Abstract. Paroxysmal eruptions, characterized by sudden and vigorous explosive activity, are common events at many open-vent volcanoes. Stromboli volcano, Italy, is well-known for its nearly continuous degassing activity and mild explosions from the summit craters, occasionally punctuated by energetic, short-lived paroxysms. Here, we analyse multi-parameter geophysical data recorded at Stromboli in early July 2024, during activity that led to a paroxysmal eruption on 11 July. We use seismic, infrasound and ground deformation data, complemented by visual and Unoccupied Aircraft System observations, to identify key geophysical precursors to the explosive activity and reconstruct the sequence of events. Elevated levels of volcanic tremor and Very Long Period (VLP) seismicity accompanied moderate explosive activity, lava emission and small collapses from the north crater, leading to a major explosion on 4 July, 2024 at 12:16 (UTC). Collapse activity from the North crater area continued throughout July 7, while effusive activity occurred from two closely-spaced vents located on the Sciara del Fuoco slope, on the Northwest flank of the volcano. On 11 July, a rapid increase in ground deformation preceded, by approximately 10 minutes, a paroxysmal event at 12:08 (UTC); the explosion produced a 5 km-high eruptive column and pyroclastic density currents along Sciara del Fuoco. We infer that the early activity in July was linked to eruption of resident magma within the shallowest parts of the volcano plumbing. This was followed by lowering of the magma level within the conduit system as indicated by the location of newly opened effusive vents The rapid inflation observed before the paroxysmal explosion on 11 July is consistent with the rapid expansion of gas-rich magma rising from depth, as frequently suggested at Stromboli during energetic explosive events. Our results provide additional valuable insights into the eruptive dynamics of Stromboli and other open-conduit volcanoes, and emphasize the importance of integrated geophysical observations for understanding eruption dynamics, their forecasting and associated risk mitigation.
<p>Detecting and notifying ongoing volcanic explosive eruptions can support the activities of the Volcanic Ash Advisory Centres (VAAC) in their contribution to the International Airways Volcano Watch. However, local monitoring systems are missing on many active volcanoes. Here, the use of a global monitoring that, even with lower reliability, can allow a fast response. Many studies have shown so far the utility and potential of long-range infrasound monitoring for this aim, but still open questions remain concerning the real efficiency and reliability of such a system.</p><p>In this study we investigate the potential of the infrasound network of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to detect volcanic explosive eruptions at large distances. We apply a procedure based on the Infrasound Parameter (IP) calculated from a single array to selected volcanoes by accounting for realistic infrasound propagation conditions.</p><p>The procedure was applied to data recorded by the I06AU infrasound array (Cocos Island) between January 2012 and December 2019 and targeting Indonesian volcanoes at source-to-receiver distances ranging between 1000 and 2000 km, where activity from 11 volcanoes was reported in the period of analysis with an energy spanning from mild explosions to VEI4 eruptions.</p><p>The system reliability was evaluated from the ratio between real ones and the total number of notifications provided from I06AU array for each volcano.</p><p>The IP was calculated following previous studies and improved with new constraints accounting for the source strength and signal persistency. These allowed us to improve significantly the system reliability for events VEI3 or greater and strongly reduce the number of false alerts. Still, undetected explosive events remain due to unfavorable propagation conditions and unresolved ambiguity due to short spacing among volcanoes with respect to the array. We propose to solve this last issue by considering volcanic sectors rather than single volcanic edifices. Instead of a notification for a single volcano, an alert for an area of interest could be issued to draw the attention and trigger further analysis of satellite images by the VAACs.</p><p>This study is performed to improve the Volcanic Information System (VIS) proposed and developed in the framework of FP7 and H2020 ARISE projects.</p>
Glacier break-off events constitute a severe hazard in Alpine regions and their effects are expected to increase soon because of climate changes. Within this rapidly changing scenario, the development and implementation of new monitoring solutions and warning systems, able to detect collapses and possibly estimate the volumes, is of critical importance. In this paper we present the analysis of avalanching activity from Planpincieux glacier (Aosta valley) through infrasound data collected by a small aperture (~ 150 m) array deployed at short distance (~ 2000 m) from the hanging front. The analysis is performed over five time periods between August 2020 and December 2022 summing up into 360 days. From a data set of confirmed events, infrasound wave parameters (intensity, peak amplitude, frequency and duration) are compared with collapse volumes estimated from photogrammetry and experimental relations are defined. Morerover, characteristics of infrasound signals of confirmed events are used to extract signals that are likely produced by collapses from the whole dataset of infrasound detections and a volumetric flux of collapses from the front of the Planpincieux glacier is derived through time.  
