2013 M7.5 Queen Charlotte Fault Earthquake

Mainshock and Aftershocks: 

A magnitude 7.5 earthquake occurred on Friday, January 4 at 11:58 pm AKST (January 5, 8:58 UTC) in southeastern Alaska (red star on the map). It was located 113 km (71 miles) WSW of Craig and 114 km (71 miles) S of Port Alexander. Alaska Eaerthquake Center reported about 350 aftershocks (open circles) through the end of 2013. Due to off-shore location of these earthquakes and sparse seismic station caverage, reliable locations can only be obtained for magnitude 2.5 and greater events. Twenty aftershocks had magnitudes of 4.0 or greater. The largest aftershock, magnitude 5.8, occurred on January 31 at 0:53 am AKST (9:53 UTC). The nearest seismic stations are located in Craig and Sitka (seismic stations are indicated by red triangles on the map).

Felt Reports: 

This earthquake was felt widely in southeast Alaska and British Columbia, and as far as Seattle, Washington. Maximum intensity of shaking, V - moderate, was reported in Klawock, Hydaburg, Hyder, and Craig. Click here for DYFI map. Several larger aftershocks were also felt. No damage has been reported, however some residents reported items falling off the shelves.

Tectonic Setting: 

This is the largest event to occur in the region since the magnitude 6.8 earthquake on June 28, 2004. The M 7.5 earthquake occurred on the Queen Charlotte fault system. This is a strike-slip fault that marks the boundary between the Pacific crustal plate to the southwest and the North American plate to the northeast. The largest recorded earthquake that had previously ruptured this section of the fault was the magnitude 8.1 on August 22, 1949. A magnitude 7.6 earthquake occurred on July 30, 1972. The January 5 event was located near the northern end of the 1949 rupture and south of the 1972 event, i.e. it most likely occurred in the remaining rupture gap.

Source Mechanism: 

The elastic-wave radiation pattern of the M7.5 event is consistent with the earthquake occurring as the result of right-lateral strike-slip faulting on a northwest-striking fault - as expected from the tectonic situation of the earthquake.

Tsunami: 

No wide spread devastating tsunami was generated by this event. Measured wave heights in southeast Alaska communities were under 1 inch.