Options
Sileo, G.
Loading...
2 results
Now showing 1 - 2 of 2
- PublicationOpen AccessActive compressional tectonics, Quaternary capable faults, and the seismic landscape of the Po Plain (N Italy)(2012)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Michetti, A.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Giardina, F.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Livio, F.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Mueller, K.; University of Colorado, Department of Geological Sciences, Boulder, CO, USA ;Serva, L.; ISPRA, Dipartimento Difesa del Suolo/Servizio Geologico d’Italia, Rome, Italy ;Sileo, G.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Vittori, E.; ISPRA, Dipartimento Difesa del Suolo/Servizio Geologico d’Italia, Rome, Italy ;Devoti, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Riguzzi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Carcano, C.; Burren Resources Petroleum Ltd, Baza Burren, Burun Field, Balkanabat, Turkmenistan ;Rogledi, S.; ENI Exploration and Production, San Donato Milanese (Milan), Italy ;Bonadeo, L.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Brunamonte, F.; Università dell'Insubria, Dipartimento di Scienza e Alta Tecnologia, Como, Italy ;Fioraso, G.; Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche (CNR), Turin, Italy; ; ; ; ; ; ; ; ; ; ; ; ; It is commonly believed that the Po Plain is an area of low seismic haz- ard. This conclusion is essentially a combination of two factors: (1) the historical record of earthquakes, which shows a relatively small number of events of moderate magnitude, and only two significant earthquakes, which occurred in the Middle Ages; and (2) the lack of ad-hoc research on the geology of earthquakes in this area, as although many studies have highlighted the local Quaternary tectonics, only a very few of them have discussed the observed evidence in terms of seismic hazard. In contrast, the data presented in the present study strongly suggest that the level of earthquake hazard in the Po Plain is comparable to that of the well- known seismic areas of the Apennine range, at least in terms of maxi- mum magnitudes. Indeed, the high population density and the concentration of industrial facilities make the Po Plain today one of the more high-risk areas of the Italian territory. The Po Plain represents the foredeep of two growing mountain belts, the southern Alps and the north- ern Apennines. Recently, modern active tectonics studies have been con- ducted along its margins to the south, along the northern Apennine Piedmont belt, and to the northeast, along the eastern southern Alpine Piedmont belt. However, in the central and western sectors of the Po Plain, where the south-verging western southern Alpine front links up with the north-verging Monferrato, Emilia and Ferrara arcs, the Qua- ternary history of tectonic deformation and faulting are still relatively poorly understood. These lie beneath the relatively flat alluvial surface of the Po River, and provide the evidence for paleoseismicity and the result- ing seismic hazard. In this review, we compile the data from the literature to reassess the style and magnitude of the ongoing crustal deformation and the associated earthquake faulting. This includes detailed informa- tion on historical and instrumental seismicity, extensive subsurface in- formation from the ENI industrial exploration, structural interpretation of three regional seismic reflection profiles, analysis of novel global posi- tioning system data, field mapping at selected key areas, and new paleo- seismological investigations. We show that along the western southern Alpine belt between Lake Garda and Lake Maggiore, the active tectonic setting is characterized by a segmented belt of fault-propagation folds. These are 50 km wide, and are controlled by the growth of out-of-se- quence, 10-to-20-km-long, north and south verging thrusts. Regional global positioning system data show ongoing shortening rates of the order of 1 mm/yr. Quaternary fault slip rates typically range between 0.2 mm/yr and 0.4 mm/yr. Pleistocene shortening is obvious not only along the western southern Alpine outer fronts that are buried beneath the Po Plain, but also along the south Alpine foothills between Brescia and Varese. Similar styles and rates of active folding and thrusting have also been documented along the frontal sector of the northern