A 5.6-magnitude earthquake hit near Mendocino County early last week.
The tremor rippled through Northern California across the area.
Phones across the Bay Area blared with ShakeAlert warnings.
The shaking hit San Francisco and several towns nearby.
Reports say little damage showed up shortly after.
Officials keep checking further tremors.
They urge people to remain prepared as a precaution.
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