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La sequenza sismica del dell'Emilia 2012: un primo rapporto D.Piccinini (1) G.Saccorotti (1,2)

La sequenza sismica del dell'Emilia 2012: un primo rapporto D.Piccinini (1) G.Saccorotti (1,2) Istituto Nazionale di Geofisica e Vulcanologia Fondazione Prato Ricerche. THIS TALK Description of the sequence Rapid Response Spatio-Temporal behaviour Focal Mechanisms

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La sequenza sismica del dell'Emilia 2012: un primo rapporto D.Piccinini (1) G.Saccorotti (1,2)

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  1. La sequenza sismica del dell'Emilia 2012: un primo rapporto D.Piccinini (1) G.Saccorotti(1,2) Istituto Nazionale di Geofisica e Vulcanologia Fondazione Prato Ricerche

  2. THIS TALK • Description of the sequence Rapid Response Spatio-Temporal behaviour Focal Mechanisms Coseismic Deformation • Preliminary source estimates Source imaging from Array Analisys EGF Source Time Function

  3. Seismicity Map of Italy

  4. Seismicity Map of Italy

  5. Seismotectonic Focal mechanisms: compression in Po plain, extension at the Thyrrenian side of the orogen

  6. Instrumental Seismicity (2005-12.31.2011)

  7. Instrumental Seismicity (1.1.2012-present)

  8. INGV Permanent Network

  9. Rapid Response Network EQ occurrence [04:03 Local Time] First temporary station in acquisition since 10 AM (1 PM in real time) First 24 h : 8 temporary seismic station installed (4 stand alone + 4 real time) First 48 h : 16 temporary seismic station installed (8 stand alone + 8 real time) The INGV groups (Milano, Ancona, Roma, Arezzo, Grottaminarda, Bologna, Pisa) Abruzzese Luigi, Augliera Paolo, Bono Andrea, Carannante Simona, Cardinale Vincenzo, Castagnozzi Angelo, Cattaneo Marco, Cecere, Gianpaolo, Colasanti Gianfranco, Colasanti Marco, Criscuoli Fabio, D’Alema Ezio, D’Ambrosio Ciriaco, De Gori Pasquale, De Luca Giovanni, Falco Luigi, Fiaschi Andrea, Franceschina Gianlorenzo, Giovani Lucian,Improta Luigi, Ladina Chiara, Lauciani Valentino, Lovati Sara, Mandiello Alfonso, Marcocci Carlo, Margheriti Lucia,Marzorati Simone, Massa Marco, Mazza Salvatore, Minichiello Felice, Monachesi Giancarlo,Moretti Milena, Moschillo Raffaele,Piccinini Davide, Pignone Maurizio, Pintore Stefano, Pondrelli Silvia, Quintiliani Matteo, Serratore Andrea, Valoroso Luisa Half oh them are Temporary Employed @ INGV !!

  10. Rapid Response Network 22 Seismic Stations 6 component (Velocimeter + Accelerometers)

  11. Seismic Network ± 60 Seismic Stations are running in the area

  12. Temporal evolution of the sequence 20 May 2012 Mw=5.9 2012-05-29 11:00:25.000 5.2 2012-05-29 10:55:57.000 5.3 2012-05-29 07:00:03.000 5.8 2012-05-20 13:18:02.000 5.1 2012-05-20 02:07:31.000 5.1 2012-05-20 02:03:53.000 5.9

  13. Temporal evolution of the sequence Seismicity migrates West and deepens with time

  14. Temporal evolution of the sequence Most energetic events (Ml > 4)

  15. Focal Mechanisms Focal Solutions indicate an EW-oriented fracture

  16. Coseismic Deformation (from SAR) S. Salvi (pers. comm)

  17. Coseismic Deformation (from SAR) S. Salvi (pers. comm)

  18. Coseismic Deformation (from SAR) S. Salvi (pers. comm)

  19. Coseismic Deformation (from GPS) R. Devoti (pers. comm)

  20. The ruptured fault vs known structures • First-order consistency between tentative fault plane and local structures imaged by active seismics.

  21. Plane-Wave Fitting of Array Data Data: a set of 11 AVT stations, Z-component Theory : Dt = SDr Dt inter-station delay times (estimated from cross-correlation; S = vector slowness (wave vector) Dr inter-station position vector

  22. Plane-Wave Fitting of Array Data Processing – 1 Seismograms alignment to the expected time delays assuming back-azimuth to epicenter = 325°, and a ray parameter = 0.125 s/km (Apparent Velocity = 8 km/s)

  23. Plane-Wave Fitting of Array Data • Processing – 2 Low-Pass filter 3 Hz 2-s-long windows 0.1 s window shift Correlation Threshold 0.8 Evidences for 2 separate pulses

  24. Plane-Wave Fitting of Array Data • Processing – 3 Back-Projection of Seismic Rays onto a vertical plane passing through the hypocenter. Apparent velocity is taken as a proxy for Source Depth • Evidences for westward rupture propagation • Rupture velocity of 1st pulse is too high ! W E

  25. Directivity Effect

  26. Source Time Function from Empirical Green's Function deconvolution t ~ 4.5s) • U(w) = S(w)*P(w) → S(w) = U(w) / P(w) P(w) is usually calculated, but in can also be derived from a similar earthquake (Empirical Green's Function).

  27. Source Time Function from Empirical Green's Function deconvolution Main rupture has a duration of 4-5 s

  28. Thanks for your attention

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