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Seismology Versus Infrasound: Which Monitoring Technique Is Better for Detecting Advancing Lahars?

Description: 

Recent studies have reported on remote detection of small secondary lahars using infrasound (low frequency acoustic) arrays at Fuego Volcano (Guatemala). They demonstrated that the frequent small secondary lahars generate a unique infrasound signature that is detectable when the lahar is more than 5 km away from the recording site. At Fuego’s Ceniza drainage these early warning detections precede the arrival of the actual lahar by as much as 20 to 30 minutes. This precursor can be enough time to provide an early notification and complement subsequent alerts triggered by AFM systems (geophone seismology), which are particularly effective when situated adjacent to a drainage. AFMs, using relatively high frequency seismic sensing, is a much more established tool for monitoring lahar activity. In this work we evaluate the advantages and disadvantages of infrasound versus seismic monitoring the small secondary lahars at Fuego.

We use a dataset of dozens of lahars from 2022 during which a seismo-acoustic installation was situated adjacent to Ceniza at 14 km flow distance from the volcano. We observe that AFM monitoring has some distinct advantages, over infrasound, including a fundamentally less-noise signal associated with the passing of the flow. Infrasound monitoring at Fuego, in particular, is complicated by multiple other sources of signal and noise, such as from volcanic vent activity, thunderstorms, aircraft, and wind. An advantage to infrasound, however, is that it appears to be uniquely sensitive to more distant sources. While high frequency seismic ground vibrations appear to attenuate relatively rapidly, such that the lahars are not seismically detectable further than a few kilometers, arrays of (as few as two) infrasound sensors appear capable of detecting more distant sources using modified beam forming techniques where the direction of incident infrasound is constrained by knowledge of the volcano’s drainages. With knowledge of the lahar’s flow path infrasound can be used to reliably detect many (but not all) of the lahar signals up to tens of minutes before they arrive at the monitoring site.

Session: Detecting, Characterizing and Monitoring Mass Movements [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Jeffrey

Student Presenter: No

Invited Presentation: 

Authors