http://hdl.handle.net/2122/253 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/6021 Titolo: Array measurements of deep tremor signals in the Cascadia subduction zone<br/><br/>Autori: La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; McCausland, W.; University of Washington, Seattle, USA; Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Malone, S.; University of Washington, Seattle, USA; Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: Preliminary analysis of deep tremor recorded during July, 2004, in the Cascadia Subduction zone shows that the use of small aperture arrays can resolve the slowness and back azimuth of seismic waves with a useful resolution. Data were collected by three dense arrays of short-period seismometers specifically deployed in the Puget Sound area under an US-Italy-Canada cooperative effort. Slowness analyses at the three arrays indicate that the 2-4 Hz tremor wave-field is composed by waves propagating with apparent velocities higher than 4 km/s. Combining this with polarisation analysis show these waves to be transverse (SH) waves. However, P-waves, though smaller in amplitude, can be detected by different slowness values obtained for the radial and transverse components. The intersection of wave vectors determined by the back azimuth and slowness values measured at the three arrays provides a preliminary estimate of source location for a sample of the recorded deep tremor. http://hdl.handle.net/2122/6011 Titolo: Can Earth's rotation and tidal despinning drive plate tectonics?<br/><br/>Autori: Riguzzi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Panza, G.; Dipartimento di Scienze della Terra, Università di Trieste, and ICTP, Italy; Varga, P.; Geodetic and Geophysical Research Institute, Seismological Observatory, Budapest, Hungary; Doglioni, C.; Dipartimento di Scienze della Terra, Università Sapienza, Roma, Italy<br/><br/>Abstract: We re-evaluate the possibility that Earth's rotation contributes to plate tectonics on the basis of the followingobservations: 1) plates move along a westerly polarized flow that forms an angle relative to the equator closeto the revolution plane of the Moon; 2) plate boundaries are asymmetric, being their geographic polaritythe first order controlling parameter; unlike recent analysis, the slab dip is confirmed to be steeper alongW-directed subduction zones; 3) the global seismicity depends on latitude and correlates with the decadaloscillations of the excess length of day (LOD); 4) the Earth's deceleration supplies energy to plate tectonicscomparable to the computed budget dissipated by the deformation processes; 5) the Gutenberg–Richterlaw supports that the whole lithosphere is a self-organized system in critical state, i.e., a force is actingcontemporaneously on all the plates and distributes the energy over the whole lithospheric shell, acondition that can be satisfied by a force acting at the astronomical scale.Assuming an ultra-low viscosity layer in the upper asthenosphere, the horizontal component of the tidaloscillation and torque would be able to slowly shift the lithosphere relative to the mantle. http://hdl.handle.net/2122/5970 Titolo: An Orogenic Model Consistent with Earth Expansion<br/><br/>Autori: Strutinski, C.<br/><br/>Curatori: Barone, M.; Selleri, F.<br/><br/>Abstract: The paper presents the author's view on orogeny, as opposed to the crustal shortening assumption of plate tectonics. It is shown that first order tectonic transport takes place not across but along the strike of orogens. Accordingly orogens are considered to be megashears of the crust. They are of two types, due to their location and specific tectonic environment: equatorial and circum-pacific orogens. As none of them implies subduction, they are consistent with the assumption of an expanding Earth. http://hdl.handle.net/2122/5964 Titolo: Reply to the comment by G. Capponi et al. on "Subduction polarity reversal at the junction between the Western Alps and the Northern Apennines, Italy", by G. Vignaroli et al. (Tectonophysics, 2008, 450, 34-50)<br/><br/>Autori: Vignaroli, G.; Univ Roma Tre, Dipartimento Sci Geol, Rome, Italy; Faccenna, C.; Univ Roma Tre, Dipartimento Sci Geol, Rome, Italy; Jolivet, L.; Univ Paris 06, Lab Tecton, CNRS, UMR 7072, F-75252 Paris 05, France; Piromallo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Rossetti, F.; Univ Roma Tre, Dipartimento Sci Geol, Rome, Italy<br/><br/>Abstract: We first would like to thank Capponi et al. (2008) for their comments and criticisms on our paper, offering us the opportunity to discuss the data and the model presented in Vignaroli et al. (2008a) and clarify the geological rationale behind our manuscript. Vignaroli et al. (2008a) presented a large-scale reconstruction on the evolution of the Western Alpine–Northern Apennine junction, based on shallow