Short-term volcanic hazard assessment through Bayesian inference: Retrospective application to the Pinatubo 1991 volcanic crisis

© 2014 . One of the most challenging aspects of managing a volcanic crisis is the interpretation of the monitoring data, so as to anticipate to the evolution of the unrest and implement timely mitigation actions. An unrest episode may include different stages or time intervals of increasing activity that may or may not precede a volcanic eruption, depending on the causes of the unrest (magmatic, geothermal or tectonic). Therefore, one of the main goals in monitoring volcanic unrest is to forecast whether or not such increase of activity will end up with an eruption, and if this is the case, how, when, and where this eruption will take place. As an alternative method to expert elicitation for assessing and merging monitoring data and relevant past information, we present a probabilistic method to transform precursory activity into the probability of experiencing a significant variation by the next time interval (i.e. the next step in the unrest), given its preceding evolution, and by further estimating the probability of the occurrence of a particular eruptive scenario combining monitoring and past data. With the 1991 Pinatubo volcanic crisis as a reference, we have developed such a method to assess short-term volcanic hazard using Bayesian inference.This research has been partially funded by the European Commission (FP7 Theme: ENV.2011.1.3.3-1; Grant 282759: VUELCO) and by the Aon Benfield UCL Hazard Centre. All data and information used to reproduce the results in the case study have been extracted from the public source Punongbayan and Newhall (1996) edited monograph on the Mt Pinatubo eruption.Peer Reviewe

A short review of our current understanding of the development of ring faults during collapse caldera formation

The term collapse caldera refers to those volcanic depressions resulting from the sinking of the chamber roof due to the rapid withdrawal of magma during the course of an eruption. During the last three decades, collapse caldera dynamics has been the focus of attention of numerous, theoretical, numerical, and experimental studies. Nonetheless, even if there is a tendency to go for a general and comprehensive caldera dynamics model, some key aspects remain unclear, controversial or completely unsolved. This is the case of ring fault nucleation points and propagation and dip direction. Since direct information on calderas' deeper structure comes mainly from partially eroded calderas or few witnessed collapses, ring faults layout at depth remains still uncertain. This has generated a strong debate over the detailed internal fault and fracture configuration of a caldera collapse and, in more detail, how ring faults initiate and propagate. We offer here a very short description of the main results obtained by those analog and theoretical/mathematical models applied to the study of collapse caldera formation. We place special attention on those observations related to the nucleation and propagation of the collapse-controlling ring faults. This summary is relevant to understand the current state-of-the-art of this topic and it should be taken under consideration in future works dealing with collapse caldera dynamics.Adelina Geyer is grateful for her Juan de la Cierva post-doctoral grant (JCI-2010-06092) and her Ramón y Cajal contract (RYC-2012-11024).Peer Reviewe

Stress field control during large caldera-forming eruptions

Crustal stress field can have a significant influence on the way magma is channeled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs) can erupt hundreds to thousands of cubic kilometers of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 –1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a shallow magma (3–5km deep) chamber that in turn is fed by a deeper magma reservoir (>∼10 km deep), both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma (>107 Pa s) can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events. © 2016 Costa and Martí.Peer reviewe

Erupciones hidromagmáticas en el volcanismo cuaternario de Olot (Girona)

10 páginas, 9 figuras, 1 tabla.[ES] En el presente trabajo se pone de manifiesto la importancia del volcanismo explosivo en el marco del volcanismo cuaternario de Girona, especialmente en la zona de Olot donde se concentran los episodios más recientes. Se han reconocido catorce edificios volcánicos que presentan alguna fase explosiva freatomagmática o freática durante su evolución. La actividad hidromagmática da lugar a una amplia diversidad de depósitos piroclásticos, cuyo estudio ha permitido distinguir varias secuencias eruptivas entre estos volcanes. Las diferencias en el comportamiento explosivo de unos volcanes a otros son debidas fundamentalmente a las distintas formas de interacción agua/magma en cada volcán, las cuales están determinadas por la estructura geológica de los últimos centenares de metros de la corteza y, especialmente, por las características hidrogeológicos del terreno.[EN] This paper makes clear the importance of the explosive volcanism is the field of the quaternary volcanism of Girona, especially in Olot area where the most recent episodes aare concentrated. Fourteen volcanic cones undergoing some phreatomagmatic or phereatic explosive phases during their evolution have been identified. The hydromagmatic activity gives rise to a wide variety of pyroclastic deposits, whose study has enable to distinguish several eruptive sequences in these volcanoes. The differences of explosive ways of water/magma interaction in each volcano, which are determined by the geogical structure of the last hundreds of metres of the crust and, especially, by the hydrogeological features of the ground.Peer reviewe

A new Volcanic managEment Risk Database desIgn (VERDI): Application to El Hierro Island (Canary Islands)

