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Terrain characterization and structural control of the Auca Mahuida volcanism (Neuquén Basin, Argentina)

Wed, 31 Oct 2012 23:00:00 GMT

Title: Terrain characterization and structural control of the Auca Mahuida volcanism (Neuquén Basin, Argentina) Authors: Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Longo, M.; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Geomorphometric parameters (slope, aspect, valley depth, and areal density of cones) derived from a moderate resolution digital elevation model with a grid spacing of 100 m are used in an attempt to interpret the tectonic/structural features related to surface deformation in the Auca Mahuida volcanic terrain (Neuquén Basin, Argentina). The Auca Mahuida (2.03–0.88 Ma) is the southernmost volcanic field of the Payenia volcanic province, in the Andean foreland. The foreland is subjected to an E–W compression related to the eastward migration of the N–S striking thrust front of the Andes. The geomorphometric analysis indicates that the Auca Mahuida consists of a basal, E–W elongated lava field with monogenic vents and a summit, polygenic, also E–W elongated, cone. A N100◦E striking fault controls the southern flank of the field, which is also affected by scarps related to erosional and gravity-controlled processes. The drainage network shows a pseudo-radial pattern around the summit cone, and the Auca Mahuida’s deepest valley is structurally controlled by a NNW–SSE striking fault affecting the sedimentary basement. The volcanic field lies on a NE to E dipping substratum. The areal distribution of the monogenic cones is consistent with ascent of magmas along E–W striking fractures, and with elastic models of a pressurized hole (magma chamber) subjected to an E–W compression. At Auca Mahuida, the ascent of melts from the mantle is controlled, in the overriding crust, by tectonic structures formed in response to the E–W compression of the Andes.

Integrating geologic fault data into tsunami hazard studies

Thu, 18 Apr 2013 22:00:00 GMT

Title: Integrating geologic fault data into tsunami hazard studies Authors: Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Kastelic, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Romano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Lorito, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present the realization of a fault-source data set designed to become the starting point in regional-scale tsunami hazard studies. Our approach focuses on the parametric fault characterization in terms of geometry, kinematics, and assessment of activity rates, and includes a systematic classification in six justification levels of epistemic uncertainty related with the existence and behaviour of fault sources. We set up a case study in the central Mediterranean Sea, an area at the intersection of the European, African, and Aegean plates, characterized by a complex and debated tectonic structure and where several tsunamis occurred in the past. Using tsunami scenarios of maximum wave height due to crustal earthquakes (Mw=7) and subduction earthquakes (Mw=7 and Mw=8), we illustrate first-order consequences of critical choices in addressing the seismogenic and tsunamigenic potentials of fault sources. Although tsunamis generated by Mw=8 earthquakes predictably affect the entire basin, the impact of tsunamis generated by Mw=7 earthquakes on either crustal or subduction fault sources can still be strong at many locales. Such scenarios show how the relative location/orientation of faults with respect to target coastlines coupled with bathymetric features suggest avoiding the preselection of fault sources without addressing their possible impact onto hazard analysis results.

The Earth Expansion Evidence – A Challenge for Geology, Geophysics and Astronomy

Fri, 30 Nov 2012 23:00:00 GMT

Title: The Earth Expansion Evidence – A Challenge for Geology, Geophysics and Astronomy Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Boschi, E.; University of Bologna; Cwojdzinski, S.; Polish Geological Survey Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Boschi, Enzo; University of Bologna; Cwojdzinski, Stefan; Polish Geological Survey

New kinematic constraints of the western Doruneh fault, north-eastern Iran, from interseismic deformation analysis

Sun, 20 May 2012 22:00:00 GMT

Title: New kinematic constraints of the western Doruneh fault, north-eastern Iran, from interseismic deformation analysis Authors: Pezzo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Atzori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Shabanian, E.; CEREGE - AIX-MARSEILLE UNIVERSITE; Bellier, O.; CEREGE - AIX-MARSEILLE UNIVERSITE; Farbod, Y.; CEREGE - AIX-MARSEILLE UNIVERSITE Abstract: We used the SBAS DInSAR analysis technique to estimate the interseismic deformation along the western part of the Doruneh fault system (DFS), northeastern Iran. We processed 90 ENVISAT images from four different frames from ascending and descending orbits. Three of the ground velocity maps show a significant interseismic signal. Using a simple dislocation approach we model 2-D velocity profiles concerning three InSAR data set relative to the western part of the DFS, obtaining a good fit to the observations. The resulting model indicates that a slip rate of ∼5mmyr−1 accumulates on the fault below 10 km depth, and that in its western sector the Doruneh fault is not purely strike-slip (left-lateral) as in its central part, but shows a significant thrust component. Based on published geological observations, and assuming that all interseismic deformation is recovered with a single event, we can estimate a characteristic recurrence interval between 630 and 1400 yr.

