654 research outputs found
Near-Real-Time Tephra Fallout Assessment at Mt. Etna, Italy
During explosive eruptions, emergency responders and government agencies need to make fast decisions that should be based on an accurate forecast of tephra dispersal and assessment of the expected impact. Here, we propose a new operational tephra fallout monitoring and forecasting system based on quantitative volcanological observations and modelling. The new system runs at the Istituto Nazionale di GeoïŹsica e Vulcanologia, Osservatorio Etneo (INGV-OE) and is able to provide a reliable hazard assessment to the National Department of Civil Protection (DPC) during explosive eruptions. The new operational system combines data from low-cost calibrated visible cameras and satellite images to estimate the variation of column height with time and model volcanic plume and fallout in near-real-time(NRT). The new system has three main objectives: (i) to determine column height in NRT using multiple sensors (calibrated cameras and satellite images); (ii) to compute isomass and isopleth maps of tephra deposits in NRT; (iii) to help the DPC to best select the eruption scenarios run daily by INGV-OE every three hours. A particular novel feature of the new system is the computation of an isopleth map, which helps to identify the region of sedimentation of large clasts (â„5 cm) that could cause injuries to tourists, hikers, guides, and scientists, as well as damage buildings in the proximity of the summit craters. The proposed system could be easily adapted to other volcano observatories worldwide.Publishedid 29876V. PericolositĂ vulcanica e contributi alla stima del rischioJCR Journa
A Statistical Approach to Evaluate the Tephra Deposit and Ash Concentration from Puff Model Forecasts
In this paper we present a new statistical approach able to provide tephra deposit load and ash concentration
using PUFF, a lagrangian model widely used to forecast volcanic ash dispersal during volcanic crisis. We
perform a parametric study in order to analyze the influence of each input parameter on model outputs. For
this test, we simulate two eruptive scenarios like to the 2001 (Scenario 1) and 1998 (Scenario 2) Etna
eruptions using high resolution weather data and a domain of 170 x 170 km. Results show that for both
scenarios, we are able to calculate the tephra deposit load and ash concentration but the use of millions of
particles is required. Specifically, up to 33 and 220 millions of particles were necessary to accurately
predict the tephra deposit and ash concentration in air, respectively. This is approximately two orders of
magnitude larger than values typically considered running PUFF. The parametric study shows that the
horizontal diffusion coefficient, the time step of the simulations, the topography and the standard deviation
of the particle distribution greatly affect the model outputs. We also validate the model by best fit
procedures. Results show a good comparison between field data of the 2001 Etna eruption and PUFF
simulations, being inside 5 and 1/5 times the observed data, comparable with results of Eulerian models.
This work will allow to reliably outlining the areas of contaminated airspace using PUFF or any other
lagrangian model in order to define the No Fly Zone and ensure the safety to aviation operations as required
after the Eyjafjallajökull eruption
BET_VH: a probabilistic tool for long-term volcanic hazard assessment
In this paper, we illustrate a Bayesian Event Tree to estimate Volcanic Hazard (BET_VH). The procedure enables us to calculate the probability of any kind of long-term hazardous event for which we are interested, accounting for the intrinsic stochastic nature of volcanic eruptions and our limited knowledge regarding related processes. For the input, the code incorporates results from numerical models simulating the impact of hazardous volcanic phenomena on an area and data from the eruptive history. For the output, the code provides a wide and exhaustive set of spatiotemporal probabilities of different events; these probabilities are estimated by means of a Bayesian approach that allows all uncertainties to be properly accounted for. The code is able to deal with many eruptive settings simultaneously, weighting each with its own probability of occurrence. In a companion paper, we give a detailed example of application of this tool to the Campi Flegrei caldera, in order to estimate the hazard from tephra fall. © The Author(s) 2010
The impact of ensemble meteorology on inverse modeling estimates of volcano emissions and ash dispersion forecasts: GrĂmsvötn 2011
Volcanic ash can interact with the earth system on many temporal and spatial scales and is
