It's called the Hayward Fault and scientists from the U.S. Geological Survey say it will likely produce an earthquake with a magnitude 6.8 or greater sometime over the next 30 years.
VIDEO: How active is the Hayward Fault?
It's already overdue.
The last major quake on the Hayward Fault was on October 21, 1868. That's 149 years ago.
LIST: Bay Area earthquake tracker
On average, the Hayward Fault has a major quake every 140 years. When it does, experts say the damage will be catastrophic.
Watch the video to learn more about the Hayward Fault and how it is a driving force behind other Bay Area faults, including the one that caused the destructive Napa quake in 2014.
Click here for the latest coverage on earthquakes here in the Bay Area and around the world.
VIDEO: What to pack in your earthquake emergency kit