QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3md

Earthquake near Diablo, CA

No earthquake was likely felt in Diablo in the 24 hours to 12:00 pm PST (20:00 UTC). The last one was M 2.5, 18 km (11 mi) NNW, at 1:23 am PST on 2 November 2026, estimated intensity II (weak) in town; 39 felt reports to USGS. Every earthquake near Diablo

This page: a magnitude 2.3 earthquake was recorded 2 km (1 mi) west-northwest of Diablo, CA, at 6:06 pm PST on 20 February 2018 (02:06 UTC), 7.7 km deep. 16 people have reported feeling it to USGS.

USGS: 2km WNW of Diablo, CA

8 km (5 mi) SE of Walnut Creek, CA · 39 km (24 mi) E of San Francisco, CA

6:06 pm PST, Feb 20, 2018 · · 7.7 km deep · released about 91 lb of TNT

Every earthquake near Diablo Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 9 kmAlameda County 23 kmSolano County 47 kmSan Mateo County 59 kmSan Joaquin County 63 kmMarin County 71 kmSanta Clara County 74 kmNapa County 80 kmSacramento County 87 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
6:06 pm PST on 20 February 2018 ()
Where
2 km (1 mi) west-northwest of Diablo, CA · earthquakes near Diablo
Magnitude
M 2.3 (md)
Depth
7.7 km below the surface
Felt
16 reports · strongest reported intensity III
Nearest
Contra Costa County, 9 km NNE
Nearest mapped fault
Calaveras fault, 4 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 3186 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 18 km (11 mi) from the epicentre. In Diablo, 2 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: Danville 3 km, intensity II · Alamo 5 km, intensity II · San Ramon 7 km, intensity II · Walnut Creek 10 km, intensity II · Lafayette 13 km, intensity II · Pleasant Hill 14 km, intensity II · Concord 16 km, intensity II · Dublin 16 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 91 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 170,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 120,000× the energy of this one
  3. Around the size people start to feel M 3.0 10× the energy of this one
  4. This earthquake M 2.3 about 91 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 4.4 on 2018-01-04 — about 1,200 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.8 The 1980 Livermore, California Earthquake · 19 km E of this epicentre
  2. 5.7 15 km NE of East Foothills, California · 48 km SSE of this epicentre
  3. 5.5 6 km NNE of East Foothills, California · 49 km SSE of this epicentre
  4. 5.4 9 km NE of Livermore, California · 26 km ESE of this epicentre
  5. 5.3 The 1957 San Francisco, California Earthquake · 48 km WSW 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 37.8447, -121.9792. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 9 km (5 mi) NNE earthquakes near Contra Costa County
Alameda County, CA 23 km (14 mi) SSE earthquakes near Alameda County
Solano County, CA 47 km (29 mi) N earthquakes near Solano County
San Mateo County, CA 59 km (37 mi) SW earthquakes near San Mateo County
San Joaquin County, CA 63 km (39 mi) E earthquakes near San Joaquin County
Marin County, CA 71 km (44 mi) WNW earthquakes near Marin County

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

Aftershocks so far

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

  1. 1.7 2km NW of Castro Valley, CA
  2. 2.1 4km ESE of San Ramon, CA
  3. 2.8 2km E of Pacheco, CA
  4. 2.6 12km WNW of Rio Vista, CA
  5. 2.7 0km WNW of Diablo, CA
  6. 1.7 2km WSW of Diablo, CA
  7. 1.6 10km NE of Milpitas, CA
  8. 1.8 3km NNE of Fremont, CA
  9. 2.2 1km NE of San Leandro, CA
  10. 1.6 9km SSW of Brentwood, CA
  11. 2.4 8km SSW of Brentwood, CA
  12. 1.6 0km WNW of Diablo, CA
  13. 1.6 2km W of Diablo, CA
  14. 2.8 3km NNW of Piedmont, CA
  15. 1.7 2km WSW of Diablo, 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.