U.S. Tsunami Hazard National Tsunami 

Hazard Mitigation 

Program

T sunamis are infrequent high-impact events that have the potential to 

cause fatalities and damage on the coast. Since the beginning of the 19th 

century, tsunamis have caused more than 700 deaths and almost $2 

billion1 in damage to U.S. coastal states and territories.

To better understand the U.S. tsunami hazard and prepare for the impacts of 

tsunamis on U.S. coasts, the National Tsunami Hazard Mitigation Program 

assessed the hazard for nine broad coastal regions. While a tsunami can strike 

any U.S. coast, the hazard level varies. Hazard levels reported here are qualitative 

and based largely on the historical record (through 2014), geological evidence, 

and location relative to tsunami sources, all of which provide clues to what might 

happen in the future. 

The hazard is greatest for coastlines near subduction zones, which are particularly 

active seismic zones, where large earthquakes can produce damaging waves that 

threaten nearby and distant coasts. Dangerous subduction zones ring the Pacific 

Ocean and can also be found around the Caribbean.

The West Coast states of 

Washington, Oregon, and California have experienced tsunamis from as far away as Alaska, 

South America, Japan, and Russia. The most damaging on record is the tsunami caused by 

the 1964 Great Alaska earthquake. More recently, harbors in the region were damaged by 

events in Japan (2011) and Chile (2010). Other tsunamis in the region were produced by 

local earthquakes and landslides (both underwater and from land). Locally, the greatest 

threat is from the Cascadia subduction zone, which stretches from northern California to 

southern Canada. Large Cascadia earthquakes occur every 500 years, on average. According 

to geological data in the Pacific Northwest, the last great Cascadia earthquake occurred in 

1700. It produced a tsunami that crossed the Pacific Ocean and caused damage and deaths 

in Japan. The next Cascadia event will significantly impact the region and the nation.

Reported tsunamis: Earliest: 1812 | Total events: 94 | Events with runups above one 

meter: 17 | Total damage: $241 million1 | Total deaths: 25

Given its location near some of the most 

dangerous seismic zones in the world, a number of damaging tsunamis have affected 

the Pacific Coast of Alaska. Historic events include the tsunamis that devastated coastal 

communities in March 1964, which were produced by the largest recorded earthquake in 

U.S. history and associated underwater landslides. Due to Alaska’s steep terrain, landslides 

and icefalls have also caused tsunamis in Alaska. The highest tsunami in recorded history 

occurred in 1958 when an earthquake-generated landslide produced a tsunami that 

cleared trees up to 525 meters (1,722 feet) above Lituya Bay. Volcanic activity has also 

caused tsunamis in Alaska as demonstrated by the Augustine Volcano in 1883.

Reported tsunamis: Earliest: 1737 | Total events: 100 | Events with runups above one 

meter: 22 | Total damage: $688 million1 | Total deaths: 222

Hawaii has a long history 

of damaging tsunamis. Its tsunami record includes events caused by 

earthquakes both near and far. Significant tsunamis were produced locally 

in 1868 and 1975, but the majority of Hawaii’s destructive tsunamis were 

produced by distant subduction zone earthquakes. Notable distant tsunamis 

came from Chile (1837, 1877, 1960), Russia (1923, 1952), Alaska (1946, 1957), 

and Japan (2011). Underwater landslides also pose a threat, and volcanic 

activity was responsible for a tsunami in 1919.

Reported tsunamis: Earliest: 1812 | Total events: 134 | Events with runups 

above one meter: 30 | Total damage: $622 million1 | Total deaths: 293

Tsunamis with runups over one meter (3.28 feet) are particularly 

dangerous to people and property, but smaller tsunamis also pose threats. 

(Runup is the maximum elevation of the tsunami flooding on shore.)

 There are no tsunamis or 

significant earthquakes on record for the region, which is not seismically 

active and is not near a subduction zone.

Approximately 95% of reported U.S. tsunami strikes were to Pacific states and territories.

U.S. West Coast: High to Very High

Alaska Arctic Coast: Very Low

Alaska: High to Very High

Hawaii: High to Very High

1

All dollar figures adjusted for inflation (2016)
May 2016

Understanding the hazard is an important first 

step in understanding risk. More research remains 

to be done to better understand the hazard and 

the potential losses. These hazard levels are based 

on brief and incomplete historical records. Events 

may have been unreported or underreported or 

may have happened in unpopulated areas and 

gone undetected. The tsunami hazard exists for all 

coastal U.S. states and territories.

