Expert: Tsunamis usually travel at a speed of at least 800 km/h

A tsunami typically travels at a speed of at least 800 km/h, but its waves are difficult to see in the open ocean. If the water rises by half a meter or a meter, that's a significant amount. The worst is when it reaches the coast," geologist Prof. Jerzy Żaba from the University of Silesia told PAP.

On Tuesday, a magnitude 8.7 earthquake was recorded off the eastern coast of Kamchatka, in the far eastern part of Russia, the United States Geological Survey (USGS) reported. The Russian service reported that the quake, which had its hypocenter at a depth of approximately 19 km, caused no casualties. It emphasized that the quakes were shallow and strong enough to trigger tsunami waves.

Indeed, after the earthquake, waves 3-5 meters high struck the town of Severo-Kurilsk in the northern part of the Kuril Islands, Russian media reported. The water carried fishing boats moored in the port out to sea and flooded a fish processing plant. Meanwhile, on Sakhalin Island, the power grid was damaged, and power outages occurred, RIA Novosti reported. There were no reports of fatalities.

According to the USGS, the coasts of Russia and Japan, as well as the western Pacific island of Guam and the Mariana Islands, are most at risk of tsunamis. The Japan Meteorological Agency has also issued a warning. Alerts also cover the United States (California, Oregon, and Washington, and southern Alaska) and Canada (Haida Gwaii, the northern and central coasts of British Columbia, and the northeastern and western coasts of Vancouver Island).

"For such a wave to form, there must be movement of the seabed. The part of the land covered by water must move: either up or down," seismologist Prof. Dr. hab. Wojciech Dębski from the Institute of Geophysics of the Polish Academy of Sciences explained in an earlier interview with PAP. He added that then "the entire enormous mass of water shifts and moves in different directions."

Geologist Prof. Jerzy Żaba from the University of Silesia explained in an interview with the Polish Press Agency (PAP) that tsunamis do not occur when an earthquake occurs inland, far from the ocean. "In such a case, there is usually greater damage caused by the ground vibrations themselves. However, if the earthquake occurs at the bottom of the ocean, the damage caused by the vibrations is minimal, but the damage caused by the tsunami wave is significant," he explained.

He recalled the December 2004 earthquake in the Indian Ocean. "At that time, its magnitude was estimated at at least 9 on the Richter scale. That earthquake also very quickly triggered a catastrophic tsunami that killed at least 250,000 people," he said.

He noted that tsunamis typically travel at speeds of at least 800 km per hour. "In the open ocean, tsunami waves are difficult to see. If the water rises by half a meter or a meter, that's a lot. The worst is when the tsunami reaches the coast. If it's flat and occupied by villages or cities, the destruction is massive," the expert said.

Professor Dębski noted that tsunami warnings typically cover vast areas following major earthquakes. Currently, these areas include regions on both sides of the Pacific Ocean.

– The catastrophic tsunami of December 2004 in the Indian Ocean region also caused significant destruction on the coasts of Africa, even in southern Africa – he recalled.

Kamchatka, the Russian Far East, and Japan are located on the "Pacific Ring of Fire," a highly seismically active part of the world. This zone runs along the Pacific Ocean coast—from New Zealand, through parts of Southeast Asia, Japan, Kamchatka, Alaska, and the western coasts of the Americas.

Experts predict that aftershocks with a magnitude of up to 7.5 will continue for at least a month after the recent earthquake in Kamchatka. Professor Wojciech Dębski spoke to PAP about such phenomena: "After a shock of this type, we can expect aftershocks to last up to six months. The strongest ones will last for the next dozen or so days. After that, the shocks will become increasingly weaker and less frequent."

In an earlier interview with PAP, Professor Grzegorz Lizurek from the Institute of Geophysics of the Polish Academy of Sciences recalled the largest earthquake ever measured. It occurred in Chile in 1960, with a magnitude of 9.5. The largest such event this century, in Japan in 2011, in the "Pacific Ring of Fire" region, had a magnitude of 9.1. "It killed 15,000 people, mostly victims of the accompanying tsunami," the geophysicist said.

As he explained, the Richter scale, which we use to describe earthquakes, is a logarithmic scale: – This means that an earthquake with a magnitude of 8 is 10 times stronger than an earthquake with a magnitude of 7.

According to the USGS, there have been seven earthquakes of magnitude 8.3 or greater off the coast of Kamchatka since 1900. The strongest was the November 4, 1952, magnitude 9.0 quake, which produced waves over 9 meters high off the coast of Hawaii, more than 5,000 km away. (PAP)

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