Detection of directivity in seismic site response from microtremor spectral analysis (Articolo in rivista)

Type
Label
  • Detection of directivity in seismic site response from microtremor spectral analysis (Articolo in rivista) (literal)
Anno
  • 2008-01-01T00:00:00+01:00 (literal)
Alternative label
  • Del Gaudio V.; Coccia S.; Wasowski J.; Gallipoli M.R.; Mucciarelli M (2008)
    Detection of directivity in seismic site response from microtremor spectral analysis
    in Natural hazards and earth system sciences (Print)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Del Gaudio V.; Coccia S.; Wasowski J.; Gallipoli M.R.; Mucciarelli M (literal)
Pagina inizio
  • 1 (literal)
Pagina fine
  • 12 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 8 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, Italy Istituto di Ricerca per la Protezione Idrogeologica, Consiglio Nazionale delle Ricerche, Bari, Italy Istituto di Metodologie per le Analisi Ambientale, Consiglio Nazionale delle Ricerche, Tito Scalo, Potenza, Italy Dipartimento di Strutture, Geotecnica, Geologia Applicata all'Ingegneria, Universit`a degli Studi della Basilicata, Potenza, Italy (literal)
Titolo
  • Detection of directivity in seismic site response from microtremor spectral analysis (literal)
Abstract
  • Recent observations have shown that slope response to seismic shaking can be characterised by directional variations of a factor of 2-3 or larger, with maxima oriented along local topography features (e. g. maximum slope direction). This phenomenon appears influenced by slope material properties and has occasionally been detected on landslide-prone slopes, where a down-slope directed amplification could enhance susceptibility to seismically-induced landsliding. The exact conditions for the occurrence of directional amplification remain still unclear and the implementation of investigation techniques capable to reveal the presence of such phenomena is desirable. To this purpose we tested the applicability of a method commonly used to evaluate site resonance properties (Horizontal to Vertical Noise Ratio - HVNR or Nakamura's method) as reconnaissance technique for the identification of site response directivity. Measurements of the azimuthal variation of H/V spectral ratios (i.e. between horizontal and vertical component) of ambient microtremors were conducted in a landslide-prone study area of central Italy where a local accelerometric network had previously provided evidence of directivity phenomena on some slopes. The test results were compared with average H/V spectral ratios obtained for low-to-moderate earthquakes recorded by the accelerometric stations. In general, noise and seismic recordings provided different amplitudes of spectral ratios at similar frequencies, likely because of differences in signal and instrument characteristics. Nevertheless, both kinds of recordings showed that at sites affected by site response directivity major H/V peaks have orientations consistent (within 20 degrees-30 degrees) with the direction of maximum shaking energy. Therefore, HVNR appears to be a promising technique for identifying seismic response directivity. Furthermore, in a comparative test conducted on a slope mantled in part by a deep-seated landslide we detected spectral peaks with orientations close to the maximum slope direction, whereas no evidence of directivity was found outside the slide boundaries. This indicates the influence of the landslide body on seismic response directivity. (literal)
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