QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

Earthquake near Bonny Doon, CA

No earthquake was likely felt in Bonny Doon in the 24 hours to 4:19 am PST (12:19 UTC). The last one was M 3.8, 79 km (49 mi) N, at 8:30 am PDT on 13 August 2026, estimated intensity II (weak) in town; 7,876 felt reports to USGS. Every earthquake near Bonny Doon

This page: a magnitude 2.1 earthquake was recorded 15 km (9 mi) south of Bonny Doon, CA, at 3:18 am PDT on 18 October 2018 (10:18 UTC), 6.5 km deep.

USGS: 15km S of Bonny Doon, CA

15 km (9 mi) WSW of Santa Cruz, CA · 54 km (34 mi) SW of San Jose, CA

3:18 am PDT, Oct 18, 2018 · · 6.5 km deep · released about 47 lb of TNT

10 km30 km60 km120 km N Santa Cruz County 19 kmSanta Clara County 56 kmSan Mateo County 59 kmAlameda County 86 kmSan Benito County 103 kmMonterey County 107 kmContra Costa County 114 kmSan Francisco County 118 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
3:18 am PDT on 18 October 2018 ()
Where
15 km (9 mi) south of Bonny Doon, CA · earthquakes near Bonny Doon
Magnitude
M 2.1 (md)
Depth
6.5 km below the surface
Felt
no reports yet
Nearest
Santa Cruz County, 19 km NE
Nearest mapped fault
San Gregorio fault, 1 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 2946 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 16 km (10 mi) from the epicentre. In Bonny Doon, 15 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: Santa Cruz 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 47 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 320,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 230,000× the energy of this one
  3. Around the size people start to feel M 3.0 20× the energy of this one
  4. This earthquake M 2.1 about 47 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 19 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 The 1989 Loma Prieta, California Earthquake · 30 km ENE of this epicentre
  2. 6.3 22 km S of Davenport, California · 11 km S of this epicentre
  3. 6.3 16 km SW of Davenport, California · 14 km W of this epicentre
  4. 6.1 Near San Jose, California · 47 km NE of this epicentre
  5. 5.8 Near Watsonville, California · 43 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 36.9077, -122.1810. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Santa Cruz County, CA 19 km (12 mi) NE earthquakes near Santa Cruz County
Santa Clara County, CA 56 km (35 mi) NE earthquakes near Santa Clara County
San Mateo County, CA 59 km (37 mi) NNW earthquakes near San Mateo County
Alameda County, CA 86 km (53 mi) NNE earthquakes near Alameda County
San Benito County, CA 103 km (64 mi) ESE earthquakes near San Benito County
Monterey County, CA 107 km (67 mi) SE earthquakes near Monterey County

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

Aftershocks so far

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

  1. 2.4 21km NW of Pacific Grove, CA
  2. 1.6 4km SE of Portola Valley, CA
  3. 1.8 8km E of Interlaken, CA
  4. 2.3 2km E of Bonny Doon, CA
  5. 2.0 7km WSW of Gilroy, CA
  6. 1.6 20km WNW of Boulder Creek, CA
  7. 1.8 21km W of Boulder Creek, CA
  8. 2.5 20km WNW of Boulder Creek, CA
  9. 2.8 21km WNW of Boulder Creek, CA
  10. 1.9 20km WNW of Boulder Creek, CA
  11. 2.2 5km WSW of Cupertino, CA
  12. 2.9 3km NNE of Corralitos, CA
  13. 2.0 5km NW of Del Monte Forest, CA
  14. 1.9 3km S of Loyola, CA
  15. 1.7 7km WSW of Gilroy, 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.