Earthquake magnitude 4.7 hits California coast, USA
The tremor was recorded west of Petrolia and triggered a tsunami warning.
A magnitude 4.7 earthquake was recorded on the night of August 28, 2026, with its epicenter located 85 kilometres west of the city of Petrolia, California, United States. The shaking occurred at 23:41 Brasília time and led to the issuance of a tsunami warning, according to the United States Geological Survey (USGS).
Characteristics of the tremor
The technical data provided by the USGS detail that the quake had a relatively shallow depth of only 10 kilometres. Epicenters closer to the surface tend to be felt with greater intensity at the surface. The location 85 km offshore indicates that the seismic event occurred beneath the Pacific Ocean, an area known for its geological activity.
A magnitude of 4.7 is considered a moderate earthquake. Although not among the highest, tremors of this intensity can be clearly perceived by populations near the epicenter, especially when they occur at shallow depths, as was the case here.
Tsunami warning and estimated impact
The issuance of a tsunami warning by the USGS is a standard procedure for underwater earthquakes that have the potential to generate anomalous waves, even if only of small proportion. This type of alert serves to mobilise coastal communities and authorities to monitor the situation and take precautions if necessary.
Despite the warning, the USGS's initial impact assessment classified the event as "green". This rating suggests an estimated impact that is small, indicating that widespread damage or fatalities are unlikely, according to the agency's early projections. Nonetheless, caution regarding tsunamis remains.
Public perception and monitoring
So far, 252 people have reported feeling the tremor in the affected region, corroborating the moderate nature of the quake and its perception by the local population. These reports are important for the USGS, as they help map the area of earthquake perception and refine impact estimates.
In the absence of detailed press sources on the concrete effects of the earthquake, authorities continue to actively monitor the situation. The priority is to verify any consequences for the coastal population and infrastructure, especially given the possibility of minor sea‑level anomalies. New information will be released as the situation assessment progresses.
Seismic data: USGS.
Source: USGS (United States Geological Survey)