California's towering redwood trees have long stood atop a hidden earthquake threat that could unleash widespread devastation if it awakens.
Geologists have confirmed a previously unmapped active fault in Humboldt County after uncovering evidence that it produced at least four major earthquakes over the past 20,000 years.
The Shively Fault lies near the small community of Shively within the Mendocino Triple Junction, where three tectonic plates collide, making it California's most seismically active region.
Researchers say the fault could be capable of producing a magnitude 7 or greater earthquake if their mapping confirms it extends beyond the currently identified section.
An earthquake of that magnitude could produce widespread, damaging shaking across parts of Northern California.
