A sign noting a tsunami hazard zone is posted on a fence in California overlooking the Pacific Ocean. Credit: NOAA
Spending time at the beach is often a defining part of summer, but what happens when an extreme event like a tsunami threatens the coast? These events can happen suddenly, bringing dangerous, fast-moving water and putting lives and property at risk.
For coastal communities across the Pacific, this possibility became reality on July 29, 2025, when an 8.8 magnitude earthquake struck off Russia’s Kamchatka Peninsula. The earthquake resulted in a tsunami — a series of extremely long waves caused by a large and sudden displacement of ocean water — triggering tsunami alerts across the Pacific Ocean.
Real-time monitoring of water levels is critical to keeping people safe during extreme weather events, such as tsunamis, hurricanes, and high tide flooding. Scientists at NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS) measure water levels and other coastal conditions in real-time through a national network of tide gauges. The gauges are highly accurate and provide publicly available water level information 24-hours a day — for use in disaster preparedness and response, marine navigation, coastal planning, restoration efforts, and more.
NOAA’s network of tide gauges includes tsunami-capable tide gauges that disseminate water level data every minute. The U.S. Tsunami Warning Centers rely on the data for monitoring and response efforts, and specifically to update emergency managers about the continued risk to their coasts and harbor operations.
Detecting the Wave
In the United States, the Kamchatka tsunami was detected in Alaska, along the West Coast from Washington to California, and in Hawaii and American Samoa. As the tsunami traveled across the Pacific, the Tsunami Warning Centers used real-time data from the tide gauges to update forecasts with the best available information on wave heights and arrival times.
Propagation animation of the July 29, 2025, Kamchatka tsunami across the Pacific Ocean. The animation is a NOAA research product, not an official forecast. Credit: NOAA
NOAA’s tide gauge at Amchitka, Alaska, part of the Aleutian Islands, was the first station to record the tsunami, with a wave measurement (peak-to-trough) of 2.86 feet. Water level oscillations continued at the station as additional waves passed through the area. About 45 minutes later and nearly 200 miles to the east, the tide gauge at Adak, Alaska, detected the wave. The data from the stations enabled the Tsunami Warning Centers to update their forecasts that provided the U.S. West Coast with 8 to 12 hours of lead time before the tsunami arrived.
Water level data showing the tsunami wave’s impact at Amchitka, Alaska on July 30, 2025. Credit: NOAA
The tide gauge at Kahului Harbor, Hawaii, recorded the largest wave amplitude with a maximum peak-to-trough measurement of 11.44 feet. The wave caused a rapid rise in water levels, leading to a maximum water height of 4.49 feet above mean higher high water, the highest water level ever observed at the station.
Nearly five hours after the tsunami hit Hawaii, it reached Crescent City, California, which is vulnerable to tsunamis due to an underwater ridge and canyon zone that funnels wave energy towards the coastal town, and a harbor that amplifies tsunami impacts. However, the Tsunami Warning Center’s accurate and timely forecasts enabled coastal managers to issue evacuation orders hours before the wave hit, allowing the community to take action. The tide gauge recorded a peak-to-trough measurement of 7.42 feet — the largest wave measurement along the U.S. continental coast for this event.
Water level data showing the tsunami wave’s impact at Crescent City, California on July 30, 2025. Credit: NOAA
The vast scale of this event was best captured by the tide gauge at Pago Pago, American Samoa, located almost 5,000 miles from the Kamchatka Peninsula. The rapid rise in water levels as the tsunami met the shore, and the recorded peak-to-trough measurement of 6.25 feet, resulted in minor damage to floating piers located in Pago Pago Harbor.
Floating piers in Pago Pago Harbor, American Samoa, suffered minor damage from the tsunami. Credit: American Samoa Department of Marine and Wildlife Resources
Value of NOAA Tide Gauge Data
Water level data from NOAA’s tsunami-capable tide gauges are an essential part of the U.S. Tsunami Warning System. The real-time data enables the quick detection of changing water levels caused by tsunamis, thereby improving the accuracy of forecasts and allowing emergency managers and communities to make informed decisions and take life-saving measures with confidence. Paired with data from deep-ocean buoys, the tide gauges provide critical information to scientists, who in turn alert and inform decision-makers to mitigate tsunami impacts on U.S. coasts.
Learn more about NOAA tide gauges and view real-time data at tideandcurrents.noaa.gov.