caa a22 4500 475825950 CHVBK 20180406123828.0 cr unu---uuuuu 170329e20000101xx s 000 0 eng 10.1007/PL00008909 doi (NATIONALLICENCE)springer-10.1007/PL00008909 A model for the magmatic-hydrothermal system at Mount Rainier, Washington, from seismic and geochemical observations [Elektronische Daten] [S. C. Moran, D. R. Zimbelman, S. D. Malone]  Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an average of one to two high-frequency volcano-tectonic (or VT) earthquakes occurring directly beneath the summit in a given month. Despite this level of seismicity, little is known about its cause. The VT earthquakes occur at a steady rate in several clusters below the inferred base of the Quaternary volcanic edifice. More than half of 18 focal mechanisms determined for these events are normal, and most stress axes deviate significantly from the regional stress field. We argue that these characteristics are most consistent with earthquakes in response to processes associated with circulation of fluids and magmatic gases within and below the base of the edifice.Circulation of these fluids and gases has weakened rock and reduced effective stress to the point that gravity-induced brittle fracture, due to the weight of the overlying edifice, can occur. Results from seismic tomography and rock, water, and gas geochemistry studies support this interpretation. We combine constraints from these studies into a model for the magmatic system that includes a large volume of hot rock (temperatures greater than the brittle-ductile transition) with small pockets of melt and/or hot fluids at depths of 8-18 km below the summit. We infer that fluids and heat from this volume reach the edifice via a narrow conduit, resulting in fumarolic activity at the summit, hydrothermal alteration of the edifice, and seismicity. Springer-Verlag Berlin Heidelberg, 2000 Key words Mount Rainier nationallicence Seismicity nationallicence Geochemistry nationallicence Magmatic-hydrothermal system model nationallicence Volcano monitoring nationallicence Moran S. C. U.S. Geological Survey, Alaska Volcano Observatory, 4200 University Drive, Anchorage, AK 99508, USA e-mail: smoran@usgs.gov, US aut Zimbelman D. R. P.O. Box 1878, White Salmon, WA 98672-1878, USA, US aut Malone S. D. University of Washington, Geophysics Program, Box 351650, Seattle, WA 98195-1650, USA, US aut https://doi.org/10.1007/PL00008909 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/PL00008909 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Moran S. C. U.S. Geological Survey, Alaska Volcano Observatory, 4200 University Drive, Anchorage, AK 99508, USA e-mail: smoran@usgs.gov, US aut NATIONALLICENCE 700 1- Zimbelman D. R. P.O. Box 1878, White Salmon, WA 98672-1878, USA, US aut NATIONALLICENCE 700 1- Malone S. D. University of Washington, Geophysics Program, Box 351650, Seattle, WA 98195-1650, USA, US aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer