DSpace Community:
http://hdl.handle.net/2122/270
2014-12-19T09:22:32ZA first look at the Gargano (southern Italy) seismicity as seen by the local scale OTRIONS seismic network
http://hdl.handle.net/2122/9174
Title: A first look at the Gargano (southern Italy) seismicity as seen by the local scale OTRIONS seismic network
Authors: De Lorenzo, S.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari; Romeo, A.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari; Falco, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Michele, M.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari; Tallarico, A.; Università di Bari "Aldo Moro", Dipartimento di Scienze della Terra e Geoambientali, Bari
Abstract: On April 2013, a local scale seismic network, named OTRIONS, composed of twelve short period (1 Hz) three component seismometers, has been located in the northern part of the Apulia (southern Italy). In the first two months of data acquisition, the network recorded about one hundred very small (ML<2) magnitude earthquakes. A three-layer 1D VP velocity model was preliminarily computed, using the recordings of earthquakes occurred in the area in the period 2006-2012 and recorded by the national seismic network of INGV (Istituto Nazionale di Geofisica e Vulcanologia). This model was calibrated by means of a multi-scale approach, based on a global search of the minimum misfit between observed and theoretical travel times. At each step of the inversion, a grid-search technique was implemented to infer the elastic properties of the layers, by using HYPO71 to compute the forward models. In a further step, we used P and S travel times of both INGV and OTRIONS events to infer a minimum 1D VP velocity model, using a classical linearized inversion approach. Owing to the relatively small number of data and poor coverage of the area, in the inversion procedure, the VP/VS ratio was fixed to 1.82, as inferred from a modified Wadati diagram. The final 1D velocity model was obtained by averaging the inversion results arising from nine different initial velocity models. The inferred VP velocity model shows a gradual increase of P wave velocity with increasing the depth. The model is well constrained by data until to a depth of about 25-30 km.2014-06-30T22:00:00ZRay theory formulation and ray tracing method. Application in ionospheric propagation
http://hdl.handle.net/2122/9139
Title: Ray theory formulation and ray tracing method. Application in ionospheric propagation
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, S.; Dipartimento di Fisica, Università “Sapienza”, p.le Aldo Moro 2, 00185 Roma, Italia
Abstract: This work will lead to ray theory and ray tracing formulation. To deal with this problem the theory of classical geometrical optics is presented, and applications to ionospheric propagation will be described. This provides useful theoretical basis for scientists involved in research on radio propagation in inhomogeneous anisotropic media, especially in a magneto-plasma. Application in high frequencies (HF) radio propagation, radio communication, over-the-horizon-radar (OTHR) coordinate registration and related homing techniques for direction finding of HF wave, all rely on ray tracing computational algorithm. In this theory the formulation of the canonical, or Hamiltonian, equations related to the ray, which allow calculating the wave direction of propagation in a continuous, inhomogeneous and anisotropic medium with minor gradient, will be dealt. At least six Hamilton’s equations will be written both in Cartesian and spherical coordinates in the simplest way. These will be achieved by introducing the refractive surface index equations and the ray surface equations in an appropriate free-dimensional space. By the combination of these equations even the Fermat’s principle will be derived to give more generality to the formulation of ray theory. It will be shown that the canonical equations are dependent on a constant quantity H and the Cartesian coordinates and components of wave vector along the ray path. These quantities respectively indicated as ri(τ), pi(τ) are dependent on the parameter τ, that must increase monotonically along the path. Effectively, the procedure described above is the ray tracing formulation. In ray tracing computational techniques, the most convenient Hamiltonian describing the medium can be adopted, and the simplest way to choose properly H will be discussed. Finally, a system of equations, which can be numerically solved, is generated.2014-10-22T22:00:00ZThe calculation of ionospheric absorption with modern computers
http://hdl.handle.net/2122/9104
Title: The calculation of ionospheric absorption with modern computers
