FROM DRAWING ANTICLINE AXES TO 3D MODELLING OF SEISMOGENIC SOURCES: EVOLUTION OF SEISMOTECTONIC MAPP...
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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

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: [email protected]

(**) ISPRA, Servizio Geologico d’Italia/Dipartimento Difesa del Suolo, [email protected]

(°) Dipartimento di Scienze della Terra, Università di Pavia,

[email protected]


Burrato p diss working group

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


Burrato p diss working group

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.


Burrato p diss working group

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


Burrato p diss working group

ACTIVE DEFORMATION: GPS

Devoti et al., 2011


Burrato p diss working group

REGIONAL vs LOCAL TECTONIC SIGNAL

Regional subsidence due to NA mountain building

Blind faulting and folding

Fantoni & Franciosi, 2010


Burrato p diss working group

BUILDING A SEISMOGENIC SOURCE MODEL

Input: subsurface geological and geophysical data

MILANO

VENEZIA

BOLOGNA

Bigi et al., 1992 – ModelloStrutturaled’Italia

AA.VV.


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

COSEISMIC SURFACE DISPLACEMENT

SAR imagefrom: http://comunicazione.ingv.it/primo-piano/report_sar_ingv_emilia_2.pdf


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

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


Burrato p diss working group

DATASET

Regional cross sections

1

Shallowsections – CARG Project-RER

Sectionsmodifiedfrom:

Fantoni et al., 2009

Toscani et al., 2006

Maesano et al., 2011 - GeoItalia


Burrato p diss working group

CONSTRUCTION OF 3D MODELS FROM 2D SECTIONS

2

Maesano et al., 2011 - GeoItalia


Burrato p diss working group

DECOMPACTION

10% thickness changes at anticline axes

Up to 40% thickness changes in synclines

3

Maesano et al., 2011 - GeoItalia


Burrato p diss working group

RESULTS

Romagna Folds

Emilia Folds

Ferrara Folds

Age (My)

Maesano et al., 2011 - GeoItalia


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