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 sequenceRapid ResponseSpatio-Temporal behaviourFocal MechanismsCoseismic Deformation

Preliminary source estimatesSource imaging from Array AnalisysEGF Source Time Function

Seismicity Map of Italy

Seismicity Map of Italy

Seismotectonic

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

Instrumental Seismicity (2005-12.31.2011)

Instrumental Seismicity (1.1.2012-present)

INGV Permanent Network

Rapid Response Network

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)

EQ occurrence [04:03 Local Time]

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 !!

Rapid Response Network

22 Seismic Stations 6 component(Velocimeter + Accelerometers)

Seismic Network

± 60 Seismic Stations are running in the area

20 May 2012Mw=5.9

2012-05-29 11:00:25.0005.22012-05-29 10:55:57.0005.32012-05-29 07:00:03.0005.82012-05-20 13:18:02.0005.12012-05-20 02:07:31.0005.12012-05-20 02:03:53.0005.9

Temporal evolution of the sequence

Temporal evolution of the sequence

Seismicity migrates West and deepens with time

Most energetic events (Ml > 4)

Temporal evolution of the sequence

Focal Mechanisms

Focal Solutions indicate an EW-oriented fracture

Coseismic Deformation(from SAR)

S. Salvi (pers. comm)

Coseismic Deformation(from SAR)

S. Salvi (pers. comm)

Coseismic Deformation(from SAR)

S. Salvi (pers. comm)

Coseismic Deformation(from GPS)

R. Devoti (pers. comm)

First-order consistency between tentative fault plane and local structures imaged by active seismics.

The ruptured fault vs known structures

Plane-Wave Fitting of Array Data

Data: a set of 11 AVT stations, Z-component

Theory : t = S r

t inter-station delay times (estimated from cross-correlation;S = vector slowness (wave vector)r inter-station position vector

Plane-Wave Fitting of Array Data

Processing – 1Seismograms 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)

Plane-Wave Fitting of Array Data

Processing – 2

Low-Pass filter 3 Hz2-s-long windows0.1 s window shiftCorrelation Threshold 0.8

Evidences for 2 separate pulses

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

Directivity Effect

Source Time Function from Empirical Green's Function deconvolution

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).

~ 4.5s)

Source Time Function from Empirical Green's Function deconvolution

Main rupture has a duration of 4-5 s

Thanks for your attention