Department of Physics "Edoardo Amaldi"

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Seminars of Earth and Environmental Physics

2008-2009

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Coordinator: Prof. Wolfango Plastino

(for any informations and suggestions please contact:

e-mail plastino@fis.uniroma3.it , phone +39 06 57337277, fax +39 06 57337102)

.You may also browse through our seminars archive

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• Isotopic evidence for transport of water masses from the Pacific to Indian Ocean and their accumulation in the subtropical gyre

          by P. P. Povinec

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Prof. Pavel P. Povinec (Comenius University - Department of Nuclear Physics, Bratislava, Slovakia)

Monday, 15th September 2008, 3:00pm (Aula C, Department of Physics "E. Amaldi")

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Abstract

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The South Indian Ocean has been playing a key role in the exchange of water masses between Equatorial regions and Antarctica, important for better understanding of global oceanic processes and the climate. Radioactive and stable isotopes have been used as tools for tracing water masses in the World Ocean, however, only limited information has been available for the South Indian Ocean. We are tracing anthropogenic ³H, ¹⁴C and ¹²⁹I about four decades after their main injection on the ocean surface, supported by stable isotope tracers of water (δ²H and δ¹⁸O). The observed concentrations in seawater samples collected in the Crozet Basin during the ANTARES IV expedition were surprisingly high, comparable with levels observed in the NW Pacific, evidencing a radionuclide transport from the North Pacific via Indonesian seas to the South Indian Ocean. Further, an accumulation of tracers have been observed in the subtropical gyre of the Indian Ocean, with environmental consequences for the protection of the marine environment from land-based sources of the World Ocean.

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• Climatic Impact of Eruptions

          by R. Scandone

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Prof. Roberto Scandone (University of Roma Tre - Department of Physics, Rome, Italy)

Monday, 6th October 2008, 3:00pm (Aula C, Department of Physics "E. Amaldi")

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Abstract

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Volcanic eruption can disrupt life and environment on a local scale in the range of tens of kilometers because of transport on the ground of eruption products . Air transported particles, and aerosols, dispersed by an eruption plume can instead be transported all over the globe and significantly affect the amount of incident radiation.
Significant climactic effects of violent volcanic eruption have been reported in the recent history and had widespread influence at global scale.
The eruption of Laki, in Iceland, in 1783 caused a volcanic haze all over Europe in the summer of 1783 and caused an extensive famine that is thought to be among the causes of social troubles that affected France.
The eruption of Krakatou in Indonesia, in 1883 caused visible sunlight phenomena all over the world but had a limited climactic impact. On the contrary the more violent eruption of Tambora in the island of Sumbawa in Indonesia in 1815 caused a significant cooling all over the world with loss of crops and famine in North America, Europe and Asia. This on turn caused the spread of typhoid fever in Northern Europe.
A much larger eruption occurred on Toba 75000 years ago and caused a world climatic disruption for a period longer than 50 years.
Should a similar eruption occur in our times, it would cause the decadence of what is called the western civilization.

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• The Kyoto Protocol: why has not it yet failed?

          by G. Scarano

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Prof. Giovanni Scarano (University of Roma Tre - Department of Economics, Rome, Italy)

Thursday, 23rd October 2008, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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The Kyoto Protocol came into force on February 16^th 2005 and today shows the strengths and weaknesses of any international treaty. Before its ultimate success, in fact, many analysts were convinced of the need for a structural failure. Its fortune depends on adequate explanation, in order to avoid inadequate conclusions in the future.
The seminar will attempt to reconstruct the negotiations in order to highlight some contradictions and some turning points that can provide answers to the question in the title, in the light of the conclusions that can be drawn from theoretical models on international negotiations.

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• Plate tectonics: how and why?

          by C. Doglioni

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Prof. Carlo Doglioni (University of Rome "La Sapienza" - Department of Earth Sciences, Rome, Italy)

Thursday, 27th November 2008, 4:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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The Earth is a lively planet in which internal convection continuously stratifies the planet, sinking the heavier elements and upraising the lighter ones. The growth of the inner core, and the mantle degassing feeding the atmosphere, are two effects of this ongoing mechanism that allows life on Earth. Plate tectonics is part of the convective system. We have good evidences on how lithospheric plates move relative to each other. However it is still not clear what is driving them. The presently most accepted theory invokes the negative buoyancy of the slabs in moving the lithosphere, but there are plates moving even without any attached subduction zone. Moreover, the required slab pull is greater than the strength the lithosphere can sustain under extension. Therefore the slab pull is very unlikely the only engine of plate tectonics. A number of geological and geophysical signatures rather supports the contribution of the Earth's rotation both in terms of direction and energy in controlling geodynamics.

