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Piersanti, Antonio
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Piersanti, Antonio
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antonio.piersanti@ingv.it
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76 results
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- PublicationRestrictedThe effect of global seismicity on the polar motion of a viscoelastic EarthWe evaluate the polar drift of a stratified viscoelastic Earth, generated by 20 years of global seismicity (from the Centroid Moment Tensor catalog, 1977–1997). Our estimate is better than that of Soldati and Spada [1999] because it accounts for the effects, previously neglected, of earthquakes at depths larger than 80 km. In fact, we show that deep focus and intermediate‐depth focus seismic events tend to affect the Earth's inertia tensor more significantly than shallow ones; specifically, we find that the mean rate of polar drift (evaluated over a 6‐year time interval immediately following the seismic event) due to a vertical dip‐slip source at the bottom of the asthenosphere (280 km depth in our model) is 5 times larger than that generated by an analogous source, located at the boundary between lithosphere and asthenosphere (80 km depth). We conclude, nevertheless, that global seismic activity is not able to alter significantly the rotational parameters of the Earth: according to our computations, the changes that it induces in the inertia tensor result in an average polar drift that is still significantly smaller than the observed one.
161 3 - PublicationRestrictedA forward test for interaction between remote earthquakes and volcanic eruptions: the case of Sumatra (June 2000) and Denali (November 2002) earthquakes(2004-09)
; ; ; ; ; ; ;Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Zencher, F.; Alma Mater Studiorum, Universita` di Bologna ;Casarotti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; ; ; ; ; We propose a formal procedure to validate the hypothesis of a causal relationship between great tectonic earthquakes and volcanic eruptions through a forward statistical test. This approach allows such a hypothesis to be evaluated in an objective way, ruling out any possible unconscious overfitting of the past data. The procedure consists of two steps: (a) the computation of the stress perturbation in a volcanic area due to some selected seismic event, by means of a spherical, layered, viscoelastic and self- gravitating earth model; and (b) the application of a statistical test to check the differences in the spatio-temporal distribution of eruptions before and after the earthquake, weighting each eruption with the stress perturbation induced at the volcano at the time of the eruption. Finally, for the sake of example, we apply the method to the case of the recent Engano earthquake in Sumatra (June 2000) and the Denali earthquake in Alaska (November 2002).256 24 - PublicationOpen AccessApplication of the Post-Widder Laplace inversion algorithm to postseismic rebound models(2008-05)
; ; ; ;Spada, Giorgio ;Cannelli, Valentina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Melini, Daniele; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Spada, Giorgio; Istituto di Fisica, Università di Urbino "Carlo Bo" - Urbino, Italy; ; ; Istituto di Fisica, Università di Urbino "Carlo Bo" - Urbino, ItalyThe postseismic response of a viscoelastic Earth can be computed analytically with a normal-mode approach, based on the application of propagator methods. This framework suffers from many limitations, mostly connected with the solution of the secular equation, whose degree scales with the number of viscoelastic layers so that only low-resolution models can be practically solved. Recently, a viable alternative to the normal-mode approach has been proposed, based on the Post-Widder inversion formula. This method allows to overcome some of the intrinsic limitations of the normal-mode approach, so that Earth models with arbitrary radial resolution can be employed and general linear non-Maxwell rheologies can be implemented. In this work, we test the robustness of the method against a standard normal-mode approach in order to optimize computation performance while ensuring the solution stability. As an application, we address the issue of finding the minimum number of layers with distinct elastic properties needed to accurately describe the postseismic relaxation of a realistic Earth model.221 125 - PublicationOpen AccessGrain size and flow volume effects on granular flow mobility in numerical simulations: 3-D discrete element modeling of flows of angular rock fragments.(2015)
