Transitions in subduction zone properties align with long-term topographic growth (Cascadia, USA)

Lorenz Michel-Wolf, Todd A. Ehlers, Rebecca Bendick

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Simple mechanical models of the earthquake cycle assume that interseismic elastic deformation is recovered during earthquakes, closing the strain budget of steady and episodic slip on the deep and shallow subduction interfaces, respectively. However, elevated topography in the forearc high requires that some deformation is not recovered over each elastic cycle. Here, we compare constraints on deformation over decadal to million-year timescales to disentangle contributions from elastic (recoverable) and inelastic (unrecoverable) deformation within the Olympic Mountains of the Cascadia Subduction Zone. Over timescales of 103 – 106 yrs, elevated topography, permanent deformation, and denudation (from thermochronometry and cosmogenic nuclide data) accumulate in an area adjacent, but not identical, to the maximum in geodetically observed reduced vertical velocity and surface upwarping over tens of years. The domains of geodetic and geomorphic maximum uplift occur over a 20-60 km wide zone overlying the up-dip limits of the zone of conditional frictional stability at the subduction interface. We attribute geologic-scale orogenesis, accumulation of topography and advection of rocks in the active orogen to unrecoverable deformation as stress is relayed up-dip through parts of the subduction interface and dissipated in the overriding plate.

    Original languageEnglish
    Article number117363
    JournalEarth and Planetary Science Letters
    Volume580
    DOIs
    StatePublished - Feb 15 2022

    Keywords

    • long-term deformation
    • mechanics
    • seismic cycle
    • subduction zone
    • thermochronometry

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