a significant hazard to aircraft. In the event of a volcanic eruption, fast and robust decisions need to be
made by aviation authorities about which routes are safe to operate. Such decisions take into account
forecasts of ash location issued by Volcanic Ash Advisory Centers (VAACs) which are informed
by simulations from Volcanic Ash Transport and Dispersion (VATD) models. The estimation of the
time-evolving vertical distribution of ash emissions for use in VATD simulations in real time is difficult
which can lead to large uncertainty in these forecasts. This study presents a method for constraining
the ash emission estimates by combining an inversion modeling technique with an ensemble of
meteorological forecasts, resulting in an ensemble of ash emission estimates. These estimates of
ash emissions can be used to produce a robust ash forecast consistent with observations. This new
ensemble approach is applied to the 2011 eruption of the Icelandic volcano GrĂmsvötn. The resulting
emission profiles each have a similar temporal evolution but there are differences in the magnitude
of ash emitted at different heights. For this eruption, the impact of precipitation uncertainty (and the
associated wet deposition of ash) on the estimate of the total amount of ash emitted is larger than
the impact of the uncertainty in the wind fields. Despite the differences that are dominated by
wet deposition uncertainty, the ensemble inversion provides confidence that the reduction of the
unconstrained emissions (a priori), particularly above 4 km, is robust across all members. In this case,
the use of posterior emission profiles greatly reduces the magnitude and extent of the forecast ash
cloud. The ensemble of posterior emission profiles gives a range of ash column loadings much closer
in agreement with a set of independent satellite retrievals in comparison to the a priori emissions.
Furthermore, airspace containing volcanic ash concentrations deemed to be associated with the
highest risk (likelihood of exceeding a high concentration threshold) to aviation are reduced by
over 85%. Such improvements could have large implications in emergency response situations.
Future research will focus on quantifying the impact of uncertainty in precipitation forecasts on
wet deposition in other eruptions and developing an inversion system that makes use of the
state-of-the-art meteorological ensembles which has the potential to be used in an operational setting
A comprehensive volcanic hazard assessment for Mount Meager Volcanic Complex, B.C.
Mount Meager Volcanic Complex located in south-western British Columbia exhibits possible volcanic activity in the form of hydrothermal features such as several hot springs around the base and a fumarole field in the northeast corner of the complex. Operational infrastructure, including a run-of-river hydroelectric project, is present in the vicinity of the volcano and a significant population exists only 60 km downstream. Up until now, no volcanic hazard assessment or accompanying map existed for Mount Meager. Hazard assessments are important tools used to understand, manage and reduce the risks associated with volcanic environments. This thesis investigates the potential primary volcanic hazards associated with a future explosive eruption at Mount Meager. These hazards are identified as lahars, pyroclastic density currents and volcanic ash. With the use of numerical modelling programs, the distribution, timescales, intensity of inundation and other parameters are investigated. Finally, a suite of scenario-based preliminary hazard maps have been produced to visually display these hazards as a communication tool. This information relays hazard information to stakeholders with a vested interest in the potential risks involved with any future explosive volcanic event from Mount Meager
A multi-scale risk assessment for tephra fallout and airborne concentration from multiple Icelandic volcanoes â Part 1: Hazard assessment
This is the final version of the article. Available from EGU via the DOI in this record.In order to assist the elaboration of proactive measures for the management of future volcanic eruptions in Iceland, we developed a new scenario-based approach to assess the hazard associated with tephra dispersal and sedimentation at various scales and for multiple sources. The target volcanoes are Hekla, Katla, Eyjafjallajökull and Askja, selected either for their high probabilities of eruption and/or their high potential impact. By coupling tephrostratigraphic studies, probabilistic techniques and modelling, we developed comprehensive eruption scenarios for both short- and long-lasting eruptions and compiled hazard maps for