Cautionary Analysis of Spectral Radiance from Io’s Active Volcanoes Derived from Galileo Near-Infrared Mapping Spectrometer Data

Between 1996 and 2001, the Galileo Near-Infrared Mapping Spectrometer (NIMS) obtained 190 observations of the volcanic Jovian moon Io. Rathbun et al. (2018) [Astron. J., 156, 207] published a list of 287 measurements of 3.5 μm spectral radiance from some of Io’s active volcanoes, derived from a subset of the NIMS data. However, the spectral radiances reported by Rathbun et al. are lower, in some cases by multiple orders of magnitude, than other analyses of the same observations and spectral radiances derived from contemporaneous ground-based data. In many cases, the Rathbun et al. hot-spot radiances are underreported by a factor of π, likely due to a mistake in unit conversion. For a small number of powerful hot spots, additional discrepancies appear to be the result of poor fits to data limited in wavelength range by NIMS detector saturation and a methodology that discards short-wavelength NIMS data that otherwise would have provided more robust temperature model fits.

Scattering strength at active volcanoes in Japan as inferred from the peak ratio analysis of teleseismic P waves

Small-scale seismic velocity heterogeneity has been studied through the calculation of peak amplitude ratio as a means to quantify the strength of seismic wave scattering at volcanoes in Japan. This ratio is defined as the ratio of the maximum (peak) P wave energy in the transverse component seismogram envelope over that of the three-component sum seismogram envelope (transverse + radial + vertical). According to the previous study using Japan’s Hi-net seismometer network, the peak ratio is observed to be larger near the (active) quaternary volcanoes. However, these Hi-net stations are not positioned on the volcanoes themselves. This study systematically examines the peak ratios at 47 active volcanoes across Japan, using seismometers operated by the Japan Meteorological Agency (JMA). Analyses were performed at four frequency bands: 0.5–1, 1–2, 2–4, and 4–8 Hz. We found that the JMA stations yield higher peak ratios than the Hi-net stations. Their differences are statistically significant at the 99.9% confidence level in all frequency bands. We also examined the differences between the ground surface and borehole stations of the JMA network. The former shows larger peak ratios, and for most frequency bands, the differences are also statistically significant at the 99.9% confidence level. This suggests an intensification of small-scale medium heterogeneities especially at shallow depths at active volcanoes, and that scattering might have been enhanced at the very shallow parts. Graphical Abstract

Modeling Volcano-Magmatic Systems: Workshop Report for the Modeling Collaboratory for Subduction Research Coordination Network

This document summarizes the outcomes of the Modeling Collaboratory for Subduction Zone Science (MCS) Volcanic Systems Workshop and presents a vision for advancing collaborative modeling of volcano-magmatic systems. The U.S. Geological Survey (USGS) has identified 161 potentially active volcanoes in the United States and its territories, of which 57 are considered to be high or very high threats (Ewert et al., 2018). All western states, including Alaska and Hawaii, have potentially active volcanoes. Eruptions range from the quiet effusion of sluggish lava flows over hours to decades to immense explosive ejections of tephra which produce massive calderas.Understanding these volcanoes and assessing their threat to society requires the development of quantitative models, rooted in physics and chemistry, which can be used to interpret diverse observations including real-time monitoring data. Existing models have tremendously advanced our understanding of volcanic systems and have improved our ability to assess hazards and forecast future activity, contributing directly to reductions in the number of lives lost to volcanic eruptions and helping mitigate their costs to society. Magmatic system models also provide a quantitative framework for understanding processes that occur at depth beneath volcanoes, linking volcanic systems with a broad range of deeper processes associated with the production, transport, and storage of magma and associated fluids above subducting slabs.Despite this exciting progress much remains to be accomplished and workshop participants identified several important opportunities. First and foremost is the recognition that enhanced support for the development and dissemination of volcano-magmatic system models and associated methodologies will enable advances in ways not currently possible. A key outcome of the workshops is a recognition of the transformative potential of diverse groups of scientists working together on common problems. Support for collaborative working groups will enable communication across disciplines and between modelers and non-modelers, leveraging expertise from scientists studying different aspects of volcano-magmatic systems, and between geoscientists and outside experts from fields such as mathematics, statistics, and material sciences. Better support will also enable modelers to more fully verify, validate, benchmark, and document their codes, and also provide new training opportunities. Enhanced model sharing and interoperability will reduce the need for different groups to independently duplicate (re-invent) code and increase confidence in published results. This report lays out a proposal for a collaborative modeling environment that is centered in large part around community working groups manifested as workshops, summer schools, and sustained long-term research collaborations involving diverse groups of scientists working on common problems. Programmatic support is envisioned in the form of enhanced student and postdoc funding for model development, incentives and support for cross-disciplinary collaborative research projects, and related support for these activities. This support will fundamentally improve our ability to integrate and interpret observations using volcanic and magmatic system models.

