Long period seismic source characterization at Popocatépetl volcano, Mexico

Abstract

The seismicity of Popocatépetl is dominated by long‐period and very‐long period signals associated with hydrothermal processes and magmatic degassing. We model the source mechanism of repetitive long‐period signals in the 0.4–2 s band from a 15‐station broadband network by stacking long‐period events with similar waveforms to improve the signal‐to‐noise ratio. The data are well fitted by a point source located within the summit crater ∼250 m below the crater floor and ∼200 m from the inferred magma conduit. The inferred source includes a volumetric component that can be modeled as resonance of a horizontal steam‐filled crack and a vertical single force component. The long‐period events are thought to be related to the interaction between the magmatic system and a perched hydrothermal system. Repetitive injection of fluid into the horizontal fracture and subsequent sudden discharge when a critical pressure threshold is met provides a non‐destructive source process.