Following an 8.8 magnitude earthquake in eastern Russia, over a dozen nations are on alert for potential tsunami activity.
The earthquake, which struck Russia’s Kamchatka Peninsula on Wednesday morning, has already caused tsunami waves on Japan’s Hokkaido coast. In Hawaii, residents have been advised to seek higher ground as tsunami sirens sound. Tsunami alerts of varying degrees have also been issued for much of the West Coast, Alaska, and other Pacific countries.
Here’s what you should know about tsunamis.
What is a tsunami?
According to the , a tsunami is a series of powerful waves triggered by earthquakes or underwater volcanic eruptions. These events can cause sudden displacement of ocean water, leading to strong currents and large waves that grow taller as they approach the shore.
Tsunami waves radiate outward in all directions, capable of traveling at jet plane speeds across deep ocean waters, slowing down as they enter shallower areas.
Tsunamis are made up of multiple waves that can occur over a long time. The first wave isn’t always the largest; subsequent waves can suddenly and dramatically increase in size. Large tsunamis can persist for days. Japan has that tsunamis resulting from the Kamchatka quake may last more than a day.
How are tsunamis forecast?
Although several countries have issued tsunami forecasts, the severity of tsunamis from this earthquake will likely vary. Waves that struck the Russian port town of Severo-Kurilsk reached heights of 10-13 ft (3-4 m), while those hitting Japan’s Hokkaido coast measured around 12 in (30 cm) to 16 in (40 cm).
The states that precise tsunami predictions are impossible. Instead, tsunami warning centers use the size and location of the preceding earthquake, along with forecast models, to estimate wave height, location, and arrival times once a tsunami is detected.
The NOAA uses in collaboration with an international network to detect, measure, and report tsunamis in real-time. This system measures changes in water pressure as a tsunami wave passes.
What to do in a tsunami warning
The U.S. uses a four-level alert system for tsunamis: warning, advisory, watch, and information statement, in order of decreasing severity, according to the .
Be alert for natural signs of a tsunami, such as a loud roar from the ocean or a sudden rise or fall in water levels. A rapid withdrawal of water from the shoreline can indicate an impending tsunami.
A tsunami warning is the highest level of alert. The NWS defines it as: “Take Action—Danger! A tsunami that may cause widespread flooding is expected or occurring. Dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival.”
If a tsunami warning is issued, evacuate immediately to high ground as far inland as possible (at least 100 ft above sea level or one mile inland) and follow the directions of local authorities. Some threatened areas, , also provide emergency shelters for evacuees.
While it’s best to move to higher ground, the NWS notes that most tall buildings aren’t designed to withstand tsunami forces. If no other option exists, the upper floors of some strong, tall buildings may offer some protection.
The Department of Homeland Security’s advises that if you’re on a boat at sea during a tsunami warning, head to deep water. If you’re in a harbor, leave the boat and move to a safe inland location.
What to do in a tsunami advisory
A tsunami advisory is the second-highest alert level issued by the NWS. The agency describes it as: “Take Action—A tsunami with potential for strong currents or waves dangerous to those in or very near the water is expected or occurring. There may be flooding of beach and harbor areas.”
It’s recommended to stay out of the water and away from beaches and waterways, and to follow instructions from local authorities.
What other tsunami alerts mean
The NWS defines a tsunami watch as: “Be Prepared—A distant earthquake has occurred. A tsunami is possible.” During a tsunami watch, stay informed and be ready to take action if needed.
A tsunami information statement, the lowest alert level, means: “Relax—An earthquake has occurred, but there is no threat or it was very far away and the threat has not been determined. In most cases, there is no threat of a destructive tsunami.”
For international partners in the Pacific and Caribbean, the U.S. issues tsunami threats rather than alerts. According to the NWS, a threat message outlines potential impacts on people, structures, and ecosystems. Other countries then decide what alert to issue.
Many countries use tiered alert systems, often with different terminology. Check local emergency management systems for alerts and instructions. For more information from various tsunami warning systems, visit or consult your local weather or emergency management center, such as and .
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