Though the first wave arrived at 3 a.m. local time with waves of up to 12 feet, there were no deaths in Hawai‘i, thanks to early warning systems that gave residents more than eight hours’ notice.
The tsunami did, however, cause $30 million in damages. But it highlighted the importance and effectiveness of early warning systems for saving lives.
Tsunamis and Hawai‘i Today
Today, Hawai‘i continues to conduct regular tsunami drills and has evacuation routes and sirens in place to protect residents and visitors from future threats.
Its remote location helps. Often, the power of the tsunami fades before it reaches these isolated islands. But, as the above incidents (and others) have shown, that isn’t always the case.
Tsunami waves travel about 500 miles per hour on the open ocean. They are often small, making them barely noticeable to ships in deep water. They slow down to about 20 to 30 miles per hour upon reaching shallow, coastal waters and build to their maximum heights.
If you want to learn more about tsunamis, check out the Pacific Tsunami Museum in Hilo on your next visit. Though small, it will provide some perspective on how tsunamis impact the Pacific Islands and those who call them home.