A MASSIVE 7.4-magnitude earthquake struck off Russia's far east today prompting a tsunami warning being sounded for all coasts within 190 miles of the epicentre.

The colossal quake, which initially measured at 7.8, struck 55 miles southwest of Nikol'skoye at a depth of 33 km, the United States Geological Survey said.

There have no immediate reports of damage to the remote and sparsely populated area, according to Russian news agencies.

Earthquakes are caused by the movement of tectonic plates.

Some 80 per cent occur around the rim of the Pacific Ocean.

The plates - giant rock slabs that make up the Earth's upper layer - are always slowly moving.

They often collide and slide against each other, according to National Geographic.

This impact can be unnoticeable on the surface but can cause immense stress between the plates.

When this stress is released, it causes massive vibrations, called seismic waves, often hundreds of miles through the rock to the surface.

There are fears that there is a "big one" on the way after a flurry of volcanic activity in the Pacific's "Ring of Fire".

A study from California says that the cluster of tremors around the planet's so-called Ring of Fire- a horseshoe-shaped geological disaster zone - could indicate the "big one" is due to hit.

The research, published in the journal Science Advances, involved analysis of 101 major earthquakes around the Pacific Ring of Fire between 1990 and 2016.