Northern California felt a flurry of small earthquakes this week, with more than two dozen tremors recorded within 24 hours, according to a report by Charisma News citing the Daily Mail.

A preliminary report from the U.S. Geological Survey (USGS) and UC Berkeley recorded a magnitude 2.7 earthquake about four miles northwest of The Geysers on November 2. The shaking from the swarm was described as minor, and no damage or injuries from the current tremors were reported.

Scientists urge caution against reading too much into a swarm on its own. According to the USGS, small earthquake swarms frequently occur without a larger earthquake following. Tremors around The Geysers also have a known local cause: geothermal operations there, including steam withdrawal and water injection, can trigger small earthquakes, and such tremors do not necessarily indicate a rupture on the San Andreas Fault.

At the same time, researchers say the broader picture in California deserves serious attention. USGS seismologist Ned Field told the San Francisco Chronicle in September that the fault system appears primed, and that residents would be wise to be ready. USGS calculations reported by the Chronicle put the Bay Area's chance of a magnitude 6.7 or stronger earthquake over the next 30 years at 74.1 percent across the region's faults collectively, and 25.5 percent for the San Andreas Fault specifically within the Bay Area. Those are long-term probabilities, not a prediction that a major quake is imminent.

Elsewhere in the Bay Area, recurring swarms around San Ramon have prompted closer investigation. Cal State East Bay reported in May that geology professor Luther Strayer and students were working with USGS scientists to deploy temporary seismometers to pinpoint the faults involved.

A study published this year modeled roughly 1,000 years of earthquake history along the southern San Andreas and San Jacinto faults and found that some present-day stress levels reached or exceeded the highest values in the simulation. Researchers identified Cajon Pass as an “earthquake gate,” a junction where a rupture could stop or cross between fault systems; a combined rupture could expose a wider region to damaging shaking. Lead researcher Liliane Burkhard stressed in a University of Bern release that the study is not a prediction of when an earthquake will occur, while describing the system as critically stressed.

The potential consequences of a major rupture are sobering, and they are best understood as planning scenarios, not forecasts. A USGS ShakeOut planning scenario modeled a magnitude 7.8 earthquake rupturing 186 miles of the southern San Andreas, with ground displacement of about six to 23 feet. Roads and rail lines crossing the rupture could break, damaged aqueducts and pipelines could interrupt essential services, and fires and landslides would compound the destruction. The original 2008 ShakeOut report estimated about 1,800 deaths and $213 billion in economic losses under that hypothetical scenario — figures that describe one possible disaster, not the expected outcome of this week's tremors.

For Californians, the message from scientists is steady rather than sensational: small swarms come and go, a great earthquake cannot be timed in advance, and the prudent course is to prepare homes, families, and churches now — while the ground is still.