LOS ANGELES - A tsunami warning has been issued for the central and northern California coast and Oregon, the National Weather Service announced early Friday.
In the San Francisco Bay Area, an emergency warning system announcement for a tsunami warning was broadcast just after 1 a.m. Waves could begin arriving in Crescent City, Calif., at 7:23 a.m. and the Bay Area shortly after 8 a.m. local time.
A lower-level tsunami advisory was issued for the Southern California coast south of Point Concepcion, which includes southern San Luis Obispo County and the counties of Ventura, Los Angeles, Orange and San Diego.
According to the weather service, those living in tsunami warning areas near the beach or in low-lying regions "should move immediately inland to higher ground and away from all harbors and inlets, including those sheltered directly from the sea."
"Those feeling the earth shake, seeing unusual wave action, or the water level rising or receding may have only a few minutes before the tsunami arrival and should move immediately. Homes and small buildings are not designed to withstand tsunami impacts."
A tsunami warning means that a tsunami "with significant widespread inundation is imminent or expected. Warnings indicate that widespread dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after the initial wave arrival.
A tsunami advisory means a tsunami capable of producing strong currents or waves dangerous to anyone in or very near the water is expected, but widespread inundation is not expected.
Still, currents may be hazardous to swimmers and boats, the weather service said.
The waves were expected to hit Santa Barbara at 8:17 a.m. and Santa Monica and San Pedro harbors at 8:32 a.m.
Authorities said they will update current conditions hourly in areas under an advisory until the warning is either upgraded or they determine the event poses no further threat.
According to the weather service "the potential exists for a tsunami 3 feet or less in Southern and Central California."
Tsunamis less than 3 feet would cause damage only at the local harbors, caused by strong currents entering and exiting for several hours.
The West Coast and Alaska Tsunami Warning Center has issued more details about the potential for small waves hitting the California coast due to the Japan earthquake.
Estimated arrival times:
PORT SAN LUIS HARBOR 8:09 a.m.
SANTA BARBARA HARBOR 8:17 a.m.
SANTA MONICA: 8:32 a.m.
SAN PEDRO 8:32 a.m.
NEWPORT BEACH 8:45 a.m.
LA JOLLA 8:48 a.m.
Officials don't expect the waves to cause damage. But as a precaution, officials are likely to urge people to avoid beach areas.
Officials said people living in low-lying coastal areas should seek higher ground as a precaution and listen for special instructions from emergency agencies. Unusual wave action from the quake might last for several hours.