Authors: Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: New outcomes are proposed for ionospheric absorption starting from the Appleton-Hartree formula, in its complete form. The range of applicability is discussed for the approximate formulae, which are usually employed in the calculation of non-deviative absorption coefficient. These results were achieved by performing a more refined approximation that is valid under quasi-longitudinal (QL) propagation conditions. The more refined QL approximation and the usually employed non-deviative absorption are compared with that derived from a complete formulation. Their expressions, nothing complicated, can usefully be implemented in a software program running on modern computers. Moreover, the importance of considering Booker’s rule is highlighted. A radio link of ground range D = 1000 km was also simulated using ray tracing for a sample daytime ionosphere. Finally, some estimations of the integrated absorption for the radio link considered are provided for different frequencies.2014-10-14T22:00:00ZScientific review on the ionospheric absorption and research prospects of a Complex Eikonal model for one-layer ionosphere
http://hdl.handle.net/2122/9071
Title: Scientific review on the ionospheric absorption and research prospects of a Complex Eikonal model for one-layer ionosphere
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Ippolito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Thepresent paper conducts a scientific review on ionospheric absorption, extrapolating the research prospects of a complex eikonal
model for one-layer ionosphere. As regards the scientific review, here a quasi-longitudinal (QL) approximation for nondeviative
absorption is deduced which is more refined than the corresponding equation reported by Davies (1990). As regards the research
prospects, a complex eikonal model for one-layer ionosphere is analyzed in depth here, already discussed by Settimi et al. (2013). A
simple formula is deduced for a simplified problem. A flat, layered ionospheric medium is considered, without any horizontal
gradient. The authors prove that the QL nondeviative amplitude absorption according to the complex eikonal model is more
accurate than Rawer’s theory (1976) in the range of middle critical frequencies.2014-08-05T22:00:00ZUnusual nighttime impulsive foF2 enhancements at low latitudes: Phenomenology and possible explanations
http://hdl.handle.net/2122/9046
Title: Unusual nighttime impulsive foF2 enhancements at low latitudes: Phenomenology and possible explanations
Authors: Perna, L.; Dipartimento di Fisica, Universita` di Roma “La Sapienza”; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fagundes, P. R.; Universidade do Vale do Paraı´ba, 12244-000 Sa˜o Jose´ dos Campos, Brazil; de Jesus, R.; Universidade do Vale do Paraı´ba, 12244-000 Sa˜o Jose´ dos Campos, Brazil; Cabrera, M. A.; Laboratorio de Ionosfera, Departamento de Fısica, FACET, Universidad Nacional de Tucumán, 4000 Tucumán, Argentina; Ezquer, R. G.; Laboratorio de Ionosfera, Departamento de Fısica, FACET, Universidad Nacional de Tucumán, 4000 Tucumán, Argentina
Abstract: This paper is focused on unusual nighttime impulsive electron density enhancements that are rarely observed at low latitudes on a
wide region of South America, under quiet and medium/high geomagnetic conditions. The phenomenon under investigation is very peculiar because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. The phenomenon was studied and analyzed using both the F2 layer critical frequency (foF2) and the virtual height of the base of the F region (h'F) values recorded at five ionospheric stations widely distributed in space, namely: Jicamarca (-12.0°, -76.8°, magnetic latitude -2.0°), Peru; Sao Luis (-2.6°, -44.2°, magnetic latitude +6.2°), Cachoeira Paulista (-22.4°, -44.6°, magnetic latitude -13.4°), and Sao Jose´ dos Campos (-23.2°, -45.9°, magnetic latitude -14.1°), Brazil; Tucumán (-26.9°, -65.4°, magnetic latitude -16.8°), Argentina. In a more
restricted region over Tucumán, the phenomenon was also investigated by the total electron content (TEC) maps computed by using measurements from 12 GPS receivers. A detailed analysis of isoheight ionosonde plots suggests that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could play a significant role in causing the phenomenon both for quiet and for medium/high geomagnetic activity; in the latter case however a recharging of the fountain effect, due to electric fields penetrating from the
magnetosphere, joins the TID propagation and plays an as much significant role in causing impulsive electron density enhancements.2014-07-31T22:00:00ZImplementazione di un sistema di monitoraggio sismico dell’area garganica
