The 2013 M7.5 Earthquake Near Edna Bay, Alaska

On January 5, 2013, at 08:58 UTC, a magnitude 7.5 earthquake struck 110 km southwest of Edna Bay, Alaska, at a shallow depth of 8.7 km. This event occurred within the tectonically active southeastern Alaska region, part of the Pacific Ring of Fire where the Pacific Plate interacts with the North American Plate along major strike-slip faults. Southeastern Alaska experiences frequent seismicity due to right-lateral transform motion along the Queen Charlotte Fault system, which accommodates much of the relative plate motion at rates exceeding 5 cm per year. The shallow focal depth of the 2013 event is consistent with rupture within the brittle upper crust of this transform boundary. The earthquake's location places it near the northern extension of the fault zone that extends from offshore British Columbia into the Gulf of Alaska. The broader geological setting features complex interactions including oblique subduction to the west and transform faulting to the east. The region lies near the transition between the Cascadia subduction zone and the Queen Charlotte transform, resulting in a mix of thrust, strike-slip, and normal faulting mechanisms. Historical records document multiple strong earthquakes in the area, underscoring its high seismic hazard. Paleoseismic studies indicate recurrent large-magnitude events along the Queen Charlotte Fault over the Holocene. Since 2000, the M7.5 event of January 5, 2013, stands as the strongest recorded in the immediate vicinity, with no comparable magnitude earthquakes occurring at the same location through the present. Aftershock sequences following such events typically decay over weeks to months, though the 2013 sequence remained modest in comparison to other regional M7+ quakes. Ongoing monitoring by seismic networks continues to refine understanding of fault segmentation and strain accumulation in this remote area. The combination of shallow depth and proximity to the plate boundary highlights the potential for strong ground shaking and secondary hazards such as landslides in coastal terrain.

References

USGS Earthquake Catalog (event parameters) Alaska Earthquake Center regional reports