Earthquake · reviewed by a seismologist
M 1.7md
Earthquake near Day Valley, CA
No earthquake was likely felt in Day Valley in the 24 hours to 11:46 pm PST (07:46 UTC). The last one was M 1.8, 10 km (6 mi) NNW, at 10:49 pm PDT on 29 October 2026, estimated intensity II (weak) in town. Every earthquake near Day Valley
This page: a magnitude 1.7 earthquake was recorded 7 km (4 mi) north of Day Valley, CA, at 12:15 am PST on 21 December 2020 (08:15 UTC), 2.6 km deep. 1 person has reported feeling it to USGS.
USGS: 7km N of Day Valley, CA
22 km (14 mi) S of San Jose, CA · 21 km (13 mi) NNW of Watsonville, CA
- When
- 12:15 am PST on 21 December 2020 ()
- Where
- 7 km (4 mi) north of Day Valley, CA · earthquakes near Day Valley
- Magnitude
- M 1.7 (md)
- Depth
- 2.6 km below the surface
- Felt
- 1 report
- Nearest
- Santa Cruz County, 17 km SW
- Nearest mapped fault
- Sargent fault, 1 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 2143 days ago
Earthquake alerts for Day Valley, CA
Get a notification in this browser when USGS records an earthquake near Day Valley, CA. No account or email needed.
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 12 km (7 mi) from the epicentre. In Day Valley, 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.
Earthquakes near other towns within 30 km: Lexington Hills, Corralitos, Aptos, Seacliff, Rio Del Mar, Scotts Valley.
How big was it?
This earthquake released about 10 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,500,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
- Around the size people start to feel M 3.0 92× the energy of this one
- This earthquake M 1.7 about 10 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 4.1 on 2017-10-10 — about 4,000 times the energy of this one.
Before 2016, the USGS record lists 30 earthquakes of M5 or more within 50 km; the five largest:
- 6.9 The 1989 Loma Prieta, California Earthquake · 7 km SSW of this epicentre
- 6.5 Near Morgan Hill, California · 19 km E of this epicentre
- 6.3 22 km S of Davenport, California · 45 km SW of this epicentre
- 6.3 16 km SW of Davenport, California · 47 km WSW of this epicentre
- 6.2 Near San Jose, California · 23 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 37.0977, -121.8552. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Santa Cruz County, CA | 17 km (10 mi) | SW | earthquakes near Santa Cruz County |
| Santa Clara County, CA | 20 km (13 mi) | NE | earthquakes near Santa Clara County |
| San Mateo County, CA | 58 km (36 mi) | NW | earthquakes near San Mateo County |
| Alameda County, CA | 61 km (38 mi) | N | earthquakes near Alameda County |
| San Benito County, CA | 87 km (54 mi) | SE | earthquakes near San Benito County |
| Stanislaus County, CA | 91 km (57 mi) | NE | earthquakes near Stanislaus County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
54 earthquakes have been recorded within 50 km since this one.
- 2.1 8km ESE of Fremont, CA
- 2.0 11km NE of Milpitas, CA
- 1.6 11km NE of Milpitas, CA
- 1.6 10km NE of Milpitas, CA
- 1.5 10km NE of Milpitas, CA
- 1.8 10km NE of Milpitas, CA
- 3.2 10km NE of Milpitas, CA
- 2.0 9km E of Alum Rock, CA
- 1.7 3km E of Aromas, CA
- 2.2 12km WSW of Saratoga, CA
- 1.9 12km ESE of Gilroy, CA
- 1.8 12km ESE of Gilroy, CA
- 1.7 9km NNW of Hollister, CA
- 1.9 12km ESE of Gilroy, CA
- 1.7 5km N of Aromas, 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.