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Volcano-tectonic interactions at Sabancaya volcano, Peru: eruptions, magmatic inflation, moderate earthquakes, and fault creep
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  • Patricia MacQueen,
  • Francisco Delgado,
  • Kevin A Reath,
  • Matthew E Pritchard,
  • Marco Bagnardi,
  • Pietro Milillo,
  • Paul R. Lundgren,
  • Orlando Macedo,
  • Victor Aguilar,
  • Mayra Ortega,
  • Rosa Anccasi,
  • Ivonne Alejandra Lazarte Zerpa,
  • Rafael Miranda
Patricia MacQueen
Cornell University

Corresponding Author:[email protected]

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Francisco Delgado
Institut de Physique du Globe de Paris
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Kevin A Reath
Cornell University, Dept. of Earth and Atmospheric Sciences
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Matthew E Pritchard
Cornell University
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Marco Bagnardi
Goddard Space Flight Center
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Pietro Milillo
California Institute of Technology
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Paul R. Lundgren
Jet Propulsion Laboratory, California Institute of Technology
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Orlando Macedo
Universidad Nacional de San Agustín de Arequipa
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Victor Aguilar
Instituto Geofisico del Peru
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Mayra Ortega
INGEMMET Volcano Observatory
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Rosa Anccasi
INGEMMET Volcano Observatory
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Ivonne Alejandra Lazarte Zerpa
INGEMMET Volcano Observatory
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Rafael Miranda
INGEMMET Volcano Observatory
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Abstract

We present evidence of volcano-tectonic interactions at Sabancaya volcano that we relate to episodic magma injection and high regional fluid pore pressures. We present a surface deformation time series at Sabancaya including observations from ERS-1/2, Envisat, Sentinel-1, COSMO-SkyMed, and TerraSAR-X that spans June 1992 - February 2019. These data show deep seated inflation northwest of Sabancaya from 1992-1997 and 2013-2019, as well as creep and rupture on multiple faults. Afterslip on the Mojopampa fault following a 2013 Mw 5.9 earthquake is anomalously long-lived, continuing for at least six years. The best fit fault plane for the afterslip is right-lateral motion on an EW striking fault at 1 km depth. We also model surface deformation from two 2017 earthquakes (Mw 4.4 and Mw 5.2) on unnamed faults, for which the best fit models are NW striking normal faults at 1-2 km depth. Our best fit model for a magmatic inflation source (13 km depth, volume change of 0.04 to 0.05 km^3 yr^-1), induces positive Coulomb static stress changes on these modeled fault planes. Comparing these deformation results with evidence from satellite thermal and degassing data, field observations, and seismic records, we interpret strong pre-eruptive seismicity at Sabancaya as a consequence of magmatic intrusions destabilizing tectonic faults critically stressed by regionally high fluid pressures. High fluid pressure likely also promotes fault creep driven by static stress transfer from the inflation source. We speculate that strong seismicity near volcanoes will be most likely with high pore fluid pressures and significant, offset magmatic inflation.
May 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 5. 10.1029/2019JB019281