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Newhall, Chris
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- PublicationOpen AccessSearching for patterns in caldera unrestThe ultimate goal of volcanology is forecasting eruptions. This task is particularly challenging at calderas, where unrest is frequent, affects wider areas and its evidence is often masked by the activity of hydrothermal systems. A recent study has compiled a database on caldera unrest, derived from seismicity, geodetic, gravity, and geochemical monitoring data at calderas worldwide, from 1988 to 2014. Here we exploit this database, searching for the most recurring features of unrest and, in turn, its possible dynamics. In particular, we focus on (a) the duration of unrest at calderas; (b) recurring patterns in unrest; (c) unrest episodes culminating in eruptions, including time-predictability or size-predictability and a multivariate regression analysis. Our analysis indicates that preeruptive unrest is shorter than noneruptive unrest, partic- ularly with open or semiplugged calderas, calderas with mafic or mixed composition of past eruptive prod- ucts, or unrest driven by mafic magma; conversely, lack of data on preeruptive unrest driven by felsic magma and/or at felsic or plugged calderas prevents an analysis of these specific subsets. In addition, 72% of preeruptive unrest lasts <10 months and shows high seismicity and degassing. The remaining 28% (a) is essentially aseismic in calderas with open-conduit (17%), or (b) lasts between 10 and 18 months, with seis- micity and degassing, constituting a longer-duration tail of the preeruptive unrest with seismicity and degassing (11%). Surface deformation is not always reliable to characterize preeruptive unrest. Our analysis suggests that magma may withstand only a limited period of ‘‘eruptability,’’ before becoming stored in the upper crust.
202 34 - PublicationRestrictedThe scientific management of volcanic crises(2012)
; ; ; ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Newhall, C.; Earth Observatory of Singapore ;Woo, G.; Risk Management Solutions; ; Sound scientific management of volcanic crises is the primary tool to reduce significantly volcanic risk in the short-term. At present, a wide variety of qualitative or semi-quantitative strategies is adopted, and there is not yet a commonly accepted quantitative and general strategy. Pre-eruptive processes are extremely com- plicated, with many degrees of freedom nonlinearly coupled, and poorly known, so scientists must quantify eruption forecasts through the use of probabilities. On the other hand, this also forces decision-makers to make decisions under uncertainty. We review the present state of the art in this field in order to identify the main gaps of the existing procedures. Then, we put forward a general quantitative procedure that may overcome the present barriers, providing guidelines on how probabilities may be used to take rational miti- gation actions. These procedures constitute a crucial link between science and society; they can be used to establish objective and transparent decision-making protocols and also clarify the role and responsibility of each partner involved in managing a crisis.131 17 - PublicationOpen AccessVolcano observatory best practices (VOBP) workshops - a summary of findings and best-practice recommendations(2019)
; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ;We summarize major findings and best-practice recommendations from three Volcano Observatory Best Practices (VOBP) workshops, which were held in 2011, 2013 and 2016. The workshops brought together representatives from the majority of the world’s volcano observatories for the purpose of sharing information on the operation and practice of these institutions and making best practice recommendations. The first workshop focused on eruption forecasting, the second on hazard communication, and the third on long-term hazard assessment. Subsequent VOBP workshops will address additional issues of broad interest to the international volcano observatory community. The objective of VOBP is to develop synergy among volcano hazards programs and their observatories internationally, so as to more rapidly and broadly advance the field of applied volcanology. Each of the workshop summaries presented here include best practice recommendations for consideration by the world’s volcano observatories.251 19 - PublicationRestrictedQuantifying probabilities of volcanic events: The example of volcanic hazard at Mount Vesuvius(2004)
; ; ; ; ; ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Sandri, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Gasparini, P.; Dipartimento di Fisica, Universita di Napoli ‘‘Federico II,’’ Naples, Italy. ;Newhall, C.; U.S. Geological Survey, University of Washington, Seattle, Washington, USA ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; ; ; ; We describe an event tree scheme to quantitatively estimate both long- and short-term volcanic hazard. The procedure is based on a Bayesian approach that produces a probability estimation of any possible event in which we are interested and can make use of all available information including theoretical models, historical and geological data, and monitoring observations. The main steps in the procedure are (1) to estimate an a priori probability distribution based upon theoretical knowledge, (2) to modify that using past data, and (3) to modify it further using current monitoring data. The scheme allows epistemic and aleatoric uncertainties to be dealt with in a formal way, through estimation of probability distributions at each node of the event tree. We then describe an application of the method to the case of Mount Vesuvius. Although the primary intent of the example is to illustrate the methodology, one result of this application merits special mention. The present emergency response plan for Mount Vesuvius is referenced to a maximum expected event (MEE), the largest out of all the possible eruptions within the next few decades. Our calculation suggest that there is a nonnegligible (1 – 20%) chance that the next eruption could be larger than that stipulated in the present MEE. The methodology allows all assumptions and thresholds to be clearly identified and provides a rational means for their revision if new data or information are obtained.189 21 - PublicationRestrictedProbabilistic Volcanic Hazard and Risk Assessment(2007)
; ; ; ; ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Newhall, C.; U.S. Geological Survey ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; No abstract154 631