Earthquakes beneath and around Denali are very common and in fact encapsulate three stories of Alaska seismicity in one location. Last night’s (Tuesday 31 January) magnitude 5.2 earthquake is just one part of the Denali regional story.
While the majority of the earthquakes are small and shallow, deeper earthquakes are also frequent. A map view of earthquakes does not accurately portray the threefold nature of the region.
The cross section in the figure here shows the most recent two weeks of seismicity. Denali sits directly above the subducting Pacific Plate at a point where it reaches depths of about 70-90 miles. The forces pulling, squeezing and breaking the subducting plate cause earthquakes within the plate, as was the case with last night’s earthquake.
The magnitude 7.1 Iniskin Earthquake in January 2016 was a reminder of the potential for large earthquakes of this style.
The shallow earthquakes to the north and west of Denali occur in the Kantishna seismic cluster, the second player in the story. This area experiences thousands of persistent small earthquakes annually, believed to accommodate deformation between the Denali Fault to the south and the Minto Flats Seismic Zone to the north.
The Denali Fault, a large-scale strike-slip fault and third player in the story, passes through interior Alaska just north of Denali, directly between Denali and the Kantishna seismic cluster. The Denali Fault is capable of large earthquakes, as witnessed on November 3, 2002 when a magnitude 7.9 earthquake ruptured an approximately 140 mile long portion of the fault to the east of Denali.
The Alaska Earthquake Center and the Denali National Park and Preserve have worked in cooperation for years to monitor earthquakes in and around the park. We operate four seismic sites within the park boundaries and several others surrounding it. Park visitors often report feeling earthquakes. Most often those earthquakes occur in the Kantishna seismic cluster.
This past year we created a video telling the story of earthquakes in and around the park for use in the Eielson Visitors Center. The video can be found at https://youtu.be/l1JTtSqPSRQ.
Cross section of earthquakes beneath Denali. The Kantishna seismic cluster is outlined as well as the location of the January 31, magnitude 5.2 earthquake. The plate boundaries are for reference and approximate and not to scale.