A 6.7-magnitude quake or larger along the San Andreas Fault in Southern California could kill an estimated 1,800 people, injure 53,000 and result in $214 billion in damage.
Here's what you need to know about that massive fault zone and what it means for future California quakes.
The San Andreas fault zone is an 800-mile boundary between the Pacific tectonic plate to the west and the North American plate to the east.
The last major quake to occur along the San Andreas fault zone was in 1906, when a 7.9-magnitude earthquake and subsequent fire leveled parts of San Francisco and killed 3,000 people, the deadliest in US history.
But going more than 100 years without major seismic activity along the fault zone is an anomaly, geologists say, and could portend a massive earthquake along the infamous fault.