Why Russia's megathrust earthquake was among biggest ever recorded, but damage was minimal
But it has not proved as destructive as experts feared.
Here are the factors that contributed to that outcome.
It was among the 10 strongest ever recorded.
The magnitude-8.8 earthquake was the largest since 2011, when a magnitude-9.1 tremor and subsequent tsunami struck off the coast of Japan and killed more than 15,000 people.
Wednesday's earthquake, known as the Kamchatka earthquake, is considered a megathrust earthquake — common to each of the planet's largest recorded quakes.
Earth's outer layers are split into 15 slabs known as tectonic plates.
These plates slowly shift around — moving a few centimetres every year — and often get stuck against each other due to friction.
When that happens, stress builds up over time until the plates suddenly shift and cause seismic waves that shake the ground.
Megathrust earthquakes occur when one tectonic plate has been forced underneath another — a phenomenon known as subduction.
In this case, it was the Pacific plate beneath the North American plate.
Stephen Hicks, an environmental seismology expert at University College London, said megathrust earthquakes "cause some of the world's largest ruptures and trans-ocean tsunamis".
Tsunamis occur when earthquakes displace large amounts of ocean water.
Megathrust quakes often cause tsunamis because the faults they cause tend to come to, or even directly penetrate, the sea floor, Dr Hicks said.
How much of the sea floor moves influences whether a tsunami is formed, and how big it might become, added Lisa McNeill, a tectonics professor at the University of Southampton.
"Some fault movements don't move the sea floor much, and so, there is no tsunami," she said.
In the case of the Kamchatka earthquake, a large slip occurred and generated a tsunami, Dr McNeill added.
Despite the earthquake triggering tsunami warnings across the Pacific Ocean, no deaths were recorded, and minimal structural damage was reported.
Maximum wave heights of five metres were observed in Kamchatka yesterday — a tenth of the heights recorded after the Tohoku Earthquake in 2011, which triggered the Fukushima Daiichi nuclear disaster.
Waves in Hawaii reached a maximum height of about 1.7 metres.
Meghan Miller, a professor of seismology at Australian National University, said where earthquakes strike has a major impact on the severity of subsequent tsunamis.
"For the tsunami and earthquake that happened in Japan in 2011, the distances [to land] were much closer," she told ABC Radio National Breakfast.
Dr McNeill said the height of tsunami waves can also be affected by the shape of the sea floor near the coast.
"[The waves] are small at sea but travel fast, and it is when they reach shallow water that they build in height again," she said.
"[A] tsunami can have varied heights on one coastline, and it could generate surprisingly large wave heights."
She added that wave heights recorded after the Kamchatka earthquake were still "significant", but the potential for destruction was minimised.
The tremor triggered tsunami warnings across the Pacific Ocean, as far away as Hawaii, Chile, and Ecuador.
"This has been established in the Pacific since the 1960s, and people therefore receive warnings about the tsunami and can evacuate," she said.
"It is harder for those living close to the earthquake as they have less time, but the earthquake is their warning of a tsunami and [the] prompt to move to higher ground."
Many nations with sea borders have government-run programs to detect and monitor threats caused by earthquakes and tsunamis that may impact the region, and are charged with alerting communities of incoming threats and issuing evacuation orders.
There were no warning systems in place in the Indian Ocean when the 2004 Boxing Day tsunami occurred.
The enormity of the natural disaster's death toll, estimated to be about 225,000, is attributed to the lack of evacuation alerts.
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Krasheninnikov volcano in Russia's east erupts for the first time in 600 years
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ABC News
6 days ago
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Why Russia's megathrust earthquake was among biggest ever recorded, but damage was minimal
One of the largest earthquakes in recorded history set off tsunami warnings across the Pacific Ocean on Wednesday. But it has not proved as destructive as experts feared. Here are the factors that contributed to that outcome. It was among the 10 strongest ever recorded. The magnitude-8.8 earthquake was the largest since 2011, when a magnitude-9.1 tremor and subsequent tsunami struck off the coast of Japan and killed more than 15,000 people. Wednesday's earthquake, known as the Kamchatka earthquake, is considered a megathrust earthquake — common to each of the planet's largest recorded quakes. Earth's outer layers are split into 15 slabs known as tectonic plates. These plates slowly shift around — moving a few centimetres every year — and often get stuck against each other due to friction. When that happens, stress builds up over time until the plates suddenly shift and cause seismic waves that shake the ground. Megathrust earthquakes occur when one tectonic plate has been forced underneath another — a phenomenon known as subduction. In this case, it was the Pacific plate beneath the North American plate. Stephen Hicks, an environmental seismology expert at University College London, said megathrust earthquakes "cause some of the world's largest ruptures and trans-ocean tsunamis". Tsunamis occur when earthquakes displace large amounts of ocean water. Megathrust quakes often cause tsunamis because the faults they cause tend to come to, or even directly penetrate, the sea floor, Dr Hicks said. How much of the sea floor moves influences whether a tsunami is formed, and how big it might become, added Lisa McNeill, a tectonics professor at the University of Southampton. "Some fault movements don't move the sea floor much, and so, there is no tsunami," she said. In the case of the Kamchatka earthquake, a large slip occurred and generated a tsunami, Dr McNeill added. Despite the earthquake triggering tsunami warnings across the Pacific Ocean, no deaths were recorded, and minimal structural damage was reported. Maximum