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• The geophysical monitoring of the explosive volcanic activity

          by M. Ripepe

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Dr Maurizio Ripepe (University of Florence - Department of Earth Sciences, Florence, Italy)

Thursday, 11th December 2008, 3:00pm (Aula C, Department of Physics "E. Amaldi")

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Abstract

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Dynamics of the explosive volcanisms is one of the most and best investigated volcanic phenomena. These data show that, although eruptions can be roughly grouped into two characteristic styles, activity shows significant short-term variability in many of the monitored geophysical parameters.
Explosive activity of Stromboli is commonly explained in terms of the dynamics of large gas slugs that ascend the magma conduit to burst at the free surface. This simple physical model has now strong evidence from both geophysical and geochemical point of view. In recent years a large number of geophysical experiments have improved enormously our knowledge of the explosive system. In particular, integration of infrasonic, thermal, seismic and ground deformation data have provided crucial constraints on the shallow system geometry and dynamics.
The main effort of operating an integrated geophysical network is to easily and quickly cross-checking the multi-parametric information relative to both internal (seismicity and deformations) and external (infrasound and thermal) volcanic processes in order to simplify data interpretation and to provide a reliable image of ongoing eruptions.

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• Stochastic models of earthquake clustering

          by R. Console

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Dr Rodolfo Console (National Institute of Geophysics and Volcanology, Rome, Italy)

Thursday, 22nd January 2009, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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A large quantity of studies carried out in the past on the field of earthquake prediction have not leaded to a general agreement about their validity. In this context, there has recently been among scientists an increased interest in the issue of statistical validation of earthquake forecasting models. In this respect, a commonly accepted rule is that the construction of an earthquake forecasting model should necessarily follow all of the following four steps:
- Formulation of the idea upon which the hypothesis (theory, model) should be based, generally on the basis of retrospective phenomenological observations;
- Set up of the hypothesis in quantitative form, through the definition of the necessary parameters achievable from the retrospective analysis (learning phase).
- Test of the hypothesis on a data set independent of the data set used in the learning phase, possibly obtained after such a phase.
- Application of the methodology to real cases
Among the many statistical methods applied to test forecasting models, the likelihood criterion is one of those that have gained most popularity. As an example of time-dependent earthquake forecast hypotheses let’s consider the so called Epidemic Type Aftershock Sequence (ETAS) model that has become very popular in the last decade. In this model every event is potentially triggered by all the previous events and every event can trigger subsequent events according to their relative time-space distance. Consequently, a definition of the words foreshock, mainshock and aftershock is not necessary. The ETAS model is mainly based on the following assumptions:
- The magnitude distribution is the same for all the earthquakes (Gutenberg-Richter law);
- The occurrence rate density is the superposition of a time independent (poissonian) component and the triggered seismic activity;
- The time independent, spatially variable component is obtained from the catalog of the past seismicity through a smoothing procedure;
- The occurrence rate of triggered events depends exponentially on the magnitude of every preceding event;
- The spatial distribution of triggered events is described by an isotropic function around the epicenter of every previous event, decaying with distance;
- The temporal behavior of triggered events is described by the Omori law starting from the occurrence time of every previous event,
The application to the seismic activity recorded in Central Apennines (Italy) during a seismic sequence shows how the ETAS model can fit both the spatial and the temporal features of the observed seismicity both.
The algorithm described in this presentation is being used for test purposes in a real-time application in the National Observation Center of the Italian seismicity, and has to be implemented in one or more of the testing Centers of Collaboratory for the Study of the Earthquake Predictability (CSEP).

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• Physical constraints for models of earthquake clustering

          by R. Console

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Dr Rodolfo Console (National Institute of Geophysics and Volcanology, Rome, Italy)

Thursday, 29th January 2009, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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In the last decade, several statistical models for both short-term and long-term earthquake occurrence have been developed and tested, proving a fairly good performance in earthquake forecasting. In particular, a number of studies have considered the ETAS model, for short-term earthquake clustering, and the BPT distribution, among the long-term renewal models. However, statistical models, describing the behavior of large sets of earthquake, fail in forecasting with high reliability the behavior of a single earthquake source.
On the other hand, in the recent years, studies about earthquake mechanics and laboratory experiments on the friction constitutive laws of faults have increased our knowledge of the earthquake nucleation process. Nevertheless, these physical studies allow only simulations of earthquake source behavior, and have never proved predictive capability in real cases.
It is hopeful that the integration of physical and statistical approaches, that up to now have been studied by different groups of seismologists, can improve our ability of describing the earthquake process with the aim of a better predictive capability. The stress interaction among seismic sources is taken as an example of physical modeling of the earthquake process. This modeling requires two distinct ingredients: (a) the computation of the co-seismic Coulomb stress change produced by slip on a fault, on other faults that can potentially generate subsequent earthquakes; and (b) the Dieterich (1994) rate-and-state constitutive law, as a possible physical justification of the Omori law describing typical aftershock decay.
First, this presentation considers the Dieterich’s rate-and-state model as a component that can be included in the ETAS model for the time decay of the triggered events, allowing a substantial reduction of the number of free parameters needed in the purely statistical model. Lastly, an example of a full physically based model of short-term earthquake interaction with only one free parameter, based on the computation Coulomb stress change, is considered.
The application of both these models is made on the series of moderate seismic events occurred in the Central Apennines (Italy) in 1997.

