After a massive earthquake off the coast of Kamchatka, a peninsula in the far east of Russia, on July 30 2025, the world watched as the resultant tsunami spread from the epicentre and across the Pacific Ocean at the speed of a jet plane.
In some local areas, such as in Russia’s northern Kuril Islands, tsunami waves reached heights of over three metres. However, across the Pacific there was widespread relief in the hours that followed as the feared scenario of large waves striking coastal communities did not materialise. Why was this?
Not all underwater earthquakes result in tsunamis. For a tsunami to be generated, the Earth’s crust at the earthquake site must be pushed upwards in a movement known as vertical displacement. This typically occurs during reverse faulting, or its shallow-angled form known as thrust faulting, where one block of the Earth’s crust is forced up and over another, along what is called a fault plane.
