QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Sierra Madre, CA

No earthquake was likely felt in Sierra Madre in the 24 hours to 3:19 am PST (11:19 UTC). The last one was M 3.8, 70 km (44 mi) WNW, at 8:00 pm PDT on 29 September 2026, estimated intensity II (weak) in town; 199 felt reports to USGS. Every earthquake near Sierra Madre

This page: a magnitude 1.6 earthquake was recorded in Sierra Madre, CA, at 8:20 pm PDT on 27 April 2021 (03:20 UTC), 9.2 km deep.

USGS: 1km W of Sierra Madre, CA

in Arcadia, CA · 35 km (22 mi) ENE of Los Angeles, CA

8:20 pm PDT, Apr 27, 2021 · · 9.2 km deep · released about 7.1 lb of TNT

Every earthquake near Sierra Madre Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Los Angeles County 18 kmOrange County 60 kmVentura County 100 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
8:20 pm PDT on 27 April 2021 ()
Where
in Sierra Madre, CA · earthquakes near Sierra Madre
Magnitude
M 1.6 (ml)
Depth
9.2 km below the surface
Felt
no reports yet
Nearest
Los Angeles County, 18 km WNW
Nearest mapped fault
Sierra Madre 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 2024 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. 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: Sierra Madre in town, intensity II · Arcadia 4 km, intensity II · Temple City 6 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 7.1 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 2,100,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,500,000× 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 7.1 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 4.5 on 2020-09-19 — about 28,000 times the energy of this one.

Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.7 Northridge, California, earthquake · 43 km W of this epicentre
  2. 6.6 1971 San Fernando Earthquake, California · 40 km NW of this epicentre
  3. 5.9 The 1987 Whittier Narrows, California Earthquake · 11 km S of this epicentre
  4. 5.9 1km ENE of Granada Hills, California · 41 km WNW of this epicentre
  5. 5.8 10km SSW of Agua Dulce, CA · 40 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 34.1623, -118.0683. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Los Angeles County, CA 18 km (11 mi) WNW earthquakes near Los Angeles County
Orange County, CA 60 km (38 mi) SSE earthquakes near Orange County
Ventura County, CA 100 km (62 mi) WNW earthquakes near Ventura County

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

Aftershocks so far

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

  1. 1.7 5km ENE of Villa Park, CA
  2. 1.7 8km E of Yorba Linda, CA
  3. 1.5 7km NW of Rancho Cucamonga, CA
  4. 2.3 11km E of Yorba Linda, CA
  5. 1.9 1km SW of Sherman Oaks, CA
  6. 1.8 6km SE of Ontario, CA
  7. 2.2 2km ENE of Gardena, CA
  8. 2.9 5km SSE of Rancho Cucamonga, CA
  9. 2.8 2km E of Wrightwood, CA
  10. 2.3 3km NNE of El Segundo, CA
  11. 1.7 3km NE of Placentia, CA
  12. 1.5 2km E of El Segundo, CA
  13. 3.2 4km NNE of El Segundo, CA
  14. 2.0 5km SW of Sherman Oaks, CA
  15. 2.8 4km WSW of Hermosa Beach, 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.