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Toscani, G.
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Toscani, G.
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- PublicationOpen AccessSlip-rates of blind thrusts in slow deforming areas: examples from the Po Plain (Italy)(2015-01-02)
; ; ; ; ;Maesano, F. A.; ISPRA Servizio Geologico d’Italia, Via Vitaliano Brancati, 48, 00144 Roma, Italy ;D'Ambrogi, C.; ISPRA Servizio Geologico d’Italia, Via Vitaliano Brancati, 48, 00144 Roma, Italy ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Toscani, G.; Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia, Via Ferrata, 1 - 27100; ; ; We calculate Plio-Pleistocene slip rates on the blind thrusts of the outer Northern Apennines fronts, that are the potential sources of highly damaging earthquakes, as shown by the MW 6.1-6.0, 2012 Emilia-Romagna seismic sequence. Slip rates are a key parameter for understanding the seismogenic potential of active fault systems and assessing the seismic hazard they pose, however, they are difficult to calculate in slow deforming areas like the Po Plain where faulting and folding is mostly blind. To overcome this, we developed a workflow which included the preparation of a homogeneous regional dataset of geological and geophysical subsurface information, rich in Plio- Pleistocene data. We then constructed 3D geological models around selected individual structures to decompact the clastic units and restore the slip on the fault planes. The back-stripping of the differential compaction eliminates unwanted overestimation of the slip rates due to compactioninduced differential subsidence. Finally, to restore the displacement we used different methods according to the deformation style, i.e. Fault Parallel Flow for faulted horizons, trishear and elastic dislocation modeling for fault-propagation folds. The result of our study is the compilation of a slip rate database integrating former published values with 28 new values covering a time interval from the Pliocene to the present. It contains data on 14 individual blind thrusts including the Mirandola thrust, seismogenic source of the 29 May 2012, MW 6.0 earthquake. Our study highlights that the investigated thrusts were active with rates ranging between 0.1-1.0 mm/yr during the last 1.81 Myr. The Mirandola thrust slipped at 0.86±0.38 mm/yr during the last 0.4 Myr. These rates calculated with an homogeneous methodology through the entire Po Plain can be charged entirely to the thrust activity and not to secondary effects like the differential compaction of sediments across the structures.442 475 - PublicationOpen AccessThe effects of pre-existing discontinuities on the surface expression of normal faults: Insights from wet-clay analogue modeling(2016-01-29)
; ; ; ; ; ; ;Bonini, L.; Dipartimento di Matematica e Geoscienze, Università di Trieste, Italy ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Toscani, G.; Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia, Pavia, Italy ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Seno, S.; Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia, Pavia, Italy ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; We use wet-clay analogue models to investigate how pre-existing discontinuities (i.e. structures inherited from previous tectonic phases) affect the evolution of a normal fault at the Earth's surface. To this end we first perform a series of three reference experiments driven by a 45° dipping master fault unaffected by pre-existing discontinuities to generate a mechanically isotropic learning set of models. We then replicate the experiment six times introducing a 60°-dipping precut in the clay cake, each time with a different attitude and orientation with respect to an initially-blind, 45°-dipping, master normal fault. In all experiments the precut intersects the vertical projection of the master fault halfway between the center and the right-hand lateral tip. All other conditions are identical for all seven models. By comparing the results obtained from the mechanically isotropic experiments with results from experiments with precuts we find that the surface evolution of the normal fault varies depending on the precut orientation. In most cases the parameters of newly-forming faults are strongly influenced. The largest influence is exerted by synthetic and antithetic discontinuities trending respectively at 30° and 45° from the strike of the master fault, whereas a synthetic discontinuity at 60° and an antithetic discontinuity at 30° show moderate influence. Little influence is exerted by a synthetic discontinuity at 45° and an antithetic discontinuity at 60° from the strike of the master