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Santini, Stefano
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Santini, Stefano
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Santini, S.
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santini@fis.uniurb.it
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25 results
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- PublicationOpen AccessGeothermal Model of the Shallow Crustal Structure across the “Mountain Front Fault” in Western Lurestan, Zagros Thrust Belt, Iran(2019)
; ; ; ; ; ; ; ; ; The Zagros thrust belt is a zone of deformed crustal rocks well exposed along the southwest region of Iran. To obtain a better knowledge of this mountain chain, we elaborated a 2D model reproducing the thermal structure of the “Mountain Front Fault”. This study, which is focused on the Lurestan region, is based on a model made by merging published sections and available information on the depth of the Moho. We present the isotherms and the geotherms calculated using an analytical methodology. The calculation procedure includes the temperature variation due to the re-equilibrated conductive state after thrusting, frictional heating, heat flow density data, and a series of geologically derived constraints. In order to perform the temperature calculations, the crustal structure in the Lurestan region is simplified as composed of two domains: A lower unit made by crystalline basement and an upper unit including all the lithostratigraphic units forming the sedimentary cover. The resulting model is compared with the numerical results obtained by previous studies to improve the description of the thermal structure of this geologically important area.62 21 - PublicationOpen AccessFOCAL MECHANISMS AND TECTONIC SEISMOLOGICAL EVIDENCES IN THE PESARO AND URBINO PROVINCE(2006-06-19)
; ; ;Santini, S.; Universita' di Urbino - Istituto di Fisica, via S. Chiara 27, Urbino ;Martellini, A.; Universita' di Urbino - Istituto di Fisica, via S. Chiara 27, Urbino ;; ; ; ; ;Colantoni, P. ;Menichetti, M.Nesci, O.A focal mechanism study was carried out concerning seismic events occurred in the Pesaro and Urbino province from 1990 to 2002, using data recorded by the seismic network of the Istituto Nazionale di Geofisica e Vulcanologia. Analysis of these data showed that events can be considered in different sectors having similar seismological evidence. Focal mechanisms show that events belonging to the same sector have generally a well defined seismological evidence. In particular, it was possible to point out clearly an extensional stress regime in the axial sector and a compressional one in the sector from the high valley of the Marecchia river to the low valley of the Metauro river. The Adriatic off-shore sector shows not clear evidence of a nevertheless possible active compression; on the other hand no earthquake with magnitude greater than 5 occurred in the zone of northern Marche Adriatic off-shore in historical and recent times.142 194 - PublicationOpen AccessTwo-Dimensional Geothermal Model of the Peruvian Andes above the Nazca Ridge Subduction(2023)
; ; ; ; ; ; ; ; ; The aseismicNazca Ridge produces localized flat-slab subduction beneath the South American margin at latitudes 10 to 15 S. The geological evolution and the spatio-temporal pattern of deformation of the upper plate have been strongly influenced by the presence of the flat slab. In this study, we investigated the lithospheric thermal structure of this region by elaborating a 2D geothermal model along a section across the top of the Nazca Ridge, the Peru–Chile trench, the Andean Cordillera, and the Amazonian Basin, for a total length of 1000 km. For the sake of modelling, the crust of the overriding plate was subdivided into two parts, i.e., a sedimentary cover (including the entire lithostratigraphic sequence) and a crystalline basement. Applying an analytical methodology, we calculated geotherms and isotherms by setting (i) thickness, (ii) density, (iii) heat production, and (iv) thermal conductivity for each geological unit and considering (v) heat flux at theMoho, (vi) frictional heating produced by faults, and (vii) plate convergence rate. The resulting model could make a significant advance in our understanding of how flat slab geometry associated with the Nazca Ridge subduction affects the thermal structure and hence the tectonic evolution of the region.22 8 - PublicationOpen AccessMontefeltro seismicity: from Serpieri's seismograph to the RSNC seismograph station(2000-06)
