QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8mw

Earthquake near Gilroy, CA

No earthquake was likely felt in Gilroy in the 24 hours to 5:27 pm PST (01:27 UTC). The last one was M 2.5, 9 km (6 mi) E, at 7:27 pm PST on 1 November 2026, estimated intensity II (weak) in town; 2 felt reports to USGS. Every earthquake near Gilroy

This page: a magnitude 3.8 earthquake was recorded 9 km (6 mi) east-northeast of Gilroy, CA, at 5:38 pm PST on 21 February 2021 (01:38 UTC), 6.2 km deep. 1,014 people have reported feeling it to USGS.

USGS: 9km ENE of Gilroy, CA

10 km (7 mi) ENE of Gilroy, CA · 41 km (25 mi) SE of San Jose, CA

5:38 pm PST, Feb 21, 2021 · · 6.2 km deep · released about 6.6 tons of TNT

10 km30 km60 km120 km N Santa Clara County 27 kmSanta Cruz County 47 kmSan Benito County 60 kmMerced County 69 kmStanislaus County 71 kmAlameda County 77 kmSan Mateo County 89 kmMonterey County 91 kmSan Joaquin County 101 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
5:38 pm PST on 21 February 2021 ()
Where
9 km (6 mi) east-northeast of Gilroy, CA · earthquakes near Gilroy
Magnitude
M 3.8 (mw)
Depth
6.2 km below the surface
Felt
1,014 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
Santa Clara County, 27 km NW
Nearest mapped fault
Calaveras 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 2017 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 80 km (50 mi) from the epicentre. In Gilroy, 9 km away, the estimate is intensity III (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: Gilroy 9 km, intensity III · Morgan Hill 18 km, intensity III · Hollister 23 km, intensity III · Watsonville 29 km, intensity III · Prunedale 35 km, intensity III · Capitola 43 km, intensity II · Salinas 44 km, intensity II · Live Oak 45 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 6.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 26,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,100× the energy of this one
  3. Magna, Utah 2020 M 5.7 810× the energy of this one
  4. This earthquake M 3.8 about 6.6 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 14× more

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 4.7 on 2019-10-15 — about 27 times the energy of this one.

Before 2016, the USGS record lists 28 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 The 1989 Loma Prieta, California Earthquake · 36 km W of this epicentre
  2. 6.5 Near Morgan Hill, California · 16 km WNW of this epicentre
  3. 6.2 Near San Jose, California · 40 km NW of this epicentre
  4. 6.2 The 1984 Morgan Hill, California Earthquake · 34 km NNW of this epicentre
  5. 6.1 Near San Jose, California · 33 km WNW 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 37.0457, -121.4782. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Santa Clara County, CA 27 km (17 mi) NW earthquakes near Santa Clara County
Santa Cruz County, CA 47 km (29 mi) W earthquakes near Santa Cruz County
San Benito County, CA 60 km (37 mi) SE earthquakes near San Benito County
Merced County, CA 69 km (43 mi) ENE earthquakes near Merced County
Stanislaus County, CA 71 km (44 mi) NE earthquakes near Stanislaus County
Alameda County, CA 77 km (48 mi) NNW earthquakes near Alameda County

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

Aftershocks so far

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

  1. 1.8 6km S of San Juan Bautista, CA
  2. 1.9 6km S of San Juan Bautista, CA
  3. 2.5 6km S of San Juan Bautista, CA
  4. 1.5 6km S of San Juan Bautista, CA
  5. 3.3 6km SSE of San Juan Bautista, CA
  6. 2.3 12km NNE of Hollister, CA
  7. 2.6 7km E of Alum Rock, CA
  8. 1.7 12km NNE of Hollister, CA
  9. 1.9 10km E of Gilroy, CA
  10. 1.8 11km SW of Ridgemark, CA
  11. 1.9 8km NE of Ridgemark, CA
  12. 2.8 8km NE of Ridgemark, CA
  13. 3.2 10km E of Gilroy, CA
  14. 1.7 8km NE of Ridgemark, CA
  15. 2.5 15km ENE of Alum Rock, 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.