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Detecting Repeating Icequakes at Llaima and Villarrica Volcanoes, Chile

Session: Critical Zone, Environmental and Cryospheric Seismology [Poster]

Type: Poster

Date: 4/22/2021

Presentation Time: 03:45 PM Pacific

Description: 

The evaluation of seismic activity at ice-covered volcanoes is challenging as volcanic and glacial earthquakes (i.e. icequakes) can have overlapping characteristics (i.e. frequencies, waveform shape and magnitude). However, icequakes have only been described at a handful of volcanoes around the world that currently host one or more glaciers. Here we present results from the first study to target glacial activity at active ice-covered volcanoes in the Southern Chile. The primary focus so far has been on Llaima volcano, one of the largest and most active volcanoes in the region while hosting >14 km² of glacial ice on the flanks. A combination of automatic multi-station event detection and waveform cross-correlation to find candidate repeating icequakes in seismic data from the permanent volcano monitoring network recorded in early 2019. We identified dozens of low magnitude families of repeating seismic events across two months, the largest of which included over 200 events. These results are comparable to observations from seismic data recorded at Llaima volcano during the same time period in 2015. The persistent, repetitive nature of these events combined with their waveform characteristics and source locations suggest they originated from multiple sub-glacial stick-slip sources around the upper flanks of the volcano. We also targeted Villarrica volcano in early 2020 with a network of seismo-acoustic sensors to record glacial activity in concurrence with the ongoing eruptive activity at the summit. Altogether, results so far suggest icequakes may be more common than previously thought and has implications for how seismic data at ice-covered volcanoes may be used for assessing future eruptive potential. Furthermore, this study highlights how existing volcano seismic networks could be used to evaluate sub-glacial properties at hundreds of volcanoes around the world.

Presenting Author: Oliver Lamb

Student Presenter: No

Authors