Ballistic ejecta and eruption condition of the vulcanian explosion of Shinmoedake volcano, Kyushu, Japan on 1 February, 2011

Abstract

The physical condition of the 1 February, 2011, vulcanian explosion at Shinmoedake volcano, Japan, is estimated based on the size of impact craters created by ballistic ejecta, using a ballistic trajectory model and a scaling law for impact crater formation. The initial velocity, impact velocity and mass of ejecta were estimated at 240-290 m/s, 140 ± 20 m/s and 1-3 ton, respectively. The gas mass fraction at the source was calculated to be 0.04-0.1, using the initial velocity and a theoretical model of vulcanian explosion. This gas mass fraction is higher than the petrologically estimated value for pre-eruptive magma. Low-angle jets from the explosion and the estimated depth and size of a pressurized gas region suggest a shallow source inside the lava dome. The observation and results imply that segregation and accumulation of gas in a shallow conduit played a role in an increase of excess pressure immediately below the dome surface, prior to the vulcanian explosion.

Rapid hazard assessment of volcanic ballistic projectiles using long-exposure photographs: insights from the 2010 eruptions at Tungurahua volcano, Ecuador

“…Comparing with other studies, metric-size ballistic projectiles are not typical of Strombolian and Sub-Plinian activity and are more common during Vulcanian explosions [Maeno et al 2013;Bombrun et al 2015;Taddeucci et al 2017]. Based on the size/velocity inverse relationship [Bombrun et al 2015], the maximum launching velocities observed for metric-size projectiles at Tungurahua are higher than those expected for Strombolian activity (<100 m s −1 for >0.6-m-diameter blocks) with velocities up to 117-135 m s −1 , 143-162 m s −1 and 144-153 m s −1 for January, May-June and November eruptions respectively.…”

“…In Ecuador, two volcanologists from the Instituto Geofísico de la Escuela Politécnica Nacional, Victor Hugo Pérez and Álvaro Sanchez, died from a phreatic explosion in March 12th 1993. This hazard is mainly studied through field work on impact craters and deposits [Alatorre-Ibargüengoitia et al 2012;Maeno et al 2013] and/or monitoring (punctual or continuous) at currently active volcanoes [Chouet et al 1974;Ripepe et al 1993;Hort and Seyfried 1998;Dubosclard et al 2003;Andronico et al 2008;Gouhier and Donnadieu 2011;Taddeucci et al 2012b;Dürig et al 2015]. Hazard assessment is generally completed with numerical simulations that require a large number of eruptive source parameters: the projectiles properties (size, density and shape), the atmospheric conditions (temperature and pressure at different altitude, speed of tailwind), the explosion characteristics (launching velocity and angle, extent of reduced drag zone), and the local topography [Mastin 2001].…”

The Communication and Risk Management of Volcanic Ballistic Hazards

“…Generally, the distance travelled and the total area impacted by ballistics increases with increasing explosivity, i.e. particles generally travel further and cover a greater area in Vulcanian eruptions (Nairn and Self 1978;Alatorre-Ibargüengoitia et al 2012;Maeno et al 2013) compared with Strombolian eruptions (Harris et al 2012;Gurioli et al 2013;Turtle et al 2016). However, eruptions can be directed, ejecting ballistics at low angles and at distances greater than those from more vertically directed eruptions Tsunematsu et al 2016).…”

“…Mapped deposits from past eruptions are often not symmetrical around the vent, reflecting this directionality (Minakami 1942;Fudali and Melson 1972;Steinberg and Lorenz 1983;Kilgour et al 2010;Houghton et al 2011;Gurioli et al 2013;Fitzgerald et al 2014), and are sometimes the result of the crater and surrounding topography Tsunematsu et al 2016). Detailed descriptions and maps of ballistic impact distributions are rare, but those published may contain some of the following data: maximum ballistic travel distances (Steinberg and Lorenz 1983;Robertson et al 1998;Kaneko et al 2016); the outer edges of a ballistic field (Minakami 1942;Nairn and Self 1978;Yamagishi and Feebrey 1994); and/or maximum particle (Nairn and Self 1978;Steinberg and Lorenz 1983;Robertson et al 1998;Swanson et al 2012) or crater size (Robertson et al 1998;Maeno et al 2013;Kaneko et al 2016). When isopleths of particle size are included these rarely contain individual measurements and may be severely limited by the availability of only specific mapped locations (e.g., Kilgour et al 2010;Houghton et al 2011).…”

“…1d) are also common occurrences from ballistics during explosive eruptions. The high kinetic and thermal energy of ballistics can puncture, dent, melt, burn and knock down structures and their associated systems, such as power supply and telecommunication masts; crater roads; and crush and potentially ignite crops (Booth 1979;Calvari et al 2006;Pistolesi et al 2008;Alatorre-Ibargüengoitia et al 2012;Wardman et al 2012;Maeno et al 2013;Fitzgerald et al 2014;Jenkins et al 2014). Blong (1981), Pomonis et al (1999) and Jenkins et al (2014) estimate a ballistic only needs 400-1000 J of kinetic energy to penetrate a metal sheet roof, far less than the estimated kinetic energy of ballistics (*10 6 J) from VEI 2-4 eruptions (Alatorre-Ibargüengoitia et al 2012).…”