; ; ;Cagnoli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; The results of three-dimensional discrete element modeling (DEM) presented in this paper confirm the grain size and flow volume effects on granular flow mobility that were observed in laboratory experiments where batches of granular material traveled down a curved chute. Our numerical simulations are able to predict the correct relative mobility of the granular flows because they take into account particle interactions and, thus, the energy dissipated by the flows. The results illustrated here are obtained without prior fine tuning of the parameter values to get the desired output. The grain size and flow volume effects can be expressed by a linear relationship between scaling parameters where the finer the grain size or the smaller the flow volume, the more mobile the centre of mass of the granular flows. The numerical simulations reveal also the effect of the initial compaction of the granular masses before release. The larger the initial compaction, the more mobile the centre of mass of the granular flows. Both grain size effect and compaction effect are explained by different particle agitations per unit of flow mass that cause different energy dissipations per unit of travel distance. The volume effect is explained by the backward accretion of the deposits that occurs wherever there is a change of slope (either gradual or abrupt). Our results are relevant for the understanding of the travel and deposition mechanisms of geophysical flows such as rock avalanches and pyroclastic flows.295 245 - PublicationOpen AccessPostseismic stress diffusion associated with Sumatra earthquake(2007-04-15)
; ; ; ; ;Pisani, A. R.; Istituto Nazionale di Geofisica e Vulcanologia - Roma - Italy ;Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia - Roma - Italy ;Volpe, M.; Istituto Nazionale di Geofisica e Vulcanologia - Roma - Italy ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia - Roma - Italy; ; ; The giant megathrust occurred on 26th December 2004 off the west coast of northern Sumatra perturbated the stress field configuration over a wide area surrounding the event source. By means of a viscoelastic spherical model of global postseismic deformation and a new computational finite elements package (FEMSA) we perform an analysis of the stress diffusion following the earthquake near and far from the Sunda trench. We evaluated the stress changes due to the Sumatra earthquake by projecting the Coulomb stress over the sequence of aftershocks taken from various catalogues in a time window spanning about two years and then we considered the possibility that the Sumatra event could have affected subsequent events very far from the source.162 195 - PublicationOpen AccessPostseismic signature of the 2004 Sumatra earthquake on low degree gravity harmonics(2008)
; ; ; ; ;Cannelli, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; ; ; We perform an extensive analysis of the low degree gravitt field harmonics measured by the GRACE mission, in order to find a signature of the postseismic relaxation following the 2004 Sumatra earthquake. We find a statistically significant perturbation in the secular trend of low degree zonal coefficients ($J_l$) in correspondence of the 2004 Sumatra earthquake, and a similar perturbation, but with weak associated statistical significance, also in the non-zonal coefficients. Technical features and results of such analysis are discussed. The time-dependent postseismic evolution of harmonic coefficients is modeled for various asthenosphere viscosity values, using a theoretical model of global postseismic deformation. The observed change in secular trend is found to be consistent with our modeling results but it cannot be used to discriminate between viscosities. A forward modeling of the perturbations to time-dependent zonal variation rates following the Sumatra earthquake for various astenospheric viscosities is provided. As a result, an evident signature of the Sumatra earthquake on $\dot{J}_l$ time series is expected for asthenospheric viscosity values below $10^{18}$ Pa s. Therefore, long term $\dot{J}_l$ time histories from SLR geodetic missions will be able to put constraints on the asthenosphere viscosity, if such a signature is evidenced from data or, at least, put lower limits if no significant perturbation will be observed.259 231 - PublicationOpen AccessThe 2009 L’Aquila earthquake coseismic rupture: open issues and new insights from 3D finite element inversion of GPS, InSAR and strong motion data(2015-05-15)
; ; ; ; ; ; ; We present a Finite Element inverse analysis of the static deformation field for the Mw= 6.3, 2009 L’Aquila earthquake, in order to infer the rupture slip distribution on the fault plane. An univocal solution for the rupture slip distribution has not been reached yet with negative impact for reliable hazard scenarios in a densely populated area. In this study, Finite Element computed Green’s functions were implemented in a linear joint inversion scheme of geodetic (GPS and InSAR) and seismological (strong motion) coseismic deformation data. In order to fully exploit the informative power of our dense dataset and to honor the complexities of the real Earth, we implemented an optimized source model, represented by a fault plane subdivided in variable size patches, embedded in a high-resolution realistic three-dimensional model of the Apenninic seismo-tectonic setting, accounting for topographic reliefs and rheological heterogeneities deduced from local tomography. We infer that the investigated inversion domain contains two minima configurations in the solution space, i.e. a single- and a double-patch slip distribution, which are almost equivalent, so that the available datasets and numerical models are not able to univocally discriminate between them. Nevertheless our findings suggest that a two high-slip patch pattern is slightly favoured.305 140 - PublicationOpen AccessProgetto per la misura, raccolta e trasmissione di dati di emissione radon per stazioni sismiche multiparametriche(2020-04-01)
