QuakeIndex

Earthquake · reviewed by a seismologist

M 2.2md

Earthquake near Los Altos Hills, CA

No earthquake was likely felt in Los Altos Hills in the 24 hours to 12:38 pm PST (20:38 UTC). The last one was M 2.0, 10 km (6 mi) SE, at 9:23 am PST on 10 November 2026, estimated intensity II (weak) in town; 4 felt reports to USGS. Every earthquake near Los Altos Hills

This page: a magnitude 2.2 earthquake was recorded in Los Altos Hills, CA, at 1:01 am PST on 18 January 2021 (09:01 UTC), 4.7 km deep. 10 people have reported feeling it to USGS.

USGS: 2km S of Los Altos Hills, CA

30 km (18 mi) WNW of San Jose, CA · in Palo Alto, CA

1:01 am PST, Jan 18, 2021 · · 4.7 km deep · released about 60 lb of TNT

Every earthquake near Los Altos Hills Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 21 kmAlameda County 37 kmSanta Cruz County 41 kmSanta Clara County 43 kmContra Costa County 64 kmSan Francisco County 89 kmMarin County 93 kmSan Joaquin County 99 kmSolano County 102 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
1:01 am PST on 18 January 2021 ()
Where
in Los Altos Hills, CA · earthquakes near Los Altos Hills
Magnitude
M 2.2 (md)
Depth
4.7 km below the surface
Felt
10 reports · strongest reported intensity III
Nearest
San Mateo County, 21 km WNW
Nearest mapped fault
Monte Vista-Shannon fault, 2 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 2116 days ago

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 18 km (11 mi) from the epicentre. 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: Los Altos 3 km, intensity II · Mountain View 5 km, intensity II · Palo Alto 9 km, intensity II · Sunnyvale 9 km, intensity II · Cupertino 10 km, intensity II · Menlo Park 11 km, intensity II · East Palo Alto 12 km, intensity II · Saratoga 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 60 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.2 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 250,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 180,000× the energy of this one
  3. Around the size people start to feel M 3.0 16× the energy of this one
  4. This earthquake M 2.2 about 60 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 680 times the energy of this one.

Before 2016, the USGS record lists 17 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 The 1989 Loma Prieta, California Earthquake · 43 km SSE of this epicentre
  2. 6.2 Near San Jose, California · 31 km ESE of this epicentre
  3. 6.2 The 1984 Morgan Hill, California Earthquake · 41 km E of this epicentre
  4. 6.1 Near San Jose, California · 35 km ESE of this epicentre
  5. 5.8 7 km NNW of Boulder Creek, California · 19 km S 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 37.3637, -122.1377. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Mateo County, CA 21 km (13 mi) WNW earthquakes near San Mateo County
Alameda County, CA 37 km (23 mi) NNE earthquakes near Alameda County
Santa Cruz County, CA 41 km (25 mi) SSE earthquakes near Santa Cruz County
Santa Clara County, CA 43 km (27 mi) ESE earthquakes near Santa Clara County
Contra Costa County, CA 64 km (40 mi) NNE earthquakes near Contra Costa County
San Francisco County, CA 89 km (55 mi) WNW earthquakes near San Francisco County

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

Aftershocks so far

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

  1. 2.5 15km N of Morgan Hill, CA
  2. 3.6 15km N of Morgan Hill, CA
  3. 2.3 6km WSW of Colma, CA
  4. 2.2 14km SE of Livermore, CA
  5. 1.5 9km ENE of Milpitas, CA
  6. 2.1 3km WNW of Pacifica, CA
  7. 2.0 9km ENE of Milpitas, CA
  8. 2.3 14km SE of Livermore, CA
  9. 2.9 14km SE of Livermore, CA
  10. 1.6 10km NE of Milpitas, CA
  11. 2.1 4km WSW of Pleasanton, CA
  12. 1.9 9km NNE of Alum Rock, CA
  13. 2.6 7km E of Alum Rock, CA
  14. 2.5 15km ENE of Alum Rock, CA
  15. 1.7 10km SE of Sunol, 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.