Discriminating Between Spatial and Temporal Variations in Seismic Anisotropy at Active Volcanoes

<p>This thesis addresses the measurement and interpretation of seismic anisotropy around active volcanoes via shear wave splitting analysis. An overpressured magma reservoir will exert a stress on the surrounding country rock that may or may not be manifest as observable strain. Shear wave splitting analysis can be a useful indicator of stress in the crust and hence, the pressure induced by magma movement. Changes in shear wave splitting have already been observed at Mt. Ruapehu following eruptions in 1995/1996 and are inferred to be caused by changes in local stress in response to magma pressure. One of the main problems with the interpretation of temporal changes in shear wave splitting is the possibility of spatial variations being sampled along differing raypaths and being interpreted as temporal changes. Using a dense observational network and an automated shear wave splitting analysis, we examine local earthquakes occurring in 2008 within 100 km of Mt. Ruapehu. We note a strong azimuthal dependence of the fast direction of anisotropy (phi) and so introduce a spatial averaging technique and a two-dimensional tomography of recorded delay times (dt), to observe the spatial variation in more detail. Using this new method of mapping shear wave splitting parameters, we have created a benchmark of spatial variations in shear wave anisotropy around Mt. Ruapehu, against which future temporal changes may be measured. The observed anisotropy is used to define regions in which phi agrees with stress estimations from focal mechanism inversions, suggesting stress-induced anisotropy, and those in which phi aligns with structural features such as fault strikes, suggesting structural anisotropy. Data from past deployments of three-component seismometers have been analysed in the same way as those recorded during the 2008 experiment and the results compared. We identify a stable region of strong anisotropy, interpreted to be caused by schistose mineral alignment, and a transient region of strong anisotropy centred on the volcano during the major magmatic eruption of 1995. We also introduce a method of analysing temporal variations in seismic anisotropy at active volcanoes by using tight clusters of earthquakes and highly correlated multiplets. At Mt. Ruapehu, changes in shear wave splitting parameters associated with the 2006 and 2007 phreatic eruptions are detected using a cluster of earthquakes to the west of the volcano. Similar analyses using another cluster and multiplets from the stable region of strong anisotropy do not reveal temporal changes, although examination of the waveform codas of the repeating earthquakes reveals systematic changes that we interpret as being caused by seismic scatterers associated with the 2006 and 2007 eruptions. These scatterers appear to contaminate the shear wave coda and so inhibit the detection of any subtle changes in shear wave splitting parameters. Finally, we apply some of these methods to data from the 2008 eruption of Okmok volcano, Alaska. Shear wave splitting analysis at Okmok reveals a change in anisotropy associated with the 2008 eruption. This change however, is attributed to a change in dominant hypocentre location. Multiplet analysis at Okmok volcano reveals a similar scatterer contamination of the shear wave arrival. This spurious phase is interpreted to be an S to P conversion from interaction with the magma reservoir.</p>

Discriminating Between Spatial and Temporal Variations in Seismic Anisotropy at Active Volcanoes

