Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Ridgemark, CA
No earthquake was likely felt in Ridgemark in the 24 hours to 8:31 pm PST (04:31 UTC). The last one was M 2.4, 8 km (5 mi) S, at 8:53 pm PST on 5 November 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Ridgemark
This page: a magnitude 2.8 earthquake was recorded 9 km (5 mi) northeast of Ridgemark, CA, at 4:29 pm PDT on 24 March 2021 (23:29 UTC), 7.3 km deep. 15 people have reported feeling it to USGS.
USGS: 8km NE of Ridgemark, CA
66 km (41 mi) SE of San Jose, CA · 29 km (18 mi) ESE of Gilroy, CA
- When
- 4:29 pm PDT on 24 March 2021 ()
- Where
- 9 km (5 mi) northeast of Ridgemark, CA · earthquakes near Ridgemark
- Magnitude
- M 2.8 (md)
- Depth
- 7.3 km below the surface
- Felt
- 15 reports · strongest reported intensity III
- Nearest
- San Benito County, 35 km SE
- Nearest mapped fault
- Quien Sabe fault, under 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 1989 days ago
Earthquake alerts for Ridgemark, CA
Get a notification in this browser when USGS records an earthquake near Ridgemark, 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 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 27 km (17 mi) from the epicentre. In Ridgemark, 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: Hollister 9 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 490 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 31,000× the energy of this one
- Magna, Utah 2020 M 5.7 22,000× the energy of this one
- Around the size people start to feel M 3.0 1.9× the energy of this one
- This earthquake M 2.8 about 490 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 710 times the energy of this one.
Before 2016, the USGS record lists 23 earthquakes of M5 or more within 50 km; the five largest:
- 6.5 Near Morgan Hill, California · 40 km NW of this epicentre
- 5.9 10 km SE of Tres Pinos, California · 17 km SSE of this epicentre
- 5.8 Near Watsonville, California · 36 km WNW of this epicentre
- 5.8 Near Paicines, California · 23 km SSE of this epicentre
- 5.8 The 1979 Coyote Lake, California Earthquake · 32 km NW 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 36.8707, -121.3035. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Benito County, CA | 35 km (22 mi) | SE | earthquakes near San Benito County |
| Santa Clara County, CA | 52 km (32 mi) | NW | earthquakes near Santa Clara County |
| Merced County, CA | 63 km (39 mi) | NE | earthquakes near Merced County |
| Santa Cruz County, CA | 65 km (40 mi) | WNW | earthquakes near Santa Cruz County |
| Monterey County, CA | 70 km (44 mi) | S | earthquakes near Monterey County |
| Stanislaus County, CA | 81 km (51 mi) | NNE | earthquakes near Stanislaus 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.
- 2.4 13km NW of Pinnacles, CA
- 1.6 25km SSW of Los Banos, CA
- 2.0 4km N of Hollister, CA
- 2.5 7km NNW of Pinnacles, CA
- 2.0 2km SSW of Hollister, CA
- 1.5 12km NW of Pinnacles, CA
- 1.5 9km NNE of Gonzales, CA
- 2.1 16km NW of Pinnacles, CA
- 1.9 7km NNW of Pinnacles, CA
- 2.8 9km SSE of San Juan Bautista, CA
- 2.3 9km SSE of San Juan Bautista, CA
- 1.8 7km SW of Ridgemark, CA
- 3.0 3km SW of San Juan Bautista, CA
- 2.2 6km NNW of Pinnacles, CA
- 1.9 5km ESE of Interlaken, 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.