; ;Santini, S.; Istituto di Fisica, Università di Urbino, ItalyIn recent years, the recovery of some historical documents has permitted us to operate the seismographs used by Alessandro Serpieri (1823-1885) at the Observatory of the University of Urbino in the XIX century. The space-time concept of sensor network was already clear to Serpieri and he tried to apply this concept to the analysis of seismic phenomena in Italy. This paper reviews the history of the Urbino Observatory from Serpieri's age to present times. The historical region of Montefeltro, where Urbino is the main town, is affected by seismicity with typical magnitudes between 2.2 and 2.5. Most of these events occur in the upper 15 km of the crust. The seismicity of the neighbouring regions is mainly concentrated in three zones: Northern Rimini, the Apennine belt and the Sibillini Mountain area. From the overall data, it is possible to infer that there is a basin characterised by microseismicity and essentially dominated by a compressive tectonic regime in the Montefeltro area. Furthermore seismological data seem to show a "quiet" segment, separating the extension area from the compression area, characterised by a low concentration of seismic events.521 399 - PublicationOpen AccessA numerical study for convection in a cylindrical model with continuously varying viscosity(1996-05)
; ; ; ; ;Fanucci, F.; Istituto di Geodinamica, Università di Urbino, Italy ;Megna, A.; Istituto Nazionale di Geofisica, Roma, Italy ;Santini, S.; Istituto di Fisica, Università di Urbino, Italy ;Vetrano, F.; Osservatorio Geofisico Storico, Università di Urbino, Italy; ; ;In the framework of a cylindrical symmetry model for convective motions in the asthenosphere, a new profile for the viscosity coefficient depending on depth is suggested here. The numerical elaboration of the above mentioned model leads to interesting results which fit well with experimental observations. In particular these continuously varying viscosity solutions probably describe the convective motions within the Earth better than simple constant viscosity solutions. Consequently the temperature values seem to be a realistic representation of the possible thermal behaviour in the upper mantle.148 128 - PublicationOpen AccessLa sismicità del Montefeltro (Appennino settentrionale, Italia centrale) nel periodo 2005-2017(2019-12)
; ; ; ; ; ; ; In questo articolo viene esaminata la sismicità del Montefeltro, una regione storica dell’Appennino settentrionale, nell’Italia centrale. L’analisi si concentra sull’attività sismica avvenuta nel periodo 20052017, periodo durante il quale la Rete Sismica Nazionale (RSN) ha avuto nella regione un sostanziale miglioramento. Il data set selezionato consiste di 402 eventi per un totale di circa 7000 tempi di arrivo di fasi P e S. Gli eventi sono stati integrati con nuove letture e rilocalizzati con il programma Hypoellipse. I risultati mostrano una sismicità di fondo sporadica, sebbene piuttosto diffusa nell’area, contrassegnata da tre piccole sequenze fortemente clusterizzate nel tempo e nello spazio. Le più importanti sono avvenute nel settembreottobre 2005 (magnitudo massima ML=3.2) e nell’agostosettembre 2006 (magnitudo massima ML=3.7), rispettivamente nei dintorni dei comuni di Macerata Feltria e Casteldelci. L’evoluzione spaziotemporale di questi due episodi evidenzia un rilascio di energia tipico degli sciami sismici. Un’altra peculiare caratteristica del pattern di sismicità è rappresentata dall’occorrenza di eventi anche nella crosta inferiore e nel mantello superiore fino a profondità di almeno 50 km.189 95 - PublicationOpen AccessA note on Northern Marche seismicity: new focal mechanisms and seismological evidence(2003)
; ;Santini, S.; Istituto di Fisica dell Università di Urbino, ItalyA geodynamic interpretation of the Northern Marche region is diffi cult, the zone being characterized by complex structures which cannot be defi ned in the form of a simple, standard model. It is unquestionable that the geodynamic setting, whatever it is, bears a strong infl uence on the seismic hazard assessment of a region, and this is the background reason for the present note. In order to obtain a more detailed picture of seismological evidence in this zone, 11 new fault plane solutions of crustal events with 2.9 < M < 4.3 were calculated, using data recorded by the national seismic network of the Istituto Nazionale di Geofi sica e Vulcanologia in the period 1990-2000. The aim is to add local information to the previous studies by Frepoli and Amato (1997, 2000). A possible result of this new study is the division of the Northern Marche region into three areas with different focal mechanism categories: the inner area of the Apenninic belt, the Adriatic on-shore and the Adriatic off-shore. This note is intended to be a contribution to update seismological evidence in the Northern Marche region.148 566 - PublicationOpen AccessThe August 17, 1999 Izmit, Turkey, earthquake: slip distribution from dislocation modeling of DInSAR and surface offset(2002-06)
; ; ; ; ; ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cinti, F. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dragoni, M.; Dipartimento di Fisisca, Univ. di Bologna, Italy ;Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Santini, S.; Dipartimento di Fisica, Univ. di Urbino, Italy; ; ;; We show the results of application of Differential SAR Interferometry to the MW 7.4, August 17, 1999, Izmit earthquake, Western Turkey. The differential interferogram is obtained using an interferometric ERS2 ascending pair with a time interval of 35 days (August 13th - September 17th). The fringe pattern clearly defines the coseismic displacement field extended in an area of about 100 km N-S and 120 km E-W. The analysis of the interferogram shows the right-lateral strike-slip movement on the activated section of the North Anatolian fault system. The maximum SAR-detected displacement ranges between 117.6 cm and 134.4 cm in the proximity of Gölcük. We invert SAR data for uniform dislocation on a single fault plane using a Montecarlo procedure, with the aim of testing a large set of a priori possible asperity distributions on the fault. We then use a forward modeling approach to evaluate the slip variability for the dislocation using additional constraints as surface offsets and seismicity distribution: in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocation model. Misfits between SAR data and modeled slant range displacements are generally low for all our models (~ 12 cm). Our results indicate that slip is concentrated in the central-western part of the fault, in the upper 10-15 km, tapering to the fault tips. For the Izmit case, we note that a well constrained fault model can be obtained only integrating DInSAR data with additional observations. This is mainly due to an undersampling of the displacement field by DInSAR, caused by decorrelation and lack of image data.266 442 - PublicationOpen AccessNormal-fault stress and displacement through finite-element analysis(2005-12)
; ; ; ;Megna, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Santini, S.; Istituto di Fisica, Università degli Studi di Urbino, Italy; ; We compute displacement and stress due to a normal fault by means of two-dimensional plane-strain finite-element analysis. To do so, we apply a system of forces to the fault nodes and develop an iterative algorithm serving to determine the force magnitudes for any slip distribution. As a sample case, we compute the force magnitudes assuming uniform slip on a 10-km two-dimensional normal fault. The numerical model generates displacement and stress fields that compare well with the analytical solution. In fact, we found little difference in displacements (<5%), displacement orientation (<15°), and stress components (<35%, half of which due to slip tolerance). We analyze such misfit, and discuss how the error propagates from displacement to stress. Our scheme provides a convenient way to use the finite-elements direct method in a trial-and-error procedure to reproduce any smooth slip distribution.215 250 - PublicationOpen AccessA Waveform Dataset in Continuous Mode of the Montefeltro Seismic Network (MF) in Central-Northern Italy from 2018 to 2020(2022)
; ; ; ; ; ; ; ; ; The Montefeltro seismic network (FDSN Network code: 1S) was deployed in the Apennines area of northern Marche and southern Emilia-Romagna regions (central Italy). A temporary network was set up in December 2018 and continues to operate, with an array consisting of stations equipped with dynamic digitizers and three-component short/extended/broad band seismometers (Guralp CMG/20s and 30s, Lennartz 3D/5s, Sara SS20 3D/0.5s sensors). The network records in continuous mode at 100 sps. The data are used to analyze the seismic activity and the spatiotemporal evolution of small seismic sequences occurring in the considered area and surrounding zones, strongly clustered in time and space. The data of dataset files are mini-seed formatted and subdivided by the following tree: (1) the dataset is divided by years; (2) the dataset is then subdivided by stations; (3) finally, the data are divided by days of each year in every station folder.52 11
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