<p>This thesis addresses the measurement and interpretation of seismic anisotropy around active volcanoes via shear wave splitting analysis. An overpressured magma reservoir will exert a stress on the surrounding country rock that may or may not be manifest as observable strain. Shear wave splitting analysis can be a useful indicator of stress in the crust and hence, the pressure induced by magma movement. Changes in shear wave splitting have already been observed at Mt. Ruapehu following eruptions in 1995/1996 and are inferred to be caused by changes in local stress in response to magma pressure. One of the main problems with the interpretation of temporal changes in shear wave splitting is the possibility of spatial variations being sampled along differing raypaths and being interpreted as temporal changes. Using a dense observational network and an automated shear wave splitting analysis, we examine local earthquakes occurring in 2008 within 100 km of Mt. Ruapehu. We note a strong azimuthal dependence of the fast direction of anisotropy (phi) and so introduce a spatial averaging technique and a two-dimensional tomography of recorded delay times (dt), to observe the spatial variation in more detail. Using this new method of mapping shear wave splitting parameters, we have created a benchmark of spatial variations in shear wave anisotropy around Mt. Ruapehu, against which future temporal changes may be measured. The observed anisotropy is used to define regions in which phi agrees with stress estimations from focal mechanism inversions, suggesting stress-induced anisotropy, and those in which phi aligns with structural features such as fault strikes, suggesting structural anisotropy. Data from past deployments of three-component seismometers have been analysed in the same way as those recorded during the 2008 experiment and the results compared. We identify a stable region of strong anisotropy, interpreted to be caused by schistose mineral alignment, and a transient region of strong anisotropy centred on the volcano during the major magmatic eruption of 1995. We also introduce a method of analysing temporal variations in seismic anisotropy at active volcanoes by using tight clusters of earthquakes and highly correlated multiplets. At Mt. Ruapehu, changes in shear wave splitting parameters associated with the 2006 and 2007 phreatic eruptions are detected using a cluster of earthquakes to the west of the volcano. Similar analyses using another cluster and multiplets from the stable region of strong anisotropy do not reveal temporal changes, although examination of the waveform codas of the repeating earthquakes reveals systematic changes that we interpret as being caused by seismic scatterers associated with the 2006 and 2007 eruptions. These scatterers appear to contaminate the shear wave coda and so inhibit the detection of any subtle changes in shear wave splitting parameters. Finally, we apply some of these methods to data from the 2008 eruption of Okmok volcano, Alaska. Shear wave splitting analysis at Okmok reveals a change in anisotropy associated with the 2008 eruption. This change however, is attributed to a change in dominant hypocentre location. Multiplet analysis at Okmok volcano reveals a similar scatterer contamination of the shear wave arrival. This spurious phase is interpreted to be an S to P conversion from interaction with the magma reservoir.</p>

Volcano hazard and surveillance in Costa Rica

Costa Rica hosts ten volcanic complexes and is highly tectonically active due to its location at the interaction between the Cocos, Nazca, and Caribbean plates and the Panama microplate. Three of the five historically active volcanoes had frequent eruptions in 2019. The institutions in charge of monitoring the volcanoes of Costa Rica are the Observatorio Vulcanológico y Sismológico de Costa Rica from Universidad Nacional (OVSICORI-UNA) and the Red Sismológica Nacional (RSN: UCR-ICE that groups the Escuela Centroamericana de Geología from the Universidad de Costa Rica, and the Observatorio Sismológico y Vulcanológico de Arenal y Miravalles from the Instituto Costarricense de Electricidad; acronyms ECG, UCR, OSIVAM, and ICE). These institutions are focused on the most dangerous volcanoes, i.e. those closest to the Great Metropolitan Area (2.2 million inhabitants), which includes San José (the capital), and those near hydroelectrical and geothermal plants. In 2020, those institutions operated a network of. 59 seismic stations on volcanoes, 5 infrasound stations, 25 permanent GPS sites, 2 permanent DOAS, 3 permanent MultiGAS, 13 webcams, and performed systematic analyses in geochemistry and petrology laboratories. Those institutes routinely communicate results with the authorities in charge of crisis management nationally and internationally (Comisión Nacional de Prevención de Riesgos y Atención de Emergencias and Volcanic Ash Advisory Centre, respectively) and are always looking for more scientific collaborations. Costa Rica alberga diez complejos volcánicos y presenta una elevada actividad sísmica debido a su ubicación dentro de un marco tectónico complejo, donde interactúan las placas del Cocos, Nazca, Caribe y la microplaca de Panamá. Tres de los cinco volcanes históricamente activos han tenido frecuentes erupciones durante el 2019. Los institutos que vigilan los volcanes de Costa Rica son el Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORIUNA) y la Red Sismológica Nacional (RSN: UCR-ICE que agrupa a la Escuela Centroamericana de Geología de la Universidad de Costa Rica y al Observatorio Sismológico y Vulcanológico del Arenal y Miravalles del Instituto Costarricense de Electricidad, acrónimos en orden: ECG, UCR, OSIVAM e ICE). Estos institutos se enfocan principalmente en los volcanes que representan un alto riesgo para la capital San José y la Gran Área Metropolitana, en el centro de Costa Rica (2.2 millones de habitantes), y aquellos cerca de centrales hidroeléctricas y geotérmicas. La vigilancia se apoya en una red de 59 estaciones sísmicas, 5 medidores de infrasonido, 25 sitios GPS permanentes, 2 DOAS, 3 MultiGAS permanentes, 13 cámaras web y análisis sistemático de muestras en los laboratorios de geoquímica y petrología. Estas instituciones comunican sus resultados de forma rutinaria a las autoridades a cargo de la gestión de peligros nacionales e internacionales (Comisión Nacional de Prevención de Riegos y Atención de Emergencias y Volcanic Ash Advisory Centre, respectivamente), y permanecen en la búsqueda permanente de colaboraciones científicas.

