Infrasound detection of approaching lahars

Abstract

Infrasound may be used to detect the approach of hazardous volcanic mudflows, known as lahars, tens of minutes before their flow fronts arrive. We have analyzed signals from more than 20 secondary lahars caused by precipitation events at Fuego Volcano during Guatemala’s rainy season in May through October of 2022. We are able to quantify the capabilities of infrasound monitoring through comparison with seismic data, time lapse camera imagery, and high-resolution video of a well-recorded event on August 17. We determine that infrasound sensors, deployed adjacent to the lahar path and in small-aperture (10 s of meters) arrays, are particularly sensitive to remote detection of lahars, including small-sized events, at distances of at least 5 km. At Fuego Volcano these detections could be used to provide timely alerts of up to 30 min before lahars arrive at a downstream monitoring site, such as in the frequently impacted Ceniza drainage. We propose that continuous infrasound monitoring, from locations adjacent to a drainage, may complement seismic monitoring and serve as a valuable tool to help identify approaching hazards. On the other hand, infrasound arrays located a kilometer or more from the lahar path can be effectively used to track a lahar’s progression.

­­Dynamics of rain-triggered lahars and destructive power inferred from seismo-acoustic arrays and time-lapse camera correlation at Volcán de Fuego, Guatemala.

“…The use of infrasound (<20 Hz) as an adjunct geophysical tool presents many significant advantages to monitoring lahars, as infrasound sensors (i) act like broadband seismometers in that they can detect a wide range of frequencies and source mechanisms (Diaz-Moreno et al 2020;Sanderson et al 2021); (ii) they can be installed at distances up to ~15km without any significant attenuation of the signal (e.g. Kogelnig et al 2014;Johnson and Palma 2015;Schimmel and Hübl 2016;Coviello et al 2019;Bosa et al 2021;Johnson et al 2023); and (iii) it is a relatively cheap monitoring device that can be quickly deployed (e.g., Anderson et al 2018).…”

“…Infrasound and seismic records can also be correlated to visual data to enhance our understanding of the relationship between flow behavior and signal characteristics. Complementary time-lapse imagery allows high spatial and temporal resolution visualizations along drainages (e.g., Cole 2011;McCoy et al 2010;Starheim et al 2013;Walter et al,2018;Johnson et al 2023). These visual observations can provide more complementary data and insight into the flow dynamics of the lahar than can be inferred from geophysical records alone.…”