Hawaii Civil Defense is advising all residents in tsunami inundation zones to evacuate immediately.
The alert, issued at 10:38, reads "Leave all coastal evacuation zones immediately. Refer to Hawaiian Telcom or Paradise Pages for evacuation maps."
The earliest that hazardous waves could hit Hawaii is 2:59 a.m., said the agency, according to Pacific Tsunami Warning Center, based in Ewa Beach.
A tsunami warning was issued at 9:30 p.m. for Hawaii as a result of a 8.9-magnitude earthquake near the east coast of Honshu, Japan.
The Pacific Tsunami Warning Center issued a tsunami watch at 7:56 p.m. after the quake struck 231 miles northeast of Tokyo. The watch was upgraded to a more serious warning about 9:30 p.m.
"A tsunami has been generated that could cause damage along coastlines of all islands in the state of Hawaii," the agency said. "Urgent action should be taken to protect lives and property."
The warning center said wave heights cannot be predicted, but the first wave may not be the largest.
Chip McCreary, director of the warning center, said the latest forecast models show "wave amplitudes of up to 2 meters (6 feet) beyond normal sea levels in Hawaii.
"What these waves look like is an elevation of sea level, where the sea level will rise above it's normal level and stay high for 10 or 15 minutes before they recede," McCreary said, explaining the difference between tsunami and regular waves.
Because of the long length of tsunami waves, "they wrap around our islands very efficiently" so there is no point of impact that may see higher waves than other areas.
"There are some places that will be affected more than other places," McCreary said. "From our history, we've had bigger impacts in Hilo, kahului ahd Haleiwa and our models bear that out."
Geologists and geophysicists at the center are using observations from coastal gauges in Japan as well as deep ocean gauges deployed since the 2004 Indian Ocean earthquake, he said.
The center may be able to get a better fix on the six and time when the waves hit coastal gauges at Wake Island around 11:30 p.m. and Midway Island about 12:30 a.m., McCreary said.
Civil defense sirens sounded just before 10 p.m.
People were lining up to get gas around Oahu. Police dispatch reported arguing over gas in Ewa Beach and lines to get gas and pull into the store on Fort Weaver Road.
About an hour after the quake struck, Jake Chang, of Papakolea, was at the Aloha gas station on Vineyard Boulevard filling up his truck and a plastic gas container to power his generator.
"I was watching TV," he said. "I saw the footage of Japan. It was unreal."
The U.S. Geological Survey has recorded a half-dozen significant aftershocks — measuring between 6.3 and 7.1 in magnitude — since the initial quake.
The warning center said "all shores are at risk" in Hawaii no matter which direction they face.
"The trough of a tsunami wave may temporarily expose the seafloor, but the area will quickly flood again. Extremely strong and unusual nearshore currents can accompany a tsunami. Debris picked up and carried by a tsunami amplifies its destructive powerr. Simultaneous high tides or high surf can significantly increase the tsunami hazard."
In 1854, an earthquake measuring 8.4 on the Richter scale devastated the region from Tokai to Kyushu and killed an estimated 10,000 people. In 1896, an 8.5-magnitude earthquake hit the Sanriku coast; the earthquake and the resulting tsunami killing some 27,000 people.
Tsunami waves were reportedly observed in Hawaii and California, but no significant damage was reported.
And in 1946, an 8.1-magnitude quake hit Nankaido, killing 1,362.
Over the last century, tsunami have killed hundreds of people and caused millions of dollars of damage in Hawaii. The worst took place in 1946 when a 7.1-magnitude earthquake in the Aleutian Islands resulted in a tsunami that flooded downtown Hilo, killing 159 people. Hilo was hit again in 1960 when an 8.3-magnitude quake in Chile generated waves of up to 35 feet that destroyed buildings and caused 61 deaths.
The last significant tsunami in Hawaii occurred in 1975 when an earthquake off of the Big Island generated a 26-foot wave that killed two people and injured several others.
