Humboldt County dodged a bullet with 6.4 earthquake

FERNDALE, Calif., -  As bad as Tuesday's earthquake was, experts say it could have been much, much worse.

The epicenter of the 6.4 magnitude earthquake that jolted Humboldt County, was just off the coast and about 10 miles deep.

The area is where four major plates meet; known as the Cascadia Subduction zone. 

Normally in subduction zone, massive tectonic plates push up against each other, which cause earthquakes as one plate either climbs over or dive under the adjoining plate; quickly thrusting the sea floor upward as well as the water above it.

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"Of course, water doesn't like to make a hill so, instead, it spreads out as a tsunami wave," said Professor Harold Tobin of the University of Washington.

Professor Tobin is an earthquake and tectonic plate expert and Director of the Pacific Northwest Seismic Network.

He said North Coasters dodged the bullet of a mega tsunami because the plates stayed level like how Bay Area faults move bring less chance of tsunamis.

"The two plates slide side by side, rather than one going over the other," said Tobin.

UC Santa Barbara Professor Alex Simms,  who researches ancient earthquakes and tsunamis, said there is potential for much larger earthquakes in the future. 

"From that, we know that about every three to five hundred years is when one of these really big earthquakes happen," said Simms.

SEE ALSO: Dramatic photos from Humboldt County's 6.4-quake in Northern California

It has now been over five hundred years since a North Coast mega quake caused massive ground destruction and giant tsunamis.

"A hundred feet is entirely plausible," said Tobin. "Many of our coastal communities are certainly at risk."

In the past ninety years, there have been at least 40 other earthquakes of magnitude six or larger, six were magnitude seven or larger, all within 150 miles of Tuesday's quake.