Monitoring volcanoes in Mexico

Mexico has at least 46 volcanic centers (including monogenetic volcanic fields) that are considered active or potentially active. Due to the federal governance of the country, the Centro Nacional de Prevención de Desastres (CENAPRED) is the entity responsible for monitoring natural hazards. Individual Mexican states also monitor active volcanoes within their territoryand through local universities. Specific observatories exist for Colima, Citlaltépetl (Pico de Orizaba), San Martín Tuxtla, El Chichón, and Tacaná volcanoes, which are considered among the volcanoes with the highest hazard potential in the country. Details on instrumentation, data acquisition, hazard management, information dissemination and outreach are given for each volcano and observatory. The creation of a National Volcanological Service, based at CENAPRED and in full cooperation with local university-based observatories, would help consolidate all monitoring data and official information on active volcanoes at a single institution, procure and distribute resources, and allocate those resources according to the relative risk posed by the different volcanoes. México tiene al menos 46 centros volcánicos que podrían considerarse activos o potencialmente activos (incluyendo campos volcánicos monogenéticos). Debido al carácter federal del país, el Centro Nacional de Prevención de Desastres (CENAPRED) es la entidad responsable de monitorear los fenómenos naturales. Individualmente, algunos estados mexicanos también monitorean los volcanes activos dentro de su territorio, a través de las universidades locales, por lo que existen observatorios específicos para Colima, Citlaltépetl (Pico de Orizaba), San Martín Tuxtla, El Chichón y Tacaná; todos estos considerados entre los volcanes de mayor riesgo relativo del país. Se proporcionan detalles sobre instrumentación, adquisición de datos, gestión de riesgos y difusión y divulgación de información para cada volcán y observatorio. La creación de un Servicio Vulcanológico Nacional, con sede en CENAPRED, y en cooperación plena con los observatorios universitarios locales, ayudaría a concentrar todos los datos de monitoreo e información oficial sobre los volcanes activos en una sola institución, así como a adquirir y asignar recursos, de acuerdo con el riesgo relativo que representan los diferentes volcanes.

Active volcanism in Colombia and the role of the Servicio Geológico Colombiano

The Servicio Geológico Colombiano (SGC) was created in 1916 and has been dedicated to the research and monitoring of active volcanoes in the country since the disaster resulting from the eruption of Nevado del Ruíz Volcano in 1985, where more than 25000 people died due to lahars. Today the SGC has three Volcanological and Seismological Observatories in the cities of Manizales (SGC-OVSM), Popayán (SGC-OVSPop), and Pasto (SGC-OVSP), from where 23 active volcanoes are monitored. The three observatories manage an instrumental network of about 740 stations (permanent and portable) as well as signal repeaters, and cover the disciplines of seismology, geodesy, geochemistry, and potential field, amongst others. Volcanic hazard assessment is also carried out by the SGC, producing hazard maps and reports. These tasks are complemented by programs for promoting geoscience knowledge transfer to the public, developed through different strategies. Although at this time, data derived from volcanic monitoring are not available online, the SGC is analysing this need, for implementation in the near future. El Servicio Geológico Colombiano (SGC) fue creado en 1916, y se ha dedicado a la investigación y monitoreo de los volcanes activos en el país desde el desastre resultante de la erupción del volcán Nevado del Ruíz en 1985, donde más de 25000 personas murieron debido a la ocurrencia de lahares. Hoy en día, el SGC tiene tres Observatorios Vulcanológicos y Sismológicos en las ciudades de Manizales (SGC-OVSM), Popayán (SGC-OVSPop) y Pasto (SGC-OVSP), desde donde se monitorean 23 volcanes activos. Los tres observatorios manejan una red instrumental de aproximadamente 740 estaciones (permanentes y portátiles), como también repetidoras de señal, y cubren las disciplinas de sismología, geodesia, geoquímica y campos de potencial, entre otras. La evaluación de la amenaza volcánica también es realizada por el SGC, produciendo mapas e informes. Estas tareas se complementan con programas para promover transferencia de conocimientos geocientíficos al público, desarrollados a través de diferentes estrategias. Aunque en este momento los datos derivados del monitoreo volcánico no están disponibles en línea, el SGC está analizando esta necesidad para su implementación en un futuro cercano.