A powerful magnitude 8.0 earthquake struck off the coast of Alaska today, prompting officials to issue a tsunami warning for the state's coastal regions.http://abcnews.go.com/US/earthquake-magnitude-80-strikes-off-coast-alaska/story?id=24271613The quake, which shook an area about 15 miles from Little Sitkin Island, was initially deemed a 7.1 on the Richter scale before it was upgraded to an 8.0.