One of the most important issues in modem volcanology is the assessment of volcanic risk, which will depend - among other factors - on both the quantity and quality of the available data and an optimum storage mechanism. This will require the design of purpose-built databases that take into account data format and availability and afford easy data storage and sharing, and will provide for a more complete risk assessment that combines different analyses but avoids any duplication of information. Data contained in any such database should facilitate spatial and temporal analysis that will (1) produce probabilistic hazard models for future vent opening, (2) simulate volcanic hazards and (3) assess their socio-economic impact. We describe the design of a new spatial database structure, VERDI (Volcanic managEment Risk Database design), which allows different types of data, including geological, volcanological, meteorological, monitoring and socio-economic information, to be manipulated, organized and managed. The root of the question is to ensure that VERDI will serve as a tool for connecting different kinds of data sources, GIS platforms and modeling applications. We present an overview of the database design, its components and the attributes that play an important role in the database model. The potential of the VERDI structure and the possibilities it offers in regard to data organization are here shown through its application on El Hierro (Canary Islands). The VERDI database will provide scientists and decision makers with a useful tool that will assist to conduct volcanic risk assessment and management. (C) 2014 Elsevier B.V. All rights reservedThis research has been partially funded by the European Commission (FP7 Theme: ENV.2011.1.3.3-1; Grant 282759: VUELCO) and the MINECO grant CGL2011-16144-E.Peer Reviewe

Years to weeks of seismic unrest and magmatic intrusions precede monogenetic eruptions

Seismic, deformation, and gas activity (unrest) typically precedes volcanic eruptions. Tracking the changes of this activity with monitoring data makes it increasingly possible to successfully forecast eruptions from stratovolcanoes. However, this is not the case for monogenetic volcanoes. Eruptions from these volcanoes tend to be small but are particularly difficult to anticipate since they occur at unexpected locations and there is very limited instrumental monitoring data. Many monogenetic volcanic fields occur in high-density, populated areas and/or tourist destinations, and thus even a small eruption can have a major economic and societal impact. We have gathered the available instrumental data for unrest and combined it with new historical accounts of seismicity. Our occurrences are mainly from high magmatic flux oceanic islands (Canary Islands, Iceland, Papua New Guinea, Mexico, and Japan). We find that seismic activity may start one or two years before eruption, but it intensifies at approximately two or three months, and one or two weeks. The petrological and geochemical characteristics of the deposits show that multiple magma batches interacted in a subvolcanic reservoir, and multiple intrusions occurred on a similar time scales to the seismicity. We propose a general model for these eruptions where early dike intrusions in the crust do not erupt (e.g., stalled intrusions) and make small plumbing systems, but they probably are key in creating a thermal and rheological pathway for later dikes to be able to reach the surface. These observations provide a conceptual framework for better anticipating monogenetic eruptions in similar settings and magmatic fluxes and should lead to improved strategies for mitigation of their associated hazards and risks.This research was partly supported by the National Research Foundation Singapore, the Singapore Ministry of Education (grant MoE2014-T2-2-041), and the Research Centres of Excellence initiativePeer Reviewe

Probabilistic approach to decision-making under uncertainty during volcanic crises: retrospective application to the El Hierro (Spain) 2011 volcanic crisis

© 2014, The Author(s). Understanding the potential evolution of a volcanic crisis is crucial for designing effective mitigation strategies. This is especially the case for volcanoes close to densely populated regions, where inappropriate decisions may trigger widespread loss of life, economic disruption, and public distress. An outstanding goal for improving the management of volcanic crises, therefore, is to develop objective, real-time methodologies for evaluating how an emergency will develop and how scientists communicate with decision-makers. Here, we present a new model Bayesian Decision Model (BADEMO) that applies a general and flexible, probabilistic approach to managing volcanic crises. The model combines the hazard and risk factors that decision-makers need for a holistic analysis of a volcanic crisis. These factors include eruption scenarios and their probabilities of occurrence, the vulnerability of populations and their activities, and the costs of false alarms and failed forecasts. The model can be implemented before an emergency, to identify actions for reducing the vulnerability of a district; during an emergency, to identify the optimum mitigating actions and how these may change as new information is obtained; and after an emergency, to assess the effectiveness of a mitigating response and, from the results, to improve strategies before another crisis occurs. As illustrated by a retrospective analysis of the 2011 eruption of El Hierro, in the Canary Islands, BADEMO provides the basis for quantifying the uncertainty associated with each recommended action as an emergency evolves and serves as a mechanism for improving communications between scientists and decision-makers.This research has been funded by the European Commission (FP7 Theme: ENV.2011.1.3.3-1; Grant 282759: VUELCO).Peer Reviewe

Volcanic signatures in time gravity variations during the volcanic unrest on El Hierro (Canary Islands)