The stress field in Europe: optimal orientations with confidence limits

Mon, 31 Dec 2012 23:00:00 GMT

Title: The stress field in Europe: optimal orientations with confidence limits Authors: Carafa, M. M. C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: In this study, we modify and extend a data analysis technique to determine the stress orientations between data clusters by adding an additional constraint governing the probability algorithm. We apply this technique to produce a map of the maximum horizontal compressive stress (S_Hmax) orientations in the greater European region (including Europe, Turkey and Mediterranean Africa). Using the World Stress Map dataset release 2008, we obtain analytical probability distributions of the directional differences as a function of the angular distance, θ. We then multiply the probability distributions that are based on pre-averaged data within θ<3° of the interpolation point and determine the maximum likelihood estimate of the S_Hmax orientation. At a given distance, the probability of obtaining a particular discrepancy decreases exponentially with discrepancy. By exploiting this feature observed in the World Stress Map release 2008 dataset, we increase the robustness of our S_Hmax determinations. For a reliable determination of the most likely S_Hmax orientation, we require that 90% confidence limits be less than ±60° and a minimum of three clusters, which is achieved for 57% of the study area, with small uncertainties of less than ±10° for 7% of the area. When the data density exceeds 0.8×10^-3 data/km2, our method provides a means of reproducing significant local patterns in the stress field. Several mountain ranges in the Mediterranean display 90° changes in the S_Hmax orientation from their crests (which often experience normal faulting) and their foothills (which often experience thrust faulting). This pattern constrains the tectonic stresses to a magnitude similar to that of the topographic stresses. Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2003. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.

Active deformation along the northern margin of the Hyblean Plateau (SE Sicily) from GPS and geological data

Sat, 31 Dec 2011 23:00:00 GMT

Title: Active deformation along the northern margin of the Hyblean Plateau (SE Sicily) from GPS and geological data Authors: Bonforte, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Catalano, S.; Università degli studi di Catania; Maniscalco, R.; Università degli studi di Catania; Romagnoli, G.; Università degli studi di Catania; Sturiale, G.; Università degli studi di Catania; Tortorici, G.; Università degli studi di Catania Abstract: A diffuse fragmentation of the Nubia-Eurasia tectonic boundary, due to the propagation of distinct extensional belts, has characterised the post-collision evolution of the region. In this frame, the Hyblean Plateau was affected, since about 1.5 Ma B.P., by the propagation of the the roughly N-S trending Siculo-Calabrian Rift Zone (SCRZ in Fig.1a; MONACO & TORTORICI, 2000), an extensional belt that extends from the onshore of southern Calabria to the SE Sicily. In the Hyblean plateau the propagation of the rift zone caused the reactivation of the main previous discontinuity. The earlier SE Sicily branch of the rift zone, in fact, propagated from the Ionian coast to the Scicli Line, causing the collapse of the NEtrending Scordia-Lentini Graben, at the northern margin of the plateau. This extensional basin represents an half-graben, which is controlled by a SE-facing master fault.

A multidisciplinary study of an active fault crossing urban areas: The Trecastagni Fault at Mt. Etna (Italy)

