Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap
Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative net...
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ftunivbritcolcir:oai:circle.library.ubc.ca:2429/64405 2023-05-15T18:44:37+02:00 Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap Chuang, Yuling (Lindsay) 2018 http://hdl.handle.net/2429/64405 eng eng University of British Columbia Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ CC-BY-NC-ND Text Thesis/Dissertation 2018 ftunivbritcolcir 2019-10-15T18:24:49Z Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative network matched filtering and stacking. The timing of impulsive P (compressional) wave and S (shear) wave arrivals on template waveforms places LFEs at 40–58 km depth, near the upper envelope of intraslab seismicity and immediately updip of increased levels of intraslab seismicity. S waves at near-epicentral distances display polarities consistent with shear slip on the plate boundary. We compare characteristics of LFEs, seismicity, and tectonic structures in central Alaska with those in warm subduction zones, and propose a new model for the region’s unusual intraslab seismicity and the enigmatic Denali volcanic gap (i.e., an area of no volcanism where expected). We argue that fluids in the Yakutat plate are confined to its upper crust, and that shallow subduction leads to hydromechanical conditions at the slab interface in central Alaska akin to those in warm subduction zones where similar LFEs and tremor occur. These conditions lead to fluid expulsion at shallow depths, explaining strike-parallel alignment of tremor occurrence with the Denali volcanic gap. Moreover, the lack of double seismic zone and restriction of deep intraslab seismicity to a persistent low-velocity zone are simple consequences of anhydrous conditions prevailing in the lower crust and upper mantle of the Yakutat plate. Science, Faculty of Earth, Ocean and Atmospheric Sciences, Department of Graduate Thesis Yakutat Alaska University of British Columbia: cIRcle - UBC's Information Repository |
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University of British Columbia: cIRcle - UBC's Information Repository |
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ftunivbritcolcir |
language |
English |
description |
Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative network matched filtering and stacking. The timing of impulsive P (compressional) wave and S (shear) wave arrivals on template waveforms places LFEs at 40–58 km depth, near the upper envelope of intraslab seismicity and immediately updip of increased levels of intraslab seismicity. S waves at near-epicentral distances display polarities consistent with shear slip on the plate boundary. We compare characteristics of LFEs, seismicity, and tectonic structures in central Alaska with those in warm subduction zones, and propose a new model for the region’s unusual intraslab seismicity and the enigmatic Denali volcanic gap (i.e., an area of no volcanism where expected). We argue that fluids in the Yakutat plate are confined to its upper crust, and that shallow subduction leads to hydromechanical conditions at the slab interface in central Alaska akin to those in warm subduction zones where similar LFEs and tremor occur. These conditions lead to fluid expulsion at shallow depths, explaining strike-parallel alignment of tremor occurrence with the Denali volcanic gap. Moreover, the lack of double seismic zone and restriction of deep intraslab seismicity to a persistent low-velocity zone are simple consequences of anhydrous conditions prevailing in the lower crust and upper mantle of the Yakutat plate. Science, Faculty of Earth, Ocean and Atmospheric Sciences, Department of Graduate |
format |
Thesis |
author |
Chuang, Yuling (Lindsay) |
spellingShingle |
Chuang, Yuling (Lindsay) Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
author_facet |
Chuang, Yuling (Lindsay) |
author_sort |
Chuang, Yuling (Lindsay) |
title |
Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
title_short |
Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
title_full |
Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
title_fullStr |
Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
title_full_unstemmed |
Plateau subduction, intraslab seismicity, and the Denali (Alaska) volcanic gap |
title_sort |
plateau subduction, intraslab seismicity, and the denali (alaska) volcanic gap |
publisher |
University of British Columbia |
publishDate |
2018 |
url |
http://hdl.handle.net/2429/64405 |
genre |
Yakutat Alaska |
genre_facet |
Yakutat Alaska |
op_rights |
Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ |
op_rightsnorm |
CC-BY-NC-ND |
_version_ |
1766235412468072448 |