Maurizio Ripepe

Exploring the explosive‐effusive transition using permanent ultra‐violet cameras

Understanding the mechanisms that cause effusive eruptions is the key to mitigating their associated hazard. Here, we combine results from permanent ultra-violet (UV) cameras, and from other geophysical observations (seismic very long period, thermal, and infrasonic activity), to characterize volcanic SO2 flux regime in the period prior, during, and after Strombolis August-November 2014 effusive eruption. We show that, in the two months prior to effusion onset, the SO2 flux levels are two times average level. We explain this anomalously high SO2 regime as primarily determined by venting of rapidly rising, pressurized SO2-rich gas pockets, produced by strombolian explosions being more frequent and intense than usual. We develop a procedure to track (and count), in the UV camera record, the SO2 flux pulses produced by individual explosions and puffing activity (active degassing). We find that these SO2 pulses are far more numerous (67u2009±u200947 events/hour) before the effusion onset than during normal activity (20u2009±u200915 events/hour). This observation, combined with geophysical evidence, demonstrates an elevated gas bubble supply to the shallow conduits, causing elevated explosive and puffing activity. This increase (≥0.1 m3s-1) in magma transport rate in the north-east feeding conduits finally triggers effusion onset. Active degassing remains elevated also during the effusive phase, supporting the persistence of explosive and puffing activity during the effusive eruption, deep in the volcanic conduit. Our results demonstrate that permanent UV cameras can valuably contribute to monitoring at high sampling frequency gas dynamics and fluxes, thus opening the way to direct comparison with more established geophysical observations.

Infrasound Monitoring of Volcano-Related Hazards for Civil Protection

In the last 20 years, infrasound has increased significantly the potentials of volcano monitoring, with direct impact on risk evaluation for civil protection. Automatic systems based on infrasound are nowadays used operationally, and future improvements will reinforce this technique especially when integrated with other ground-based or satellite observations. We show how by using dedicated array processing, infrasound can be used to detect and notify, automatically and in real time, the onset of explosive eruptions and the run-out of density currents based on the apparent velocity, propagation back-azimuth, and frequency change. Such procedures have been tested and tuned for several years and are currently being applied to early warning of explosive eruption at Etna volcano and to avalanche analysis and risk forecasting in several sites in Europe.

Infrasound Monitoring of Volcanic Eruptions and Contribution of ARISE to the Volcanic Ash Advisory Centers

In the current society, volcanic eruptions can have a great impact due to the escalation in communications and transport starting from 1950. With the advent of civil aviation and the exponential growth in the air traffic, the problem of a volcanic ash encounter has become an issue of paramount importance, which needs to be addressed in real time. This chapter describes the status of the art in volcano monitoring using infrasound technology at global, regional and local scale, the contribution of the ARISE project to volcano monitoring and to Volcanic Ash Advisory Centers (VAACs), and highlights the need for an integration of the CTBT IMS infrasound network with local and regional infrasound arrays capable of providing a timely early warning to VAACs.

Long-term eruptive trends from space-based thermal and SO2 emissions: a comparative analysis of Stromboli, Batu Tara and Tinakula volcanoes

Batu Tara (Indonesia) and Tinakula (Solomon Island) are two poorly known volcanoes with morphologies and short-term eruptive activity similar to Stromboli (Italy). However, quantitative information about their long-term eruptive behaviour is limited, making the comparisons with Stromboli descriptive and based on short periods of observations. Here, we use over a decade of satellite data to measure and compare the radiant flux (2000–2017) and the SO2 mass (2004–2017) of all three volcanoes. The combined analysis of volcanic radiant power (from MODIS data) and SO2 flux (from OMI data) reveals different long-term eruptive trends and contrasting ratios of SO2/VRP. These data indicate that the eruptive mechanisms operating at each volcano are quite different. The persistent open-vent activity of Stromboli volcano is episodically interrupted by flank eruptions that drain degassed magma stored in the very shallow portion of the central conduit. In contrast, a long-lasting exponential decay of both VRP and SO2 flux observed at Batu Tara is consistent with the eruption of undegassed magma from a deep, closed magma chamber, whilst Tinakula displays multiple year-long eruptive phases, characterised by evolving gas/thermal ratios and an eruptive intensity increasing with time. Magma budget calculations for the latter volcano are consistent with eruption from a volatile-zoned magma chamber, coupled with periods of gas/magma accumulations at depth. Our results suggest that the combined analysis of satellite thermal/gas data provides a valuable tool for decrypting the long-term volcanic dynamics that could remain hidden over shorter timescales.