JUNEAU, Alaska — A powerful earthquake sparked a tsunami warning for hundreds of miles of Alaskan and Canadian coastline, but the alert was canceled when no damaging waves were generated.

The magnitude 7.5 quake and the tsunami warning that followed caused concern in some coastal communities, with alarms sounding and people rushing to higher ground for safety.

But the Alaska Tsunami Warning Center later said the waves were too small to pose a threat, reaching just six inches above normal sea level in places such as Sitka and Port Alexander.

The temblor struck at midnight and was centered about 60 miles west of Craig, Alaska, the U.S. Geological Survey said.

Seismologist Jana Pursley of the USGS said the quake was followed by six aftershocks, the strongest of which registered a 5.1 and came nearly four hours after the initial quake.

The Alaska Earthquake Information Center said the quake was widely felt but it received no reports of any damage.