The U.S. Geological Survey recorded multiple low-to-moderate earthquakes across the United States on Friday, July 31, 2026, with Alaska and California accounting for most of the day’s seismic activity.
The strongest event was a magnitude 3.8 tremor at 3:02 a.m. (UTC-05:00), centered 102 kilometers southeast of Atka, Alaska, at a depth of 3.0 kilometers, according to USGS. The second largest was a magnitude 3.2 quake at 3:10 p.m. (UTC-05:00), with its epicenter 8 kilometers west of Palomar Observatory in California at a depth of 13.7 kilometers.
Events recorded on July 31
USGS data confirmed six additional tremors throughout the day:
- Magnitude 2.5 at 3:25 a.m. (UTC-05:00), 76 km west of Petrolia, California, depth 2.8 km
- Magnitude 2.9 at 5:47 a.m. (UTC-05:00), 116 km east-northeast of Chiniak, Alaska, depth 5.0 km
- Magnitude 3.0 at 8:36 a.m. (UTC-05:00), 90 km west-southwest of Karluk, Alaska, depth 84.8 km
- Magnitude 2.7 at 9:45 a.m. (UTC-05:00), 55 km east of Denali National Park, Alaska, depth 5.0 km
- Magnitude 2.5 at 11:05 a.m. (UTC-05:00), 7 km east-northeast of Soldotna, Alaska, depth 3.6 km
- Magnitude 2.9 at 3:02 p.m. (UTC-05:00), 11 km east-southeast of Gilroy, California, depth 5.4 km
The USGS described the overall pattern as predominantly low to moderate in intensity, which it said is common in zones with active tectonic faults. California registered the highest concentration of small earthquakes on the West Coast, while Alaska and Hawaii continued recording activity linked to volcanic processes and Puerto Rico maintained movement associated with Caribbean basin dynamics.
The agency said it detects dozens, and sometimes hundreds, of seismic movements every day. The vast majority are imperceptible to the public but are recorded by seismological stations and contribute to ongoing scientific studies of the country’s tectonic behavior. Most daily earthquakes do not compromise structural integrity, the USGS noted.
Why California shakes so often
California’s persistent seismic activity is driven by its position on the boundary between the Pacific Plate and the North American Plate, according to USGS. The San Andreas Fault forms part of an extensive system of active faults running through the state that continuously releases energy through small, medium and, on occasion, large earthquakes. Specialists cited in the source consider that California will continue recording significant seismic activity for decades, given its geological location.
Alaska typically leads the entire country in total earthquakes recorded each year, a reflection of the state’s intense tectonic environment. Historical USGS records identify Alaska, California, Hawaii, Nevada, Washington, Utah and Puerto Rico as the regions with the greatest seismic activity in the United States.
ShakeAlert: the West Coast warning system
The USGS operates ShakeAlert, the official early earthquake warning system for the West Coast. The system detects a quake in its first seconds and automatically sends alerts before the strongest seismic waves reach populated areas. Depending on distance from the epicenter, people may receive several seconds of advance notice to take protective action. Alerts are delivered through the MyShake app, Wireless Emergency Alerts (WEA), Android Earthquake Alerts and compatible state emergency systems.
No method currently exists that can predict in advance when, where or how strongly an earthquake will strike, according to USGS. Modern monitoring systems can detect and characterize an event rapidly once it begins and trigger early warnings in certain regions, but they cannot anticipate a quake before it occurs.
What to do during and after a quake
U.S. authorities recommend the Drop, Cover and Hold On strategy: drop to the ground, take cover under a sturdy table and hold on until the shaking stops. They also advise staying away from windows, avoiding elevators and protecting the head and neck. After a quake, the USGS recommends checking for injured persons, inspecting for structural damage, looking for gas leaks and preparing for possible aftershocks while following instructions from local authorities.
