From slab to surface: Earthquake evidence for fluid migration at Uturuncu volcano, Bolivia

Uturuncu volcano is situated in the Bolivian Andes, directly above world's largest crustal body of silicic partial melt, Altiplano-Puna Magma Body (APMB). last erupted 250,000 years ago, yet seismically active and lies at centre a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using newly developed velocity model, delineate top bottom APMB, reveal individual faults, reconcile differences depth distribution between previous studies. Spatial clustering analysis these earthquakes reveals orientations which match stress seismic anisotropy. Earthquake b-values derived moment magnitudes (1.44±0.06) differ significantly those local magnitude measurements (0.80±0.03). From observations theoretical justification, suggest that, if possible, should be used for accurate b-value analysis. We interpret > 1 terms fluid-enhanced seismicity. Shallow yields 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults shallow hydrothermal system, likely driven by advection APMB. Intriguingly, events deeper than APMB also yield large (1.4), mapping ascent into lower crust fluids that infer as originating subducting slab. Cumulatively, results provide picture an magmatic where are exchanged across more ductile feeding shallow, fault-controlled system. Such pathways may influence our understanding arc volcanism, control future volcanic eruptions promote accumulation ore deposits.