Apennine arcs, from Torino to Ferrara, and along the base of the Apennine mountain front between Piacenza and Bologna. We selected the Brescia and Como sectors in the western southern Alps and the Monferrato and Mirandola structures in the northern Apennines as examples to illustrate the seismic landscape of the study area, in terms of typical active structural, geo- morphic and paleoseismic features. We argue that the level of earthquake hazard in the Po Plain is comparable to that of the Apennine range. On May 20, 2012, a few days after this review was formally accepted for pub- lication, a M W 5.9 earthquake ruptured the Mirandola structure. The seismic sequence following this mainshock is ongoing, and we have added further information about this event (updated on June 3rd, 2012), which substantially confirms the conclusions arrived at here.917 1055 - PublicationOpen AccessShallow subsurface structure of the 2009 April 6Mw 6.3 L’Aquila earthquake surface rupture at Paganica, investigated with ground-penetrating radar(2010-06-22)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Roberts, G.; Research School of Earth Sciences, Birkbeck/UCL, University of London ;Raithatha, B.; Research School of Earth Sciences, Birkbeck/UCL, University of London ;Sileo, G.; Universit`a degli Studi dell’Insubria–Sede di Como, Italy ;Pizzi, A.; Dipartimento di Scienze della Terra Universit`a ‘G. d’Annunzio’ Chieti, Italy ;Pucci, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Walker, J. F.; Research School of Earth Sciences, Birkbeck/UCL, University of London ;Wilkinson, M.; Department of Earth Sciences, Durham University, Science Labs, Durham ;McCaffrey, K.; Department of Earth Sciences, Durham University, Science Labs, Durham ;Phillips, R.; Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, ;Michetti, A.; Universit`a degli Studi dell’Insubria–Sede di Como, Italy ;Guerrieri, L.; Geological Survey of Italy, ISPRA–High Institute for the Environmental Protection and Research, Italy ;Blumetti, A. M.; Geological Survey of Italy, ISPRA–High Institute for the Environmental Protection and Research, Italy ;Vittori, E.; Geological Survey of Italy, ISPRA–High Institute for the Environmental Protection and Research, Italy ;Cowie, P.; Institute of Geography, School of GeoSciences, University of Edinburgh, UK ;Sammonds, P.; Research School of Earth Sciences, Birkbeck/UCL, University of London ;Galli, P.; Dipartimento della Protezione Civile Nazionale, Rome, Italy ;Boncio, P.; Dipartimento di Scienze della Terra Universit`a ‘G. d’Annunzio’ Chieti, Italy ;Bristow, C.; Research School of Earth Sciences, Birkbeck/UCL, University of London ;Walters, R.; COMET, Department of Earth Sciences, University of Oxford, Oxford, UK; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The shallow subsurface structure of the 2009 April 6 Mw 6.3 L’Aquila earthquake surface rupture at Paganica has been investigated with ground penetrating radar to study how the surface rupture relates spatially to previous surface displacements during the Holocene and Pleistocene. The discontinuous surface rupture stepped between en-echelon/parallel faults within the overall fault zone that show clear Holocene/Pleistocene offsets in the top 10 m of the subsurface. Some portions of the fault zone that show clear Holocene offsets were not ruptured in 2009, having been bypassed as the rupture stepped across a relay zone onto a fault across strike. The slip vectors, defined by opening directions across surface cracks, indicate dip-slip normal movement, whose azimuth remained constant between 210◦ and 228◦ across the zone where the rupture stepped between faults. We interpret maximum vertical offsets of the base of the Holocene summed across strike to be 4.5 m, which if averaged over 15 kyr, gives a maximum throw-rate of 0.23–0.30 mm yr–1, consistent with throw-rates implied by vertical offsets of a layer whose age we assume to be ∼33 ka. This compares with published values of 0.4 mm yr–1 for a minimum slip rate implied by offsets of Middle Pleistocene tephras, and 0.24 mm yr–1 since 24.8 kyr from palaeoseismology. The Paganica Fault, although clearly an important active structure, is not slipping fast enough to accommodate all of the 3–5 mm yr–1 of extension across this sector of the Apennines; other neighbouring range-bounding active normal faults also have a role to play in the seismic hazard.210 270