As recently as Wednesday morning, magnitude 4 earthquakes were still shaking south of Port Alexander, off the coast of Southeast Alaska, near the site of a 7.5 magnitude earthquake that triggered a tsunami warning for the coast of British Columbia up the Southeastern Alaska Panhandle on Friday.
Friday’s earthquake was the largest in the region since a 7.6 quake along the Queen Charlotte Fault Line off the coast shook the region on July 30, 1972. The largest tremor ever recorded there was magnitude 8.1 on August 22, 1949, the Alaska Earthquake Information Center reports.
In the 24 hours following Friday’s earthquake, some 150 aftershocks were recorded, all at least magnitude 2.5. Because the nearest seismic stations are in Craig and Sitka, only aftershocks with magnitude of 2.5 and greater are recorded.
The largest aftershock was a magnitude 5.1 early Saturday morning. Since then, aftershocks of magnitude 4 and above have continued. On Tuesday, three big aftershocks were recorded – one a magnitude 4.0 at 5:45 a.m., another magnitude 4.7 quake at 9:45 a.m., and the third just after 7 p.m., also at magnitude 4.7.
On Wednesday, another 4.0 earthquake hit, 54 miles south of Port Alexander and 2 miles deep, just before 6 a.m.
Up-to-date earthquake information is available at the Alaska Earthquake Information Center.