Description: Located in the central Andes, the Altiplano-Puna Volcanic Complex (APVC) is the location of an 11–1 Ma silicic volcanic field, one of the largest and youngest on Earth. Yet its magmatic/plutonic underpinnings have been seismically investigated in only a few widely spaced locations. Previous studies have identified an extensive (∼60,000 km2) low-velocity zone (LVZ) below the APVC referred to as the Altiplano-Puna Magma Body (APMB); however, insufficient seismic constraints have precluded uniquely measuring its thickness, and the volume of the APMB remains mostly constrained by varying estimates of plutonic to volcanic (P:V) ratios. Here we present new 3-D seismic images of the APVC crust based on a joint inversion of Rayleigh-wave dispersion from ambient seismic noise and P-wave receiver functions from broadband seismic stations recently deployed in the area. We identify a large ∼200 km diameter and ∼11 km thick LVZ that we interpret as the plutonic complex that sourced the voluminous APVC volcanics and show that its volume is much larger than previous estimates, perhaps as much as an order of magnitude larger. The large volume (∼500,000 km3) and shallow depth (4–25 km below sea level) of the LVZ centered on the observed surface uplift below the composite volcano Uturuncu provide strong evidence linking our imaged low-velocity body (APMB) with the presence of an amalgamated plutonic complex. We suggest the APMB retains a significant percentage (up to 25%) of partial melt, most likely in a melt-crystal mush state, and is related to the source of the continued ground deformation attributed to magma ascent beneath the APVC. The seismic imaging of this plutonic complex and the well-preserved and documented volcanic deposits allow us to make one of the best-constrained calculations of a plutonic to volcanic ratio. Although this calculation is still dependent on a few critical assumptions, the large volume of the newly imaged APMB requires a much larger ratio (20–35) than often cited in the literature. This large ratio has significant implications for both petrologic and tectonic models of this portion of the Andean arc.

Description: Questions addressing Arctic change span earthquakes, meteorology, climate, sea ice, glaciers, permafrost, and wildfire. Many change-based research questions require consistent and continuous long-term data. By co-locating a wide variety of geophysical instruments, the Alaska Geophysics Network lends itself to enhancing cross-disciplinary research. Our stations co-locate: a 3-component broadband seismometer (Nanometrics T120PH or Kinemetrics STS-4B/5A); a Vaisala WXT weather station; a MEMS state-of-health barometer; a NCPA infrasound sensor; a SETRA microbarograph; and an Onset HOBO soil temperature profile. The stations were originally part of 192 multi-sensor platforms installed across Alaska between 2014 and 2017 by the USArray seismic project, managed by the Incorporated Research Institutions for Seismology (IRIS) as part of the NSF EarthScope program. These stations vastly expanded the amount of data available in Alaska and marked the first time seismic instruments were installed in some remote locations. Following the commencement of the USArray project, the Alaska Earthquake Center adopted the best-performing stations to become part of our permanent monitoring network. Data collected by the Alaska Geophysics Network can help explore questions related to climate, earthquakes, landslides, glaciers, sea ice, weather, wildfire, and more. All data is available for public use. In this presentation, we show the extent of the network and data and examples of cross-disciplinary cryoseismology findings from the Alaska Earthquake Center using this data.