More quakes following hundreds in recent months

SAN RAMON, Calif. (KTVU) -- An earthquake swarm hits San Ramon.

The USGS recorded four tremors in less than an hour early Saturday morning.

The initial quake measured magnitude 3.1, and it hit at 12:34 a-m.

It was followed by a 1.8 tremor three minutes later, and a 1.4 aftershock seven minutes later.

The last tremor was a 1.2 at 1:11 a.m.

A few people on social media felt the shaking in bed, but there are no reports of any injuries or damage.

About 600 quakes hit the same general area in late October to early November.