A B.C. study says the fault line between two tectonic plates in the Pacific Northwest is seven kilometres deeper than originally believed.

Olympic Peninsula, Wash.

Study lead author and Simon Fraser University earth sciences professor Andrew Calvert says it's unclear what to make of the discovery. 

But he speculates it could mean the mega quake expected to hit the West Coast could occur beneath the Olympic Peninsula, south of Vancouver Island.

He says the fault line underneath Washington state is actually 27 to 42 kilometres, not 25 to 35 kilometres as previously believed.

Calvert and his team came to the conclusion by looking at how long it took seismic waves to spread throughout the Earth.

He says this vital information will help scientists refine their calculations on any ground shaking that will take place during an earthquake.

He notes a major earthquake hits B.C. every 500 years — the last one was in 1700.

The findings are published in the journal Nature Geoscience.