wave heights of five metres were observed in Kamchatka yesterday — a tenth of the heights recorded after the Tohoku Earthquake in 2011, which triggered the Fukushima Daiichi nuclear disaster. Waves in Hawaii reached a maximum height of about 1.7 metres. Meghan Miller, a professor of seismology at Australian National University, said where earthquakes strike has a major impact on the severity of subsequent tsunamis. "For the tsunami and earthquake that happened in Japan in 2011, the distances [to land] were much closer," she told ABC Radio National Breakfast. Dr McNeill said the height of tsunami waves can also be affected by the shape of the sea floor near the coast. "[The waves] are small at sea but travel fast, and it is when they reach shallow water that they build in height again," she said. "[A] tsunami can have varied heights on one coastline, and it could generate surprisingly large wave heights." She added that wave heights recorded after the Kamchatka earthquake were still "significant", but the potential for destruction was minimised. The tremor triggered tsunami warnings across the Pacific Ocean, as far away as Hawaii, Chile, and Ecuador. "This has been established in the Pacific since the 1960s, and people therefore receive warnings about the tsunami and can evacuate," she said. "It is harder for those living close to the earthquake as they have less time, but the earthquake is their warning of a tsunami and [the] prompt to move to higher ground." Many nations with sea borders have government-run programs to detect and monitor threats caused by earthquakes and tsunamis that may impact the region, and are charged with alerting communities of incoming threats and issuing evacuation orders. There were no warning systems in place in the Indian Ocean when the 2004 Boxing Day tsunami occurred. The enormity of the natural disaster's death toll, estimated to be about 225,000, is attributed to the lack of evacuation alerts.
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Why the Pacific tsunami was smaller than expected — a geologist explains
The earthquake near the east coast of the Kamchatka peninsula in Russia on July 30 2025 generated tsunami waves that have reached Hawaii and coastal areas of the US mainland. The earthquake's magnitude of 8.8 is significant, potentially making it one of the largest quakes ever recorded. Countries around much of the Pacific, including in east Asia, North and South America, issued alerts and in some cases evacuation orders in anticipation of potentially devastating waves. Waves of up to four metres hit coastal towns in Kamchatka near where the earthquake struck, apparently causing severe damage in some areas. But in other places waves have been smaller than expected, including in Japan, which is much closer to Kamchatka than most of the Pacific rim. Many warnings have now been downgraded or lifted with relatively little damage. It seems that for the size of the earthquake, the tsunami has been rather smaller than might have been the case. To understand why, we can look to geology. The earthquake was associated with the Pacific tectonic plate, one of several major pieces of the Earth's crust. This pushes north-west against the part of the North American plate that extends west into Russia, and is forced downwards beneath the Kamchatka peninsula in a process called subduction. The United States Geological Survey (USGS) says the average rate of convergence — a measure of plate movement — is around 80mm per year. This is one of the highest rates of relative movement at a plate boundary. But this movement tends to take place as an occasional sudden movement of several metres. In any earthquake of this type and size, the displacement may occur over a contact area between the two tectonic plates of slightly less than 400km by 150km, according to the USGS. The Earth's crust is made of rock that is very hard and brittle at the small scale and near the surface. But over very large areas and depths, it can deform with slightly elastic behaviour. As the subducting slab — the Pacific plate — pushes forward and descends, the depth of the ocean floor may suddenly change. A map of tsunami warnings on Wednesday stretching from the west to east of the Pacific Ocean. Nearer to the coastline, the crust of the overlying plate may be pushed upward as the other pushed underneath, or — as was the case off Sumatra in 2004 — the outer edge of the overlying plate may be dragged down somewhat before springing back a few metres. It is these near-instantaneous movements of the seabed that generate tsunami waves by displacing huge volumes of ocean water. For example, if the seabed rose just one metre across an area of 200 by 100km where the water is 1km deep, then the volume of water displaced would fill Wembley stadium to the roof 17.5 million times. A one-metre rise like this will then propagate away from the area of the uplift in all directions, interacting with normal wind-generated ocean waves, tides and the shape of the sea floor to produce a series of tsunami waves. In the open ocean, the tsunami wave would not be noticed by boats and ships, which is why a cruise ship in Hawaii was quickly moved out to sea. Waves sculpted by the seabed The tsunami waves travel across the deep ocean at up to 440 miles per hour, so they may be expected to reach any Pacific Ocean coastline within 24 hours. However, some of their energy will dissipate as they cross the ocean, so they will usually be less hazardous at the furthest coastlines away from the earthquake. The hazard arises from how the waves are modified as the seabed rises towards a shoreline. They will slow and, as a result, grow in height, creating a surge of water towards and then beyond the normal coastline. The Kamchatka earthquake was slightly deeper in the Earth's crust (20.7km) than the Sumatran earthquake of 2004 and the Japanese earthquake of 2011. This will have resulted in somewhat less vertical displacement of the seabed, with the movement of that seabed being slightly less instantaneous. This is why we've seen tsunami warnings lifted some time before any tsunami waves would have arrived there. Alan Dykes, Associate Professor in Engineering Geology, Kingston University. This article is republished from The Conversation under a Creative Commons licence. Read the original article.
