Tracking a Pyroclastic Density Current With Seismic Signals at Mt. Etna (Italy)

Pyroclastic density currents (PDCs) are dangerous flows of volcanic rock and gas that are the most deadly proximal volcano hazard. There is significant interest in better understanding PDC dynamics, however, they are challenging to study due to their extreme hazard, unpredictable occurrence, and because complex internal dynamics are obscured by visually opaque clouds of ash. PDCs exert forces on Earth's surface and generate seismic waves. Here, we use seismic data recorded by the permanent monitoring network at Mt. Etna (Italy) to track the 11 February 2014 PDC at second-scale temporal resolution and calculate a maximum velocity of 76 m/s (274 km/hr). We identify multiple pulses and show that the late-stage source locations correspond with the mapped coarse-grained PDC deposits. High temporal and spatial resolution measurements of PDC movement from seismic data can be used to inform numerical modeling of PDC dynamics and aid in hazard assessment by improving our understanding of PDC flow paths. This work illustrates how seismic signals can be used to track surficial mass movements in real-time.