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• Gyrolasers and G-Pisa

          by A. Di Virgilio

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Dr Angela Di Virgilio (National Institute of Nuclear Physics, Pisa, Italy)

Wednesday, 4th February 2009, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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Gyrolasers, lasers with a ring cavity where two modes propagate in opposite directions, are inertial device, sensitive to angular rotation, based on the Sagnac effect. Ring laser with area larger than 1 m² used in Earth Physics and Geodesy achieve the sensitivity level of 10^-12 rad/s. The basic principles and experimental problems of such device are described. G-Pisa is an experiment financed by the INFN Commission V which is investigating the feasibility of gyrolaser with area below 1 m². Gyrolasers can be used to reduce the low frequency large motion of the test masses of the third generation gravitational wave interferometric antennas and could be a powerful tool for Solid Earth Physics investigations.
G-Pisa has been assembled in July 2008, the first results are presented and discussed.

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• Ground-based radar remote sensing of explosive volcanic ash eruptions: numerical models and quantitative applications

          by F. S. Marzano

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Prof. Frank Silvio Marzano (University of Rome "La Sapienza" - Department of Electronic Engineering, Rome, Italy)

Wednesday, 18th February 2009, 3:30pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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The explosive eruptions of active volcanoes with a consequent formation of ash clouds represent a severe threat in several regions of the urbanized world. During a Plinian or a sub-Plinian eruption the injection of large amounts of fine and coarse rock fragments and corrosive gases into the troposphere and lower stratosphere is usually followed by a long lasting ashfall which can cause a variety of damages. Volcanic ash clouds are an increasing hazard to aviation safety because of growing air traffic volumes that use more efficient and susceptible jet engines. Real-time and areal monitoring of a volcano eruption, in terms of its intensity and dynamics, is not always possible by conventional visual inspections, especially during worse visibility periods which are quite common during eruption activity. Remote sensing techniques both from ground and from space represent unique tools to be exploited. In this respect, microwave weather radars can gather three-dimensional information of atmospheric scattering volumes up several hundreds of kilometers, in all weather conditions, at a fairly high spatial resolution (less than a kilometer) and with a repetition cycle of few minutes. Ground-based radar systems represent one of the best methods for determining the height and volume of volcanic eruption clouds. Single-polarization Doppler radars can measure horizontally-polarized power echo and Doppler shift from which ash content and radial velocity can be, in principle, extracted. In spite of these potentials, there are still several open issues about microwave weather radar capabilities to detect and quantitatively retrieve ash cloud parameters. A major issue is related to the aggregation of volcanic ash particles within the eruption column of explosive eruptions which has been observed at many volcanoes. It influences the residence time of ash in the atmosphere and the radiative properties of the “umbrella” cloud. Numerical experiments are helpful to explore processes occurring in the eruption column. In this study we use the plume model ATHAM (Active Tracer High Resolution Atmospheric Model) to investigate, in both time and space, processes leading to particle aggregation in the eruption column. In this work a set of numerical simulations of radar reflectivity is performed with the ATHAM model, under the same experimental conditions except for the initial size distribution, i.e. varying the radii of average mass of the two particle dimension modes. A sensitivity analysis is carried out to evaluate the possible impact of aggregate particles on microwave radar reflectivity. It is shown how dimension, composition, temperature and mass concentration are the main characteristics of eruptive cloud particles that contribute to determine different radar reflectivity responses. In order to evaluate Rayleigh scattering approximation accuracy, the ATHAM simulations of radar reflectivity are used to compare in a detailed way the Mie and Rayleigh scattering regimes at S-, C- and X-band. The relationship between radar reflectivity factor and ash concentration has been statistically derived for the various particle classes by applying a new radar reflectivity microphysical model, which was developed starting from results of numerical experiments performed with plume model ATHAM. The ash retrieval physical-statistical algorithm is based on the backscattering microphysical model of volcanic cloud particles, used within a Bayesian classification and optimal regression algorithm. In order to illustrate the potential of this microwave active remote sensing technique, the case study of the eruption of Augustine volcano in Alaska in January 2006 is described. This event was the first time that a significant volcanic eruption was observed within the nominal range of a WSR-88D. The radar data, in conjunction with pilot reports, proved to be crucial in analyzing the height and movement of volcanic ash clouds during and immediately following each eruptive event. This data greatly aided National Weather Service meteorologists in the issuance of timely and accurate warning and advisory products to aviation, public, and marine interests. An application of the retrieval technique has been shown, taking into consideration the eruption of the Augustine volcano. Volume scan data from the NEXRAD WSR-88D S-band radar, which are located 190 km from the volcano vent, are processed to identify and estimate the particles concentration in an automatic fashion. The evolution of the Augustine Vulcanian eruption is discussed in terms of radar measurements products, pointing out the unique features, the current limitations and future improvements of radar remote sensing of volcanic plumes.