geological information derived from the Northern Apennines, the Western and Ligurian Alps coupled with deep mantle structures from seismic tomography and tectonic reconstructions. The aim of this paper is then to give an alternative, though simplified, tectonic solution to the long-standing debate concerning the polarity of the subduction zone in the central Mediterranean and its linkage with the Alpine orogeny and the formation of the arcs belt. We condensed and simplified the huge wealth of geological information using cross-sections along the three orogenic segments. One of the main points of the paper is that the Voltri Massif of the Ligurian Alps is reinterpreted as an eclogitic-bearing domain exhumed by means of ductile-to-brittle extensional detachment tectonics with a top-to-the-W sense of shear. In this view, the orogenic architecture and evolution of the Ligurian Alps presents affinities (both for geometry and timing of deformation) with the widely accepted extensional structures recognized in the Western Alps, in the Northern Apennines and, in general, in Alpine-type orogenic belts of the Mediterranean. The detailed comment made by Capponi et al. (2008) is indeed centred on the tectonic structure of the Voltri Massif (probably this comment should have been addressed to our companion paper, Vignaroli et al., 2008b, focused on the Voltri Massif structures and available on-line on March 2008). The main point of the comment is that the exhumation of High-Pressure (HP) metamorphic units exposed in the Voltri Massif was produced by thrusts rather than by syn-orogenic extensional detachments. In this reply, we would first like to make some general considerations on the criteria/concepts adopted for the interpretation of the exhumation-related structures and we will then discuss point-by-point the criticism of Capponi et al., 2008 Capponi, G., Crispini, L., Scambelluri, M., 2008. Comment on "Subduction polarity reversal at the junction between the Western Alps and the Northern Apennines, Italy", by G. Vignaroli, C. Faccenna, L. Jolivet, C. Piromallo, F. Rossetti. Tectonophysics.Capponi et al. (2008). http://hdl.handle.net/2122/5879 Titolo: Roberto Mantovani (1854-1933) and his ideas on the expanding Earth, as revealed by his correspondence and manuscripts<br/><br/>Autori: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Roberto Mantovani (Parma, 25 March 1854-Paris, 10 January 1933) – a musician and geologist trained in theDuchy of Parma – was a Consul in the French island of La Réunion at the end of the nineteenth century. In 1878drawing general conclusions from the similarity in shape between the facing banks of a river that flowed in a volcanicfracture, and the way in which the layers corresponded, Mantovani formulated a mobilistic theory, attributingthe moving apart of the continents to the expansion of the entire planet. This theory is more general than thatof Wegener from the first decades of the following century. Mantovani’s hypothesis was officially recognised bythe French Geological Society in 1924, which incorporated it in its body of legitimate ideas. Encouraged by Bourcartin 1924, Wegener quoted the Italian in his famous book as one who offered ideas extraordinarily close to hisown. A letter of Mantovani to Wegener, and the sceptical answer of the German scientist, have been recentlyfound. In his letter Mantovani shows a greater awareness of the predecessors of the continental drift than Wegenerhimself. Mantovani continued to disseminate his idea up to the last years of his life. A final pamphlet, of 1930,was printed with this dedication: «to the mathematicians, physicists, astronomers, geologists, and anyone interestedin the great enigmas of the Universe». His biography has been reconstructed thanks to the correspondencescarefully conserved in the archives of the Italian Ministry of Foreign Affairs, the Ethnographic Museum Luigi Pigorini,the Società Geografica Italiana, and in the private files of his direct descendants.<br/><br/>Descrizione: Biografia di un antesignano della espansione dei fondali oceanici e della Terra. http://hdl.handle.net/2122/5784 Titolo: DTM-based morphometry of the Palinuro seamount (Eastern Tyrrhenian Sea): Geomorphological and volcanological implications<br/><br/>Autori: Passaro, S.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli; Milano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Isanto, C.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli; Ruggieri, S.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli; Tonielli, R.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli; Bruno, P. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Sprovieri, A.