Giordano Teza - Academia.edu (original) (raw)

Papers by Giordano Teza

Journal of Surveying Engineering, 2016

Lubrication by friction-induced melts has been proposed as a mechanism for fault weakening during... more Lubrication by friction-induced melts has been proposed as a mechanism for fault weakening during earthquakes. Field evidence for melt lubrication of the fault surfaces is lacking, however, although the andesitic/basaltic composition (i.e. low-viscosity melts) of the matrix of many tectonic pseudotachylytes (solidified friction-induced melts) suggests low dynamic shear strength during coseismic slip. The Gole Larghe Fault Zone is an exhumed

A representative characterization of a rock instability phenomenon is a fundamental task in the u... more A representative characterization of a rock instability phenomenon is a fundamental task in the understanding of its evolution and the forecasting of possible further slope failure. The first step towards a complete study of the unstable slope consists in its detailed geometrical, geomechanical and kinematical characterization in order to generate a high resolution 3D digital model of the investigated area,

Journal of Computing in Civil Engineering, 2013

ABSTRACT Thermal images mosaicking, registration, and analysis (THIMRAN) is a new MATLAB toolbox ... more ABSTRACT Thermal images mosaicking, registration, and analysis (THIMRAN) is a new MATLAB toolbox proposed for processing data provided by infrared thermography (IRT). The toolbox is able to perform a contactless recognition of damage of a large body like a masonry/concrete wall or a rock cliff, leading to useful information for health state evaluation and/or hazard assessment. In an IRT measurement session, a series of thermal images are acquired throughout one or more heating/cooling diurnal cycles. The proposed approach relies on evaluation of the time history of the thermal contrast related to one or more thermal transients. This is an extension to large bodies of a method currently used in laboratory nondestructive testing. The toolbox contains all the necessary functions for a complete IRT-based evaluation of a large body: (1) preliminary image processing (mosaicking, or stitching, and registration); (2) computation of thermal contrast for each image; and (3) damage recognition by means of pixel-by-pixel comparison of thermal images registered into the same reference frame. The toolbox is available as Supplemental Data of this paper. THIMRAN was applied to two case studies, i.e., a leaning bell tower and a rock cliff, which are also described. (C) 2014 American Society of Civil Engineers.

… Assembly 2009, held …, 2009

Annals of Geophysics, 2008

The results of an experiment carried out with the aim to investigate the role of surface irregula... more The results of an experiment carried out with the aim to investigate the role of surface irregularities on the intensity data provided by a terrestrial laser scanner (TLS) survey are reported here. Depending on surface roughness, the interaction between an ...

Atti della 8a Conferenza …, 2004

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... E-mail: {giordano.teza, antonio.galgaro}@unipd.it (**) Dipartimento di Elettronica e Telecomu... more ... E-mail: {giordano.teza, antonio.galgaro}@unipd.it (**) Dipartimento di Elettronica e Telecomunicazioni, Università degli Studi di Firenze, Via S. Marta, 3, 50139 Firenze (***) Dipartimento di ... luogo alla riflessione (figura 1). L'insieme dei dati di uscita è la nuvola di punti )),,( ...

Data Revues 12962074 Unassign S129620741200177x, Nov 27, 2012

Annals of geophysics = Annali di geofisica

The availability of a GPS network of 10-20 km mean size, provides good topographical support for ... more The availability of a GPS network of 10-20 km mean size, provides good topographical support for the measurement of ground displacements, even at a local scale such as a landslide. In particular, a series of multitemporal kinematic or rapid-static GPS acquisitions of a landslide allows a good characterization of its displacements if the measurements are referred to a GPS reference network. Nevertheless, a wider network formed by stations located at long distances, for example at several tens of kilometers, characterized by large spacing, can lead to results affected by high noise, degrading the accuracy of final point positions. In order to obtain an adequate GPS reference network, some virtual reference stations (VRSs) can be introduced, even if a network refinement based on VRS cannot reach the same accuracy of a real local network. Some experiments, including measurements on a real landslide, have been performed in order to evaluate the performance of this technique. The results ...

