QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6md

Earthquake near Fremont, CA

No earthquake was likely felt in Fremont in the 24 hours to 7:57 am PST (15:57 UTC). The last one was M 3.5, 49 km (31 mi) ESE, at 7:21 am PDT on 27 September 2026, estimated intensity II (weak) in town; 8 felt reports to USGS. Every earthquake near Fremont

This page: a magnitude 1.6 earthquake was recorded 5 km (3 mi) east of Fremont, CA, at 6:59 am PST on 4 December 2018 (14:59 UTC), 6.5 km deep.

USGS: 5km E of Fremont, CA

6 km (4 mi) N of Fremont, CA

6:59 am PST, Dec 4, 2018 · · 6.5 km deep · released about 7.3 lb of TNT

10 km30 km60 km120 km N Alameda County 11 kmContra Costa County 42 kmSan Mateo County 42 kmSanta Clara County 42 kmSanta Cruz County 60 kmSan Joaquin County 72 kmSolano County 80 kmStanislaus County 82 kmMarin County 91 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
6:59 am PST on 4 December 2018 ()
Where
5 km (3 mi) east of Fremont, CA · earthquakes near Fremont
Magnitude
M 1.6 (md)
Depth
6.5 km below the surface
Felt
no reports yet
Nearest
Alameda County, 11 km N
Nearest mapped fault
Hayward fault, 3 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 2900 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 9 km (6 mi) from the epicentre. In Fremont, 5 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: Fremont 5 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 7.3 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,100,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,500,000× the energy of this one
  3. Around the size people start to feel M 3.0 130× the energy of this one
  4. This earthquake M 1.6 about 7.3 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 15,000 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 Near San Jose, California · 30 km SSE of this epicentre
  2. 6.2 The 1984 Morgan Hill, California Earthquake · 34 km SE of this epicentre
  3. 6.1 Near San Jose, California · 40 km SSE of this epicentre
  4. 5.8 7 km NNW of Boulder Creek, California · 44 km SSW of this epicentre
  5. 5.8 The 1980 Livermore, California Earthquake · 36 km NNE 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 37.5463, -121.9307. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Alameda County, CA 11 km (7 mi) N earthquakes near Alameda County
Contra Costa County, CA 42 km (26 mi) N earthquakes near Contra Costa County
San Mateo County, CA 42 km (26 mi) WSW earthquakes near San Mateo County
Santa Clara County, CA 42 km (26 mi) SSE earthquakes near Santa Clara County
Santa Cruz County, CA 60 km (37 mi) S earthquakes near Santa Cruz County
San Joaquin County, CA 72 km (45 mi) NE earthquakes near San Joaquin County

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

Aftershocks so far

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

  1. 2.5 12km NNE of Morgan Hill, CA
  2. 2.7 3km NNE of San Ramon, CA
  3. 2.8 3km NE of Oakland, CA
  4. 2.4 17km ESE of Livermore, CA
  5. 1.8 8km SSE of Portola Valley, CA
  6. 2.1 3km SW of Monte Sereno, CA
  7. 1.5 3km ESE of Berkeley, CA
  8. 1.9 2km ENE of Berkeley, CA
  9. 2.0 11km NNE of Alum Rock, CA
  10. 1.8 12km SSW of Mountain House, CA
  11. 1.7 12km SSW of Mountain House, CA
  12. 1.6 14km ESE of Livermore, CA
  13. 2.0 10km ENE of Blackhawk, CA
  14. 1.9 10km ENE of Blackhawk, CA
  15. 2.2 10km ENE of Blackhawk, 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.