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli; Marsella, E.; Istituto per l'Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche, Napoli<br/><br/>Abstract: We present a high resolution DTM of the Palinuro Seamount (PS, Tyrrhenian Sea, Italy) resulting from theprocessing of multibeam swath bathymetry records acquired during the second leg of the “Aeolian 2007”cruise. PS consists of several superimposed volcanoes aligned along a N100°E strike and measures55×25 km. The western and the central sectors result from the coalescence of collapse structures (calderas)with younger volcanic cones. The eastern sector reveals a more complex and articulated structure. In thecentral sector, a volcanic crater with a well-preserved rim not obliterated by erosional events suggests avolcanological rejuvenation of this sector. The presence of flat surfaces on the top of the seamount may bedue to the formation of marine terraces during the last sea-level lowering. Lateral collapses on the northernand southern flanks of the seamount are probably related to slope instability, as suggested by the presence ofsteep slopes (25–40°). The main fault affecting PS strikes N65°E and shows a right lateral component ofmovement. E–W and N10°E striking faults are also present.Assuming that theN100°E deep-seated fault,which is responsible for theemplacement of PS,movedwith sinistralslips, we interpret the N65°E and the N10°E faults as right-lateral (second order) shear and left-lateral (thirdorder) shear, respectively. Due to the particular location of the Palinuro Seamount, the data presented here allowus to better understand the volcanism and the geodynamic processes of the Tyrrhenian Sea. http://hdl.handle.net/2122/5781 Titolo: Application of the Post-Widder Laplace inversion algorithm to postseismic rebound models<br/><br/>Autori: 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; Spada, G.; Istituto di Fisica, Università di Urbino<br/><br/>Abstract: The 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 viscoelas- tic 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 intrin- sic 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 stan- dard 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. http://hdl.handle.net/2122/5779 Titolo: HPC in global geodynamics: Advances in normal-mode analytical modeling<br/><br/>Autori: Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Analytical models based on normal-mode theory have been suc- cessfully employed for decades in the modeling of global response of the Earth to seismic dislocations, postglacial rebound and wave propagation. Despite their lim- ited capabilities with respect to fully numerical approaches, they are yet a valuable modeling tool, for instance in benchmarking applications or when automated pro- cedures have to be implemented, as in massive inversion problems when a large number of forward models have to be solved. The availability of high-performance computer systems ignited new applications for analytical modeling, allowing to re- move limiting approximations and to carry out extensive simulations on large global datasets. http://hdl.handle.net/2122/5778 Titolo: A sea level equation for seismic perturbations<br/><br/>Autori: Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Spada, G.; Istituto di Fisica, Università di Urbino; Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally self–consistent, integral sea level equation suitable for earthquakes, in which we account both for direct effects by the seismic dislocation and for the feedback from water loading associated with sea level changes. Our approach builds upon the well established theory first proposed in the realm of glacio–isostatic adjustment modeling. The seismic sea level equation is numerically implemented to model sea level signals following the 2004 Sumatra–Andaman earth- quake, showing that surface loading from ocean water redistribution (so far ignored in post–seismic deformation modeling) may account for a significant fraction of the total computed post–seismic sea level variation. http://hdl.handle.net/2122/5777 Titolo: A Sea Level Equation for seismic perturbations<br/><br/>Autori: Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Spada, G.; Istituto di Fisica, Università di Urbino; Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally self-consistent, integral sea level equation suitable for earthquakes, in which we account both for direct effects by the seismic dislocation and for the feedback from water loading associated with sea level changes. Our approach builds upon the well-established theory first proposed in the realm of glacio-isostatic adjustment modelling. The seismic sea level equation is numerically implemented to model sea level signals following the 2004 Sumatra–Andaman earthquake, showing that surface loading from ocean water redistribution (so far ignored in post-seismic deformation modelling) may account for a significant fraction of the total computed post-seismic sea level variation