October earthquake uptick south of Kaktovik
October 18, 2024

In early October, we detected a notable increase in earthquake activity about 50 miles south of Kaktovik in the northeastern corner of Alaska (Figure 1). This new cluster of events (Figure 2) is distinct and could be part of an emerging swarm that we are keeping an eye on. The expansion in our seismic network in 2019–20 in parts of the state that previously had lesser coverage (Figure 3) has allowed us to better capture seismic swarms like these.

While this area is not typically known for large earthquakes, there have been a few notable previous events, shown in Figure 3:

(1) The 2018 M6.4 Kaktovik earthquake and aftershock sequence.

AEC research seismologist Ezgi Karasözen helped describe the area's potential for damaging earthquakes in one of the few papers published on northern Brooks Range seismicity. In the paper, the team says, “The northeastern Brooks Range has been characterized as an area of low to moderate seismic hazard, but these earthquakes illustrate the potential for larger, possibly destructive events in a region earmarked for rapid resource development.”

(2) The 2018 Hulahula River earthquake swarm, briefly shown in this report https://core.ac.uk/reader/286999910, experienced periods of unrest in 2013 and 2019.

Earthquake swarms are common in the Brooks Range region. They can last for weeks, months or even years. You can read more about seismic swarms in our news story "What is an earthquake swarm?".

Generally speaking, earthquakes in the northern Brooks Range area are related to the forces that built the mountains. After the collisions that formed the mountain belt stopped, the area began “relaxing” outward, resulting in extensional and strike-slip faulting, which continues today.

Map showing cluster of earthquakes near Kaktovik.
Figure 1. Map of Alaska showing the cluster of earthquakes near Kaktovik from October 1–17, 2024. The earthquake locations are colored by depth, with red indicating shallow depths of less than 35 km (22 mi). Most earthquakes in this cluster are relatively shallow, at less than 15 km (~10 mi).

 

Charts showing the number and magnitude of earthquakes in the recent swarm.
Figure 2. Charts showing the number of earthquakes (left) and the magnitude of earthquakes (right) in the recent swarm. There are about 100 events, with magnitudes ranging from ~1.5 to ~4. Note the significant uptick in activity above background levels starting in early October.

 

Mapping showing groupings of earthquakes from different years and events.
Figure 3. Detailed map of the area shown in Figure 1, with populations of earthquakes shown in different colors. The small red dots indicate all the earthquakes between 2012 and 2022. Some fall in clusters, like the aftershock sequence from the 2018 M6.4 Kaktovik earthquake, and a distinct 2018 Hulahula River swarm. The blue dots show earthquakes in the region from January through September 2024—these mainly overlap the previously defined sequences. The yellow dots, which show all the earthquakes since October 2024, do not overlap those sequences and may be a new swarm. (Note the black triangles indicating the closest seismic stations, which allow us to better define these events.)