Infrasonic Early Warning System for Explosive Eruptions

Abstract

Explosive volcanic eruptions can eject large amounts of ash into the atmosphere, posing a serious threat to populations living near the volcano. The abrupt occurrence of such events requires a rapid response and proper volcanic hazard evaluation. Current monitoring procedures still require human intervention, which often results in significant delays between the occurrence of an eruption and notifications being dispatched. We show how dedicated infrasound array processing can be used to detect and notify the authorities, automatically and in real time, of the onset of explosive eruptions. Conceptually, our method relies on the strong coupling between infrasound and the explosive process, and it is not based on probabilistic considerations but on the ability infrasound has to detect the early stage of the explosive phase. This procedure has been tested for the last 8 years, and it is currently applied to issue early warnings for explosive eruptions at Etna Volcano. We show that the system is able to provide a prealert ~1 hr before the eruption, and it has a 96.6% success rate, with only 1.7% false positive alerts and no false negative alerts. This is, to our knowledge, the first example of an operational early warning system totally based on an unsupervised algorithm that provides automatic notifications of eruptions to a government agency. We show that the same early warning concept might be applicable to arrays at large distances (>500 km), suggesting that infrasound could be successfully used to issue automatic notifications of ongoing eruptions at regional to global scales.

Partly Cloudy With a Chance of Lava Flows: Forecasting Volcanic Eruptions in the Twenty‐First Century

“…The 1991 and 2000 eruptions of Hekla were preceded by~30 min of recognizable seismicity and strain change, and in 2000 the observations from 1991 made it possible to recognize the signs of rapid magma ascent and impending eruption (Linde et al, 1993;Sturkell et al, 2006). Similar short-term warnings of explosive eruptions can be achieved using infrasound, as at Villarica, Chile (Johnson, Watson, et al, 2018); the method has also been implemented as an early-warning system with an outstanding success rate at Etna (Ripepe et al, 2018). There is also evidence that eruption locations might be forecast on the basis of patterns in deformation data (Guldstrand et al, 2018).…”

“…The ability of volcanologists to forecast eruptions has only improved since Jaggar's time, with a number of great successes over the past several decades ranging from forecasts of small, low‐explosivity dome‐building events at Mount St. Helens, Washington (e.g., Swanson et al, ), to ash‐rich lava fountains at Mount Etna, Italy (Cassisi et al, ; Ripepe et al, ), to large explosive eruptions at Pinatubo, Philippines, and Merapi, Indonesia (e.g., Punongbayan et al, ; Surono et al, ). Many tools have also been developed for modeling the spatial extent and potential impacts of hazards like ash plumes (e.g., Schwaiger et al, ), pyroclastic density currents (e.g., Kelfoun et al, ; Pitman et al, ), lava flows (e.g., Favalli et al, ), and lahars (e.g., George & Iverson, ; Iverson & George, ; Schilling, ).…”

“…These examples highlight the challenge and importance of forecasting not only the onset of volcanic activity but also its style/magnitude and duration—information upon which evacuation strategies are commonly based (e.g., Bebbington & Jenkins, ; Papale & Marzocchi, ; Wolpert et al, ). At present, however, volcanologists have found it most feasible to forecast either the onset of eruptions at closed‐system volcanoes that have repose periods of decades or longer (e.g., Cameron et al, ; Pesicek et al, ), or repeating eruptive behavior over much shorter time scales (e.g., Blake & Cortés, ; Connor et al, ; Jenkins et al, ; Kamo & Ishihara, ; Ripepe et al, ; Swanson et al, ). This is largely due to the fact that dormant volcanoes are most likely to show signs of “waking up,” and that most forecasting efforts are rooted in pattern recognition, where patterns are thought to record specific subsurface processes such as magma ascent (e.g., White & McCausland, ).…”

“…Some of the most successful and bestdocumented eruption predictions were for the onset of lava extrusion during repeating cycles of dome growth at Mount St. Helens in 1980-1986(Swanson et al, 1983; at Soufriére Hills Volcano, Montserrat, during the 1990s (Voight et al, 1998(Voight et al, , 1999; and for ongoing explosive eruptions at Mount Etna, Italy (Ripepe et al, 2018). (These sorts of short-term predictions can be thought of as an early warning system for eruptions.)…”

Remote Detection and Location of Explosive Volcanism in Alaska With the EarthScope Transportable Array

“…Volcanic eruptions produce seismic, acoustic, and air‐ground coupled wavefields, each of which help provide constraints on internal and external volcanic processes (Chouet & Matoza, ; Fee & Matoza, ; Johnson & Ripepe, ; Matoza et al, ). Infrasound (acoustic waves <20 Hz) is well suited to remote detection (De Angelis et al, ; Fee et al, ; Garcés et al, ; Matoza et al, ; Matoza, Le Pichon, et al, ; Matoza, Vergoz, et al, ; Matoza et al, ; Ripepe et al, ). Infrasound attenuation is low, and infrasound can often be recorded thousands of kilometers from the source (Drob et al, ; Le Pichon et al, ; Waxler, ).…”