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• Primary and secondary processes at local and meso-scales causing the atmospheric pollution in urban areas

          by P. Ciccioli

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Dr Paolo Ciccioli (National Research Council - Institute of Chemical Methodologies, Rome, Italy)

Tuesday, 7th April 2009, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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Starting from the indices used to define the quality of the atmosphere in the tropospheric compartment, main processes occurring at local and meso scale determining the levels of primary and secondary pollutants in air will be presented. The main chemical mechanisms leading to the formation of secondary pollutants through the depletion of primary emitted product will be summarized and discussed, focussing on products formed by photochemical reactions. Conditions controlling the formation of the various secondary pollutants, including ozone, in urban, suburban, rural and remote areas will be analyzed, together with the main physical parameters determining the levels of pollutants in air. Precursors responsible for the formation of secondary particles and procedures used to distinguish them from those emitted from man-made processes will be presented. The link between the oxidation potential of the atmosphere and acid rain will be presented. Rome will be used as a paradigmatic case to show how primary and secondary pollution affect the air quality in an urban area. The possible options available to decision-makers to reduce pollution will be analysed and critically discussed. The importance of an integrated approach to reduce and/or mitigate the impact of atmospheric pollution on the population will be also discussed.

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• Determinism and stochasticity in the occurrence of large earthquakes

          by W. Marzocchi

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Dr Warner Marzocchi (National Institute of Geophysics and Volcanology, Rome, Italy)

Monday, 11th May 2009, 3:00pm (Aula C, Department of Physics "E. Amaldi")

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Abstract

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The occurrence of a large earthquake is the result of a complex combination of different (geo)physical processes in the Earth's lithosphere. Besides the intrinsic scientific interest, the comprehension of such processes has also a practical importance, being the primary ingredient for building reliable earthquake forecasting models and for planning sound risk mitigation actions. Nonetheless, we are still far from a satisfactory and comprehensive understanding of the earthquake occurrence process. This is one of the main reasons that stand behind the use of different, if not antithetical, models in earthquake prediction/forecasting.
From a physical point of view, many issues of earthquake occurrence process are still open. What is the role of determinism in earthquake occurrence?
Why are earthquakes not predictable in a deterministic sense? Is the apparent randomness an intrinsic feature of the process? Or is it due to our limited physical knowledge of the earthquake generating process?
In general, how do determinism and stochasticity play together in modeling earthquake occurrences?
In this talk we explore all of these issues through the comparison of the features observed in real earthquake catalogs at different time- space-magnitude scales, and the results of stochastic/deterministic mathematical models of earthquake occurrences.

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• Electrical geophysical exploration for environmental risk assessment: characterisation and monitoring of landfill sites

          by R. Di Maio

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Prof. Rosa Di Maio (University of Naples "Federico II" - Department of Earth Sciences, Naples, Italy)

Thursday, 21st May 2009, 3:00pm (Aula G, Department of Physics "E. Amaldi")

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Abstract

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The geophysical prospecting methods are able to reconstruct detailed physical and geometrical images of hidden volumes from surface measurements. In the last 20 years, they were successfully applied in environmental field, implying the identification of anomalous space variations of physical parameters, attributable to pollution phenomena inside soils and/or aquifers. In particular, the seminar is focused on the application of the electrical geophysical methodologies in the landfill site study. Landfills are amenable to electrical investigations because they usually contain waste material characterised by high electrical conductivities and chargeabilities. Moreover, the relatively high resistivity values characterising the bedrock and, when present, the geo-membranes, allow to delineate the landfill boundaries and, consequently, to outline eventual leachate escapes within the encasing rocks.
A brief scientific and technical description of some electrical geophysical techniques will be provided as well as the methodological justification of their application in the landfill research field. Examples coming from old and/or active landfill sites will be presented and discussed. Finally, some details on monitoring geophysical techniques of areas interested by pollutant fluid infiltrations will be also supplied.

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