DSpace Collection:
http://hdl.handle.net/2122/275
2015-10-01T08:20:58ZANNALS OF GEOPHYSICS: AD MAJORA
http://hdl.handle.net/2122/9916
Title: ANNALS OF GEOPHYSICS: AD MAJORA
Authors: Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianco, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caprara, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Chiodetti, A. G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Gresta, S.; Univ Catania
Abstract: Annals of Geophysics (ISSN: 1593-5213; from 2010, 2037-416X) is a bimonthly international journal, which publishes scientific papers in the field of geophysics sensu lato. It derives from Annali di Geofisica (ISSN: 0365-2556), which commenced publication in January 1948 as a quarterly periodical devoted to general geophysics, seismology, Earth magnetism, and atmospheric studies....2013-12-31T23:00:00ZPurported Precursors: Poor Predictors
http://hdl.handle.net/2122/9900
Title: Purported Precursors: Poor Predictors
Authors: Mulargia, F.; Dipartimento di Fisica e Astronomia - Università di Bologna; Gaperini, P.; Dipartimento di Fisica e Astronomia - Università di Bologna; Lolli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Stark, P. B.; Department of Statistics, Code 3860. University of California, Berkeley CA
Abstract: The destructive 2009 L’Aquila and 2012 Emilia Romagna earthquakes led the Italian Dipartimento della Protezione Civile (DPC) to fund nine groups studying seismic precursors. Three of the groups produced testable predictions by the DPC deadline of 31 May 2013, using: (1) Radon in a well in Friuli, (2) temperature, flow, CO2 flux, and other variables measured in wells in Emilia Romagna, and (3) an artificial neural network (ANN) algorithm applied to seismicity. We evaluated the geochemical precursors by comparing their success to that of an equal number of predictions at the same locations and with the same individual and total durations as the actual predictions, but at random times. This approach avoids modeling seismicity and thereby precludes concluding that predictions are “good” simply because the model for seismicity is bad. Neither precursor predicts significantly better than chance. ANN was a poor predictor of events large enough to affect public safety.2014-12-31T23:00:00ZScoring and Testing Procedures Devoted to Probabilistic Seismic Hazard Assessment
http://hdl.handle.net/2122/9871
Title: Scoring and Testing Procedures Devoted to Probabilistic Seismic Hazard Assessment
Authors: Albarello, D.; Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente, Universita` degli Studi di Siena; D’Amico, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia
Abstract: This review addresses long-term (tens of years) seismic ground-motion forecasting
(seismic hazard assessment) in the presence of alternative computational models
(the so-called epistemic uncertainty affecting hazard estimates). We review the different
approaches that have been proposed to manage epistemic uncertainty in the context of
probabilistic seismic hazard assessment (PSHA). Ex-ante procedures (based on the combination
of expert judgments about inherent characteristics of the PSHA model) and expost
approaches (based on empirical comparison of model outcomes and observations)
should not be considered as mutually exclusive alternatives but can be combined in a
coherent Bayesian view. Therefore, we propose a procedure that allows a better exploitation
of available PSHA models to obtain comprehensive estimates, which account for
both epistemic and aleatory uncertainty. We also discuss the respective roles of empirical
ex-post scoring and testing of alternative models concurring in the development of comprehensive
hazard maps. In order to show how the proposed procedure may work, we also
present a tentative application to the Italian area. In particular, four PSHA models are
evaluated ex-post against macroseismic effects actually observed in a large set of Italian
municipalities during the time span 1957–2006. This analysis shows that, when the whole
Italian area is considered, all the models provide estimates that do not agree with the
observations. However, two of them provide results that are compatible with observations,
when a subregion of Italy (Apulia Region) is considered. By focusing on this area, we
computed a comprehensive hazard curve for a single locality in order to show the feasibility
of the proposed procedure.2015-02-28T23:00:00ZVolcanic plume vent conditions retrieved from infrared images: A forward and inverse modeling approach
http://hdl.handle.net/2122/9834
Title: Volcanic plume vent conditions retrieved from infrared images: A forward and inverse modeling approach
Authors: Cerminara, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Valade, S.; Harris, A. J. L.
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 vent conditions from TIR images, and to independently estimate the mass eruption rate.
The adopted fluid-dynamic model is based on a one-dimensional, stationary description of a self-similar turbulent plume, for which an asymptotic analytical solution is obtained. The electromagnetic emission/absorption model is based on Schwarzschild's equation and on Mie's theory for disperse particles, and we assume that particles are coarser than the radiation wavelength (about 10 μm) and that scattering is negligible. In the inversion procedure, model parameter space is sampled to find the optimal set of input conditions which minimizes the difference between the experimental and the synthetic image.
