iPhone users in the San Francisco Bay Area were alerted to an earthquake today as a 5.6-magnitude tremor was detected near Redwood Valley, about 100 miles north of the city. The earthquake occurred at approximately 8:10 a.m. Pacific Time on Wednesday. The notification advised residents to “Drop, cover, hold on” if shaking intensified, as part of the United States Geological Survey’s ShakeAlert system. Some iOS versions also displayed an Apple Maps view indicating the potential shaking area.

