Skip to content
SeismoAtlas

M1.6 earthquake near San Ramon, California, United States

A magnitude 1.6 earthquake struck near San Ramon, California, United States at 03:48 local time (10:48 UTC) on 27 Sept 2026, at a depth of 8 km, according to USGS. The solution is preliminary and may be revised.

Data: USGS · updated 2026-09-27 13:17 UTC · automatic solution

Magnitude
1.6micro
duration magnitude (md)
Depth
8 km
Status
Automatic
Origin time
2026-09-27 10:48:34 UTC
Local: 27 Sept 2026, 03:48:34 (America/Los Angeles)
Epicentre
37.764° N, 122.001° W

Circles show this event and others within 30 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map

Nearby places

Distance and estimated shaking at nearby places
PlaceDistanceEst. shaking
San RamonCalifornia, United States · pop. 76,1343 kmINot felt
DanvilleCalifornia, United States · pop. 44,4006 kmINot felt
DublinCalifornia, United States · pop. 57,7219 kmINot felt
Castro ValleyCalifornia, United States · pop. 61,38811 kmINot felt
OaklandCalifornia, United States · pop. 419,26724 kmINot felt
San FranciscoCalifornia, United States · pop. 827,52637 kmINot felt
San JoseCalifornia, United States · pop. 997,36848 kmINot felt
StocktonCalifornia, United States · pop. 305,65866 kmINot felt

Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more.

Every agency's solution

Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses USGS · NC.

AgencyMagnitudeDepthEpicentreTime offsetStatus
USGS · NCheadlineNorthern California Seismic System via U.S. Geological Survey1.6 md8 km37.76° N, 122.00° W–Automatic

How big was it?

Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.

It released roughly the energy of 4 kg of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 8 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.

M1.6 releases about 7.7× the energy of M1.0, and its waves are about 3.9× taller on a seismogram. Energy: 4 kg of TNT vs 477 g of TNT.

Each square is the energy of one M1.0. Energy from log₁₀E = 1.5M + 4.8.

Aftershocks and nearby activity

19 later earthquakes within 30 km; the largest was M2.4 24 days ago. 5 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.

Aftershocks

Mainshock M1.6

19 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).

Aftershocks
Time after mainshock (hours)MagnitudeDepth (km)
35.291.78
186.250.94
194.971.77
200.331.69
368.921.46
401.961.27
402.041.715
505.931.69
517.611.87
518.491.16
518.971.46
519.331.68
519.442.47
519.791.79
540.692.47
583.491.67
689.971.315
692.021.03
718.641.110
  1. 2.4Near San Ramon, California, United States10-19 02:15
  2. 2.44 km SE of San Ramon, California, United States10-19 23:29
  3. 1.8Near San Ramon, California, United States10-19 00:24
  4. 1.7Near Pleasant Hill, California, United States10-14 04:51
  5. 1.7Near San Ramon, California, United States10-19 02:35
  6. 1.74 km NW of Orinda, California, United States10-05 13:46
  7. 1.7Near San Ramon, California, United States09-28 22:06
  8. 1.6Near Alamo, California, United States10-18 12:44
  9. 1.6Near San Ramon, California, United States10-19 02:08
  10. 1.610 km ENE of Blackhawk, California, United States10-21 18:18
  11. 1.66 km SW of Clayton, California, United States10-05 19:08
  12. 1.43 km NNE of San Leandro, California, United States10-12 19:43
  13. 1.4Near San Ramon, California, United States10-19 01:46
  14. 1.35 km SSW of Pittsburg, California, United States10-26 04:46
  15. 1.2Near Alamo, California, United States10-14 04:46
  16. 1.1Near San Ramon, California, United States10-19 01:17
  17. 1.1Near Alamo, California, United States10-27 09:26
  18. 1.06 km SSW of Moraga, California, United States10-26 06:49
  19. 0.9Near Berkeley, California, United States10-05 05:03

Did you feel it?

Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.

Reports close 14 days after an earthquake.

Reports on SeismoAtlas

No reports yet.

Event id nc75443027. First recorded here 28 Sept 2026, 17:32:08 UTC. Solutions: USGS · NC (usgs:nc75443027). Cite as: SeismoAtlas, “M1.6 earthquake near San Ramon, California, United States”, https://seismoatlas.com/earthquake/nc75443027-m1-6-earthquake-near-san-ramon-california-united-states, data from USGS.

JSON: /api/v1/events/nc75443027. SeismoAtlas is not an official warning service.