Given the large number of people who live, work, 

and play on the coast, even where the hazard level 

is low, the consequences are high. So, it is vital 

that we understand these consequences as well as 

how to prepare for and respond to tsunamis, both 

local and distant and big and small.

Historically, tsunamis in American 

Samoa have originated around the Pacific, but the greatest threat is from 

the nearby Tonga trench. This was made clear in 2009, when an earthquake 

near this subduction zone produced the worst tsunami in the territory’s 

recorded history. 

Reported tsunamis: Earliest: 1837 | Total events: 68 | Events with runups 

above one meter: 4 | Total damage: $139 million1 | Total deaths: 34

Guam and the Northern Mariana Islands have been struck by tsunamis 

from sources both local and distant (Japan and Russia, most notably). The 

region’s largest tsunami on record was produced by a large earthquake 

off Guam in 1849. The greatest threat is from the nearby Marianas trench, 

another significant subduction zone. 

Reported tsunamis: Earliest: 1849 | Total events: 25 | Events with runups 

above one meter: 4 | Total deaths: 1

The U.S. Atlantic tsunami hazard is greatest for Puerto Rico and the U.S. 

Virgin Islands. Just to the north of the islands, in the Atlantic Ocean, lies the 

Puerto Rico trench, a dangerous subduction zone like those in the Pacific. 

However, most of the recorded tsunamis in the region were produced by 

local earthquakes outside of the trench, most notably in 1867 and 1918, 

or in the broader Caribbean region, like off the coast of Hispaniola (1842, 

1946, 2010). Tsunamis caused by distant earthquakes, volcanic activity, and 

underwater landslides may also affect the region.

Reported tsunamis: Earliest: 1690 | Total events: 13 | Events with runups 

above one meter: 4 | Total damage: $63 million1 | Total deaths: 164

The history of U.S. Atlantic 

Coast tsunamis is short, but shows that tsunamis can happen in the region. Key events 

include an earthquake (1886) and an underwater landslide (1964) that both produced 

small local tsunamis. Also, a tsunami produced by an earthquake-generated landslide off 

Newfoundland, Canada (1929) recorded as small waves along the U.S. coast, but caused 

death and destruction near its source. There is no subduction zone along the U.S. Atlantic 

Coast, and earthquakes are not as large or as frequent as in other regions. Underwater 

landslides and meteotsunamis are the most likely source of tsunami waves in the region. 

More distant tsunami threats come from the Puerto Rico trench, the Canary Islands, and the 

Azores–Gibraltar fault zone.

Reported tsunamis: Earliest: 1886 | Total events: 8

Like the U.S. Atlantic Coast, the U.S. Gulf Coast is not 

near a subduction zone, and there has not been much tsunami or seismic activity recorded 

in the region. Still, evidence suggests a tsunami is possible. An earthquake off Puerto Rico 

(1918) produced the only tsunami on record for the Gulf Coast. However, the geography of 

the Gulf may reduce the impact of most distant tsunamis. Geologic evidence in the Gulf of 

Mexico points to underwater landslides as the region’s likeliest tsunami source.

Reported tsunamis: Earliest: 1918 | Total events: 1 Earthquakes and earthquake-generated landslides caused more 

than 90% of the tsunamis reported in the United States.

American Samoa: High

Guam and Northern Mariana Islands: High

Puerto Rico and the U.S. Virgin Islands: High

Learn more about tsunamis:

www.tsunami.gov

U.S. Atlantic Coast: Very Low to Low

U.S. Gulf Coast: Very Low

This information is based on the national 

tsunami hazard assessments conducted 

for the National Tsunami Hazard 

Mitigation Program by the National 

Oceanic and Atmospheric Administration 

and the U.S. Geological Survey. The 

assessments are available at http:// 

nws.weather.gov/nthmp/ushazard.html.

The National Tsunami Hazard Mitigation 

Program is a partnership of federal and 

state agencies that works to protect 

lives and reduce economic losses from 

tsunamis through hazard assessment, 

warning guidance, and mitigation. Learn 

more at http://nws.weather.gov/nthmp/. 1

All dollar figures adjusted for inflation (2016)