Application of the inversion procedure to an ash plume at Santiaguito (Santa Maria volcano, Guatemala) has allowed us to retrieve the main plume input parameters, namely mass flow rate, initial radius, velocity, temperature, gas mass ratio, entrainment coefficient and their related uncertainty. Moreover, by coupling with the electromagnetic model we have been able to obtain a reliable estimate of the equivalent Sauter diameter 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.2014-12-31T23:00:00ZModeling the dynamics of a geothermal reservoir fed by gravity driven flow through overstanding saturated rocks
http://hdl.handle.net/2122/9781
Title: Modeling the dynamics of a geothermal reservoir fed by gravity driven flow through overstanding saturated rocks
Authors: Cerminara, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Fasano, A.
Abstract: We formulate a mathematical model for a geothermal basin with an idealized geometry characterized by: (1) radial symmetry around an extracting well (or a cluster of wells), (2) a relatively thin horizontal fractured layer lying underneath a low permeability, low porosity rock layer, saturated with water. Vaporization is allowed only at the boundary of the extracting well (or well cluster). The model is based on the assumption that the flow from the reservoir to the well is fed by a gravity driven flow through the overstanding rocks. Despite the various simplifying assumptions, the resulting mathematical problem is considerably difficult also because we consider the effect of thermal expansion and thermal variation of viscosity. Though there is no evidence that the assumed configuration of the basin approaches the structure of a known geothermal field, the results obtained match with surprising accuracy the data of a specific field in the Mt. Amiata area (data kindly provided by ENEL Green Power through Tuscany Region).2012-03-29T22:00:00ZComment on “General Orthogonal Regression Relations between Body-Wave and Moment Magnitudes” by Ranjit Das, H. R. Wason, and M. L. Sharma
http://hdl.handle.net/2122/9550
Title: Comment on “General Orthogonal Regression Relations between Body-Wave and Moment Magnitudes” by Ranjit Das, H. R. Wason, and M. L. Sharma
Authors: Gasperini, P.; Università di Bologna - Dipartimento di Fisica e Astronomia; Lolli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia
Abstract: Das et al. (2013) describe a modification of the general orthogonal regression (GOR) method (Fuller, 1987) applied to the magnitude conversion problem that the same authors have already published at least twice in other journals (Das et al., 2012; Wason et al., 2012). Unfortunately, as more ex- haustively discussed in our comment to Wason et al. (2012), published by the Geophysical Journal International (Gasperini and Lolli, 2014), some assumptions made by the authors are wrong and therefore their method has to be rejected....2014-02-28T23:00:00ZComment on ‘Magnitude conversion problem using general orthogonal regression’ by H. R. Wason, Ranjit Das and M. L. Sharma, (Geophys. J. Int., 190, 1091–1096)
http://hdl.handle.net/2122/9549
Title: Comment on ‘Magnitude conversion problem using general orthogonal regression’ by H. R. Wason, Ranjit Das and M. L. Sharma, (Geophys. J. Int., 190, 1091–1096)
Authors: Gasperini, P.; Università di Bologna - Dipartimento di Fisica e Astronomia; Lolli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia
Abstract: The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.g. Ms or mb) to another (e.g. Mw), using the coefficients computed by the general orthogonal regression method (Fuller) is biased if the observed values of the predictor (independent) variable are used in the equation as well as the methodology they suggest to estimate the supposedly true values of the predictor variable are wrong for a number of theoretical and empirical reasons. Hence, we advise against the use of such methodology for magnitude conversions.2013-12-31T23:00:00ZRecent AEM Case Study Examples of a Full Waveform Time-Domain System for Near-Surface and Groundwater Applications
http://hdl.handle.net/2122/9500
Title: Recent AEM Case Study Examples of a Full Waveform Time-Domain System for Near-Surface and Groundwater Applications
Authors: Legault, J. M.; Geotech Ltd.; Prikhodko, A.; Geotech Ltd.; Eadie, T.; Geotech Ltd.; Kwan, K.; Geotech Ltd.; Oldenborger, G. A.; Geological Survey of Canada; Sapia, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Viezzoli, A.; Aarhus Geophysics Aps; Gloaguen, E.; Institute National Recherche Scientifique; Smith, B. D.; USGS Crustal Geophysics and Geochemistry Center; Best, M. E.; Bemex Consulting International
Abstract: Early time or high frequency airborne electromagnetic data (AEM) are desirable for shallow sounding or mapping of resistive areas but this poses difficulties due to a variety of issues, such as system bandwidth, system calibration and parasitic loop capacitance. In an effort to address this issue, a continued system design strategy, aimed at improving its early-channel VTEM data, has achieved fully calibrated, quantitative measurements closer to the transmitter current turn-off, while maintaining reasonably optimal deep penetration characteristics. The new design implementation, known as “Full Waveform” VTEM was previously described by Legault et al. (2012). This paper presents some case-study examples of a Full Waveform helicopter time-domain EM system for near-surface applications2013-10-31T23:00:00ZIncorporating a-priori information into AEM inversion for geological and hydrogeological mapping of the Spiritwood Valley Aquifer, Manitoba, Canada
