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41.
Jan Lindsay Warner Marzocchi Gill Jolly Robert Constantinescu Jacopo Selva Laura Sandri 《Bulletin of Volcanology》2010,72(2):185-204
The Auckland Volcanic Field (AVF) is a young basaltic field that lies beneath the urban area of Auckland, New Zealand’s largest
city. Over the past 250,000 years the AVF has produced at least 49 basaltic centers; the last eruption was only 600 years
ago. In recognition of the high risk associated with a possible future eruption in Auckland, the New Zealand government ran
Exercise Ruaumoko in March 2008, a test of New Zealand’s nation-wide preparedness for responding to a major disaster resulting from a volcanic
eruption in Auckland City. The exercise scenario was developed in secret, and covered the period of precursory activity up
until the eruption. During Exercise Ruaumoko we adapted a recently developed statistical code for eruption forecasting, namely
BET_EF (Bayesian Event Tree for Eruption Forecasting), to independently track the unrest evolution and to forecast the most
likely onset time, location and style of the initial phase of the simulated eruption. The code was set up before the start
of the exercise by entering reliable information on the past history of the AVF as well as the monitoring signals expected
in the event of magmatic unrest and an impending eruption. The average probabilities calculated by BET_EF during Exercise
Ruaumoko corresponded well to the probabilities subjectively (and independently) estimated by the advising scientists (differences
of few percentage units), and provided a sound forecast of the timing (before the event, the eruption probability reached
90%) and location of the eruption. This application of BET_EF to a volcanic field that has experienced no historical activity
and for which otherwise limited prior information is available shows its versatility and potential usefulness as a tool to
aid decision-making for a wide range of volcano types. Our near real-time application of BET_EF during Exercise Ruaumoko highlighted
its potential to clarify and possibly optimize decision-making procedures in a future AVF eruption crisis, and as a rational
starting point for discussions in a scientific advisory group. It also stimulated valuable scientific discussion around how
a future AVF eruption might progress, and highlighted areas of future volcanological research that would reduce epistemic
uncertainties through the development of better input models. 相似文献
42.
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. 相似文献
43.
Bayesian event tree for eruption forecasting (BET_EF) at Vesuvius,Italy: a retrospective forward application to the 1631 eruption 总被引：1，自引：0，他引：1
Laura Sandri Emanuela Guidoboni Warner Marzocchi Jacopo Selva 《Bulletin of Volcanology》2009,71(7):729-745
Reliable forecasting of the next eruption at Vesuvius is the main scientific factor in defining effective strategies to reduce
volcanic risk in one of the most dangerous volcanic areas of the world. In this paper, we apply a recently developed probabilistic
code for eruption forecasting to new and independent historical data related to the pre-eruptive phase of the 1631 eruption.
The results obtained point out three main issues: (1) the importance of “cold” historical data (according to Guidoboni 2008) related to pre-eruptive phases for evaluating forecasting tools and possibly refining them; (2) the BET_EF code implemented
for Vesuvius would have forecasted the 1631 eruption satisfactorily, marking different stages of the pre-eruptive phase; (3)
the code shows that pre-eruptive signals that significantly increase the probability of eruption were likely detected more
than 2 months before the event. 相似文献
44.
J. Aguzzi J. Sanchez-Pardo J.A. García F. Sard 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1894-1905
Few studies have been conducted to quantify and understand the role of melatonin in invertebrates, and particularly in crustaceans and in deep-sea animals. In this study, we examined day–night differences in haemolymph melatonin of the burrowing decapod crustacean Nephrops norvegicus (L.) during exposure to cycles of monochromatic blue light (480 nm) and darkness cycles of 10 and 0.1 lx. These differential intensity conditions simulate illumination at the depth of the shelf (80–100 m) and of the slope (300–400 m), where these lobster populations are chiefly found in the Western Mediterranean Sea. Our objectives were: (a) to verify the presence of melatonin in the haemolymph of this species using liquid chromatography/tandem mass spectrometry (LC–MS/MS) and fluorescence HPLC (HPLC); and (b) to study the relationship between diel variations in melatonin concentration and locomotor rhythms, in order to examine whether the former influences behaviour. Melatonin was identified in LC–MS/MS by Q1 and Q3 mass peaks at an elution time of 3.7 min, and it was also detected by HPLC. Melatonin concentration was found to be two orders of magnitude higher at 10 lx (4.8±5.3 ng ml−1) than at 0.1 lx (0.06±0.03 ng ml−1). Also, the increase at daytime in 10 lx was absent in 0.1 lx. When the locomotor rhythm of animals exposed to both photoperiod regimes was compared, the diel periodicity was found to be preserved, but the timing of activity shifted from night to day. Extrapolating these data to the field, we interpret our results to mean that locomotor activity preserves its diel character, but not its phase and amplitude, in a bathymetric range where haemolymph melatonin reduces its concentration and rhythmic fluctuation. 相似文献
45.
Hydrogeology Journal - This study aims to determine the groundwater flow in a large area of the Venice (northeast Italy) lagoon that is under great anthropogenic pressure, which is influencing the... 相似文献
46.
