Perspectives and Limitations of Long-Range Infrasound Monitoring of Volcanic Eruptions with the Volcanic Information System: Operational Insights from the Historical Analysis of June 2011 Cordón Caulle and 2015 Calbuco Eruptions, Chile

Volcanoes produce infrasound –acoustic waves below 20 Hz– during explosive eruptions. Often, these eruptions inject large amounts of ash into the atmosphere, reaching altitudes of commercial flights (~8-12 km), thus posing a direct threat to civil aviation worldwide. Infrasound can travel up to thousands of kilometers through the atmosphere and is therefore a promising tool to remotely (>250 km) detect volcanic eruptions and alert experts and authorities of the danger by an ash cloud. Long-range infrasound records have been investigated for many explosive eruptions, but its efficiency as a monitoring system has not been addressed in details yet.

 

The Volcanic Information System (VIS) was created within the Atmospheric dynamics Research InfraStructure in Europe (ARISE) projects under the European Commission’s programs FP7 and H2020), and originally in collaboration with the Toulouse Volcanic Ash Advisory Centre (VAAC), as a prototype monitoring system that uses long-range (>250 km) infrasound to remotely detect and notify of explosive eruptions. The integration of the VIS into the EPOS Thematic Core Service Volcano Observation (TCS-VO) or HOTVOLC web-GIS interface (OPGC, CNRS-INSU) is currently being discussed within the European Geo-INQUIRE project (HORIZON-INFRA-2021-SERV-01).

 

The VIS is designed to use global observations from the International Monitoring System (IMS) infrasound network (currently comprising 54 of 60 planned stations), and it can also incorporate non-IMS infrasound array data. To remotely detect an eruption, the VIS relies on the Infrasound Parameter (IP), which is a data-derived measure accounting for propagation effects, detection persistency, and amplitude at each detecting station.

 

The efficiency of this methodology has been investigated extensively considering 10 years of global explosive activity. Recently, we have expanded the VIS capabilities to use open-access streamlined and standardized IMS-derived infrasound array signal processing data products, and to allow the incorporation of pre-calculated propagation effects in the form of back-azimuth deviation interpolations for each source-station pair.

In the current study, we focus on two similar energetic explosive eruptions (June 2011 at Cordón Caulle and April 2015 at Calbuco, Chile) to assess the reliability of the VIS to detect, locate and raise automatic notifications for the VAACs. We base this on open-access data from 2011 to 2015 of IMS stations up to ~4800 km away from both volcanoes. With operability in mind, we show how this methodology could be implemented in different scenarios, e.g. for monitoring Mount Etna, Italy.