The Kamchatka earthquake, the sixth-largest recorded by modern seismographs over the past century, followed a foreshock 10 days earlier, Risk Frontiers says in a report on whether the event was foreseeable.

The 8.8-magnitude quake on July 30 damaged infrastructure, caused power and mobile phone service outages in eastern Russia and triggered a tsunami.

Ten days earlier the region was shaken by a 7.4-magnitude quake, and a year before it experienced a 7.1-magnitude event.

“It is generally understood that large earthquakes are not always preceded by foreshocks. However, the ... Kamchatka earthquake provides an example of one that was,” the catastrophe modeller’s report says. 

Earthquake researchers have found only 1% of subduction earthquakes with magnitudes of at least seven are preceded by foreshocks.

The Japan Meteorological Agency last year issued its first “mega-earthquake advisory” –  later cancelled – after a 7.1-magnitude event off the island of Kyushu. Risk Frontiers says the agency probably operates on a higher likelihood than 1%, but notes Kamchatka is outside its domain.

The July event has been compared with the 8.8- to 9-magnitude 1952 Kamchatka quake.

The Pacific plate is converging in a northwest direction with the Okhotsk plate at a rate of about 75mm a year and, since 1952, there has been about 5.2 metres of convergence – about the same as the average amount of slip released in this year’s quake.

“This indicates that the occurrence of the 2025 earthquake following the 1952 earthquake was foreseeable in a long-term sense,” the report says.

The report is available here.