Fragility curves (FCs) constitute an emerging tool for the seismic risk assessment of all elements at risk. They express the probability of a structure being damaged beyond a specific damage state for a given seismic input motion parameter, incorporating the most important sources of uncertainties, that is, seismic demand, capacity and definition of damage states. Nevertheless, the implementation of FCs in loss/risk assessments introduces other important sources of uncertainty, related to the usually limited knowledge about the elements at risk (e.g., inventory, typology). In this paper, within a Bayesian framework, it is developed a general methodology to combine into a single model (Bayesian combined model, BCM) the information provided by multiple FC models, weighting them according to their credibility/applicability, and independent past data. This combination enables to efficiently capture inter-model variability (IMV) and to propagate it into risk/loss assessments, allowing the treatment of a large spectrum of vulnerability-related uncertainties, usually neglected. As case study, FCs for shallow tunnels in alluvial deposits, when subjected to transversal seismic loading, are developed with two conventional procedures, based on a quasi-static numerical approach. Noteworthy, loss/risk assessments resulting from such conventional methods show significant unexpected differences. Conventional fragilities are then combined in a Bayesian framework, in which also probability values are treated as random variables, characterized by their probability density functions. The results show that BCM efficiently projects the whole variability of input models into risk/loss estimations. This demonstrates that BCM is a suitable framework to treat IMV in vulnerability assessments, in a straightforward and explicit manner. 相似文献
47.
Frequency‐dependent multi‐offset phase analysis of surface waves: an example of high‐resolution characterization of a riparian aquifer 
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下载免费PDF全文 Giulio Vignoli Isabella Gervasio Giuseppe Brancatelli Jacopo Boaga Bruno Della Vedova Giorgio Cassiani 《Geophysical Prospecting》2016,64(1):102-111
Multi‐offset phase analysis of seismic surface waves is an established technique for the extraction of dispersion curves with high spatial resolution and, consequently, for the investigation of the subsurface in terms of shear wave velocity distribution. However, field applications are rarely documented in the published literature. In this paper, we discuss an implementation of the multi‐offset phase analysis consisting of the estimation of the Rayleigh wave velocity by means of a moving window with a frequency‐dependent length. This allows maximizing the lateral resolution at high frequencies while warranting stability at the lower frequencies. In this way, we can retrieve the shallow lateral variability with high accuracy and, at the same time, obtain a robust surface‐wave velocity measurement at depth. In this paper, we apply this methodology to a dataset collected for hydrogeophysical purposes and compare the inversion results with those obtained by using refraction seismics and electrical resistivity tomography. The surface‐wave results are in good agreement with those provided by the other methods and demonstrate a superior capability in retrieving both lateral and vertical velocity variations, including inversions. Our results are further corroborated by the lithological information from a borehole drilled on the acquisition line. The availability of multi‐offset phase analysis data also allows disentangling a fairly complex interpretation of the other geophysical results. 相似文献
48.
Uncertainty forecast from 3-D super-ensemble multi-model combination: validation and calibration 总被引：1，自引：1，他引：0
Measurements collected during the Recognized Environmental Picture 2010 experiment (REP10) in the Ligurian Sea are used to
evaluate 3-D super-ensemble (3DSE) 72-hour temperature predictions and their associated uncertainty. The 3DSE reduces the
total Root-Mean-Square Difference by 12 and 32% respectively with reference to the ensemble mean and the most accurate of
the models when comparing to regularly distributed surface temperature data. When validating against irregularly distributed
in situ observations, the 3DSE, ensemble mean and most accurate model lead to similar scores. The 3DSE temperature uncertainty
estimate is obtained from the product of a posteriori model weight error covariances by an operator containing model forecast
values. This uncertainty prediction is evaluated using a criterion based on the 2.5th and 97.5th percentiles of the error
distribution. The 3DSE error is found to be on average underestimated during the forecast period, reflecting (i) the influence
of ocean dynamics and (ii) inaccuracies in the a priori weight error correlations. A calibration of the theoretical 3DSE uncertainty
is proposed for the REP10 scenario, based on a time-evolving amplification coefficient applied to the a posteriori weight
error covariance matrix. This calibration allows the end-user to be confident that, on average, the true ocean state lies
in the −2/+2 3DSE uncertainty range in 95% of the cases. 相似文献
49.
50.
Daniele Andronico Antonio Cristaldi Paola Del Carlo Jacopo Taddeucci 《Journal of Volcanology and Geothermal Research》2009,180(2-4):110
The 2002–03 flank eruption of Etna was characterized by two months of explosive activity that produced copious ash fallout, constituting a major source of hazard and damage over all eastern Sicily. Most of the tephra were erupted from vents at 2750 and 2800 m elevation on the S flank of the volcano, where different eruptive styles alternated. The dominant style of explosive activity consisted of discrete to pulsing magma jets mounted by wide ash plumes, which we refer to as ash-rich jets and plumes. Similarly, ash-rich explosive activity was also briefly observed during the 2001 flank eruption of Etna, but is otherwise fairly uncommon in the recent history of Etna. Here, we describe the features of the 2002–03 explosive activity and compare it with the 2001 eruption in order to characterize ash-rich jets and plumes and their transition with other eruptive styles, including Strombolian and ash explosions, mainly through chemical, componentry and morphology investigations of erupted ash. Past models explain the transition between different styles of basaltic explosive activity only in terms of flow conditions of gas and liquid. Our findings suggest that the abundant presence of a solid phase (microlites) may also control vent degassing and consequent magma fragmentation and eruptive style. In fact, in contrast with the Strombolian or Hawaiian microlite-poor, fluidal, sideromelane clasts, ash-rich jets and plumes produce crystal-rich tachylite clasts with evidence of brittle fragmentation, suggesting that high groundmass crystallinity of the very top part of the magma column may reduce bubble movement while increasing fragmentation efficiency. 相似文献