QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Portola, CA

No earthquake was likely felt in Portola in the 24 hours to 5:54 am PST (13:54 UTC). The last one was M 2.7, 8 km (5 mi) N, at 8:16 am PST on 10 November 2026, estimated intensity III (weak) in town; 9 felt reports to USGS. Every earthquake near Portola

This page: a magnitude 1.6 earthquake was recorded 32 km (20 mi) southwest of Portola, CA, at 5:01 pm PDT on 9 May 2023 (00:01 UTC), 9.6 km deep.

USGS: Northern California

5:01 pm PDT, May 9, 2023 · · 9.6 km deep · released about 7.6 lb of TNT

Every earthquake near Portola Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Sierra County 16 kmNevada County 32 kmPlumas County 47 kmPlacer County 58 kmYuba County 65 kmButte County 78 kmEl Dorado County 90 kmCarson City 95 kmStorey 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
5:01 pm PDT on 9 May 2023 ()
Where
32 km (20 mi) southwest of Portola, CA · earthquakes near Portola
Magnitude
M 1.6 (ml)
Depth
9.6 km below the surface
Felt
no reports yet
Nearest
Sierra County, 16 km E
Nearest mapped fault
Mohawk Valley fault, 18 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 1283 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 6 km (4 mi) from the epicentre. In Portola, 32 km away, the estimate is intensity I (not felt). 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.

How big was it?

This earthquake released about 7.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,400,000× the energy of this one
  3. Around the size people start to feel M 3.0 130× the energy of this one
  4. This earthquake M 1.6 about 7.6 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 2021-05-07 — about 38,000 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.9 West of Downieville, California · 27 km WSW of this epicentre
  2. 5.9 9 km NW of Truckee, California · 43 km ESE of this epicentre
  3. 5.6 5 km NE of Loyalton, California · 46 km ENE of this epicentre
  4. 5.3 11 km N of Soda Springs, California · 31 km ESE of this epicentre
  5. 5.2 3 km N of Blairsden, California · 27 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 39.5818, -120.7042. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Sierra County, CA 16 km (10 mi) E earthquakes near Sierra County
Nevada County, CA 32 km (20 mi) S earthquakes near Nevada County
Plumas County, CA 47 km (29 mi) NNW earthquakes near Plumas County
Placer County, CA 58 km (36 mi) S earthquakes near Placer County
Yuba County, CA 65 km (40 mi) WSW earthquakes near Yuba County
Butte County, CA 78 km (48 mi) W earthquakes near Butte County

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

Aftershocks so far

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

  1. 1.5 9 km SSE of Sierraville, California
  2. 1.7 4 km SW of Sierra Brooks, California
  3. 1.7 7 km ENE of East Quincy, California
  4. 2.2 4 km NNW of Spring Garden, CA
  5. 2.2 5 km NNE of East Quincy, CA
  6. 3.4 4 km ENE of East Quincy, CA
  7. 2.0 4 km SW of Whitehawk, California
  8. 2.2 9 km SE of Meadow Valley, CA
  9. 1.6 Northern California
  10. 1.9 6 km S of Sierraville, California
  11. 1.8 6 km S of Sierraville, California
  12. 2.2 9 km N of Truckee, CA
  13. 2.3 1 km E of Johnsville, CA
  14. 2.2 8 km S of Spring Garden, CA
  15. 2.2 6 km NNW of Truckee, 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.