M2.3 Earthquake near Alum Rock, CA — 28 July 2026
A minor earthquake of magnitude 2.3 was recorded near Alum Rock, CA on , with an epicentre 8 km northeast of Alum Rock, at a focal depth of 8.3 km.
Time (UTC): 2026-07-28 22:39:10
Time (your timezone): —
Magnitude: 2.3 (minor)
Focal depth: 8.3 km (shallow)
Epicentre: 37.4100, -121.7530
Location: 8 km NE of Alum Rock, CA
USGS link to NOAA tsunami information: Not linked
Review status: Automatic
Source: USGS event page
How strong was this earthquake?
Minor earthquakes in this range are felt by people close to the epicentre as a brief jolt or rattle, but they very rarely cause any damage.
A magnitude 2.3 earthquake radiates roughly 40 kg of TNT equivalent in seismic energy.
The USGS assigns this earthquake a significance score of 80, which is below the USGS threshold of more than 600 for its significant-earthquake list. The ranking combines magnitude with available Did You Feel It responses and PAGER alert level; it is not a direct measurement of damage.
Where was the epicentre?
The epicentre was located at 37.4100, -121.7530 — 8 km northeast of Alum Rock. The closest other recorded event was a magnitude 2.3 earthquake 56 km south-southeast of here on 01 August 2026.
Why the 8 km depth matters
At 8 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.
This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, events this small are usually detected by instruments rather than people. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.
What does the tsunami information flag mean?
The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M2.3 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.
How earthquakes generate tsunamis, and what the alert levels mean →
Aftershocks and local seismic history
192 further earthquakes have been recorded within about 150 km of the epicentre in the 4 days since this event, the largest of them magnitude 4.3.
21 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.6 event near Redwood Valley on 24 June 2026. This M2.3 event released about 92,257 times less energy than that event.
How long aftershock sequences last, and how large they get →
Where this event sits in the record
This earthquake is part of the July 2026 worldwide record. Browse the full monthly archive to compare periods.
Nearest recorded earthquakes to this epicentre
- M2.3 earthquake near Gilroy, CA — (56 km SSE)
- M1.6 earthquake near Albany, CA — (71 km NW)
- M1.0 earthquake near Larkfield-Wikiup, CA — (150 km NW)
- M1.7 earthquake near New Idria, CA — (151 km SSE)
- M0.2 earthquake near The Geysers, CA — (178 km NNW)
- M1.3 earthquake near The Geysers, CA — (179 km NNW)
- M1.3 earthquake near The Geysers, CA — (182 km NNW)
- M0.7 earthquake near The Geysers, CA — (182 km NNW)
- M0.7 earthquake near The Geysers, CA — (182 km NNW)
- M1.0 earthquake near Cobb, CA — (183 km NNW)
Other magnitude 2 earthquakes worldwide
- M2.5 earthquake near Charlotte Amalie, U.S. Virgin Islands —
- M2.1 earthquake near Progreso, B.C., MX —
- M2.3 earthquake near Progreso, B.C., MX —
- M2.5 earthquake near Ninilchik, Alaska —
- M2.1 earthquake near Pāhala, Hawaii —
- M2.1 earthquake near Stovepipe Wells, CA —
- M2.3 earthquake near Nile, Washington —
- M2.0 earthquake near Pāhala, Hawaii —
Questions about this earthquake
How strong is a magnitude 2.3 earthquake?
Minor earthquakes in this range are felt by people close to the epicentre as a brief jolt or rattle, but they very rarely cause any damage. A magnitude 2.3 earthquake radiates roughly 40 kg of TNT equivalent in seismic energy.
How deep was the earthquake near Alum Rock?
At 8 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.
Was the M2.3 earthquake near Alum Rock felt?
This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, events this small are usually detected by instruments rather than people. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.
What does the USGS tsunami field mean for this event?
The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M2.3 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.
Have there been aftershocks?
192 further earthquakes have been recorded within about 150 km of the epicentre in the 4 days since this event, the largest of them magnitude 4.3.
How often do earthquakes happen near Alum Rock?
21 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.6 event near Redwood Valley on 24 June 2026. This M2.3 event released about 92,257 times less energy than that event.