Volcanic explosive eruptions produce large amounts of low-frequency (250 km) with sustained ash-columns and provide early warnings to mitigate the risk that eruptions pose to civil aviation. Additionally, it can reconstruct the chronology of eruptions, and provide volcanic source constraints (acoustic intensity, gas flow, etc.). The system is designed to integrate the IMS and national infrasound stations to gather all available infrasound detections in the area of interest. The detections rely on the Progressive Multi-Channel Correlation (PMCC) method, which separates coherent infrasound waves (detections) from noise. The VIS is based on the Infrasound Parameter (IP) criterion to establish when an eruption is in course, accounting for atmospheric propagation effects, detection persistency, and amplitude. An operational VIS demonstrator will be deployed on servers of the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC, CNRS-INSU and University Clermont Auvergne) to monitor Mt. Etna and Stromboli in real-time using data from the Amiata infrasound array (AMT) operated by the University of Florence. The data products of the VIS demonstrator will be available through an application programming interface (API) hosted at OPGC, where also an archived catalogue of European volcano eruptions and the real-time data products for AMT will be hosted.As part of the European Geo-INQUIRE project (HORIZON-INFRA-2021-SERV-01), the VIS will be integrated into the Thematic Core Service Volcano Observation (TCS-VO) of the European Plate Observing System (EPOS). Future developments will include integration into web services such as the HOTVOLC web-GIS interface (OPGC, CNRS-INSU) or the EPOS Data Portal.
Detecting and notifying ongoing volcanic explosive eruptions is crucial in supporting the Volcanic Ash Advisory Centre (VAAC). However, local monitoring systems are missing at many active volcanoes, but long range infrasound monitoring might provide useful information if able to detect and notify volcanic explosive events. Indeed, many studies have already highlighted the utility and the potential of long-range infrasound monitoring for this aim, but still open questions remain concerning its actual efficiency and reliability. In this study we investigate the potential of the IS06 array (Cocos Island, Australia) of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to remotely detect volcanic explosive eruptions in the Indonesian Arc between 2012 and 2019, when 11 volcanoes, positioned at a distance between 1000 and 2000 km from the array, erupted with an energy spanning from mild explosions to VEI (Volcanic Explosivity Index) 4 eruptions. For each volcano, using infrasonic data recorded at a single array and accounting for realistic infrasound propagation conditions, we calculate a range corrected Infrasound Parameter (IP) and propose two additional empirical thresholds on signal strength and persistency. The IP is used eventually to define an alert whenever an established threshold is exceeded and the corresponding reliability estimated. Results show that the range corrected IP is highly reliable for events VEI = 3 or greater under favorable propagation conditions, but smaller scale short-lasting explosive eruptions still remain usually undetected. Unresolved ambiguity remains due to short spacing among volcanoes with respect to the array. For regional scale monitoring purposes, this can be solved only considering volcanic sectors rather than single volcanic edifices that, despite preventing unambiguous notification of a given volcano, might allow to increase the attention of the VAAC over a specific area.
Supplementary Dataset containing windowed seismic traces for the 29 June 2022 fireball event near the Azores in the North Atlantic, as studied in the manuscript entitled, "Exclusive seismoacoustic detection and characterisation of an unseen and unheard fireball in the North Atlantic" by Stephen P. Hicks and Sandro B. Matos, et al. A Python Jupyter Notebook is also provided that reproduces the main figures of the paper.
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