QuakeIndex

chemical explosion · reviewed by a seismologist

M 1.7ml

Earthquake near Lake Forest, CA

No earthquake was likely felt in Lake Forest in the 24 hours to 3:22 am PST (11:22 UTC). The last one was M 3.5, 48 km (30 mi) SSW, at 1:22 pm PDT on 5 October 2026, estimated intensity II (weak) in town; 126 felt reports to USGS. Every earthquake near Lake Forest

No: USGS classifies this as a chemical explosion, not an earthquake. A magnitude 1.7 chemical explosion was recorded 7 km (4 mi) northeast of Lake Forest, CA, at 9:52 pm PDT on 27 June 2018 (04:52 UTC), less than 1 km deep.

USGS: 2km E of Foothill Ranch, CA

5 km (3 mi) NE of Lake Forest, CA · 81 km (50 mi) ESE of Los Angeles, CA

9:52 pm PDT, Jun 27, 2018 · · 0.0 km deep · released about 11 lb of TNT

Every earthquake near Lake Forest Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Orange County 13 kmLos Angeles County 81 kmSan Diego County 109 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
9:52 pm PDT on 27 June 2018 ()
Where
7 km (4 mi) northeast of Lake Forest, CA · earthquakes near Lake Forest
Magnitude
M 1.7 (ml)
Depth
0.0 km below the surface
Felt
no reports yet
Nearest
Orange County, 13 km W
Nearest mapped fault
San Joaquin Hills thrust, 10 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 3030 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 12 km (7 mi) from the epicentre. In Lake Forest, 7 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: Rancho Santa Margarita 6 km, intensity II · Lake Forest 7 km, intensity II · Mission Viejo 10 km, intensity II · Laguna Hills 11 km, intensity II. Estimated for each town centre; each link is that town's own record.

USGS catalogues this as chemical explosion, not an earthquake.

How big was it?

This earthquake released about 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 970,000× the energy of this one
  3. Around the size people start to feel M 3.0 86× the energy of this one
  4. This earthquake M 1.7 about 11 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 9 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 The 1933 Long Beach, California Earthquake · 34 km W of this epicentre
  2. 6.0 The 1910 Lake Elsinore, California Earthquake · 22 km E of this epicentre
  3. 5.4 5km S of Chino Hills, CA · 32 km NNW of this epicentre
  4. 5.3 7km W of Newport Beach, CA · 35 km WSW of this epicentre
  5. 5.2 8km ENE of Trabuco Canyon, CA · 11 km E 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 33.6870, -117.6343. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Orange County, CA 13 km (8 mi) W earthquakes near Orange County
Los Angeles County, CA 81 km (50 mi) NW earthquakes near Los Angeles County
San Diego County, CA 109 km (67 mi) SE earthquakes near San Diego County

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

Aftershocks so far

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

  1. 1.9 9km ENE of Villa Park, CA
  2. 1.6 4km SE of Home Gardens, CA
  3. 1.5 2km SE of Home Gardens, CA
  4. 1.8 3km S of Huntington Beach, CA
  5. 1.6 26km SW of Dana Point, CA
  6. 2.5 2km NE of Villa Park, CA
  7. 1.9 4km SE of Home Gardens, CA
  8. 1.7 1km ENE of Yorba Linda, CA
  9. 1.5 4km SSE of Home Gardens, CA
  10. 2.3 3km SSE of Charter Oak, CA
  11. 1.5 2km SE of Home Gardens, CA
  12. 2.6 13km NE of Trabuco Canyon, CA
  13. 1.6 1km SSE of Placentia, CA
  14. 1.9 9km SSW of Wildomar, CA
  15. 1.9 2km WSW of Yorba Linda, 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.