M 3.3 - 18 km WSW of Johannesburg, CA
Areazine synthesizes this USGS earthquake report directly from USGS's official public data feed. See our methodology for full source attribution and refresh cadence.
A magnitude 3.3 earthquake occurred 18 km west-southwest of Johannesburg, California on April 28, 2026.
What this USGS earthquake report tells you, and what most readers miss
This notice was issued by USGS on June 7, 2026 and geographically references Southern California. Its severity classification of "low" signals how the issuing agency weighs the risk of harm if no action is taken - "critical" and "high" tier alerts typically carry direct consumer actions, while "medium" and "low" tend toward informational guidance or monitoring advisories. The category it belongs to - Earthquakes - determines the monitoring protocol behind it, which shapes what follow-up action (checking for structural damage, watching for aftershocks, reviewing local building codes) is relevant and which agency holds authority over the assessment.
Most readers skim a notice like this, check whether they are personally affected, and move on. The more useful lens is to read it as a data point about the issuing system: how quickly USGS detected the hazard, how precise the geographic or product-identifier scope is, and whether similar notices have clustered in the same category or region in the last 90 days. Cluster patterns frequently precede a broader regulatory action, a single localized USGS earthquake report is isolated; three of them within a quarter often indicate a supply-chain, infrastructure, or seasonal driver that will keep producing notices until something structural changes.
For decision-making, Areazine pairs each alert with the original agency URL, the full agency name, and a timestamp so you can verify the notice against the primary source before acting on it. Tags on this item (earthquake, seismic, usgs, California) map to related alerts in the same area of risk - browsing them together gives a clearer picture than any single notice alone, because the shape of an ongoing issue only becomes visible across multiple sequential alerts.
What Happened
A M 3.3 ml earthquake struck at 12:00:57 UTC on April 28, 2026 (Unix time 1780020057490). The event was located 18 km WSW of Johannesburg, CA, at a depth of 6.88 km.
Location Details
The epicenter was at coordinates 35.2997°N, 117.8120°W. The shallow depth of 6.88 km classifies this as a shallow earthquake (less than 20 km).
Impact Assessment
No felt reports were recorded. There was no tsunami advisory (tsunami field = 0) and no alert level issued.
What You Should Know
Earthquakes of this magnitude (M 2.5-3.9) are often felt but rarely cause damage. Minor aftershocks remain possible.
Source
Original source: USGS Official Notice ↗
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All Earthquakes →Frequently Asked Questions
Common questions about this USGS earthquake report.