fault. We provide a ranking chart to assess fault-to-discontinuity interactions with respect to essential surface fault descriptors, such as segmentation, vertical-displacement profile, maximum displacement, and length, often used as proxies to infer fault properties at depth. Considering a single descriptor, the amount of deviation induced by different precuts varies from case to case in a rather unpredictable fashion. Multiple observables should be taken into consideration when analyzing normal faults evolving next to pre-existing discontinuities.567 197 - PublicationOpen AccessDeriving thrust fault slip rates from geological modeling: examples from the Marche coastal and offshore contraction belt, Northern Apennines, Italy.(2013)
; ; ; ; ; ; ;Maesano, F. E. ;Toscani, G.; Dipartimento di Scienze della Terra e dell'Ambiente, Università di Pavia ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Mirabella, F.; Dipartimento di Scienze della Terra, Università di Perugia ;D'ambrogi, C.; ISPRA - Servizio Geologico d'Italia ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;; ; ; ; We present a reconstruction of the central Marche thrust system in the central-northern Adriatic domain aimed at constraining the geometry of the active faults deemed to be potential sources of moderate to large earthquakes in this region and at evaluating their long-term slip rates. This system of contractional structures is associated with fault-propagation folds outcropping along the coast or buried in the offshore that have been active at least since about 3Myr. The ongoing deformation of the coastal and offshore Marche thrust system is associated with moderate historical and instrumental seismicity and recorded in sedimentary and geomorphic features. In this study, we use subsurface data coming from both published and original sources. These comprise cross-sections, seismic lines, subsurface maps and borehole data to constrain geometrically coherent local 3D geological models, with particular focus on the Pliocene and Pleistocene units. Two sections crossing five main faults and correlative anticlines are extracted to calculate slip rates on the driving thrust faults. Our slip rate calculation procedure includes a) the assessment of the onset time which is based on the sedimentary and structural architecture, b) the decompaction of clastic units where necessary, and c) the restoration of the slip on the fault planes. The assessment of the differential compaction history of clastic rocks eliminates the effects of compaction-induced subsidence which determine unwanted overestimation of slip rates. To restore the displacement along the analyzed structures, we use two different methods on the basis of the deformation style: the fault parallel flow algorithm for faulted horizons and the trishear algorithm for fault-propagation folds. The time of fault onset ranges between 5.3-2.2 Myr; overall the average slip rates of the various thrusts are in the range of 0.26-1.35 mm/yr.516 916 - PublicationRestrictedModes of fault reactivation from analogue modeling experiments: implications for the seismotectonics of the southern Adriatic foreland (Italy)(2007)
; ; ; ; ; ; ;Di Bucci, D.; Dipartimento della Protezione Civile, Roma, Italia ;Ravaglia, A.; Midland Valley Exploration Ltd., Glasgow, UK ;Seno, S.; Dipartimento di Scienze della Terra, Università di Pavia, Pavia, Italia ;Toscani, G.; Dipartimento di Scienze della Terra, Università di Pavia, Pavia, Italia ;Fracassi, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ;; ; ; The active tectonics at the front of the Southern Apennines and in the Adriatic foreland is characterized by E-W striking, right-lateral seismogenic faults, interpreted as reactivated inherited discontinuities. The best studied among these is the Molise-Gondola shear zone (MGsz). The interaction of these shear zones with the Apennines chain is not yet clear. To address this open question we developed a set of scaled analogue experiments, aimed at analyzing: 1) how dextral strike-slip motion along a pre-existing zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge; 2) the propagation of deformation as a function of increasing displacement; 3) any insights on the active tectonics of Southern Italy. Our results stress the primary role played by these inherited structures when reactivated, and confirm that regional EW dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the Southern Apennines.357 675 - PublicationOpen AccessLand subsidence along the Ionian coast of SE Sicily (Italy), detection and analysis via Small Baseline Subset (SBAS) multitemporal differential SAR interferometry(2012)
