The Rialto Fire Department reported that a series of small earthquakes shook the northwestern portion of the city Thursday morning.

A 4.3 magnitude earthquake struck San Bernardino County on Thursday morning, adding to a week of natural disruptions across California.

A few minutes later, another 3.1-magnitude quake hit the Rialto area at 9:36 a.m. The USGS said it could be felt in parts of Riverside County, including Jurupa Valley and Eastvale. Jones said all the earthquakes took place in an area known as the "Fontana trend,