The USGS said a 2.7 magnitude quake struck at 8:16 a.m. ora locale, followed by a 3.0 temblor about 10 minutes later and a 1.3. magnitude quake in the same area.
Two minutes after 9 a.m., a third 3.3-magnitude quake hit the northern reservoir area.
The quakes were all centered along the Calaveras fault system, which is located in the hills east of the San Francisco Bay Area.
Data from the USGS shows the quakes were widely felt by people in the Fremont, Milpitas, and San Jose areas.
“I was just sitting on them bricks right there and I just felt a little jolt,” Milpitas resident Jeff Gio told KPIX-TV after feeling the strongest jolt after 9 a.m.
There were no reports of damage or injuries from either of the earthquakes.
The earthquake swarm on Tuesday was the second in three days for the Milpitas area.
Area residents on Tuesday brushed off the recent activity as just another day living in the Golden State.
“It’s just California, it is what it is,” Norman Arnold of Milpitas told KPIX.
The region is located along the volatile “Ring of Fire” seismic fault system that circles the Pacific Ocean.
This area is the location of most of Earth’s subduction zones, where oceanic plates slide under the lighter continental plates.
Earthquakes tend to happen when those plates scrape or subside underneath each other, and when that happens at sea it can spawn tsunamis.