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  • 1
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    Geodetic slip-rates from block-modeling of a dense GPS velocity field in Italy: new clues on seismic potential from comparison with seismic moment release (2014)
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    Publication Date: 2014-05-15
    Description: The growing number of GPS stations in Italy and surrounding regions allows to study, with increasingly spatial details, the velocity gradients across the major seismogenic faults belonging to the complex Central Mediterranean segment of the Nubia-Eurasia plate boundary. If the regional scale pattern of the strain-rate field has been already constrained by several authors, adopting different schemes of sparse velocities interpolation algorithms, showing consistency with seismotectonics data, an estimate of the geodetic slilp-rates at a regional scale is still missing. In this work we use data from 〉 1000 GPS stations to determine a uniformly defined velocity field, though the analysis of position time-series realized in the ITRF08 reference frame. We use an elastic block-modeling approach to model interseismic fault slip-rates while accounting for rotations of crustal blocks within the complex Central Mediterranean microplates mosaic. We use available catalogues of active faults and instrumental seismicity to define the model geometry, where faults are parameterized as uniformly slipping rectangular planes. The model provides a good fit to the horizontal velocities and fault kinematics that are largely consistent with other geological and seismotectonics information. The estimated geodetic slip-rates are generally faster than the geological ones, considering the large uncertainties associated to the available geologic rates. We use the best-fit block model to calculate a continuous horizontal velocity field and the resulting strain-rate field, which is converted into seismic-moment accumulation rate. We compare the geodetic moment rate with the seismic moment rate obtained from summation of historical and instrumental seismic catalogues, homogeneously pre-processed. The comparison shows areas characterized by moment deficits, opening new clues on the seismic potential of Italy.
    Description: Unpublished
    Description: San Francisco, CA, USA
    Description: 2T. Tettonica attiva
    Description: open
    Keywords: block modeling ; GPS velocities ; geodetic slip-rates ; geodetic strain-rates ; seismic moment release ; seismic potential ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 2
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    Kinematic model of active extension across the Umbria-Marche Apennines from GPS measurements: fault slip-rates and interseismic coupling of the Alto Tiberina low-angle normal fault (2014)
    Details
    Publication Date: 2017-04-04
    Description: The Umbria-Marche Apennines are characterized mainly by SW-NE oriented extensional deformation and most of major historical and instrumental earthquakes occurred mainly on the western side of chain, bounded by west-dipping buried high-angle normal faults. Recent studies about the northernmost part of Umbria-Marche region show seismic and tectonic activity on correspondence of the east-dipping Alto Tiberina (AT) low-angle normal fault (LANF), which is widely documented by geological data and deep seismic reflection profiles. In this area which of the known fault systems play a major role in accommodating the extension, and which are the modes (seismic VS aseismic deformation) this extension is taken up, is still a debated topic. During last years on Umbria-Marche Apennines close to Gubbio fault (GuF) a dense network of continuous GPS stations, belonging to the RING-INGV network, has been installed, improving significantly the spatial resolution of the detectable geodetic gradients. We used a self-consistent kinematic block modeling to study this sector of the Umbria-Marche Apennines, in order to understand which fault system is accommodating the tectonic extension. We found that both fault systems, i.e. the Alto Tiberina LANF and the antithetic high-angle normal faults, are needed to better reproduce the nearfield GPS velocities, obtaining kinematic agreement with geological slip-rates. Moreover we parameterized the ATF fault as a, more realistic, curved surface to infer the distribution of interseismic coupling (IC), which is validated by numerous resolution tests. The obtained IC distribution shows a correlation between relocated microseismicity and uncoupled patches attributed to aseismic creeping behavior, which could be explained by the presence of fluid overpressure. Otherwise this correlation has been verified with a very small quantity of events (almost 400) and it might be of interest to evaluate this correlation with future available data.
    Description: Published
    Description: Trieste (Italy)
    Description: 2T. Tettonica attiva
    Description: open
    Keywords: Alto Tiberina LANF ; interseismic coupling ; fault creeping ; long-term fault slip-rates ; block modeling ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Extended abstract
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  • 3
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    Kinematic block modeling of GPS velocities in Italy and seismic potential (2014)
    Details
    Publication Date: 2017-04-04
    Description: We use a dense GPS velocity field, from the analysis of 〉1000 continuous stations, and elastic block modeling to study the interseismic strain accumulation along the Alpine and Apennines active tectonic belts in Italy. We consider available fault catalogues, instrumental and historical seismicity to determine the blocks boundaries geometry, parameterized as uniformly slipping rectangular planes. We invert horizontal velocities to estimate Euler vectors of tectonic blocks together with slip-rates at block-bounding faults. When allowed by density of GPS data, we optimize faults dip and locking-depth by searching the parameters that provide the best fit to local GPS data. Overall we obtain a good fit of the horizontal velocities and geodetic slip rates that are kinematically consistent with available geological and seismotectonic information. We use the best-fit geometric and kinematic model parameters to compute the expected GPS velocities over a dense regular grid. Denser model velocities are used to estimate the velocity gradient field on a regular grid, made by cell elements of 0.25°x0.25°. Geodetic strain-rates at each cell are converted into seismic moment accumulation rates, following the Kostrov formulation, considering as seismogenic thickness values obtained from a crustal (EPcrust) model and earthquake hypocentral distribution. Geodetic moment accumulation rates are compared with seismic moment rates released by earthquakes, obtained from the analysis of a seismic catalogue realized by merging several instrumental and historical catalogues covering the 1600-2012 timespan, and uniformly defined moment magnitudes. The comparison between geodetic moment accumulation rates and seismic moment release rates highlights regions with significant moment deficits but also areas with a surplus of the seismic moment released, with important implications for seismic hazard evaluations and assumptions behind the approach used in this work.
    Description: Published
    Description: “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Sicily, IT
    Description: 2T. Tettonica attiva
    Description: open
    Keywords: Block Modeling ; geodetic strain rates ; interseismic deformation ; seismic moment release ; seismic potential ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Abstract
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