Insights into Lithospheric Domains and Melt Production Along the Alaskan Subduction Margin from Rayleigh and Shear Wave Velocity Structure

The Alaskan Subduction Zone displays high levels of seismicity and volcanism, yet the character of these tectonic processes vary dramatically along the system. The eastern portion of the margin has generated historic earthquakes such as the 1964 Good Friday Earthquake, while the western portion generates more numerous but smaller events, a difference supported by GPS estimates of plate locking along the system. Similarly, silica content and other geochemical markers vary from east to west. Our study incorporates OBS and land seismic data from the 2018-2019 AACSE deployment with data from the Alaska TA and other regional networks to build a broad model extending from the Alaskan Cordillera to the Aleutian Peninsula and offshore. We first measure Rayleigh wave phase velocities up to a period of 180s using the two plane wave method, and then invert for 3D shear wave velocities in the lower crust and upper mantle. Our Rayleigh wave and preliminary shear wave models provide evidence for low velocity regions beneath and north of the Aleutian volcanic arc with upper mantle shear wave velocities generally decreasing to the west, low velocities at shallow depth beneath the Wrangell Volcanic Field, and continuation between the Pacific and Yakutat slabs, characterized by distinct bend and changes in velocity structure between the segments.