July 30, 2025 Kamchatka earthquake of 8.8 magnitude is one of 10 strongest quakes ever recorded
There were 50 earthquakes with over 5 magnitude in the Kuril-Kamchatka arc, including the July 20, 2025 quake of 7.4 magnitude and three 6.6 magnitude earthquakes, preceding the July 30, 2025 quake of 8.8 magnitude. The 7.4 magnitude quake on July 20, 2025 may be a foreshock
A powerful earthquake of 8.8 magnitude hit near Russia’s Kamchatka peninsula at around 5 am Indian time on July 30, 2025. Occurring at a depth of 20.7 km, the Kamchatka earthquake is a shallow focus earthquake. The earthquake was caused by a reverse fault (thrust fault), where the hanging wall moved up relative to the footwall. It is among the ten strongest quakes in recorded history and the strongest worldwide since 2011. The shallow quake off the Kamchatka Peninsula damaged buildings and injured several people in the remote Russian region
The epicentre of the July 30 quake is located along the Kuril-Kamchatka arc, a well-known subduction zone. The Pacific plate moving at rate of about 80 mm per year relative to the North American plate — one of the fastest convergent margins in the world — in a north-westward direction dived below the North American plate. The Pacific plate being an oceanic plate is heavier than the North American plate, which is a continental plate, and hence always subducts below the American plate. The closest place to the epicentre is Petropavlovsk-Kamchatsky, Kamchatka with a population of 1,81,216, and is located 119 km west northwest of the epicentre.
Tectonically active arc
The Kuril-Kamchatka arc is tectonically active with several earthquakes of 8 magnitude occurring at shallow depths. In 1952, a magnitude 9.0 earthquake occurred in the same subduction zone at about the same depth of 21.6 km and about 30 km away from July 30 quake of 8.8 magnitude.
The Kuril-Kamchatka arc has been seismically very active in recent months. Preceding the July 30, 2025 quake of 8.8 magnitude, there were 50 earthquakes with over 5 magnitude, including the July 20, 2025 quake of 7.4 magnitude and three 6.6 magnitude earthquakes, as per the USGS website. “As of 1 pm Indian time June 30, 2025, there have been 50 aftershocks”, says Dr. Chandha. “The 7.4 magnitude quake on July 20, 2025 may be a foreshock.”
Since it is a thrust fault, a huge mass of land would have been vertically displaced. According Dr. R.K Chadha, former scientist at NGRI and currently a Raja Ramanna Fellow at NGRI, the vertical displacement of the seafloor may have been two-three metres. An earthquake of this magnitude would have fractured for a length of about 400 km with a zone width of 150 km, he says. The USGS website also speculates that the July 30 quake would have a length of 390 km and width of 140 km. In subduction zones, the fault length will generally be longer, whereas on land, the fault length will be half in length for the same magnitude, he adds. However, in the case of the March 28, 2025 Myanmar earthquake occurring at a depth of 10 km, the fault length was about 460 km though it was expected to be only about 150-200 km, Dr. Chadha adds.
How tsunami waves are generated
A huge parcel of seafloor of about 400 km in length and 150 km in width suddenly moving vertically upwards by two-three metres causes a huge displacement of water thereby generating tsunami waves. Tsunami waves propagate with maximum energy and velocity in the direction perpendicular to the direction of the fault strike. “The fault strike direction of the July 30 earthquake is nearly NE-SW. Though Japan is very close to the epicentre, it will not face very high and destructive tsunami waves as Japan is located south of the epicentre. The tsunami waves striking Japan will be around two feet in height,” says Dr. Chadha. The Japan Weather Agency had upgraded its warning, saying it expected tsunami waves of up to three metres, but waves of 40 cm were recorded so far. But places on the west coast of the U.S. can face taller and powerful tsunami waves though they are located hundreds of kilometres away.
