QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mw

Earthquake near Aromas, CA

No earthquake was likely felt in Aromas in the 24 hours to 2:54 am PST (10:54 UTC). The last one was M 2.0, 11 km (7 mi) SE, at 2:11 am PST on 11 November 2026, estimated intensity II (weak) in town. Every earthquake near Aromas

This page: a magnitude 4.2 earthquake was recorded 4 km (2 mi) southeast of Aromas, CA, at 8:01 pm PST on 16 January 2021 (04:01 UTC), 8.3 km deep. 13,081 people have reported feeling it to USGS.

USGS: 4km SE of Aromas, CA

51 km (32 mi) SSE of San Jose, CA · 16 km (10 mi) S of Gilroy, CA

8:01 pm PST, Jan 16, 2021 · · 8.3 km deep · released about 30 tons of TNT

Every earthquake near Aromas Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Cruz County 39 kmSanta Clara County 40 kmSan Benito County 55 kmMonterey County 75 kmMerced County 87 kmAlameda County 91 kmSan Mateo County 91 kmStanislaus County 94 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
8:01 pm PST on 16 January 2021 ()
Where
4 km (2 mi) southeast of Aromas, CA · earthquakes near Aromas
Magnitude
M 4.2 (mw)
Depth
8.3 km below the surface
Felt
13,081 reports · strongest reported intensity V
Measured shaking
intensity V (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest
Santa Cruz County, 39 km WNW
Nearest mapped fault
San Andreas 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 774 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 112 km (70 mi) from the epicentre. In Aromas, 4 km away, the estimate is intensity IV (light). 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: Prunedale 11 km, intensity IV · Watsonville 14 km, intensity IV · Gilroy 16 km, intensity IV · Hollister 19 km, intensity III · Salinas 21 km, intensity III · Morgan Hill 30 km, intensity III · Capitola 33 km, intensity III · Live Oak 35 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 30 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 5,600× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 250× the energy of this one
  3. Magna, Utah 2020 M 5.7 180× the energy of this one
  4. This earthquake M 4.2 about 30 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 63× 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 5.8 times the energy of this one.

Before 2016, the USGS record lists 29 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 The 1989 Loma Prieta, California Earthquake · 30 km NW of this epicentre
  2. 6.5 Near Morgan Hill, California · 27 km N of this epicentre
  3. 6.2 The 1984 Morgan Hill, California Earthquake · 50 km N of this epicentre
  4. 6.1 Near San Jose, California · 41 km NNW of this epicentre
  5. 5.9 10 km SE of Tres Pinos, California · 38 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 36.8673, -121.6105. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Santa Cruz County, CA 39 km (24 mi) WNW earthquakes near Santa Cruz County
Santa Clara County, CA 40 km (25 mi) N earthquakes near Santa Clara County
San Benito County, CA 55 km (34 mi) ESE earthquakes near San Benito County
Monterey County, CA 75 km (46 mi) SSE earthquakes near Monterey County
Merced County, CA 87 km (54 mi) ENE earthquakes near Merced County
Alameda County, CA 91 km (56 mi) NNW earthquakes near Alameda County

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

Aftershocks so far

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

  1. 2.9 9km SSW of Tres Pinos, CA
  2. 1.9 6km SSW of Gilroy, CA
  3. 1.7 8km NW of Pinnacles, CA
  4. 1.6 16km NW of Pinnacles, CA
  5. 2.3 10km ENE of Morgan Hill, CA
  6. 2.0 13km S of Tres Pinos, CA
  7. 3.8 9km ENE of Gilroy, CA
  8. 1.7 2km SE of Tres Pinos, CA
  9. 2.0 1km NNE of Tres Pinos, CA
  10. 1.6 8km NE of Interlaken, CA
  11. 1.7 6km SW of Gilroy, CA
  12. 1.5 8km NNW of Pinnacles, CA
  13. 1.9 16km E of Seven Trees, CA
  14. 2.1 13km NW of Pinnacles, CA
  15. 1.8 13km NW of Pinnacles, 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.