A "quake swarm" that has shaken southern California with hundreds of moderate temblors in quick succession is fueling jitters in the Golden State, long braced for the Big One.

The quakes, which began Sunday and could last for a few days according to experts, were mostly moderate but included several over 5.0 in magnitude, causing minor damage in the town of Brawley, near the Mexican border.

While nobody was injured -- and as seismologists stress it does not increase the risk of a massive earthquake the region has long feared -- it has inevitably fueled anxiety.

On Sunday, quakes could be felt as far away as San Diego on the West Coast and inland east into Arizona, as well as Orange County further north towards Los Angeles.

Geologists say a quake capable of causing widespread destruction is 99 percent certain of hitting California within the next three decades. A magnitude 7.8 quake could kill 1,800 people, injure 50,000 more and damage 300,000 buildings.