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The Crustal Magmatic Structure Beneath the Denali Volcanic Gap in Central Alaska Across the Denali Fault

Description: 

Within the active subduction system, the presence of the Denali Volcanic Gap (DVG), a ~400 km region separating active volcanism of the Aleutian Arc to the west and the Wrangell volcanoes to the east, remains enigmatic. It is unclear if the subduction system is producing and storing magmatic material at the bottom of the crust or if high stresses in the crust impede the transport of material in the mid-crust, thus stalling volcanic activity. To better understand the effects of tectonic forces in the south-central Alaska upper crust, we present a 270 km long and 15 km deep 2-D shear wave velocity model of south-central Alaska across the Denali fault. We use data from a linear temporary node deployment with more than 300 geophone stations and broadband stations available in the area. We use single beamforming/slant stacking to enhance the ambient noise cross-correlation signals and simultaneously measure location-dependent Rayleigh wave phase velocity and ellipticity or horizontal to vertical (H/V) amplitude ratios. We perform 1-D Markov chain Monte Carlo joint inversions of Rayleigh wave phase velocities and H/V ratios to calculate the shear wave velocity profile. Our main observations include a low-velocity zone below the Denali Volcanic Gap, the fold-and-thrust belt in the northern flank of the Alaska Range, and the Denali fault as a narrow localized low-velocity anomaly extending to at least 12 km depth. The low-velocity anomaly below the DVG could be associated with the accumulation of melt storage of subduction-related material in the mid-crust.

Session: Cordilleran Strike-Slip Faults as Seismogenic and Seismological Features - I

Type: Oral

Date: 5/2/2024

Presentation Time: 05:30 PM (local time)

Presenting Author: Santiago

Student Presenter: Yes

Invited Presentation: Yes

Authors