The epicenter was 400 miles southwest of Anchorage, Alaska, and 20 miles down in the Earth. It struck around Midnight Pacific time. No tsunami is expected at this time. For more see the link from Earthsky.org. The map is from the USGS via Earthsky.
This earthquake is a ring of fire event, and may very well be related to the volcano eruption in Japan the day before. (see the previous post below this post.)