A series of rapid earthquakes occurred on August 13 in California's San Francisco Bay Area, striking along the Hayward Fault, a geological feature described by experts as "America's most dangerous." The initial earthquake, measuring a magnitude 4.1, was later downgraded to a 3.8 by the U.S. Geological Survey (USGS). It struck at approximately 8:30 a.m. local time, 14 miles from San Francisco.
This primary tremor was followed by three smaller aftershocks between 12:07 p.m. and 12:38 p.m. ET, recorded at magnitudes 3.0, 2.8, and 1.7. Reports of feeling the initial earthquake came from a wide area, extending as far east as Sacramento, about 75 miles from San Francisco. The Bay Area is home to nearly eight million people.
The swarm took place along the Hayward Fault, a 74-mile-long fault line that is part of the larger San Andreas fault system. Scientists have previously warned about the potential for a major seismic event on the Hayward Fault, noting its capability to produce earthquakes exceeding magnitude 7.0 and its status as being significantly overdue for a large-scale tremor. USGS scientists have indicated a 95 percent probability of an earthquake of magnitude 6.7 or greater striking the Bay Area by 2043.
