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Burrato P. & DISS Working Group

FROM DRAWING ANTICLINE AXES TO 3D MODELLING OF SEISMOGENIC SOURCES: EVOLUTION OF SEISMOTECTONIC MAPPING IN THE PO PLAIN. Burrato P. & DISS Working Group (S. Barba, R. Basili , U. Fracassi , V. Kastelic , M.M. Tiberti , P. Vannoli , G. Valensise )

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Burrato P. & DISS Working Group

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  1. FROM DRAWING ANTICLINE AXES TO 3D MODELLING OF SEISMOGENIC SOURCES: EVOLUTION OF SEISMOTECTONIC MAPPING IN THE PO PLAIN Burrato P. & DISS Working Group (S. Barba, R. Basili, U. Fracassi, V. Kastelic, M.M. Tiberti, P. Vannoli, G. Valensise) MaesanoF.E. *, D’Ambrogi C.**, Toscani G.° (*) Francesco Emanuele Maesano: framae80@gmail.com (**) ISPRA, Servizio Geologico d’Italia/Dipartimento Difesa del Suolo, chiara.dambrogi@isprambiente.it (°) Dipartimento di Scienze della Terra, Università di Pavia, toscani@dst.unipv.it

  2. I terremoti del 20 e 29 Maggio 2012 sonostatieventiinattesi? Dalpuntodi vista geologico no! Seismogenic Sources from: Database ofPotentialSourcesforEarthquakesLargerthan M 5.5 in Italy INGV, 2001

  3. THE PROBLEM • The Po Plain is a challenging area for active tectonics studies. • In this almost flat region: • Strain rates are low; • Seismicity is moderate and infrequent; • Regional tectonic signal is larger than local ones; • Sedimentary rates are much higher than tectonic ones; • Locally, large man-induced vertical ground motion. • Hence: • Faulting and folding is almost everywhere blind. • To identify and characterize Seismogenic Sources we need an approach that integrates morphotectonic analysis and (possibly) high resolution subsurface geological and geophysical datasets.

  4. ACTIVE DEFORMATION: GPS GPS velocities not able to capture the activity of the outer blind thrust fronts! May-June 2012 Emilia seismic sequence (M5.9-5.8) Bennett et al., 2012 Active shortening localized along the mountain front

  5. ACTIVE DEFORMATION: GPS Devoti et al., 2011

  6. REGIONAL vs LOCAL TECTONIC SIGNAL Regional subsidence due to NA mountain building Blind faulting and folding Fantoni & Franciosi, 2010

  7. BUILDING A SEISMOGENIC SOURCE MODEL Input: subsurface geological and geophysical data MILANO VENEZIA BOLOGNA Bigi et al., 1992 – ModelloStrutturaled’Italia AA.VV.

  8. BUILDING A SEISMOGENIC SOURCE MODEL Input: geomorphology and near-surface geological data 3 4 1 2 1- Trino Vercellese 2- San Colombano 3- Romanengo 4- Monte Netto-Castenedolo-Ciliverghe Burrato et al., 2003

  9. FROM GEOLOGICAL/GEOMORPHOLOGICAL DATA TO SEISMOGENIC SOURCES DISS v. 3.1.1 - http://diss.rm.ingv.it/diss/ • GIS based database • Web interface • Google Earth

  10. FROM GEOLOGICAL/GEOMORPHOLOGICAL DATA TO SEISMOGENIC SOURCES DISS v. 3.1.1 - http://diss.rm.ingv.it/diss/ ITCS050 ITCS049 ITCS051 ITCS012 ITCS011 Bigi et al., 1992 – ModelloStrutturaled’Italia

  11. GROWTH STRATA ACROSS THE MIRANDOLA ANTICLINE thickening thinning A 0.40 My B 0.65 My C 3.6 My S N Topography Growth strata Horizon A Horizon B 0.40 My 0.65 My 3.60 My Horizon C Burrato et al., 2003

  12. AES7-8 125-0 ka AES4-6 400-125 ka AEI 650-400 ka Vert. ex. 50x RER-ENI Agip, 1998 SAR: http://comunicazione.ingv.it/primo-piano/report_sar_ingv_emilia_2.pdf

  13. REFINING SR CALCULATIONS USING HIGH RESOLUTION DATA Compaction Up to 50% Compaction Up to 15% Scrocca et al., 2007 – Mirandola anticline Uplift rate 0.4-0 Ma interval 0.65 mm/a wo differential compaction Burrato et al., 2003 0.23 mm/a w decompaction workflow Scrocca et al., 2007

  14. COSEISMIC SURFACE DISPLACEMENT SAR imagefrom: http://comunicazione.ingv.it/primo-piano/report_sar_ingv_emilia_2.pdf

  15. DRAINAGE EVOLUTION IN THE EMILIA PLAIN Po River before VIII centuryb.C. Secchia River XII-XV century A.D. Panaro River Reconstruction based on Castaldiniet al. (1979) Burrato et al., 2003

  16. DRAINAGE ANOMALIES IN THE EMILIA PLAIN 26 >15° 25 23 24 Contour-lines (5m) Topographic gradient Avg drainage direction >15° Anomalous reach base map from: Geomorphological Map of the Po Plain (1997) Burrato et al., 2003

  17. DISPLACEMENT MODELING Mirandola Source Length 18 km Width 14 km Min depth 6 km Max depth 12 km Strike N100 Dip 25° Rake 90° Max M 6.5 Vertical displacement for 1 km of slip Po River Secchia River Panaro River 20 km Burrato et al., 2003

  18. CALCULATING SLIP RATE USING DISLOCATION MODELING 1.68 mm/y Expected Vertical displacement 389 m x 1000 m slip Topography NOT CONSIDERING DIFFERENTIAL COMPACTION! • 260 m x 670 m of slip in 400 Ky on a 25° dipping fault Horizon A Horizon B 0.40 My 0.65 My 3.60 My Horizon C N S Burrato et al., 2003

  19. Fault propagationfolds: trishear A NEW APPROACH: FROM RAW DATA TO SR Dataset 1 2 3 4 Dislocatedhorizons: fault parallel flow 3D models Decompaction Shallowsurfaces: Dislocationmodeling Maesano et al., 2011 - GeoItalia

  20. DATASET Regional cross sections 1 Shallowsections – CARG Project-RER Sectionsmodifiedfrom: Fantoni et al., 2009 Toscani et al., 2006 Maesano et al., 2011 - GeoItalia

  21. CONSTRUCTION OF 3D MODELS FROM 2D SECTIONS 2 Maesano et al., 2011 - GeoItalia

  22. DECOMPACTION 10% thickness changes at anticline axes Up to 40% thickness changes in synclines 3 Maesano et al., 2011 - GeoItalia

  23. RESULTS Romagna Folds Emilia Folds Ferrara Folds Age (My) Maesano et al., 2011 - GeoItalia

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