Earthquake near Half Moon Bay, CA

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 Half Moon Bay, 3 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: Half Moon Bay 3 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 58 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 5.8 260,000× 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 58 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 4.4 on 2018-01-04 — about 1,900 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 7.9 The 1906 San Francisco, California Earthquake · 36 km NNW of this epicentre Apr 18, 1906
2. 5.8 7 km NNW of Boulder Creek, California · 38 km SE of this epicentre Sep 5, 1955
3. 5.5 Santa Cruz Mountains, California · 49 km SE of this epicentre Nov 9, 1914
4. 5.3 The 1957 San Francisco, California Earthquake · 26 km N of this epicentre Mar 22, 1957
5. 5.1 7 km SW of Monte Sereno, California · 44 km SE of this epicentre Oct 18, 1989

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 37.4368, -122.4410. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 1.8 3km ESE of Pacifica, CA 13:40 UTC
2. 1.8 7km SSE of Portola Valley, CA 09:10 UTC
3. 1.7 1km W of Pacifica, CA 14:09 UTC
4. 2.2 1km WSW of Pacifica, CA 14:09 UTC
5. 1.6 3km E of Oakland, CA 13:03 UTC
6. 1.5 7km ESE of Fremont, CA 19:43 UTC
7. 1.6 6km SSE of Portola Valley, CA 18:08 UTC
8. 2.5 6km SSE of Portola Valley, CA 11:08 UTC
9. 1.9 8km S of Sunol, CA 23:09 UTC
10. 2.2 34km W of Bonny Doon, CA 10:03 UTC
11. 2.1 1km E of Piedmont, CA 13:51 UTC
12. 2.0 4km SSE of Highlands-Baywood Park, CA 14:24 UTC
13. 1.9 2km N of Castro Valley, CA 07:09 UTC
14. 1.6 5km E of Fremont, CA 11:32 UTC
15. 1.6 7km S of Muir Beach, CA 00:59 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 15:33 UTC. 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.