ABSTRACT Pseudotachylytes are solidified friction-induced melts recording a seismic rupture and m... more ABSTRACT Pseudotachylytes are solidified friction-induced melts recording a seismic rupture and made of survivor clasts suspended in a glassy-like matrix . The pseudotachylyte microstructure enables to estimate several earthquake source parameters (e.g. seismic energy budget at a point of a fault). However, these estimates require the discrimination among pre-seismic, co-seismic and post-seismic microstructures. Modeling the thermal evolution of the frictional melt might help in understanding the formation and preservation of pseudotachylytes microstructures. A 3-D model for the thermal evolution of friction melt layers and of survivor clasts within the melt is proposed here. The model is based on Finite Element commercial code COMSOL Multiphysics™. The model boundary conditions are based on a pseudotachylyte belonging to the Gole Larghe Fault Zone in the granitic Adamello batholith, Italy, and which has been previously used to estimate the earthquake surface energy from the internal fragmentation observed in plagioclase survivor clasts . In our model, we have considered clasts with different composition (quartz and plagioclase), size (from 0.1 to 2.0 mm), position within the melt layer and initial temperature (250, 850 and 1000°C). The pseudotachylytes vein is 6 mm thick, and the initial melt temperature is in the range of 1450 and 1750°C. Results show that the cooling rate of clasts suspended in the frictional melt strongly depends on the position of the clast within the vein. For example, the core of a plagioclase clast with initial temperature of 850°C, immersed in a 1750°C melt, never reaches complete melting (i) at the vein center, in the case of a radius larger than 1.5 mm, and (ii) at the vein margin, whatever its size. In particular, clast portions closer to the contact with the wall rock never undergo melting. As a consequence, the plagioclase clast internal fragmentation, referable to the initial stages of coseismic slip, can be potentially preserved from melting, allowing the estimate of the surface energy and thus the estimate of the local energy budget of an earthquake.

$Research paper thumbnail of Rockfall precursor detection based on rock fracturing monitoring by means of optical fibre sensors$

International Journal of Sustainable Materials and Structural Systems, 2013

The monitoring of the acoustic emissions (AEs) due to rock fracturing allows the detection of the... more The monitoring of the acoustic emissions (AEs) due to rock fracturing allows the detection of the rockfall precursor signals, leading to a strong improvement of the real time assessment of the induced risk. A network of piezoelectric sensors (PZTs) provides reliable AE data, as testified by a series of applications in non-destructive testing, but PZTs are strongly affected by lightings and electromagnetic interference. In order to avoid such PZT drawbacks and limitations and therefore to allow the rock fracturing monitoring in unstable slopes, two FOS architectures (referred to as fibre coil sensor and ferrule top cantilever) have been recently proposed in previous works from the same authors. In this paper, the two sensors are tested in a more realistic scenario, by monitoring AE in a rock block in which crack is induced by highly expansive mortar; complementary activities, mainly aimed at the recognition of the type of expected signals and optimisation of the sensor array in the framework of the monitoring system, are also described here.

Natural Hazards, 2014

Rock cliff monitoring to evaluate related rockfall hazard requires a deep knowledge of the geomet... more Rock cliff monitoring to evaluate related rockfall hazard requires a deep knowledge of the geometry and kinematics of the rock mass and a real-time survey of some key features. If a sedimentary rock system has sloping discontinuity planes, an open joint could become a potential sliding surface and its conditions must be monitored. It is the case of the Passo della Morte landslide (Carnic Alps, Northeastern Italy), where sub-vertical joints exist. Remote sensing techniques such as terrestrial laser scanning (TLS) and infrared thermography (IRT) allow a fast and efficient contactless geometrical and geomechanical examination of a rock mass. Therefore, they can be used to recognize those joints that require monitoring with on-site instrumentation such as extensometers and/or inclinometers, or also acoustic emission sensors, aiding the arrangement of monitoring systems which are generally quite expensive to install. Repeated IRT surveys would provide useful information about the evolution of unstable slopes, thus suggesting how the on-site monitoring system could be improved. Moreover, data gathered by TLS and IRT can be directly used in landslide hazard assessment. In the test site, an open joint was recognized together with a fair joint that could change in the next future. The results were validated by means of extensometer data.

Environmental Earth Sciences, 2014

Determining the suitability of a local area at a regional or local scale for the geothermal appli... more Determining the suitability of a local area at a regional or local scale for the geothermal application of low enthalpy systems requires the knowledge of rock thermal conductivity values to evaluate the possibility of low-enthalpy heat exchange. A digital cartographic tool is also needed to synthesize the thermal properties of the underground. This tool should be easily accessible and upgradeable and thus suitable for territorial planning and environmental control. In order to address these key issues, a methodological approach was developed within the framework of the national VIGOR Project, dedicated to evaluating the geothermal potential in southern Italy. In this paper the region of Calabria was selected as a case study. Around 70 samples that were representative of the main geological formations were collected from all over the area. Thermal property tests were carried out both in dry and wet conditions, using a thermal device in accordance with the modified transient plane source method. The thermal conductivity values were then compared with data from the international literature. In order to consider the influence of the entire stratigraphic sequence on the thermal conductivity parameters, a geostatistical analysis of the available lithostratigraphic data was performed using the MATLAB toolbox Modalstrata, specially developed for this purpose. A comprehensive geothermal subsurface characterization of Calabria was thus obtained.

