a controlled-source experiment to investigate the origin of wavefield polarization in fault zones...

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A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1 , Antonio Rovelli 2 , Fabrizio Cara 2 , Pier Paolo Bruno 3 , Michele Punzo 4 , and Francesco Varriale 5 1 Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Seismology and Tectonophysics , Roma, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy 4 Consiglio Nazionale delle Ricerche, IAMC, Napoli, Italy 5 AMRA, Napoli, Italy

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Page 1: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

A controlled-source experiment to investigate the origin of wavefield polarization in fault zones

Giuseppe Di Giulio1, Antonio Rovelli2, Fabrizio Cara2, Pier Paolo Bruno3, Michele Punzo4, and Francesco Varriale5

1 Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy

2 Istituto Nazionale di Geofisica e Vulcanologia, Seismology and Tectonophysics , Roma, Italy

3 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy

4 Consiglio Nazionale delle Ricerche, IAMC, Napoli, Italy

5 AMRA, Napoli, Italy

Page 2: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Seismotectonic setting (after Monaco et al., 2005)

White arrows represent the horizontal displacement vectors as measured by Bonforte et

al. (2008) between July 2005 and June 2006.

Faults on Mt. Etna

10 cm

10 cm

The study area: the Pernicana Fault

Rigano et al (2008) observe a strong wavefield polarization in fault zones

Page 3: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Ambient noise

Earthquakes

Page 4: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

What is the origin of the strong horizontal polarization in the fault zone?

Page 5: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Summit crater, Mt. EtnaFalsaperla et al. 2010, JGR

At the crater stations, horizontal site polarization is independent of the source position and seismic signal nature (earthquakes, exposive volcanic episodes, tremor) and tends to be transversal to the radial fracture field

Page 6: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Vertical excitation, sweep modality

The controlled-source experiment

Page 7: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Eccitazione orizzontale e profili stazioni

Page 8: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

A source-controlled experiment on Mt. Etna to investigate the origin of wavefield polarization in fault zones

Radial component corresponds to ''the natural site polarization''

5-Hz band-pass filter

Comp. Z

Distance 300 m

Comp. Radial

Distance 300 m

Comp. Transverse

Distance 300 m

Comp. Z

Distance 10 m

Comp. Radial

Distance 10 m

Comp. Tranverse

Distance 10 m

Array layout N240, Source Polarization N330 ''Natural Site Polarization''

Page 9: A controlled-source experiment to investigate the origin of wavefield polarization in fault zones Giuseppe Di Giulio 1, Antonio Rovelli 2, Fabrizio Cara

Signal bp 5 Hz

Array layout N240, Source Polarization N330 ''Natural Site Polarization''

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m

Noise lp 2 Hz

Noise bp 5 Hz

Signal bp 5 Hz

Noise lp 2 Hz

Noise bp 5 Hz

Array layout N330, Source Polarization N240

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