Small tremor of magnitude 3.9 just reported 3 miles southeast of San Ramon, California, United States

A very shallow magnitude 3.9 earthquake was reported early evening near San Ramon, Contra Costa County, California, USA.
According to the European-Mediterranean Seismological Centre (EMSC), the quake hit on Saturday, December 20th, 2025, at 6:31 pm local time at a very shallow depth of 6 miles. Shallow earthquakes are felt more strongly than deeper ones as they are closer to the surface. The exact magnitude, epicenter, and depth of the quake might be revised within the next few hours or minutes as seismologists review data and refine their calculations, or as other agencies issue their report.
Based on the preliminary seismic data, the quake should not have caused any significant damage, but was probably felt by many people as light vibration in the area of the epicenter.
Weak shaking might have been felt in San Ramon (pop. 76,100) located 3 miles from the epicenter, Dublin (pop. 57,700) 3 miles away, Danville (pop. 44,400) 6 miles away, Pleasanton (pop. 79,500) 7 miles away, Hayward (pop. 158,300) 10 miles away, Livermore (pop. 88,100) 10 miles away, and San Leandro (pop. 90,700) 12 miles away.
Other towns or cities near the epicenter where the quake might have been felt as very weak shaking include San Francisco (pop. 827,500) located 26 miles from the epicenter, and San Jose (pop. 997,400) 28 miles away.

Earthquake data:
Date & time: Dec 21, 2025 02:31 am (Universal Time) local time (21 Dec 2025 02:31 GMT)
Magnitude: 3.8
Depth: 9.60 km
Epicenter latitude / longitude: 37.75°N / 121.94°W (Contra Costa County, California, United States)
Primary data source: USGS
https://www.volcanodiscovery.com/earthquake/news/290000/Small-tremor-of-magnitude-39-just-reported-3-miles-southeast-of-San-Ramon-California-United-States.html