8.8 earthquake off Russia sparks Tsunami alerts: What is Shallow Reverse Faulting that may have unleashed the monster tremor?

A powerful magnitude 8.8 earthquake struck Russia’s Far East on Wednesday, triggering tsunami waves that hit coastal towns in Russia and Japan and prompted widespread evacuations around the Pacific Rim.

Russia's emergencies ministry said a tsunami hit and flooded the port town of Severo-Kurilsk, where the population of around 2,000 people was evacuated.

Wednesday’s earthquake was the strongest in Russia’s Kamchatka region since 1952, according to the Russian Academy of Sciences. The quake struck near the same area as a powerful 9.0 earthquake in 1952 that caused a massive tsunami across the Pacific, the USGS said. So far, at least six aftershocks have hit the region, including one measuring 6.9 and another 6.3.

Scientists believe the quake was caused by shallow reverse faulting, a type of tectonic activity that can generate the most destructive seismic events.

What is Shallow Reverse Faulting?

In geology, reverse faulting (or thrust faulting) occurs when one block of the Earth's crust is pushed up over another due to compressional forces. It’s the opposite of a normal fault, where blocks pull apart.

“Shallow” means the rupture occurred near the Earth's surface, typically within the top 70 km of the crust.

These shallow events are more dangerous because the seismic energy has less distance to dissipate before reaching populated areas.

In Wednesday’s case, the US Geological Survey (USGS) and Russia’s Geophysical Service reported that the earthquake’s epicentre was off the Kamchatka Peninsula, a tectonically active zone where the Pacific Plate is diving under the North American Plate.

How this triggered tsunamis?

Shallow reverse faulting, especially under the seabed, often causes tsunamis. When the seafloor suddenly shifts upward, it pushes the water above it, creating powerful waves. These waves can travel at high speeds across the ocean and cause destruction even thousands of kilometres away.

In Japan, Fukushima nuclear plant workers were evacuated, reflecting deep concerns over a repeat of the 2011 disaster. Coastal train services were suspended across Yokohama, Chiba, and Izu. Mobile tsunami alerts were issued in California, while the Philippines and Taiwan also asked coastal residents to evacuate inland.

Why it’s alarming

Shallow reverse faulting is dangerous because it can cause multiple disasters at once—strong ground shaking, powerful aftershocks (like the 6.9 and 6.3 already reported), tsunamis, and serious damage to infrastructure. These events happen quickly, leaving little time for governments to respond before the tsunami hits within minutes of the quake.