M3.7 earthquake shakes rural Lake County near Bartlett Springs fault
An M3.7 earthquake struck 18 km northeast of Upper Lake, California on March 26, 2026 at 10:24 AM PDT (17:24:54 UTC). USGS placed the epicenter in Lake County at a depth of 7.3 kilometers, about 3.5 km from the mapped trace of the Bartlett Springs fault system (Bartlett Springs section).
USGS reviewed the event and assigned a moment magnitude (Mw) of 3.7. Sixty-two "Did You Feel It?" reports were submitted, with a community-reported intensity (CDI) of 4.6 — a level consistent with light shaking felt by most people indoors.
The depth of 7.3 km is in the shallow-crustal range, where earthquakes typically produce more noticeable surface shaking than deeper events of the same magnitude.
USGS catalog data shows one other M3.7+ earthquake within 20 km of this epicenter in the past decade, suggesting events of this size occur about once every 10 years at this location. USGS PAGER did not produce a population-exposure estimate for this event. ShakeMap modeled a maximum instrumental intensity (MMI) of 3.6.
Lake County has a population of approximately 64,700.
Event data
- Magnitude: M3.7 (Mw)
- Depth: 7.31 km
- Time: 2026-03-26 10:24 AM PDT (17:24:54 UTC)
- Coordinates: 39.2935°N, -122.7768°W
- County: Lake
- Nearest mapped fault: Bartlett Springs fault system (Bartlett Springs section), 3.5 km
- USGS event page: https://earthquake.usgs.gov/earthquakes/eventpage/nc75333407