Earthquake in Russia: Why it is difficult to predict the size of the waves when a tsunami occurs

- Author, Writing
- Author's title, BBC News World
30 julio 2025

Updated 8 hours

The powerful earthquake that has occurred off the coast of the Russian Peninsula of Kamchatka unleashed a tsunami alert in much of the Pacific Ocean.

The authorities of Russia, Japan, the United States, Colombia, Mexico, Ecuador, Peru and Chile issued evacuation orders for the areas where the waves were expected to impact.

The waves reported in places like Hawai and California (USA) have not been particularly large and some countries have already raised the alert or have reduced it to warning

But early alert is essential to avoid the loss of human lives.

From the devastating earthquake and tsunami of the Indian Ocean of 2004, in which almost 250,000 people died in 17 countries, international early alert systems have been developed, which have contributed to mitigate the ravages of these natural phenomena.

Thanks to these systems, equipped with seabed with sensors and an infrastructure to alert affected countries, it can be forecast on which costs will imapact the waves and orient, thus, the necessary evacuation measures.

But the progress of a tsunami and the effects on the coast depend, to a large extent, on the depth of the seabed and the topography of the coast, so it is not always easy to predict how height the wave will have when reaching the ground.

A man passes in front of a showcase with a television in which they alert the tsunami.

How tsunamis occur

The term “tsunami” comes from the Japanese word that means “wave of bay”, due to the devastating effects that it usually has in low height coastal areas.

The tsunamis are immense waves that are formed when a sudden displacement of the sea or the ocean occurs.

The origin of this water displacement is usually an earthquake in the seabed or near it.

Map of the earthquake location against Russia and the affected areas.

But it is not the only reason.

A landslide, a volcanic eruption, certain types of atmospheric conditions or even the impact of a meteorite can also generate tsunamis.

These forces create waves that spread in all directions from their origin. The waves of tsunami are very long, being able to reach the hundreds or thousands of kilometers, sometimes crossing whole oceanic basins.

Unlike the waves that are formed by the wind, which occur only on the surface of the sea, the tsunamis displace the entire water column, from the surface to the seabed, so they have great force.

How tsunamis move

Like the waves in a water pond when a stone is thrown, the tsunamis form sets of waves that spread as concentric circles from their origin.

When a tsunami occurs, the speed of its waves depends on the depth of the ocean.

In very deep waters, the tsunamis can move at large speeds, reaching even the 800 kilometers per hour, according to the page of the National Office of Oceanic and Atmospheric Administration (NOAA, for its acronym in English), the United States Scientific Agency that monitors, among other things, tsunamis.

However, ships do not usually notice the displacement of a tsunami, since on the high seas these waves barely reach 30 centimeters, making them almost imperceptible.

The evaluation and information on tsunamis in deep waters, which are known by the acronym in English (Dart) and that are formed by a buoy and some sensors, allow to detect small changes in the height of the sea level and transmit this information to the tsunamis alert centers.

When is the wave dangerous

For the usual, the tsunamis are only dangerous when they approach the coast.

Those 30 centimeters of almost imperceptible height on the high seas can become waves of up to 30 meters that sweep unstoppable with everything that is in its path, just like a rapid flood or a tide that rises quickly.

As the waves of the tsunami reach shallow waters, their speed slows down when it comes into contact with the bottom, descending up to 30-50 km/h. The wavelength is also reduced, compacting the waves and making them grow in height.

This occurs because the water that moves faster near the surface accumulates, creating a wall of water.

As explained by the University of Hawaii in Manoa, although the wavelength decreases, it still has a long period, so it may take a long time to reach its maximum height.

The first wave of Tsunami can be preceded by a depression, which resembles a tide that goes back very rapidly, but then advances towards the coast with force.

In general, there are between six and eight waves in a set of tsunami waves. The first may not be the biggest. The time between the successive ridges of the waves can vary between 5 and 90 minutes, according to the American University.

A large tsunami can flood low coastal areas in more than a kilometer and a half inland.

In general, the areas that are in danger when a tsunami away from the coast is produced are those that are below 15 meters above the height of the sea and less than a kilometer away from the sea.

For tsunamis with a nearby origin, all coastal places below 30 meters above sea level can be in danger.

Why it is difficult to predict the exact height of the wave

As with the earthquakes generated by most tsunamis, scientists cannot predict when or where the following tsunami will occur.

However, experience with these phenomena in the past provides experts with valuable information that allows them to know what earthquakes can generate tsunamis and inform, in this way, the population to be safe.

The time it takes to detect a tsunami depends on the distance from the origin of the same and the closest detection system, be it a Dart system or a coastal station that measures the water level.

This can fluctuate between five minutes and two hours.

Depending on the depth of the seabed and the topography of the coast, the waves can suffer a considerable refraction, a process that can concentrate its energy in concrete areas of the coast and, therefore, further increase its height, according to the International Tsunamis Information Center (ITIC) of UNESCO.

If the tsunami waves arrive with the high tide, or if there are simultaneous storm waves in the area, the effects will be cumulative and flood and destruction will be even greater, itic explains.