Geologists are cracking open a mysterious fault found in a northern California forest that they believe remains active and able to cause earthquakes — shortly after a powerful NorCal quake.

The scientists are digging up the Humboldt County fault to investigate.

“We felt really confident but we needed to go explore by excavating it,” Mark Hemphill-Haley, professor emeritus of geology at Cal Poly Humboldt, told SFGATE. “We have since discovered that it’s a very well-presented reverse fault.”

California Geological Survey geologist Jason Patton first found evidence of a fault in the Shively, California, area four years ago. He used a remote sensing method called lidar to examine the surface of the Earth and discovered the fault.

He and Hemphill-Haley decided to work together in digging up the fault, which they believe is still active after four large earthquakes in the last 20,000 years.

The team, with funding from the US Geological Survey, has dug a 30 feet wide and 15 feet deep trench and is currently gathering data from it.

As the scientists examined the trench, a 5.6-magnitude earthquake hit neighboring Mendocino County Wednesday. The quake caused some injuries and damage to several businesses.

But the Shively fault could be responsible for a much more devastating earthquake.

Patton and Hemphill-Haley’s team thinks the fault could produce a magnitude 7 earthquake, more than 100 times stronger than the recent Mendocino shake according to the USGS.

Only about a dozen-and-a-half earthquakes 7.0 or above have struck California in the last century. Scientists are hopeful the additional data will prepare them for the next big one.

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But there’s concern that the Pacific Ring of Fire, which includes California and encompasses thousands of miles from the bottom tip of South America to the coast of Australia, could produce more devastating quakes.

Two Venezuela earthquakes, a magnitude 7.2 followed by a 7.5, in Venezuela, devastated the region. The country is also located along the Ring of Fire.

The U.S. Geological Survey estimated that there’s a 40% chance the death toll could climb to at least 10,000, and a 30% chance it could even top 100,000.

“High casualties and extensive damage are probable, and the disaster is likely widespread,” the USGS warned.

The California Post reached out to the geologists for further comment.