Mon, 31 Dec 2012 23:00:00 GMT

Title: A multidisciplinary study of an active fault crossing urban areas: The Trecastagni Fault at Mt. Etna (Italy) Authors: Bonforte, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Carnazzo, A.; Provincia Regionale di Catania; Gambino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Guglielmino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Obrizzo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Puglisi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: The Trecastagni Fault is a NNW–SSE tectonic structure in the densely inhabited southern flank of Mt. Etna, characterised by evident morphological scarps and movements of normal and right-lateral type that directly affect roads and buildings. The fault is affected by continuous dynamics with intermittent accelerations accompanied with shallow seismicity. It has an important role in the instability affecting Mt. Etna's south-eastern flank and represents part of the southern boundary of the unstable sector. The motion of the fault between 2005 and 2011 has been analysed by using a multi-disciplinary approach involving terrestrial and satellite ground deformation data. Active monitoring systems able to investigate the fault in detail are extensometers, a levelling network and InSAR. Two episodes of acceleration were recorded at the end of 2009 and during 2010. Data evidences that the acceleration episodes affected only portions of the fault and that stress may accumulate and be periodically released. Although bothmagmatic processes (inflation or intrusive episodes) and flank dynamics influence the occurrence of the TF acceleration episodes, the dragging effect of the overall seaward sliding of the south-eastern flank is evident and it causes the subsidence of the hangingwall, accumulating stress on the fault that is periodically seismically released.

Integrating new and traditional approaches for the estimate of slip-rates of active faults: examples from the Mw 6.3, 2009 L’Aquila earthquake area, Central Italy

Sat, 31 Dec 2011 23:00:00 GMT

Title: Integrating new and traditional approaches for the estimate of slip-rates of active faults: examples from the Mw 6.3, 2009 L’Aquila earthquake area, Central Italy Authors: Civico, Riccardo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: This thesis developed a multidisciplinary and multi-scale investigation strategy based on the integration of traditional and innovative approaches aimed at improving the normal faults seismogenic identification and characterization, focusing mainly on slip-rate estimate as a measure of the fault activity. The L’Aquila Mw 6.3 April 6, 2009 earthquake causative fault was used as a test site for the application, testing, and refinement of traditional and/or innovative approaches, with the aim to 1) evaluate their strength or limitations 2) develop a reference approach useful for extending the investigation to other active faults in the area and 3) translate the results of the methodological approaches into new inputs to local seismic hazard. The April 6, 2009 L’Aquila earthquake occurred on a so far poorly known tectonic structure, considered having a limited seismic potential, the Paganica - San Demetrio fault system (PSDFS), and thus has highlighted the need for a detailed knowledge in terms of location, geometry, and characterization of the active faults that are the potential sources for future earthquakes. To fill the gap of knowledge enhanced by the occurrence of the 2009 L’Aquila earthquake, we developed a multidisciplinary and multiscale‐based strategy consisting of paleoseismological investigations, detailed geomorphological and geological field studies, as well as shallow geophysical imaging and an innovative methodology that uses, as an alternative paleoseismological tool, core sampling and laboratory analyses but also in situ measurements of physical properties. The integration of geomorphology, geology as well as shallow geophysics, was essential to produce a new detailed geomorphological and geological map of the PSDFS and to define its tectonic style, arrangement, kinematics, extent, geometry and internal complexities. Our investigations highlighted that the PSDFS is a 19 km-long tectonic structure characterized by a complex structural setting at the surface and that is arranged in two main sectors: the Paganica sector to the NW and the San Demetrio sector to SE. The Paganica sector is characterized by a narrow deformation zone, with a relatively small (but deep) Quaternary basin affected by few fault splays. The San Demetrio sector is characterized by a strain distribution at the surface that is accommodated by several tectonic structures, with the system opening into a set of parallel, km-spaced fault traces that exhume and dissect the Quaternary basin. The integration of all the fault displacement data and age constraints (radiocarbon dating, optically stimulated luminescence (OSL) and tephrochronology) resulting from paleoseismological, geomorphological, geophysical and geological investigations played a primary role in the estimate of the slip-rate of the PSDFS. Slip-rates were estimated for different time intervals in the Quaternary, from Early Pleistocene (1.8 Ma) to Late Holocene (last 5 ka), yielding values ranging between 0.09 and 0.58 mm/yr and providing an average Quaternary slip-rate representative for the PSDFS of 0.27 - 0.48 mm/yr. We contributed also to the understanding of the PSDFS seismic behavior and of the local seismic hazard by estimating the max expected magnitude for this fault on the basis of its length (ca. 20 km) and slip per event (up to 0.8 m), and identifying the two most active fault splays at present. Our multidisciplinary results converge toward the possibility of the occurrence of past surface faulting earthquakes characterized by a moment magnitude between 6.3 and 6.8, notably larger than the 2009 event, but compatible with the M range observed in historical earthquakes in the area. The slip-rate distribution over time and space and the tectonic style of the PSDFS suggested the occurrence of strain migration through time in the southern sector, from the easternmost basin-bounding fault splay toward the southwestern splays. This topic has a significant implication in terms of surface faulting hazard in the area, because it can contribute defining the fault splays that have a higher potential to slip during future earthquakes along the PSDFS. By a methodological point of view, the multidisciplinary and multiscale‐based investigation strategy emphasizes the advantages of the joint application of different approaches and methodologies for active faults identification and characterization. Our work suggests that each approach alone may provide sufficient information but only the application of a multidisciplinary strategy is effective in providing robust results and in defining a proper framework of active faults.

