Arthur D. Jolly

A model for developing best practice volcano monitoring: a combined threat assessment, consultation and network effectiveness approach

This paper presents a combined approach to achieving best practice volcano monitoring through a review of New Zealand’s volcano-monitoring capability as established under the GeoNet project. A series of benchmark, consultation and network performance studies were undertaken to provide a comprehensive review of volcano monitoring in New Zealand and to establish plans for future improvements in capability. The United States Geological Survey National Volcano Early Warning System method was applied to benchmark the established monitoring networks against recommendations for instrumentation based on a volcano’s threat level. Next, a consultative study of New Zealand’s volcanology research community was undertaken to canvass opinions on what future directions GeoNet volcano monitoring should take. Once the seismic network infrastructure had been built, a noise floor analysis was conducted to identify stations with poor site noise characteristics. Noise remediation for poor sites has been implemented by either re-locating the site or placing sensors in boreholes. Quality control of Global Navigation Satellite System networks is undertaken through the use of multipath parameters derived from routine processing. Finally, the performance of the monitoring networks is assessed against two recent eruptions at Mount Tongariro and White Island. This combined approach can be used as a model to assess the need for future monitoring levels on any volcano.

Capturing the Acoustic Radiation Pattern of Strombolian Eruptions using Infrasound Sensors Aboard a Tethered Aerostat, Yasur Volcano, Vanuatu

We obtained an unprecedented view of the acoustic radiation from persistent strombolian volcanic explosions at Yasur volcano, Vanuatu from the deployment of infrasound sensors attached to a tethered aerostat. While traditional ground-based infrasound arrays may sample only a small portion of the eruption pressure wavefield, we were able to densely sample angular ranges of ~200o in azimuth and ~50o in take-off angle by placing the aerostat at 38 tethered loiter positions around the active vent. The airborne data joined contemporaneously collected ground-based infrasound and video recordings over the period 29 July to 1 August 2016. We observe a persistent variation in the acoustic radiation pattern with average eastward-directed root-mean squared pressures more than 2 times larger than in other directions. The observed radiation pattern may be related to both path effects from the crater walls, and source directionality.

Seismo-acoustic wavefield of strombolian explosions at Yasur volcano, Vanuatu, using a broadband seismo-acoustic network, infrasound arrays, and infrasonic sensors on tethered balloons

Seismo-acoustic wavefields at volcanoes contain rich information on shallow magma transport and subaerial eruption processes and inform our understanding of how volcanoes work. Acoustic wavefields from eruptions are predicted to be directional, but sampling this wavefield directivity is challenging because infrasound sensors are usually deployed on the ground surface. We attempt to overcome this observational limitation using a novel deployment of infrasound sensors on tethered balloons in tandem with a suite of dense ground-based seismo-acoustic, geochemical, and eruption imaging instrumentation. We conducted a collaborative multiparametric field experiment at the active Yasur volcano, Tanna Island, Vanuatu, from 26 July to 2 August 2016. Our observations include data from a temporary network of 11 broadband seismometers, 6 single infrasonic microphones, 7 small-aperture 3-element infrasound arrays, 2 infrasound sensor packages on tethered balloons, an FTIR, a FLIR, 2 scanning Flyspecs, and various visual imaging data; scoria and ash samples were collected for petrological analyses. This unprecedented dataset should provide a unique window into processes operating in the shallow magma plumbing system and their relation to subaerial eruption dynamics.Seismo-acoustic wavefields at volcanoes contain rich information on shallow magma transport and subaerial eruption processes and inform our understanding of how volcanoes work. Acoustic wavefields from eruptions are predicted to be directional, but sampling this wavefield directivity is challenging because infrasound sensors are usually deployed on the ground surface. We attempt to overcome this observational limitation using a novel deployment of infrasound sensors on tethered balloons in tandem with a suite of dense ground-based seismo-acoustic, geochemical, and eruption imaging instrumentation. We conducted a collaborative multiparametric field experiment at the active Yasur volcano, Tanna Island, Vanuatu, from 26 July to 2 August 2016. Our observations include data from a temporary network of 11 broadband seismometers, 6 single infrasonic microphones, 7 small-aperture 3-element infrasound arrays, 2 infrasound sensor packages on tethered balloons, an FTIR, a FLIR, 2 scanning Flyspecs, and various visua...

A viscous‐to‐brittle transition in eruptions through clay suspensions

Volcanic lakes are often associated with active geothermal circulation, mineral alteration, and precipitation, each of which can complicate the analysis of shallow magma physics, geophysical signals, and chemical signals. The rheology of the lake and associated hydrothermal system affects the eruptive activity as bubbles ascend and burst through the lake producing distinct ejection behavior. We investigate such phenomena by conducting scaled experiments in which heated water-clay suspensions are decompressed rapidly from relevant pressures. After a jet phase of expanding vapor, the suspensions break up into ejecta that are either angular or droplet geometry. We parameterize these regimes and find a universal clay volume fraction of 0.28 below which the ejecta are form droplets and above which the ejecta are angular. We propose a regime diagram for optical observations of active lakes, which allows rheological characterization and informs volcanic monitoring.