; ; ; ; ; ; ; ; ; ; ; ; ; The seismic monitoring of the national territory and of the EuroMediterranean area makes use of the velocimetric, accelerometric and GPS (geodetic) data acquired by the stations of the National Seismic Network, by the RING Network and by the MedNet Network. As part of the FISR 2017 project “Integrated operating rooms and monitoring networks for the future: INGV 2.0” (2017), sensors capable of detecting both geophysical and geochemical parameters at the same time are being integrated. This technical report describes the integration of a Rn222 sensor (radon hereafter). Over the past few decades radon has found a variety of Earth Science applications, ranging from its use as a potential earthquake precursor and tectonic stress indicator to its specific role in volcanic environments, where significant changes in concentration previous or concomitant to eruptive crises are also induced by volcanic gases, CO 2 for example, which act as carriers accelerating the migration of radon through the earth’s crust and therefore its detection. In order to explore the possibility of a link between seismogenic processes and temporal variability of radon emissions, a permanent national network has been created, IRON (Italian Radon mOnitoring Network), which uses both commercial radon instruments, equipped with a proprietary system for data storage, transmission and consultation, and INGV sensors that need an interface to acquire and make data available remotely. A hardware and software interface has therefore been designed, built and tested capable of i) counting and storing the pulses in TTL format generated by the instrument which measures the 8 radon concentration in air, ii) being connected to a router for sending the acquired data to a server. A service (syncproc) was also created in PHP to query remote stations at regular intervals and collect the acquired data intended to populate a database created with MariaDB. An expressly created website allows to extract the stored data from the database and configure each installed sensor. The various software elements have been designed using open source resources.105 10 - PublicationOpen AccessA relationship between giant earthquakes and core flow instabilities?(2008-12)
; ; ; ; ; ;Cannelli, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; Giant earthquakes of exceptional energy release induce large coseismic deformation field, with measured offsets of the order of millimeter recorded by GPS stations at distances of thousand kilometers from the epicenter. The recorded deformation field is just the surface expression of a volume deformation affecting the whole Earth. According to theoretical models of global coseismic deformation, the 2004 Sumatra-Andaman earthquake, which was the second-greatest occurred in the instrumental age, is expected to have affected the core-mantle boundary with static deformations of the order of millimeter over a large area. At the same time, high-resolution core magnetic-field models based on satellite observations evidenced a short-timescale geostrophic fluid acceleration at the top of the core. These anomalies are located in a region corresponding to the Indian ocean and occur in a time window containing the earthquake occurrence. More interestingly, the acceleration pattern is close to the modeled displacement due to earthquake coseismic effects. These evidences suggest us the possible existence of a relationship between giant earthquakes and rapid perturbations in the Earth core dynamics.191 126 - PublicationOpen AccessFinite Element Modeling of the Static and Quasi-static Deformation associated with the 2004 Sumatra Earthquake(2007-06-25)
; ; ; ;Volpe, Manuela; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Casarotti, Emanuele; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piersanti, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; The great Sumatra-Andaman earthquake of December 26, 2004 was one of the largest earthquakes ever recorded since 1900. The earthquake resulted from complex slip on the fault along the subduction zone where the oceanic portion of the Indian Plate slides under the Eurasian Plate, by the Indonesian island of Sumatra. The direction of convergence of the subducting plate relative to the overriding plate is oriented oblique to the trench axis and the rupture occurred for 1200 km along the interplate megathrust. In the present work we use a new computational FEM strategy to model the co- and post-seismic deformation field associated with the Sumatra earthquake. We are able to study the joint effects of sphericity and 3D geometrical and reological heterogeneities on the investigated observables. The comparison between our synthetic results and the available deformation data will allow us to ascertain if complexities in the physical properties of the medium could play an important role in assessing the deformation field besides source properties.139 355