Earthquake · reviewed by a seismologist
M 2.1md
Earthquake near Saratoga, CA
No earthquake was likely felt in Saratoga in the 24 hours to 9:37 pm PST (05:37 UTC). The last one was M 2.0, 7 km (4 mi) NW, at 9:23 am PST on 10 November 2026, estimated intensity II (weak) in town; 4 felt reports to USGS. Every earthquake near Saratoga
This page: a magnitude 2.1 earthquake was recorded 4 km (3 mi) southwest of Saratoga, CA, at 5:56 am PDT on 18 September 2017 (12:56 UTC), 7.7 km deep. 5 people have reported feeling it to USGS.
USGS: 4 km SW of Saratoga, California
22 km (14 mi) WSW of San Jose, CA · 9 km (6 mi) S of Cupertino, CA
- When
- 5:56 am PDT on 18 September 2017 ()
- Where
- 4 km (3 mi) southwest of Saratoga, CA · earthquakes near Saratoga
- Magnitude
- M 2.1 (md)
- Depth
- 7.7 km below the surface
- Felt
- 5 reports · strongest reported intensity II
- Nearest
- Santa Cruz County, 25 km S
- Nearest mapped fault
- San Andreas 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 1558 days ago
Earthquake alerts for Saratoga, 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 15 km (9 mi) from the epicentre. In Saratoga, 4 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: Saratoga 4 km, intensity II · Los Gatos 7 km, intensity II · Cupertino 10 km, intensity II · Campbell 11 km, intensity II · Boulder Creek 14 km, intensity II · Sunnyvale 15 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 38 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 390,000× the energy of this one
- Magna, Utah 2020 M 5.7 280,000× the energy of this one
- Around the size people start to feel M 3.0 25× the energy of this one
- This earthquake M 2.1 about 38 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
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record lists 26 earthquakes of M5 or more within 50 km; the five largest:
- 6.9 The 1989 Loma Prieta, California Earthquake · 27 km SE of this epicentre
- 6.5 Near Morgan Hill, California · 40 km ESE of this epicentre
- 6.3 22 km S of Davenport, California · 49 km SSW of this epicentre
- 6.3 16 km SW of Davenport, California · 43 km SW of this epicentre
- 6.2 Near San Jose, California · 24 km ENE 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 37.2367, -122.0555. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Santa Cruz County, CA | 25 km (16 mi) | S | earthquakes near Santa Cruz County |
| Santa Clara County, CA | 32 km (20 mi) | E | earthquakes near Santa Clara County |
| San Mateo County, CA | 34 km (21 mi) | NW | earthquakes near San Mateo County |
| Alameda County, CA | 47 km (29 mi) | NNE | earthquakes near Alameda County |
| Contra Costa County, CA | 76 km (48 mi) | N | earthquakes near Contra Costa County |
| Stanislaus County, CA | 100 km (62 mi) | ENE | earthquakes near Stanislaus County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
38 earthquakes have been recorded within 50 km since this one.
- 1.7 7km E of Alum Rock, CA
- 1.9 4km NE of Portola Valley, CA
- 1.6 3 km W of Portola Valley, California
- 1.8 4 km WNW of La Honda, California
- 1.5 11 km ESE of East Foothills, California
- 1.7 1 km N of North Fair Oaks, California
- 1.6 7 km WSW of Gilroy, California
- 1.9 14 km E of Seven Trees, California
- 1.7 5 km SW of Gilroy, California
- 2.0 10 km ENE of Milpitas, California
- 2.4 7 km WSW of Gilroy, California
- 2.2 8 km ENE of San Martin, California
- 1.6 12 km ESE of East Foothills, California
- 2.7 8 km ENE of San Martin, California
- 2.3 5 km SW of Gilroy, California
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.