A 5.6-magnitude earthquake shook near Mendocino County early last week.
The tremor sent tremors through Northern California in the region.
Mobile devices across the Bay Area blared with ShakeAlert warnings.
The shaking hit San Francisco and several towns nearby.
Reports say little damage showed up right after.
Officials keep checking extra shakes.
They urge people to remain prepared just in case.
5.6 earthquake reported in Northern California, triggers alert across Bay Area San Francisco Chronicle
Shake alert lights up Bay Area phones Wednesday morning after 5.6 quake hits Mendocino KRON4
Magnitude 5.6 earthquake felt across Northern California, USGS says KCRA
Northern California hit by magnitude 5.6 earthquake in Mendocino County CBS News
Magnitude-5.6 earthquake shakes parts of Northern California NBC Los Angeles