QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7md

Earthquake near Hercules, CA

No earthquake was likely felt in Hercules in the 24 hours to 12:14 am PST (08:14 UTC). The last one was M 2.6, 17 km (11 mi) SSE, at 6:23 pm PST on 1 November 2026, estimated intensity II (weak) in town; 114 felt reports to USGS. Every earthquake near Hercules

This page: a magnitude 1.7 earthquake was recorded 3 km (2 mi) northwest of Hercules, CA, at 5:51 pm PDT on 16 May 2026 (00:51 UTC), 7.7 km deep.

USGS: 3 km NW of Hercules, CA

9 km (6 mi) SSW of Vallejo, CA · 30 km (19 mi) NNE of San Francisco, CA

5:51 pm PDT, May 16, 2026 · · 7.7 km deep · released about 11 lb of TNT

Every earthquake near Hercules Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 34 kmMarin County 38 kmSolano County 41 kmNapa County 53 kmAlameda County 55 kmSan Mateo County 69 kmSan Francisco County 72 kmSonoma County 77 kmYolo County 80 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
5:51 pm PDT on 16 May 2026 ()
Where
3 km (2 mi) northwest of Hercules, CA · earthquakes near Hercules
Magnitude
M 1.7 (md)
Depth
7.7 km below the surface
Felt
no reports yet
Nearest
Contra Costa County, 34 km ESE
Nearest mapped fault
Rodgers Creek fault, 16 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 169 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 10 km (6 mi) from the epicentre. In Hercules, 3 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

Likely felt in: Hercules 3 km, intensity II · Pinole 4 km, intensity II · Crockett 9 km, intensity II · San Pablo 9 km, intensity II · Vallejo 9 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
  3. Around the size people start to feel M 3.0 89× the energy of this one
  4. This earthquake M 1.7 about 11 lb of TNT

Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

The largest earthquake within 50 km since 2016 was M 4.5 on 2019-10-15 — about 14,000 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 7.9 The 1906 San Francisco, California Earthquake · 38 km SW of this epicentre
  2. 6.0 The 2014 South Napa, California Earthquake · 20 km N of this epicentre
  3. 5.4 South of Elmira, California · 46 km NE of this epicentre
  4. 5.3 The 1957 San Francisco, California Earthquake · 44 km SSW of this epicentre

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 38.0350, -122.3092. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 34 km (21 mi) ESE earthquakes near Contra Costa County
Marin County, CA 38 km (24 mi) W earthquakes near Marin County
Solano County, CA 41 km (26 mi) NE earthquakes near Solano County
Napa County, CA 53 km (33 mi) N earthquakes near Napa County
Alameda County, CA 55 km (34 mi) SE earthquakes near Alameda County
San Mateo County, CA 69 km (43 mi) S earthquakes near San Mateo County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

51 earthquakes have been recorded within 50 km since this one.

  1. 1.7 5 km W of Glen Ellen, CA
  2. 1.9 0 km SSW of Pleasant Hill, CA
  3. 2.1 7 km W of Kenwood, CA
  4. 2.0 2 km SSW of Alamo, CA
  5. 1.8 2 km SW of Alamo, CA
  6. 1.7 2 km ESE of Pacheco, CA
  7. 1.5 7 km E of Santa Venetia, CA
  8. 1.9 2 km SE of Oakland, CA
  9. 2.0 2 km ENE of Berkeley, CA
  10. 2.6 2 km NNE of San Leandro, CA
  11. 1.5 3 km SW of Clayton, CA
  12. 1.8 5 km SE of Napa, CA
  13. 1.5 2 km ESE of Pacifica, CA
  14. 1.9 2 km ESE of Pacheco, CA
  15. 1.8 4 km S of Pittsburg, CA

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.