A magnitude 4.2 earthquake shook the North Bay early Thursday morning shortly after midnight, waking up people across the region. The quake, centered in a rural area five miles east of Cloverdale in Sonoma County, was the second-largest earthquake anywhere in the 9-county San Francisco Bay Area in the past 12 months.

Dozens of small earthquakes have shaken the San Francisco Bay Area over the last month, rattling nerves and raising fears that more seismic events may be on the horizon. The clusters of earthquakes — the latest of which struck Monday — have all been ...