Volcanic emission and seismic tremor at Santiaguito, Guatemala: New insights from long-term seismic, infrasound and thermal measurements in 2018–2020

Abstract

Long-term instrumental monitoring of open-vent volcanoes provides the necessary datasets to characterize volcanic activity and unravel its temporal changes. This is particularly important for active lava domes, which can undergo rapid transitions in behavior over the course of their eruption. Here, we analyzed seismic, acoustic infrasound and thermographic data collected between January 2018 and September 2020 to resolve volcanic processes taking place at the Santiaguito lava dome complex in Guatemala. During this period lava effusion filled the crater of the active Caliente lava dome. The extrusive activity was accompanied by small-to-moderate explosions, prolonged episodes of gas emissions, and occasional rockfalls. Automated algorithms were applied to identify seismic signals associated with different processes and to characterize the temporal evolution of activity. We identified ~70–250 tectonic events per week and detected signals associated with gas-and ash explosions occurring at a rate of ~70–100 events/week. Lava dome growth activity was accompanied by the emplacement of a lava flow along the eastern upper flank of Caliente and seismicity possibly due to the occurrence of rockfalls. We observed episodes of harmonic tremor in seismic and acoustic data associated with sustained gas emissions, estimated to originate at shallow depths of about 500–750 m below the crater. Data indicated that both the recurrence rate of tremor (~10–50 events/week) and its duration (~40–130 min/week) were slightly lower and shorter between January 2019 and March 2020 than in rest of the study period, despite minor variations in explosive activity. Finally, within a period of 11 weeks, between 18 January and 4 April 2018, we found 129 volcano tectonic earthquakes; we were able to locate 10 of them at depths between 1.3 and 2.3 km, ~1.5 km southwest of Caliente. This multi-parametric study provides valuable insights into geophysical signals and associated processes at Santiaguito, helping to resolve temporal occurrence of each event type during protracted effusive-explosive activity.