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Abstract The iconic volcanoes of the Cascade arc stretch from Lassen Volcanic Center in northern California, through Oregon and Washington, to the Garibaldi Volcanic Belt in British Columbia. Recent studies have reviewed differences in the distribution and eruptive volumes of vents, as well as variations in geochemical compositions and heat flux along strike (amongst other characteristics). We investigate whether these along‐arc trends manifest as variations in magma storage conditions. We compile available constraints on magma storage depths from InSAR, geodetics, seismic inversions, and magnetotellurics for each major edifice and compare these to melt inclusion saturation pressures, pressures calculated using mineral‐only barometers, and constraints from experimental petrology. The availability of magma storage depth estimates varies greatly along the arc, with abundant geochemical and geophysical data available for some systems (e.g., Lassen Volcanic Center, Mount St. Helens) and very limited data available for other volcanoes, including many which are classified as “very high threat” by the USGS (e.g., Glacier Peak, Mount Baker, Mount Hood, Three Sisters). Acknowledging the limitations of data availability and the large uncertainties associated with certain methods, available data are indicative of magma storage within the upper 15 km of the crust (∼2 ± 2 kbar) beneath the main edifices. These findings are consistent with previous work recognizing barometric estimates cluster within the upper crust in many arcs worldwide. There are no clear offsets in magma storage between arc segments that are in extension, transtension or compression, although substantially more petrological work is needed for fine scale evaluation of storage pressures. 

The July 2021 Chignik earthquake (M8.2) was the biggest earthquake in the US since 1965 (Rat Islands). It ruptured a segment of the megathrust offshore of the Alaska Peninsula, which last ruptured in 1938, although there are some differences. It is also the middle of the recent AACSE project, which deployed 30 PASSCAL Broadbands, 75 OBSs, and 398 Nodes in 2018-8, making it among the best-characterized megathrust segments. This dataset contains the on-shore seismic aftershock survey, where we reoccupy several AACSE sites on the Shumagin Islands, Alaska Peninsula and Kodiak, with one new deployment on the Semidi islands close to the epicenter. Stations are deployed from Kodiak or Chignik. Sites are deployed in early August 2021, within 2 weeks of the mainshock, and continue until May-June 2022 when they are recovered. All sites have compact broadband sensors and are powered by Air-Alkaline Cells, which are relatively winter- and bear-resistant. All data are to be made open as rapidly as possible.