; ; ; ; ; ;Canova, F.; Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Pavia, Italy ;Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Toscani, G.; Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Pavia, Italy ;Seno, S.; Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Pavia, Italy; ; ; ; We present the results of a multi-temporal, differential interferometric synthetic aperture radar (DInSAR) analysis aiming to identify active surface deformation phenomena in southeastern Sicily. The study area has been chosen because of its strong seismicity, high concentration of industrial and agricultural activities, and high density of people living in the coastal area. Furthermore, the morphology, lithology and climatic feature of this sector of the Hyblean foreland are suitable for an interferometric analysis, providing a high coherence over the area. We used the Small BAseline Subset (SBAS) multitemporal DInSAR technique from Berardino et al., 2002, to calculate mean ground velocity maps and displacement time series from a large data set of European Remote Sensing Satellites (ERS 1-2) images spanning the time period 1992-2000. The reliability of the DInSAR results was tested calculating the EastSAR and UpSAR values over two permanent global positioning system (GPS) stations in the area, and comparing them with the EastGPS and UpGPS values. The residuals between GPS and DInSAR velocities were 1 and 0.6 mm/yr for the Up and East components, respectively. Four main subsiding areas, previously undetected, have been identified, in correspondence of the towns of Augusta, Siracusa, Priolo, and Villasmundo. The observed deformation phenomena are located within coastal structural basins, filled with Pleistocene and Holocence deposits, except the Villasmundo land subsidence which is located on the Hyblean plateau. The measured deformation rates reach values up to -18 mm/yr in Augusta, -6 mm/yr in Siracusa, -5 mm/yr in Villasmundo and -4.5 mm/yr in Priolo. The examination of velocity profiles, time series, and geological data allows us to relate all the detected deformation patterns primarily to groundwater over-exploitation. A multi-dimensional interpolation with kriging was performed to obtain a field subsidence map. A first order elastic deformation model was used to simulate the peculiar features of the Villasmundo subsidence268 872 - PublicationOpen AccessThe role of pre-existing discontinuities in the development of extensional faults: an analog modeling perspective(2015)
; ; ; ; ; ; ;Bonini, L.; Dipartimento di Matematica e Geoscienze, Università di Trieste, Trieste, ITALY ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Toscani, G.; Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia, ITALY ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Seno, S.; Dipartimento di Scienze della Terra e dell’Ambiente, Università di Pavia, ITALY ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; Several mountainous regions are currently affected by syn- or post-orogenic active extension. We investigate how a newly-formed normal fault interacts with structures inherited from a previous contractional phase. To this end, we use analog models that adopt an innovative technique for performing a precut that mimics such inherited structures into a clay layer; this clay layer is laid on top of a master fault simulated by two rigid blocks sliding along an inclined plane. We carry out six experiments with variously oriented precuts and compare the results with those obtained in a reference isotropic experiment. All other conditions are identical for all seven realizations. Fault evolution is monitored by taking closely-spaced snapshots analyzed through the Digital Image Correlation method. We find that the upward propagation of the normal fault can be either accelerated or decelerated depending on the presence of a precut and its orientation. Such precuts can also promote or inhibit the formation of bending-moment faults. These interactions between master fault and precut also affect the shape of the fault-related syncline-anticline pair.482 723 - PublicationOpen AccessSeismotectonics of the Southern Apennines and Adriatic foreland: insights on active regional E-W shear zones from analogue modeling(2006-08-11)
