QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5md

Earthquake near Alamo, CA

No earthquake was likely felt in Alamo in the 24 hours to 2:51 am PST (10:51 UTC). The last one was M 2.1, 11 km (7 mi) NNW, at 4:05 am PST on 8 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Alamo

This page: a magnitude 2.5 earthquake was recorded 6 km (4 mi) northeast of Alamo, CA, at 10:37 pm PDT on 14 August 2020 (05:37 UTC), 15 km deep. 48 people have reported feeling it to USGS.

USGS: 6km NE of Alamo, CA

in Walnut Creek, CA · 40 km (25 mi) ENE of San Francisco, CA

10:37 pm PDT, Aug 14, 2020 · · 15 km deep · released about 150 lb of TNT

Every earthquake near Alamo Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 4 kmAlameda County 29 kmSolano County 41 kmSan Joaquin County 63 kmSan Mateo County 63 kmMarin County 69 kmNapa County 74 kmSanta Clara County 80 kmSacramento County 83 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
10:37 pm PDT on 14 August 2020 ()
Where
6 km (4 mi) northeast of Alamo, CA · earthquakes near Alamo
Magnitude
M 2.5 (md)
Depth
15 km below the surface
Felt
48 reports · strongest reported intensity III
Nearest
Contra Costa County, 4 km NE
Nearest mapped fault
Greenville fault, 7 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 2210 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 16 km (10 mi) from the epicentre. In Alamo, 6 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: Alamo 6 km, intensity II · Walnut Creek 7 km, intensity II · Pleasant Hill 8 km, intensity II · Danville 8 km, intensity II · Concord 10 km, intensity II · Lafayette 11 km, intensity II · Pacheco 12 km, intensity II · San Ramon 13 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 150 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 100,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 72,000× the energy of this one
  3. Around the size people start to feel M 3.0 6.5× the energy of this one
  4. This earthquake M 2.5 about 150 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 1,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.0 The 2014 South Napa, California Earthquake · 45 km NW of this epicentre
  2. 5.8 The 1980 Livermore, California Earthquake · 20 km ESE of this epicentre
  3. 5.4 South of Elmira, California · 45 km N of this epicentre
  4. 5.4 9 km NE of Livermore, California · 30 km ESE of this epicentre
  5. 5.1 11 km E of Blackhawk, California · 21 km ESE 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 37.8975, -121.9888. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 4 km (3 mi) NE earthquakes near Contra Costa County
Alameda County, CA 29 km (18 mi) SSE earthquakes near Alameda County
Solano County, CA 41 km (26 mi) N earthquakes near Solano County
San Joaquin County, CA 63 km (39 mi) E earthquakes near San Joaquin County
San Mateo County, CA 63 km (39 mi) SSW earthquakes near San Mateo County
Marin County, CA 69 km (43 mi) WNW earthquakes near Marin County

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

Aftershocks so far

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

  1. 1.7 11km NE of Milpitas, CA
  2. 2.2 10km NE of Milpitas, CA
  3. 1.6 9km WSW of Mountain House, CA
  4. 1.9 10km NE of Milpitas, CA
  5. 2.5 2km ENE of San Leandro, CA
  6. 2.1 10km NE of Milpitas, CA
  7. 2.0 11km NE of Milpitas, CA
  8. 2.6 2km ENE of Pleasant Hill, CA
  9. 2.9 10km NE of Milpitas, CA
  10. 2.4 2km E of Berkeley, CA
  11. 2.6 4km ESE of Berkeley, CA
  12. 1.7 10km NE of Milpitas, CA
  13. 2.6 10km NNE of Milpitas, CA
  14. 2.0 7km S of Livermore, CA
  15. 1.9 7km S of Livermore, 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.