Magnitude 2.8 earthquake — 7 km NW of The Geysers, CA

A magnitude 2.8 earthquake has struck near The Geysers in northern California, about 115 kilometres north of San Francisco.

The tremor hit at around half past nine in the evening local time on Monday, centred roughly 7 kilometres northwest of The Geysers geothermal field in Lake County. According to the US Geological Survey, the quake occurred at a shallow depth of just under 2.5 kilometres beneath the surface.

What it would have felt like

An earthquake of this size is considered minor. People close to the epicentre might have felt a brief shake or rattle — a bit like a lorry rumbling past — but it's unlikely to have caused any damage. Those indoors would have had a better chance of noticing it than anyone outside, and light sleepers might have been woken by the jolt. Further away, most people wouldn't have felt anything at all.

Shallow quakes like this one tend to be felt more strongly at the surface than deeper ones, even when they're relatively small.

The Geysers and seismic activity

The Geysers is the world's largest geothermal power complex, where steam from deep underground is used to generate electricity. Small earthquakes are quite common in the area — partly due to natural fault activity and partly related to the geothermal operations themselves. Injecting water back into the hot rocks can sometimes trigger minor tremors, though they're generally harmless.

Local residents are fairly used to the occasional shake, and quakes of this magnitude rarely make headlines unless you happen to be sitting in your armchair when the teacups start rattling.

The USGS continues to monitor the situation, though no aftershocks or further activity have been reported at this stage.

Over to you

Were you anywhere near northern California when this one struck? Did you feel it, or do you know someone in the area who did? Perhaps you've experienced the odd tremor yourself over the years — they do say you never quite forget your first earthquake. Do share your stories in the comments below.