16-53 Constraints on serpentinization of the mantle wedge in the Cascadia subduction zone from receiver function analysis

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

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The Cascadia subduction zone in the northwestern United States is characterized by an eastward-dipping Juan de Fuca plate subducting under the North American plate. In some regions, the subducting Juan de Fuca slab exhibits a so-called “inverted Moho,” in which there is a negative seismic velocity gradient (that is, a decrease in velocity with depth) downward across the crust-mantle boundary. This inverted Moho, in combination with thermal and petrologic modeling, is compelling evidence for mantle wedge serpentinization, the phenomenon in which hydrated minerals are associated with the release of volatiles from the subducting slab into the mantle wedge. Hydrous minerals exhibit particularly strong seismic anisotropy, so investigations of seismic anisotropy at depth can shed light on their distribution. The goal of this study is to investigate the spatial distribution of serpentinized mantle wedge in the Cascadia subduction zone forearc. We employ receiver function analysis on data from 20 long-running broadband seismometers across the Cascadia subduction zone to diagnose, identify, and constrain areas of hydration by examining anisotropic signatures in the forearc mantle. Understanding Cascadia is crucial for comprehending the risks associated with natural hazards, including earthquakes, volcanic eruptions, and tsunamis in the region. Constraining the depth and prevalence of serpentinization in the region will aid in this understanding.

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