(CNN) -- A tsunami warning has been issued for the western coastal areas of the United States and Canada after a massive earthquake struck off the coast of Japan.
The West Coast and Alaska Tsunami Warning Center early Friday issued a tsunami warning for coastal areas along the United States and Canadian west coasts. The tsunami warning includes coastal areas of California and Oregon from Point Conception to the Oregon-Washington border. It also includes coastal areas of Alaska from Amchitka Pass to Attu.
Tsunami warnings were issued Friday for at least 20 countries and numerous Pacific islands, including Japan, coastal Russia and the Marcus Islands, the Northern Marianas, Wake Island, Taiwan and Guam.
Authorities in the U.S. territory of Guam said a tsunami could hit the island as early as 7:09 p.m. (4:09 a.m. ET). Sirens sounded in Hawaii around 10 p.m. Thursday (3 a.m. ET), warning residents they could expect tsunami waves five hours later.
People along coastal areas are urged to evacuate, emergency officials warned.
The tsunami could cause damage "along coastlines of all islands in the state of Hawaii," warned the U.S. National Oceanic and Atmospheric Administration in a bulletin issued at 9:31 p.m. Thursday local Hawaiian time. "Urgent action should be taken to protect lives and property."
Waves are expected to hit Hawaii around 3 a.m. Friday local time.
List of countries threatened by tsunami
Tsunamis are a series of long ocean waves that can last five to 15 minutes and cause extensive flooding in coastal areas. A succession of waves can hit -- often the highest not being the first, said CNN International meteorologist Ivan Cabrera.
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A tsunami is sweeping across the Pacific Ocean after an 8.9-magnitude earthquake struck off the northeastern coast of Honshu Island, Japan. Japan's NHK showed footage of cars, boats and buildings -- some of them ablaze -- being swept inland in Miyagi Prefecture.
The temblor is the largest earthquake since the 9.0 earthquake struck the Banda Aceh area of Indonesia on December 26, 2004, causing a massive tsunami that killed tens of thousands in more than a dozen countries around the Indian Ocean.
Tsunami waves can travel at speeds of 800 kilometers (497 miles) per hour. The earthquake, initially reported as a 7.8 earthquake, was upgraded to an 8.8 quake. The epicenter was 373 kilometers (231 miles) away from the capital, Tokyo, the United States Geological Survey said, and 24 kilometers deep -- a relatively shallow depth.
"When you jump a magnitude from 7 to 8, it's not 10 times stronger, it's a 1000 times stronger," said Cabrera. "With an 8.8 earthquake that shallow, that close to shore, there will be more than one tsunami."
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The quake struck about 2:40 p.m. local time Friday in Tokyo, interrupting a sunny spring afternoon.
"You could tell this was different, instantly ... you literally couldn't stand on your feet the ground was shaking so hard," said Matt Alt, who lives on the west side of Tokyo. "We have earthquakes from time to time, but we never feel anything like the literal magnitude of this quake."
Fires were reported around Tokyo, and a large fire at a Chiba Prefecture oil refinery northeast of Tokyo sent billowing black smoke into the sky, NHK reported.
Indian Ocean tsunami killed about 250,000 people in 14 countries. That tsunami, which washed away entire communities, caused nearly $10 billion in damage and more casualties than any other tsunami in history, according to the United Nations.