Journal of Cultural Heritage, 2014

ABSTRACT A seismic sequence that included a moment magnitude MW=5.9MW=5.9 earthquake struck three... more ABSTRACT A seismic sequence that included a moment magnitude MW=5.9MW=5.9 earthquake struck three regions of Northern Italy (Emilia Romagna, Veneto and Lombardy) in May–June 2012. The sequence caused significant damage to several historical buildings and in some cases caused complete structural collapse. Cracks appeared in the belfry and cusp of the 69 m high, ∼3° leaning bell tower of Ficarolo (Rovigo). A project aimed at studying the geometry of the tower, possible local seismic amplification and soil-structure interaction began in early 2013 before the earthquake. The data were provided by terrestrial laser scanning, low-cost operational modal analysis and geophysical measurements. The repetition of the surveys during and after the seismic sequence, which was augmented by thermal imaging measurements, allowed an evaluation of the changes caused by the earthquake. In addition to an evaluation of the damage, the data allowed the development of a method based on fast and relatively low-cost measurements that provide useful information for cultural heritage management purposes. The results highlighted that the surveys can be carried out during a seismic emergency and that preventive measures can be carried out under reasonable time and budget constraints in high seismic hazard areas.

Tectonophysics, 2005

Tectonic pseudotachylytes might be used to constrain earthquake source parameters, such as dynami... more Tectonic pseudotachylytes might be used to constrain earthquake source parameters, such as dynamic shear stress resistance, average dynamic friction and slip-weakening distance. Estimation of dynamic shear stress resistance and dynamic friction from field studies is based on the assumption that the volume of melt produced during coseismic slip is proportional to the frictional work converted to heat on the fault surface. Conditions conducive to a realistic estimate of dynamic shear resistance are: (i) the presence of large outcrop exposures that allow for estimation of the volume of pseudotachylyte; (ii) the presence of structural markers offset by faults in order to relate the displacement accommodated by the fault with the volume of melt produced; (iii) data that provide an estimate of the initial melt temperature; and (iv) determination of host-rock temperature and pressure conditions that may have existed during seismic faulting. An independent indication that steady-state friction in the presence of melts might be achieved during coseismic slip arises from the dependence of the fractal dimension of the fault profile (intersection of the fault surface with the outcrop surface) with displacement. This relation could also indicate the slipweakening distance (Hirose, T., Shimamoto, T., 2003. Fractal dimension of molten surfaces as a possible parameter to infer the slip-weakening distance of faults from natural pseudotachylytes. Journal of Structural Geology 25, 1569-1574).

Landslides, 2013

On October 12th, 2007 about 40,000m 3 of dolomitic rock detached from the northern wall of the pe... more On October 12th, 2007 about 40,000m 3 of dolomitic rock detached from the northern wall of the peak known as "Cima Una" (Val Fiscalina, Sesto Dolomites, Bolzano, Italy), and fell 900m to Fiscalina Valley below. The event generated a dense dust cloud, which traveled up to 4km from the source area. The failure surface was formed by two near-vertical surfaces, almost perpendicular to each other. The orientation of these surfaces is consistent with two of the main regional tectonic sets. Only a small portion of the fallen material appeared to be preserved as blocks deposited at the base of the rock wall. About a fifth of the fallen mass was deposited on a colluvial cone. The missing mass, estimated to be about 80%, may be represented by highly fragmented rock in part deposited as sand on the valley floor and in part dispersed as a dense dust cloud generated during the rockfall. There appears to be a deficit of deposited material, which could lead underestimation in the calculation of rock-cliff recession rates. The dynamics of the rockfall, strongly conditioned by the local topography, partially explains the intense rock breakage and the generation of the dust cloud. The rockfall was not caused by an external trigger, such as an earthquake or heavy rainfall; the failure was most likely progressive due to mechanical and physical degradation along highly stressed failure surfaces, possibly promoted by permafrost degradation and freeze and thaw processes.

Journal of Cultural Heritage, 2013

ABSTRACT The romanesque-byzantine style, 1000 year old leaning bell tower of Caorle (Venice Provi... more ABSTRACT The romanesque-byzantine style, 1000 year old leaning bell tower of Caorle (Venice Province, Italy) is a unique masonry structure, characterized by single and double lancet windows harmonically distributed on a cylinder-shaped shaft surmounted by a conic cusp. A terrestrial laser scanning (TLS) survey was carried out in 2011 and some analyses were performed on the resulting point cloud to provide the following: bell tower leaning angle, wall inclination/tapering and radius, local deviation from circular shape, and local curvature. Emphasis was placed on the changes of these quantities with elevation. In order to perform these analyses, a MATLAB/Octave toolbox was developed and is available as supplementary material of this paper. In this way, a reliable picture of the current geometry of the bell tower was obtained. In particular, a correlation between leaning angle (average value 1.4° towards East-South-East) and some surface deformations and damage (bulges, brick displacements or also material loss) was found. These results are useful for cultural heritage preservation purposes. © 2012.