Skip to main content
U.S. flag

An official website of the United States government

Seismicity and anisotropic imaging reveal an active detachment beneath the northern Alaska Range foothills

November 27, 2024

North of the Denali Fault, the collision between the Yakutat block with North America is accommodated by a fold-thrust belt giving rise to the northern Alaska Range foothills. At the western end, the Kantishna Hills anticline hosts prominent microseismicity and surface deformation, interpreted as active folding of the Kantishna Hills anticline above a midcrustal detachment. We test for this detachment by using anisotropy-aware receiver functions to image fabric contrasts within the crust in context with seismicity. Seismic stations near the crest of the Kantishna Hills anticline and near its southern flank show a single strong contrast in dipping fabric at depths of 12–13 km near microseismicity clustering depths, consistent with a detachment plane beneath the fold. A minimum b -value at 10–13 km depth is consistent with seismicity on the detachment, compatible with the imaged anisotropic contrast, while off-fault seismicity is shallower and deeper with smaller magnitudes. South-dipping imbricate thrusts in schist characterize the northern Alaska Range foothills structure. This supports our interpretation of the observed anisotropy as reflecting SSW–SSE-dipping foliation above a detachment at ∼10–13 km depth that exploits existing crustal weaknesses along subtle fabric contrasts observed in the seismically quiescent region north of the actively deforming belt.

Publication Year 2024
Title Seismicity and anisotropic imaging reveal an active detachment beneath the northern Alaska Range foothills
DOI 10.1002/9781394195947.ch21
Authors Vera Schulte-Pelkum, Adrian Bender, Natalia A. Ruppert
Publication Type Book Chapter
Publication Subtype Book Chapter
Index ID 70250848
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center Geology Minerals
Was this page helpful?