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
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 Faults on Mt. Etna 10 cm The study area: the Pernicana Fault Rigano et al (2008) observe a strong wavefield polarization in fault zones
Ambient noise Earthquakes
What is the origin of the strong horizontal polarization in the fault zone?
Summit crater, Mt. Etna Falsaperla 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
Vertical excitation, sweep modality The controlled-source experiment
Eccitazione orizzontale e profili stazioni
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''
Signal bp 5 Hz Array layout N240, Source Polarization N330 ''Natural Site Polarization'' -63 m Noise lp 2 HzNoise bp 5 Hz Signal bp 5 HzNoise lp 2 HzNoise bp 5 Hz Array layout N330, Source Polarization N m 50 m 100 m 150 m 200 m 250 m 300 m 10 m 50 m 100 m 150 m 200 m 250 m 300 m