Gravity changes occurring during the initial stage of the 2011–2012 El Hierro submarine eruption are interpreted in terms of the pre-eruptive signatures during the episode of unrest. Continuous gravity measurements were made at two sites on the island using the relative spring gravimeter LCR gPhone-054. On September 15, 2011, an observed gravity decrease of 45 μGal, associated with the southward migration of seismic epicenters, is consistent with a lateral magma migration occurred beneath the volcanic edifice, an apparently clear precursor of the eruption that took place 25 days later on October 10, 2011. High-frequency gravity signals also appeared on October 6–11, 2011, point to an interaction between a magmatic intrusion and the ocean floor was occurring. These important gravity changes, with amplitudes varying from 10 to −90 μGal, during the first three days following the onset of the eruption are consistent with the northward migration of the eruptive focus along an active eruptive fissure. An apparent correlation of gravity variations with body tide vertical strain was also noted, which could indicate that concurrent tidal triggering occurred during the initial stage of the eruption.Projects CGL2011-25494 and CGL2011-16144-E of the Spanish Ministry of Economy and Competitiveness and European Commission VULMAC-MAC/2.3/A7 (INTERREG) and VUELCO (FT7 Theme: ENV.2011.1.3.3-1; Grant 282759)Peer reviewe

Stress controls of monogenetic volcanism: A review

The factors controlling the preparation of volcanic eruptions in monogenetic fields are still poorly understood. The fact that in monogenetic volcanism each eruption has a different vent suggests that volcanic susceptibility has a high degree of randomness, so that accurate forecasting is subjected to a very high uncertainty. Recent studies on monogenetic volcanism reveal how sensitive magma migration is to the existence of changes in the stress field caused by regional and/or local tectonics or rheological contrasts (stratigraphic discontinuities). These stress variations may induce changes in the pattern of further movements of magma, thus conditioning the location of future eruptions. This implies that a precise knowledge of the stress configuration and distribution of rheological and structural discontinuities at crustal level of such volcanic systems would aid in forecasting monogenetic volcanism. This contribution reviews several basic concepts relative to the stress controls of magma transport into the brittle lithosphere, and uses this information to explain how magma migrates inside monogenetic volcanic systems and how it prepares to trigger a new eruption. © 2016 Martí, López, Bartolini, Becerril and Geyer.This research was funded by the European Commission (FP7 Theme: NV.2011.1.3.3-1; Grant 282759: VUELCO and EC ECHO Grant SI2.695524: VeTOOLS). AG thanks the support provided by the Ramón y Cajal research program (RYC-2012-11024). We thank Gregg Valentine and Alessandro Tibaldi for their useful and constructive reviews.Peer reviewe

Koulutusasteen ja sukulaisella todetun rintasyövän yhteys vaihdevuosien hormonikorvaushoidon käyttöön ja koettuun rintasyöpäriskiin

Rintasyöpä on naisten yleisin syöpä sekä maailmalla että Suomessa. Riski sairastua rintasyöpään jossakin elämänvaiheessa on jokaisella naisella noin 10 %:n luokkaa, perinnöllisen alttiuden kattaessa noin 5-10 % kaikista sairastuneista. Vaihdevuosien hormonikorvaushoidon on osoitettu lisäävän rintasyöpäriskiä ja riskitietoisuuden on todettu vaihtelevan koulutustason mukaan. Myös sukulaisella todetun rintasyövän on tutkitusti todettu vaikuttavan oman syöpäriskin arviointiin ja ohjaavan naisten terveyskäyttäytymistä. Tutkimukseni aineisto kuuluu Syöpäjärjestöjen kyselytutkimukseen Elintavat, elämänlaatu ja terveys. Se on psykososiaalinen kyselytutkimus mammografiaseulonnan elintapa- ja elämänlaatuvaikutuksista. Kyselytutkimus aloitettiin keväällä 2012 yhteistyössä Suomen Syöpärekisterin, UKK-instituutin, Terveyden ja hyvinvoinnin laitoksen sekä Tampereen yliopiston kanssa. Tutkielma perustuu ensimmäisen kierroksen kyselyihin, joita lähetettiin 5000:lle vuonna 2012 49 vuotta täyttävälle naiselle. Lomakkeita palautui yhteensä 2615. Hormonaalisia tekijöitä koskevien kysymysten pohjalta tehtiin tilastollinen analyysi käyttäen menetelmänä ristiintaulukointia ja riippuvuustarkastelussa khiin neliötestiä. Tutkielmassa selvitettiin koulutusasteen ja sukulaisella todetun rintasyövän yhteyttä vaihdevuosien hormonikorvaushoidon käyttöön ja koettuun rintasyöpäriskiin. Tuloksina saatiin, että 49-vuotiaiden naisten hormonikorvausvalmisteiden käyttö on vielä vähäistä, eikä sillä ole tilastollista yhteyttä koulutusasteeseen tai sukulaisella todettuun rintasyöpään. Rintasyöpäriskiä ei koeta yleisesti suureksi, mutta suvussa todettu rintasyöpä ja koulutusaste ovat yhteydessä rintasyöpähuolestuneisuuteen