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41.
Jacopo Belfi Nicolò Beverini Filippo Bosi Giorgio Carelli Angela Di Virgilio Dmitri Kolker Enrico Maccioni Antonello Ortolan Roberto Passaquieti Fabio Stefani 《Journal of Seismology》2012,16(4):757-766
The ring laser gyroscope ??G-Pisa?? has been taking data inside the Virgo interferometer central area with the aim of performing high sensitivity measurements of rotations in the vertical as well as in the horizontal orientation. We discuss the main characteristics of the instrument, describing its mechanical design and presenting the measured sensitivity limit. By applying a simple effective model for the laser gyroscope, we show that the stability of the sensor above 10?s of integration time is mainly limited by backscattering effects. The horizontal rotation rate signal is also compared with the signals recorded by the Virgo environmental monitoring system and by a biaxial mechanical tiltmeter rigidly fixed on top of the gyrolaser mounting frame. 相似文献
42.
Raffaele?GrassoEmail author Marco?Cococcioni Baptiste?Mourre Jacopo?Chiggiato Michel?Rixen 《Ocean Dynamics》2012,62(3):469-493
The aim of this work is to report on an activity carried out during the 2010 Recognized Environmental Picture experiment,
held in the Ligurian Sea during summer 2010. The activity was the first at-sea test of the recently developed decision support
system (DSS) for operation planning, which had previously been tested in an artificial experiment. The DSS assesses the impact
of both environmental conditions (meteorological and oceanographic) and non-environmental conditions (such as traffic density
maps) on people and assets involved in the operation and helps in deciding a course of action that allows safer operation.
More precisely, the environmental variables (such as wind speed, current speed and significant wave height) taken as input
by the DSS are the ones forecasted by a super-ensemble model, which fuses the forecasts provided by multiple forecasting centres.
The uncertainties associated with the DSS’s inputs (generally due to disagreement between forecasts) are propagated through
the DSS’s output by using the unscented transform. In this way, the system is not only able to provide a traffic light map
(run/not run the operation), but also to specify the confidence level associated with each action. This feature was tested on a particular
type of operation with underwater gliders: the glider surfacing for data transmission. It is also shown how the availability
of a glider path prediction tool provides surfacing options along the predicted path. The applicability to different operations
is demonstrated by applying the same system to support diver operations. 相似文献
43.
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
44.
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
45.
FREPPAZ Michele WILLIAMS Mark W. GABRIELI Jacopo GORRA Roberta MANIA Ilaria ASCHER-JENULL Judith EGLI Markus CELI Luisella 《山地科学学报》2021,(6):1521-1536
In the summer of 2003 and 2004, characterized by a rapid glacier retreat, a stony surface covered by well-structured organic-rich mineral debris was observed very close to the Indren glacier terminus(Monte Rosa Massif, NW Italy, 3100 m ASL), on an area covered by the glacier tongue till the year before. The origin and type of this organicrich material were investigated, in order to detect their characteristics, potential sources and fate within the foreland system. The deposits were dated using Carbon-14 and analyzed for the chemical characteristics of the organic component, the elemental composition of the mineral fraction and presence of microbial markers. The material, granular and dark in color, had a total organic carbon(TOC) content ranging between 17.4 ± 0.39 and 28.1 ± 0.63 g kg-1 dry weight(dw), significantly higher than the surrounding glacial till(~ 1.4 g kg-1 dw), although only 0.33% of it was in water soluble form. Microbial carbon(C) and nitrogen(N) accounted for 10.6% and 3.13% of TOC and total N, respectively. Dissolved nitrogen(N), mainly present as ammonium, represented 2.40% of the total N. The low aromatic component and large presence of nitrogen(N)-derived compounds suggested that most of the organic carbon(OC) in these organic-rich mineral deposits was derived from microbial cells, although the high average radiocarbon age of about 2900 years may also point to the contribution of aeolian depositions of anthropogenic or natural origin. Elemental composition and the crustal enrichment factor of trace elements in the mineral fraction of the aggregates corroborated the hypothesis that most part of the accumulated material derived from ice meltwater. Some indicators of the colonization of these deposits by microbial communities were also reported, from the abundance of DNA and phylogenetic markers, to the presence of bacterial taxa commonly able to thrive in similar habitats. All these elements suggested that such kind of deposits may have a potential role as energy and nutrient sources in recently deglaciated areas, highlighting the necessity to better understand the processes underlying their formation and their evolution. 相似文献
46.
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
47.
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
48.
The integrated use of electrical resistivity tomography (ERT) and ground penetrating radar (GPR) measurements, and in particular the joint analysis of 2D and 3D data, can represent a valid solution for target identification at complex archaeological sites. A good example, in this respect, is given by the case study of a Phoenician–Punic necropolis in the archaeological site of Nora, in southern Sardinia (Italy), where GPR and ERT measurements were collected before site excavation. In this specific case, the mix of soil and air in the buried chambers, as well as the orientation and the complex spatial distribution of these structures into the sandstone bedrock, generated a number of anomalies difficult to interpret only using 2D results. Only the integration of all GPR and ERT data in a 3D view, and the comparison with archaeological evidence after the excavation, allowed a solid interpretation of geophysical anomalies visible in the 2D sections. Overall, this case study demonstrates the efficiency of the combined use of GPR and ERT acquisitions and shows how, in general, only the joint analysis of 2D data and in a 3D view can help the interpretation of the real distribution of the buried archaeological remains at similar archaeological complex sites. 相似文献
49.
Frequency‐dependent multi‐offset phase analysis of surface waves: an example of high‐resolution characterization of a riparian aquifer
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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
50.
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