Magma-Assisted Flexure of Hawaiian Lithosphere Inferred From Three-Dimensional Models of Lithospheric Flexure and Active Source Seismic Data

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2021

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We examine the deformation of the oceanic lithosphere beneath the Hawaiian Islands using 3D numerical models that simulate realistic rheologies including brittle failure, elasticity, low-temperature plasticity and high-temperature creep. Observations of flexure are provided by seismic imagery of the top of the pre-existing oceanic crust from legacy and novel active source seismic studies. When simulating normal lithospheric temperatures along with low-temperature flow laws that are weaker than inferred from rock physics experiments, the models successfully predict flexure near the older (2-4 Myr) volcanoes, confirming the results of prior studies. However, the models fail to predict flexure near the younger (<1 Myr) volcanoes. When simulating elevated temperatures due to hotspot magma that penetrated the lithosphere localized to beneath the island chain, models provide better fits to the observed flexure near both O‘ahu (2-4 Myr) and the Island of Hawai‘i (<1 Myr). These results argue against the need to revise published flow laws for low-temperature creep, supporting recent studies modeling lithospheric flexure at various Pacific subduction zones. Instead, the results indicate thermal and likely mechanical weakening localized beneath the island chain due to magma-assisted flexure.

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Geophysics

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29 pages

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