http://hdl.handle.net/2122/9041
Title: Implementazione di un sistema di monitoraggio sismico dell’area garganica
Authors: Falco, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Michele, M.; Università di Bari Aldo Moro2014-06-25T22:00:00ZSeismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy) Earthquake of August 16, 2010
http://hdl.handle.net/2122/9028
Title: Seismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy) Earthquake of August 16, 2010
Authors: Gambino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Laudani, A.; Dipartimento di Ingegneria, Università di Roma Tre, Via V. Volterra 62, 00146 Roma, Italy; Mangiagli, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia
Abstract: We investigated the seismicity patterns associated with an earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics.2014-01-07T23:00:00ZAsh plume properties retrieved from infrared images: a forward and inverse modeling approach
http://hdl.handle.net/2122/8989
Title: Ash plume properties retrieved from infrared images: a forward and inverse modeling approach
Authors: Cerminara, M.; Scuola Normale Superiore, Pisa (Italy); Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Valade, S.; Università di Firenze, Dip.to di Scienze della Terra (Italy); Harris, A. J. L.; Université Blaise-Pascal, Clermont-Ferrand (FR)
Abstract: We present a coupled fluid-dynamic and electromagnetic model for volcanic ash plumes.
In a forward approach, the model is able to simulate the plume dynamics from prescribed input flow conditions and generate the corresponding synthetic thermal infrared (TIR) image, allowing a comparison with field-based observations. An inversion procedure is then developed to retrieve ash plume properties from TIR images.
The adopted fluid-dynamic model is based on a one-dimensional, stationary description of a self-similar (top-hat) turbulent plume, for which an asymptotic analytical solution is obtained.
The electromagnetic emission/absorption model is based on the Schwarzschild's equation and on Mie's theory for disperse particles, assuming that particles are coarser than the radiation wavelength and neglecting scattering.
In the inversion procedure, model parameters space is sampled to find the optimal set of input conditions which minimizes the difference between the experimental and the synthetic image.
Two complementary methods are discussed: the first is based on a fully two-dimensional fit of the TIR image, while the second only inverts axial data.
Due to the top-hat assumption (which overestimates density and temperature at the plume margins), the one-dimensional fit results to be more accurate. However, it cannot be used to estimate the average plume opening angle. Therefore, the entrainment coefficient can only be derived from the two-dimensional fit.
Application of the inversion procedure to an ash plume at Santiaguito volcano (Guatemala) has
allowed us to retrieve the main plume input parameters, namely the initial radius $b_0$, velocity
$U_0$, temperature $T_0$, gas mass ratio $n_0$, entrainment coefficient $k$ and their related
uncertainty. Moreover, coupling with the electromagnetic model, we have been able to
obtain a reliable estimate of the equivalent Sauter diameter $d_s$ of the total particle size
distribution.
The presented method is general and, in principle, can be applied to the spatial distribution of
particle concentration and temperature obtained by any fluid-dynamic model, either integral or
multidimensional, stationary or time-dependent, single or multiphase.
The method discussed here is fast and robust, thus indicating potential for applications to
real-time estimation of ash mass flux and particle size distribution, which is crucial for
model-based forecasts of the volcanic ash dispersal process.2013-12-31T23:00:00ZLa nuova infrastruttura di acquisizione e distribuzione dati della Rete Integrata Nazionale GPS (RING)
http://hdl.handle.net/2122/8972
Title: La nuova infrastruttura di acquisizione e distribuzione dati della Rete Integrata Nazionale GPS (RING)
Authors: Falco, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cecere, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; D'Ambrosio, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia2014-03-24T23:00:00ZGPSView: monitoraggio in tempo reale delle stazioni GPS acquisite tramite Nanometrics Libra VSAT
http://hdl.handle.net/2122/8971
Title: GPSView: monitoraggio in tempo reale delle stazioni GPS acquisite tramite Nanometrics Libra VSAT
Authors: Falco, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia2014-03-19T23:00:00Z