A little-known California fault line — already considered one of the most dangerous in the country — was rattled by another earthquake Thursday morning, shaking communities across the Bay Area and setting off a pair of aftershocks.

The 3.8-magnitude earthquake struck at 8:30 a.m. near the Oakland Zoo and Bishop O’Dowd High School, according to ABC7.

It was initially pegged at magnitude 4.1 before being downgraded.

Two aftershocks — measuring 3.0 and 2.8 — hit the same area at 9:07 a.m., according to the outlet.

Thousands of people reported feeling the initial jolt, with shaking reaching as far north as Santa Rosa and Sacramento and as far south as Santa Cruz.

The epicenter was near the Oakland Zoo, which sits directly on the notorious Hayward Fault — a 74-mile seismic scar cutting through some of the Bay Area’s most heavily populated communities, including Berkeley, Oakland and Fremont.

And scientists have long worried what could happen when the fault really lets loose.

The Hayward Fault is capable of producing earthquakes exceeding magnitude 7 and last experienced a major rupture in 1868.

Part of the larger San Andreas Fault system, the Hayward Fault is less famous than its better-known neighbor but potentially just as frightening, with experts warning that it is overdue for a major earthquake according to the Daily Mail.

Scientists estimate major quakes strike along the fault every 95 to 183 years, putting it squarely within the window for another potentially devastating rupture.

The US Geological Survey estimates the fault has a 14.3% chance of producing a magnitude 6.7 or greater earthquake by 2034 — and a 33% chance before 2043.

“This fault is what we sort of call a tectonic time bomb,” USGS earthquake geologist emeritus David Schwartz previously told the Los Angeles Times. “It’s just waiting to go off.”

Researchers at Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory have modeled what that nightmare scenario could look like, running 50 simulations of a magnitude 7 rupture.

The results were sobering: shaking in some Bay Area communities could be up to 50% stronger than previous forecasts suggested.

Their findings showed shaking in some Bay Area communities could be up to 50% stronger than earlier forecasts suggested with Oakland, Berkeley, Hayward, San Leandro, Emeryville, Alameda and Livermore among the areas vulnerable to particularly powerful ground motion.

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One USGS disaster scenario paints an even grimmer picture, estimating that a major Hayward Fault quake could kill 800 people and injure as many as 18,000.

The destruction could extend far beyond collapsed buildings.

Hundreds of fires could erupt, tens of thousands of homes could be destroyed and nearly half a million people could be displaced.

No major damage or injuries were immediately reported from Thursday’s quake.