; ; ; ; ; ; ;Di Bucci, D.; Dipartimento della Protezione Civile, Servizio Sismico Nazionale. Via Vitorchiano, 4 - 00189 ;Ravaglia, A.; Dipartimento di Scienze della Terra, Università di Pavia. Via Ferrata, 1 - 27100 Pavia, Italy (now at Midland Valley Exploration Ltd. 14 Park Circus - G3 6AX Glasgow, UK) ;Seno, S.; Dipartimento di Scienze della Terra, Università di Pavia. Via Ferrata, 1 - 27100 Pavia, Italy ;Toscani, G.; Dipartimento di Scienze della Terra, Università di Pavia. Via Ferrata, 1 - 27100 Pavia, Italy ;Fracassi, U.; Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605 - 00143 Roma, Italy ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605 - 00143 Roma, Italy; ;; ; ; The active tectonics at the front of the Southern Apennines and in the Adriatic foreland is characterized by E-W striking, right-lateral seismogenic faults, interpreted as reactivated inherited discontinuities. The best studied among these is the Molise-Gondola shear zone (MGsz). The interaction of these shear zones with the Apennines chain is not yet clear. To address this open question we developed a set of scaled analogue experiments, aimed at analyzing: 1) how dextral strike-slip motion along a pre-existing zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge; 2) the propagation of deformation as a function of displacement; 3) any insights on the active tectonics of Southern Italy. Our results stress the primary role played by these inherited structures when reactivated, and confirm that regional E-W dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the Southern Apennines.231 1324 - PublicationRestrictedReconciling deep seismogenic and shallow active faults through analogue modelling: the case of the Messina Straits (southern Italy)(2011-01-06)
; ; ; ; ; ;Bonini, L.; Dipartimento di Scienze della Terra, Università di Pavia ;Di Bucci, D.; Dipartimento della Protezione Civile ;Toscani, G.; Dipartimento di Scienze della Terra, Università di Pavia ;Seno, S.; Dipartimento di Scienze della Terra, Università di Pavia ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; The catastrophic 28 December 1908, Mw 7.1, Messina Straits earthquake was generated by a large, low-angle, SE-dipping, blind normal fault. A number of shallow, high-angle normal faults arranged in a graben-like fashion occur in the same area both on land and offshore, reaching the surface and in some instances affecting recent deposits. These faults are normally interpreted as active and have often been considered potentially seismogenic. We used an analogue modelling approach to simulate the evolution of a large, low-angle normal fault and investigate its relationships with the overlying secondary faults. We find that these faults represent the brittle surface expression of the long-term activity of the underlying master fault, and that all faults mapped by previous workers in the Messina Straits are compatible with sustained slip along the fault responsible for the 1908 earthquake. Our results confirm that analogue modelling provides a useful tool to investigate the evolution and the hierarchical relationships of fault systems, suggesting that this approach is effective in the investigation of complex seismogenic areas.276 52 - PublicationRestrictedPlio-Quaternary tectonic evolution of the Northern Apennines thrust fronts (Bologna-Ferrara section, Italy): seismotectonic implications(2009-10)
; ; ; ; ; ;Toscani, G.; Dipartimento di Scienze della Terra, Università di Pavia ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Di Bucci, D.; Dipartimento della Protezione Civile ;Seno, S.; Dipartimento di Scienze della Terra, Università di Pavia ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; The outermost, NE-verging fronts of the Northern Apennines (Italy) are overlain by a thick syntectonic sedimentary wedge filling up the basin beneath the Po Plain. Due to fast sedimentation rates and comparatively low tectonic rates, the fronts are generally buried. Evidence for their activity includes scattered historical and instrumental earthquakes and drainage anomalies controlled by growing buried anticlines. The largest earthquakes, up to Mw 5.8, are associated with active compression with a GPS-documented shortening rate <1 mm/a. We used geological, structural and morphotectonic data to draw a N-S–striking section between Bologna and Ferrara, aimed at analyzing whether and how the deformation is partitioned among the frontal thrusts of the Northern Apennines and identifying the potential sources of damaging earthquakes. We pointed out active anticlines based on the correspondence among drainage anomalies, historical seismicity and buried ramps. We also analyzed the evolution of the Plio-Quaternary deformation by modeling in a sandbox the geometry, kinematics and growth patterns of the thrust fronts. Our results (i) confirm that some of the main Quaternary thrusts are still active and (ii) highlight the partitioning of deformation in the overlap zones. We note that the extent and location of some of the active thrusts are compatible with the location and size of the main historical earthquakes and discuss the hypothesis that they may correspond to their causative seismogenic faults.241 32