The 2018 Kaktovik, Alaska Earthquakes and Their Context: Insights From Seismotectonics, Insar Geodesy, and Static Stress Changes
Description:
On August 12, 2018, a Mw=6.4 earthquake struck in the northeast Brooks Range southwest of Kaktovik, Alaska, followed by a Mw=6.0 event to the east six hours later and a multi-year-long aftershock sequence. Although they fortunately caused no injuries or damage, the Kaktovik earthquakes are notable for at least five reasons: 1) they occurred just south of the petroleum-rich 1002 Area of the Arctic National Wildlife Refuge; 2) they dwarf the previous largest earthquakes recorded in Arctic Alaska (M=5.3-5.4); 3) they occurred ~1,000 km from the southern Alaska convergent margin in a presumably low-strain-rate region; 4) their strike-slip character contrasts with their geologic setting in a fold-and-thrust belt; and 5) the USArray Transportable Array and the Sentinel-1A satellite pair allow them to be studied in high temporal and spatial resolution. We first examine the seismotectonic context and evolution of the Kaktovik sequence by assembling an integrated earthquake catalogue for northeast Alaska from eight sources. The catalogue reveals a history of seismicity in the northeast Brooks Range (including many strike-slip events), as well as a possible uptick in seismicity rate around the eventual epicenter of the second large (Mw=6.0) Kaktovik earthquake in the half-hour or so preceding it. To assess how the Kaktovik earthquakes fit into their seismotectonic context, and how they might modulate future seismicity through stress transfer, we use Interferometric Synthetic Aperture Radar (InSAR) to build slip models of the earthquakes. The InSAR displacements can be fit well by slip on a planar rupture based on the focal mechanism of the Mw=6.4 event and a lineation observed in the ascending-track interferogram, or a nonplanar rupture built from features of the descending-track interferogram. Using these two slip models, we calculate that the Kaktovik sequence slightly increased the Coulomb stress ~50 km to the south at the site of a subsequent Mw=5.3 earthquake in July 2019, and also increased Coulomb stress on faults to the north and/or northwest towards the coast.
Session: Cryptic Faults: Advances in Characterizing Low Strain Rate and Environmentally Obscured Faults - I
Type: Oral
Date: 5/1/2024
Presentation Time: 08:30 AM (local time)
Presenting Author: Chris
Student Presenter: No
Invited Presentation:
Authors
Chris Rollins Presenting Author Corresponding Author c.rollins@gns.cri.nz GNS Science |
Jeffrey Freymueller freymuel@msu.edu Michigan State University |
Xueming Xue xuexuemi@msu.edu Michigan State University |
Stephen Holtkamp stephen.holtkamp@gmail.com University of Alaska Fairbanks |
Thomas Logan talogan@alaska.edu University of Alaska Fairbanks |
Franz Meyer fjmeyer@alaska.edu University of Alaska Fairbanks |
Jason Patton jason.patton@conservation.ca.gov California Geological Survey |
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The 2018 Kaktovik, Alaska Earthquakes and Their Context: Insights From Seismotectonics, Insar Geodesy, and Static Stress Changes
Category
Cryptic Faults: Advances in Characterizing Low Strain Rate and Environmentally Obscured Faults