Earthquake · reviewed by a seismologist
M 1.9md
Earthquake near Greenfield, CA
No earthquake was likely felt in Greenfield in the 24 hours to 3:18 am PST (11:18 UTC). The last one was M 3.0, 38 km (23 mi) N, at 2:58 pm PDT on 22 October 2026, estimated intensity II (weak) in town. Every earthquake near Greenfield
This page: a magnitude 1.9 earthquake was recorded 7 km (4 mi) north-northeast of Greenfield, CA, at 3:16 pm PDT on 18 August 2021 (22:16 UTC), 4.0 km deep. 1 person has reported feeling it to USGS.
USGS: 7km NNE of Greenfield, CA
51 km (32 mi) SE of Salinas, CA · 115 km (72 mi) SSE of San Jose, CA
- When
- 3:16 pm PDT on 18 August 2021 ()
- Where
- 7 km (4 mi) north-northeast of Greenfield, CA · earthquakes near Greenfield
- Magnitude
- M 1.9 (md)
- Depth
- 4.0 km below the surface
- Felt
- 1 report · strongest reported intensity II
- Nearest
- Monterey County, 18 km SSW
- Nearest mapped fault
- San Andreas fault, 16 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 1906 days ago
Earthquake alerts for Greenfield, CA
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 14 km (9 mi) from the epicentre. In Greenfield, 7 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: Greenfield 7 km, intensity II · Soledad 12 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 19 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 810,000× the energy of this one
- Magna, Utah 2020 M 5.7 580,000× the energy of this one
- Around the size people start to feel M 3.0 51× the energy of this one
- This earthquake M 1.9 about 19 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 4.7 on 2019-10-15 — about 19,000 times the energy of this one.
Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:
- 5.9 10 km SE of Tres Pinos, California · 39 km N of this epicentre
- 5.8 Near Paicines, California · 33 km N of this epicentre
- 5.8 29 km NE of San Lucas, California · 40 km ESE of this epicentre
- 5.5 12 km S of Tres Pinos, California · 35 km NNW of this epicentre
- 5.5 3 km ENE of Tres Pinos, California · 48 km N 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 36.3785, -121.2097. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Monterey County, CA | 18 km (11 mi) | SSW | earthquakes near Monterey County |
| San Benito County, CA | 28 km (18 mi) | NNE | earthquakes near San Benito County |
| Santa Cruz County, CA | 100 km (62 mi) | NW | earthquakes near Santa Cruz County |
| Merced County, CA | 101 km (63 mi) | NNE | earthquakes near Merced County |
| Santa Clara County, CA | 103 km (64 mi) | NNW | earthquakes near Santa Clara County |
| San Luis Obispo County, CA | 130 km (81 mi) | SSE | earthquakes near San Luis Obispo County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 1.8 22km NNE of San Ardo, CA
- 1.7 14km SSE of Tres Pinos, CA
- 1.7 6km NNE of Pinnacles, CA
- 1.6 12km SE of Pinnacles, CA
- 1.6 15km SE of Pinnacles, CA
- 1.9 13km S of Tres Pinos, CA
- 2.2 13km S of Tres Pinos, CA
- 1.9 14km WNW of Pinnacles, CA
- 1.8 14km WNW of Pinnacles, CA
- 2.4 6km SE of Pinnacles, CA
- 2.0 7km ESE of Pinnacles, CA
- 1.5 17km SSE of Tres Pinos, CA
- 3.7 14km WNW of Pinnacles, CA
- 2.2 7km SE of Pinnacles, CA
- 1.5 16km SSE of Tres Pinos, 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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.