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Campillo, Michel
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Campillo, Michel
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- PublicationOpen AccessRupture history of the 1997 Umbria-Marche (Central Italy) main shocks from the inversion of GPS, DInSAR and near field strong motion data(2004)
; ; ; ; ; ; ; ;Hernandez, B.; Laboratoire de Dètection et de Gèophysique, Bruyëres-le-Ch tel, France ;Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cotton, F.; Laboratoire de Gèophysique Interne et Tectonophysique, Universitè Joseph Fourier, Grenoble, France ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Scotti, O.; Institut de Radioprotection et de Suretè Nuclèaire, Fontenay-aux-Roses, France ;Courboulex, F.; Universitè de Nice, Gèosciences Azur, Valbone, France ;Campillo, M.; Laboratoire de Gèophysique Interne et Tectonophysique, Universitè Joseph Fourier, Grenoble, France; ; ; ; ; ; We investigate the rupture history of the three largest magnitude earthquakes of the 1997 Umbria-Marche sequence by inverting GPS, DInSAR and near-source strong motion waveforms. We use the frequency domain inversion procedure proposed by Cotton and Campillo (1995) and calculate the Green s functions for a layered halfspace using the discrete wavenumber and reflectivity methods. We first invert GPS measurements and DInSAR interferograms to image the coseismic slip distribution on the fault planes in a layered half space for the two earthquakes that occurred on September 26, 1997 at 00:33 UTC (Mw = 5.7) and 09:40 UTC (Mw = 6.0) near Colfiorito. We also invert DInSAR interferograms to infer the slip distribution during the subsequent earthquake that occurred on October 14, 1997 at 15:23 UTC (Mw = 5.6) in the SE section of the seismogenic zone near Sellano. We also explore the set of acceptable solutions using a genetic algorithm to have information on the available resolution of geodetic data. The slip models obtained by geodetic data inversion are used to perform a forward modeling of strong motion waveforms for all three events. We adopt a constant rupture velocity of 2.6 km/s and a constant rise time of 1 s. Our results show that these rupture models provide an acceptable fit to recorded waveforms. Finally, we invert the recorded ground displacements, collected during the September 26th 09:40 main shock and the October 14th Sellano earthquake, to constrain the rupture history. We use the geodetic slip distribution as starting model for the iterative inversion procedure. The retrieved rupture models are consistent with those inferred from geodetic data and yield a good fit to recorded seismograms. These rupture models are characterized by a heterogeneous slip distribution and an evident rupture directivity in agreement with previous observations.348 610 - PublicationOpen AccessSeparation of Poroelastic and Elastic Processes of an Aquifer From Tectonic Phenomena Using Geodetic, Seismic, and Meteorological Data in the Pollino Region, ItalyVelocity variations obtained from ambient seismic noise are sensitive to many factors. We aimed to disentangle these processes in a 10-year-long recording of seismic noise from a single station in the Pollino region, in southern Italy. This region is characterized by aquifers and by a relatively short period of high seismic activity that included slow slip events and a urn:x-wiley:15252027:media:ggge22677:ggge22677-math-0001 earthquake that occurred on October 25, 2012. We apply two models that estimate the water level inside an aquifer, which show a good correlation with the measured urn:x-wiley:15252027:media:ggge22677:ggge22677-math-0002, showing that the velocity variations are inversely proportional to the pore pressure inside the aquifer. Our interpretation is further confirmed by geodetic measurements that show that in a direction parallel to the strike angle of the fault rupture, the expansion-contraction displacement of the zone follows the same patterns observed in the models and in the velocity variations, as a result of the pressure generated by the water on its interior. Going one step further, we analyze the nature of the small discrepancies between the measured and modeled velocity variations. These correlate well with the rainfall and with the vertical geodetic measures, which indicates an elastic response of the zone to the loading generated by the rainwater. Comparisons between these variables allow us to clearly identify the period of the seismic activity in the zone, which is represented by the characteristic drop in the seismic velocity in the period from the beginning of 2012 to mid-2013.
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