tephra ground deposition at a national scale and air concentration at a European scale using the TEPHRA2 and FALL3D models, respectively. New algorithms for the identification of realistic sets of eruptive source parameters are investigated, which assist the generation of probability density functions of eruption source parameters for the selected scenarios. Aggregation processes were accounted for using various empirical models. Outcomes, i.e. probabilities conditioned to the occurrence of an eruption, help the assessment and comparison of hazard levels at different scales. For example, at a national scale Askja has a 5â10% probability of blanketing the easternmost half of the country with a tephra accumulation of at least 1 kg mâ2. At a continental scale, Katla has a 5â10% probability of producing ash clouds with concentrations of 2 mg mâ3 over the UK, Scandinavia and northern Europe with a mean arrival time of 48â72 h and a mean persistence time of 6â18 h. In a companion paper, Scaini et al. (2014) present a vulnerability assessment for Iceland to ground deposition of tephra and for the European air traffic to airborne ash which, combined with the outcomes of the present paper, constitute one of the first comprehensive multi-scale risk assessment associated with tephra dispersal and sedimentation.S. Biass is supported by
SNF (#200021-129997) and ESF/MemoVolc (#5193) subsides.
C. Scaini is partly supported by the Spanish Research Project
ATMOST (CGL2009-10244) and by the SNF (IZK0Z2_ 142343)
Volcanic hazard assessment at the Campi Flegrei caldera
Previous and new results from probabilistic approaches based on available
volcanological data from real eruptions of Campi Flegrei, are assembled in a comprehensive
assessment of volcanic hazards at the Campi Flegrei caldera, in order to compare the volcanic
hazards related to the different types of events. Hazard maps based on a very wide set of
numerical simulations, produced using field and laboratory data as input parameters relative
to the whole range of fallout and pyroclastic-flow events and their relative occurrence,
are presented. The results allow us to quantitatively evaluate and compare the hazard
related to pyroclastic fallout and density currents (PDCs) in the Campi Flegrei area and its
surroundings, including the city of Naples.
Due to the dominant wind directions, the hazard from fallout mostly affects the area east of
the caldera, and the caldera itself, with the level of probability and expected thickness decreasing
with distance from the caldera and outside the eastern sectors. The hazard from PDCs
decrease roughly radially with distance from the caldera centre and is strongly controlled by
the topographic relief, which produces an effective barrier to propagation of PDCs to the east
and northeast, areas which include metropolitan Naples. The main result is that the metropolitan
area of Naples would be directly exposed to both fallout and PDCs. Moreover, the
level of probability for critical tephra accumulation by fallout is relatively high, even for
moderate-scale events, while, due to the presence of topographic barriers, the hazard from
PDCs is only moderate and mostly associated with the largest events
Beyond eruptive scenarios: assessing tephra fallout hazard from Neapolitan volcanoes
Assessment of volcanic hazards is necessary for risk mitigation. Typically, hazard assessment is based on one or a few, subjectively chosen representative eruptive scenarios, which use a specific combination
of eruptive sizes and intensities to represent a particular size class of eruption. While such eruptive scenarios use a range of representative members to capture a range of eruptive sizes and intensities in
order to reflect a wider size class, a scenario approach neglects to account for the intrinsic variability of volcanic eruptions, and implicitly assumes that inter-class size variability (i.e. size difference between different eruptive size classes) dominates over intra-class size variability (i.e. size difference within an
eruptive size class), the latter of which is treated as negligible. So far, no quantitative study has been undertaken to verify such an assumption. Here, we adopt a novel Probabilistic Volcanic Hazard Analysis
(PVHA) strategy, which accounts for intrinsic eruptive variabilities, to quantify the tephra fallout hazard in the Campania area. We compare the results of the new probabilistic approach with the classical
scenario approach. The results allow for determining whether a simplified scenario approach can be considered valid, and for quantifying the bias which arises when full variability is not accounted for
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