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Imaging the trans-crustal(?) magma system in models and in the Cascades

Geoffrey A.  Abers 1, Guanning Pang1, Samer Naif2, Adam J.R. Kent3, Christy B. Till4, Weston A. Thelen5, Seth C. Moran5

  • Affiliations: 1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca NY USA; 2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta GA USA; 3 College of Earth, Ocean, & Atmospheric Sciences, Oregon State University, Corvallis OR USA; 4School of Earth & Space Exploration, Arizona State University, Tempe, AZ, USA; 5Cascades Volcano Observatory, U.S. Geological Survey, Vancouver WA USA

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 3

  • Programme No: 1.5.10

  • Theme 1 > Session 5

Abstract

Most eruptions at arc volcanoes are proximally supplied from crustal magma reservoirs, although their depths and volumes are often poorly constrained. Geophysical imaging has been able to identify zones of melt accumulation in some cases, but often different imaging methods produce conflicting results, complicating comparisons between different volcanoes. To better understand the strengths and limitations among different geophysical imaging methods, and to compare them with petrological approaches, we generate a notional trans-crustal volcanic model based on common conceptual diagrams. This model system has petrologically consistent variations in bulk composition, temperature and melt fraction, all of which are converted to geophysical observables such as seismic velocity and electrical conductivity. We explore the extent to which the entire plumbing system can be imaged, and find that many common methods have high sensitivity to the upper crustal reservoir but not the entire system. As a demonstration of such imaging, we show how receiver-function-like signals can show high sensitivity to magma bodies that are comparable in size to their 5-10 km wavelengths. We document such signals at most high-threat volcanoes in the Cascades, showing consistent estimates of depths to the shallow magma system for at least six volcanoes. These images place some bounds on the amount of magma present and require that much of the magma systems persist at shallow depths for the life of the volcanoes. This approach shows for the first time consistent imaging of volcanoes along an entire arc.