http://hdl.handle.net/2122/9479
Title: Incorporating a-priori information into AEM inversion for geological and hydrogeological mapping of the Spiritwood Valley Aquifer, Manitoba, Canada
Authors: Sapia, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Oldenborger, G. A.; Geological Survey of Canada; Viezzoli, A.; Aarhus Geophysics Aps
Abstract: Buried valleys are important hydrogeological structures in Canada and other
glaciated terrains, providing sources of groundwater for drinking, agriculture and industrial
applications. Hydrgeological exploration methods such as pumping tests, boreholes coring or
ground-based geophysical methods (seismic and electrical resistivity tomography) provide limited
spatial information and are inadequate to efficiently predict the sustainability of these aquifers at
the regional scale. Airborne geophysics can be used to significantly improve geological and
hydrogeological knowledge on a regional scale. There has been demonstrated success at using
airborne electromagnetics for mapping and characterization of buried valleys in different geological
contexts (Auken et al., 2008; Jørgensen et al., 2003; Jørgensen et al., 2009; Steuer et al., 2009).
Despite the fact that both electromagnetic surveys and reflection seismic profiling are used
extensively in hydrogeological mapping, integration of the methods is a relatively unexplored
discipline (Høyer et al., 2011).
The Spiritwood Valley is a Canada-USA trans-border buried valley aquifer that runs
approximately NW – SE and extends 500 km from Manitoba, across North Dakota and into South
Dakota (Winter et al., 1984). The Spiritwood aquifer system consists of glacially deposited silt and
clay with sand and gravel bodies, infilling a broad north-south trending valley that has been
identified primarily based on water wells information (Wiecek, 2009). The valley is incised into
bedrock consisting of fractured siliceous shale.
As part of its Groundwater Geoscience Program, the Geological Survey of Canada (GSC) has
been investigating buried valley aquifers in Canada using airborne and ground-based geophysical
techniques. To obtain a regional three-dimensional assessment of complex aquifer geometries for
the Spiritwood, both geophysical and geological investigations were performed with the aim to
develop an integrated conceptual model for a quantitative description of the aquifer system.
In 2010, the Geological Survey of Canada conducted an airborne electromagnetic (AeroTEM
III) survey over a 1062 km2 area along the Spiritwood Valley, north of the US border (Oldenborger
2010a, 2010b). AEM inversion results show multiple resistive valley features inside a wider, more
conductive valley structure within the conductive bedrock (Fig. 1). Furthermore, the complexity of
the geometries, spatial distribution and size of the channels is evident. Other ground based data
collected in the survey area make it possible to provide some constraints on the AEM resistivity
model. Downhole resistivity logs were collected that provide information on the electrical model
relative to the geological layers (Crow et al., 2012). In addition, over 10 line-km of electrical
resistivity data and 42 km of high resolution landstreamer seismic reflection data (Figs. 2a, 2b) were
collected at selected sites (Oldenborger et al., 2012).
In this short paper we present results obtained from the data inversion and an example of
integration of ancillary seismic data into the AEM inversion. In particular, the elevation to a layer
(shale bedrock elevation) as interpreted from seismic is added to the inversion to constrain the
resistivity model.2012-10-31T23:00:00ZLocal geodetic and seismic energy balance for shallow earthquake prediction
http://hdl.handle.net/2122/9453
Title: Local geodetic and seismic energy balance for shallow earthquake prediction
Authors: Cannavò, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Arena, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Monaco, C.; Università degli Studi di Catania
Abstract: Earthquake analysis for prediction purposes is a delicate and still open problem largely debated among scientists. In this work, we want to show that a successful time-predictable model is possible if based on large instrumental data from dense monitoring networks. To this aim, we propose a new simple data-driven and quantitative methodology which takes into account the accumulated geodetic strain and the seismically-released strain to calculate a balance of energies. The proposed index quantifies the state of energy of the selected area and allows us to evaluate better the ingoing potential seismic risk, giving a new tool to read recurrence of small-scale and shallow earthquakes. In spite of its intrinsic simple formulation, the application of the methodology has been successfully simulated in the Eastern flank of Mt. Etna (Italy) by tuning it in the period 2007–2011 and testing it in the period 2012–2013, allowing us to predict, within days, the earthquakes with highest magnitude.2014-12-31T23:00:00Z