Volcano-Tectonic Interactions at Sabancaya Volcano, Peru: Eruptions, Magmatic Inflation, Moderate Earthquakes, and Fault Creep

Patricia Macqueen , Francisco Delgado (1) , Kevin Reath , Matthew E. Pritchard , Marco Bagnardi , Pietro Milillo , Paul Lundgren , Orlando Macedo , Victor Aguilar , Mayra Ortega , Rosa Anccasi , Ivonne Alejandra Lazarte Zerpa , Rafael Miranda

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

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 to 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 M_W 5.9 earthquake is anomalously long lived, continuing for at least 6 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 (M_W 4.4 and M_W 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 km³ 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 combining high pore fluid pressures with sufficiently large, offset magmatic inflation can promote strong earthquakes during volcanic unrest.

Mots clés: fault creep; volcano; earthquake; InSAR; remote sensing; geodesy

Domaines: Planète et Univers [physics]; Tectonique; Volcanologie

Patricia Macqueen, Francisco Delgado, Kevin Reath, Matthew E. Pritchard, Marco Bagnardi, et al.. Volcano-Tectonic Interactions at Sabancaya Volcano, Peru: Eruptions, Magmatic Inflation, Moderate Earthquakes, and Fault Creep. Journal of Geophysical Research : Solid Earth, 2020, 125, ⟨10.1029/2019JB019281⟩. ⟨insu-03748809⟩