2014 M6.0 Seward Glacier Earthquake

Mainshock and Aftershocks: 

A magnitude 6.0 earthquake occurred on Thursday, July 17 at 3:49 am AKDT (11:49 UTC) in the Saint Elias Mountains region, south of Mt. Logan under Seward glacier (large red star on the map). It occurred at a depth of 6 km (4 miles) and was located 99 km (62 miles) NNW of Yakutat, 104 km (65 miles) SW of Burwash Landing and 129 km (81 miles) ENE of Cape Yakataga. The Alaska Earthquake Center recorded nearly 600 aftershocks within first month after the mainshock (open circles on the map). The largest aftershock, magnitude 4.9, occurred 4 minutes after the mainshock. Another strong aftershock, magnitde 4.8, occurred 3 days later.

Felt Reports: 

This earthquake was felt widely in Yakutat and Yukon Territories. No reports of damage have been received. Maximum intensity of shaking, III - weak, was reported on Yakutat. NASA was conducting Multiple Altimeter Beam Experimental Lidar (MABEL) survey at the time in the area. The MABEL aircraft was also equipped with a camera, from which aeral images were obtained before and after the M6.0 earthquake. The images documented landslide triggered by the earthquake and some changes in the glacial lakes.

Tectonic Setting: 

Tectonics in this region is defined by ongoing collision of the Yakutat block with the North American plate. Complex system of thrust and strike-slip faults define boundary between these two tectonic members. High rates of mountain building and crustal uplift are present in this region, especially in the corner syntax where the strike-slip Fairweather fault connects into the Chugach-Saint Elias thrust fault and fold belt. Strong earthquakes were recorded in this region previously, such at magnitude 7.5 St.Elias earthquake in 1979 and a series of magnitude 8 earthquakes in 1899.


The elastic-wave radiation pattern of the M6.0 event indicates oblique strike-slip faulting consistent with rotational motion of the Yakutat block with respect to the North American plate.