quarry blast · reviewed by a seismologist
M 1.5md
Earthquake near Chualar, CA
No earthquake was likely felt in Chualar in the 24 hours to 2:46 am PST (10:46 UTC). The last one was M 2.7, 20 km (12 mi) NNE, at 5:38 am PDT on 29 October 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Chualar
No: USGS classifies this as a quarry blast, not an earthquake. A magnitude 1.5 quarry blast was recorded 8 km (5 mi) east of Chualar, CA, at 12:23 pm PDT on 2 October 2018 (19:23 UTC), less than 1 km deep.
USGS: 8km E of Chualar, CA
87 km (54 mi) SSE of San Jose, CA · 22 km (14 mi) ESE of Salinas, CA
- When
- 12:23 pm PDT on 2 October 2018 ()
- Where
- 8 km (5 mi) east of Chualar, CA · earthquakes near Chualar
- Magnitude
- M 1.5 (md)
- Depth
- -0.4 km below the surface
- Felt
- no reports yet
- Nearest
- San Benito County, 30 km E
- Nearest mapped fault
- San Andreas fault, 16 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 2963 days ago
Earthquake alerts for Chualar, CA
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 10 km (6 mi) from the epicentre. In Chualar, 8 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.
Earthquakes near other towns within 30 km: Gonzales, Soledad, Salinas, Boronda, Ridgemark.
USGS catalogues this as quarry blast, not an earthquake.
How big was it?
This earthquake released about 5.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,700,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
- Around the size people start to feel M 3.0 170× the energy of this one
- This earthquake M 1.5 about 5.6 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 4.6 on 2017-11-13 — about 40,000 times the energy of this one.
Before 2016, the USGS record lists 21 earthquakes of M5 or more within 50 km; the five largest:
- 5.9 10 km SE of Tres Pinos, California · 25 km NE of this epicentre
- 5.8 Near Watsonville, California · 48 km NNW of this epicentre
- 5.8 Near Paicines, California · 18 km ENE of this epicentre
- 5.5 7 km SW of Hollister, California · 24 km N of this epicentre
- 5.5 12 km S of Tres Pinos, California · 16 km NE 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 36.5815, -121.4247. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Benito County, CA | 30 km (19 mi) | E | earthquakes near San Benito County |
| Monterey County, CA | 39 km (24 mi) | SSE | earthquakes near Monterey County |
| Santa Cruz County, CA | 71 km (44 mi) | NW | earthquakes near Santa Cruz County |
| Santa Clara County, CA | 75 km (47 mi) | NNW | earthquakes near Santa Clara County |
| Merced County, CA | 92 km (57 mi) | NE | earthquakes near Merced County |
| Stanislaus County, CA | 115 km (72 mi) | NNE | earthquakes near Stanislaus County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
60 earthquakes have been recorded within 50 km since this one.
- 2.1 13km S of Tres Pinos, CA
- 1.6 16km SSE of Tres Pinos, CA
- 2.0 13km S of Tres Pinos, CA
- 2.5 13km S of Tres Pinos, CA
- 1.7 24km NE of King City, CA
- 1.8 12km S of Tres Pinos, CA
- 1.6 19km SE of Pinnacles, CA
- 1.5 13km S of Tres Pinos, CA
- 2.6 12km S of Tres Pinos, CA
- 1.8 11km S of Tres Pinos, CA
- 2.0 13km S of Tres Pinos, CA
- 2.9 13km S of Tres Pinos, CA
- 2.8 13km S of Tres Pinos, CA
- 1.9 12km S of Tres Pinos, CA
- 3.3 12km S of Tres Pinos, 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
- 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.