It is assumed that this record was not from an actual earthquake. It could be due to another (unknown) event causing the shock, such as B. Weather and sonic booms. In other cases, officially reported quakes are sometimes removed later.
This can happen when initial automatic calculations return an earthquake, but turn out to be incorrect in subsequent (manual) revision.
The first report is below:
Although our monitoring service initially determined network activity typical of an earthquake, there was no confirmation from a national or international seismological agency. Because of this, it is highly unlikely that it was caused by an earthquake.
18 Apr 12:44 UTC: First report: VolcanoDiscovery after 2 minutes.
I felt this tremor
I didn’t feel it
Date and time: April 18, 2021 12:42:43 UTC –
Size: unknown
Depth: 10.0 km
Latitude / Longitude of epicenter: 37.84875 ° N / 122.11533 ° W. 
(California, USA)
Nearest volcano: Clear Lake (137 km)
Primary data source: VolcanoDiscovery
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Data for the same earthquake reported by different authorities
Info: The more agencies report on the same quake and publish similar data, the more confidence you can have in the data. It usually takes up to a few hours for the earthquake parameters to be calculated with near optimal accuracy.
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User reports for this quake (1)
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Moraga / Very weak shaking (MMI II) / single side shaking / very brief
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