The most significant seismic event in California's history – an earthquake of 7.9 magnitude – occurred in 1857 and ruptured about 225 miles on the San Andreas Fault. That earthquake, dubbed the last "Big One," killed two people and produced shaking that lasted between one and three minutes.
Since then, California has exploded in population and has been rattled by many major earthquakes, some far more deadly and similarly strong. But Californians have also grown familiar with the existential dread of another "Big One" looming.
Researchers have long warned there will be another massive earthquake in Southern California. They just don't know when.
A recent study says warning signs continue to grow in 2026. The San Andreas and San Jacinto fault systems have reached the highest stress levels seen in the past 1,000 years, according to a study conducted at the University of Hawaiʻi at Mānoa.
The San Andreas fault runs throughout the state, passing through San Francisco and San Bernardino, while the San Jacinto fault is in Southern California and runs through Riverside, San Diego and Imperial Counties.
Since then, California has exploded in population and has been rattled by many major earthquakes, some far more deadly and similarly strong. But Californians have also grown familiar with the existential dread of another "Big One" looming.
Researchers have long warned there will be another massive earthquake in Southern California. They just don't know when.
A recent study says warning signs continue to grow in 2026. The San Andreas and San Jacinto fault systems have reached the highest stress levels seen in the past 1,000 years, according to a study conducted at the University of Hawaiʻi at Mānoa.
The San Andreas fault runs throughout the state, passing through San Francisco and San Bernardino, while the San Jacinto fault is in Southern California and runs through Riverside, San Diego and Imperial Counties.
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