Preliminary information says it was a magnitude 6.5. There are no reports of fatalities, only some injuries and landslides blocking at lest one major road.
Power outages were reported across the state and there were unconfirmed reports of injuries, according to the State Civil Defense. Problems with communication prevented more definite reports.
Gov. Linda Lingle said in a radio interview with KSSK from Hawaii Island that she had no report of any fatalities. She said boulders fell on highways, rock walls fell down and television had been knocked off of stands, she had no reports of building damage.
The quake occurred at 7:07 a.m. local time, 10 miles north-northwest of Kailua Kona, a town on the west coast of the Big Island, said Don Blakeman, a geophysicist at the National Earthquake Information Center, part of the.
The U.S. Geological Survey reported the quake had a preliminary magnitude of 6.3, along with several aftershocks, including one measuring a magnitude of 5.8.
Blakeman said there was no risk of a Pacific-wide tsunami, but a possibility of significant wave activity in Hawaii.
On Hawaii Island, also known as the Big Island, there was some damage in Kailua-Kona and landslide along a major highway, said Gerard Fryer, a geophysicist at the Pacific Tsunami Center.
Officials were concerned there may be "structural integrity" problems at the big hospital in Kona in the Big Island, Lingle said. New patients were being accepted, but kept outside.
Here's the Wikipedia entry on the Richter scale. Magnitude 6.5 is not considered a major quake, but there can be some local damage.
UPDATE: Doesn't look like there was any loss of life at all. One hospital has evacuated some patients, but is still open and accepting patients.