The 2025 Kamchatka tsunami kept the Pacific ringing for more than ten hours. Its rhythm could help tsunami warnings
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The ocean kept ringing
The buoy records hold a second story. For the first hour, seismic waves from the earthquake shook the sensors, and the records jitter at periods of a few minutes. Then the tsunami arrives, and its energy settles into a band of long periods, between about 30 and 80 minutes. It stays there. More than 10 hours after the first waves, the sea at every buoy was still oscillating in this band, far above its quiet level. The dominant period differed from one buoy to the next, most likely because each station hears the tsunami after its own journey over ridges, trenches and islands.
Physicists would say that the Pacific behaved like a bell with little damping: Struck once, it rang for a long time. For me, this ringing is the most beautiful part of the study because it shows how long the ocean keeps the memory of a single earthquake.
Why a rhythm matters
The rhythm is also useful. Bays and harbors have natural periods of their own, set by their size and depth, much like the pitch of a glass. When the incoming waves share that period, the water inside can build up far beyond the height of the waves outside, and this is resonance. The buoys register the rhythm of a tsunami hours before it reaches distant shores. Comparing that rhythm with the known natural periods of the harbors along a coast could help warning centers foresee where the waves will grow, and our study suggests that the period content of a tsunami deserves a place in warnings, next to arrival times and heights.
Seventy-three years after the magnitude 9.0 earthquake of 1952 in the same region, Kamchatka has reminded us that it is one of the most efficient tsunami sources in the Pacific. What I take from this study is encouraging: A careful model, fed only with what seismologists learned from the earthquake itself, can follow a tsunami across an ocean within about a minute. The next step is to test the same approach, and the same attention to the rhythm of the waves, on other great tsunamis.