Rapporto tecnico su: identificazione e caratterizzazione delle sorgenti sismogenetiche

Fri, 31 Dec 2004 23:00:00 GMT

Title: Rapporto tecnico su: identificazione e caratterizzazione delle sorgenti sismogenetiche Authors: Basili, Roberto; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Burrato, Pierfrancesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mariano, Sofia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mirabella, Francesco; Università degli Studi di Perugia; Ravaglia, Antonio; Valensise, Gianluca; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Vannoli, Paola; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia

A photographic dataset of the coseismic geological effects induced on the environment by the 2012 Emilia (Northern Italy) earthquake sequence

Sun, 30 Sep 2012 22:00:00 GMT

Title: A photographic dataset of the coseismic geological effects induced on the environment by the 2012 Emilia (Northern Italy) earthquake sequence Authors: Alessio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Alfonsi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Brunori, C. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Casula, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Cinti, F. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Civico, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Colini, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cucci, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; De Martini, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Falcucci, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Galadini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Gaudiosi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Gori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mariucci, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Montone, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Moro, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Nappi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Nardi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Nave, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Pantosti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Patera, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pesci, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Pignone, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Pinzi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pucci, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Vannoli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Venuti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Villani, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; EMERGEO, Working Group; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present a collection of pictures of the coseismic secondary geological effects produced on the environment by the 2012 Emilia seismic sequence in northern Italy. The May-June 2012 sequence struck a broad area located in the Po Plain region, causing 26 deaths and hundreds of injured, 15.000 homeless, severe damage of historical centres and industrial areas, and an estimated economic toll of ~2 billion of euros. The sequence included two mainshocks (Figure 1): the first one, with ML 5.9, occurred on May 20 between Finale Emilia, S. Felice sul Panaro and S. Martino Spino; the second one, with ML 5.8, occurred 12 km southwest of the previous mainshock on May 29. Both the mainshocks occurred on about E-W trending, S dipping blind thrust faults; the whole aftershocks area extends in an E-W direction for more than 50 km and includes five ML≥5.0 events and more than 1800 ML>1.5 events. Ground cracks and liquefactions were certainly the most relevant coseismic geological effects observed during the Emilia sequence. In particular, extensive liquefaction was observed over an area of ~1200 km2 following the May 20 and May 29 events. We collected all the coseismic geological evidence through field survey, helicopter and powered hang-glider trike survey, and reports from local people directly checked in the field. On the basis of their morphologic and structural characteristics the 1362 effects surveyed were grouped into three main categories: a) liquefactions related to overpressure of aquifers, occurring through several aligned vents forming coalescent flat cones (485 effects); b) liquefactions with huge amounts of liquefied sand and fine sand ejected from fractures tens of meters long (768); c) extensional fractures with small vertical throws, apparently organized in an en-echelon pattern, with no effects of liquefaction (109). The photographic dataset consists of 99 pictures of coseismic geological effects observed in 17 localities concentrated in the epicentral area. The pictures are sorted and presented by locality of observation; each photo reports several information such as the name of the site, the geographical coordinates and the type of effect observed. Figure 1 shows a map of the pictures sites along with the location of the two mainshocks; Figure 2 shows a detail of the distribution of the liquefactions in the area of S. Carlo. The complete description of the coseismic geological effects induced by the Emilia sequence, their relation with the aftershock area, the InSAR deformation area and the I>6 EMS felt area, along with the description of the technologies used for data sourcing and processing are shown in Emergeo Working Group [2012a and 2012b].