chemical explosion · reviewed by a seismologist
M 1.6md
Earthquake near Mountain House, CA
No earthquake was likely felt in Mountain House in the 24 hours to 11:49 pm PST (07:49 UTC). The last one was M 3.5, 41 km (26 mi) S, at 7:21 am PDT on 27 September 2026, estimated intensity II (weak) in town; 8 felt reports to USGS. Every earthquake near Mountain House
No: USGS classifies this as a chemical explosion, not an earthquake. A magnitude 1.6 chemical explosion was recorded 9 km (5 mi) west-southwest of Mountain House, CA, at 5:02 pm PDT on 9 October 2020 (00:02 UTC), less than 1 km deep.
USGS: 9km WSW of Mountain House, CA
13 km (8 mi) NE of Livermore, CA · 53 km (33 mi) NNE of San Jose, CA
- When
- 5:02 pm PDT on 9 October 2020 ()
- Where
- 9 km (5 mi) west-southwest of Mountain House, CA · earthquakes near Mountain House
- Magnitude
- M 1.6 (md)
- Depth
- -0.1 km below the surface
- Felt
- no reports yet
- Nearest
- Alameda County, 27 km WSW
- Nearest mapped fault
- Corral Hollow-Carnegie fault, 7 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 2224 days ago
Earthquake alerts for Mountain House, CA
Get a notification in this browser when USGS records an earthquake near Mountain House, CA. No account or email needed.
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 11 km (7 mi) from the epicentre. In Mountain House, 9 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: Byron, Livermore, Discovery Bay, Tracy, Brentwood, Pleasanton.
USGS catalogues this as chemical explosion, not an earthquake.
How big was it?
This earthquake released about 6.4 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 2,400,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,700,000× the energy of this one
- Around the size people start to feel M 3.0 150× the energy of this one
- This earthquake M 1.6 about 6.4 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 2019-10-15 — about 23,000 times the energy of this one.
Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:
- 6.2 The 1984 Morgan Hill, California Earthquake · 49 km S of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 15 km NW of this epicentre
- 5.7 15 km NE of East Foothills, California · 31 km S of this epicentre
- 5.5 6 km NNE of East Foothills, California · 38 km SSW of this epicentre
- 5.4 9 km NE of Livermore, California · 6 km W 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 37.7532, -121.6357. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Alameda County, CA | 27 km (17 mi) | WSW | earthquakes near Alameda County |
| Contra Costa County, CA | 33 km (21 mi) | NW | earthquakes near Contra Costa County |
| San Joaquin County, CA | 38 km (23 mi) | ENE | earthquakes near San Joaquin County |
| Santa Clara County, CA | 59 km (37 mi) | S | earthquakes near Santa Clara County |
| Stanislaus County, CA | 60 km (37 mi) | ESE | earthquakes near Stanislaus County |
| Solano County, CA | 63 km (39 mi) | NNW | earthquakes near Solano 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.
- 2.0 5km SW of Danville, CA
- 3.0 1km W of Concord, CA
- 1.8 6km E of Milpitas, CA
- 1.6 3km ENE of Walnut Creek, CA
- 2.1 8km ENE of Alum Rock, CA
- 1.6 10km ESE of Alum Rock, CA
- 2.1 2km WNW of Concord, CA
- 3.6 2km W of Concord, CA
- 1.6 3km ESE of Union City, CA
- 2.3 4km ENE of Walnut Creek, CA
- 3.0 8km NE of Alum Rock, CA
- 1.9 2km SE of Pacheco, CA
- 2.6 3km WNW of Concord, CA
- 1.8 9km ENE of Milpitas, CA
- 1.8 10km ESE of Livermore, 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.