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THE DEEP STRUCTURE OF THE L'AQUILA BASIN INVESTIGATED USING ARRAY MEASUREMENTS
Author(s)
Type
Extended abstract
Language
English
Obiettivo Specifico
4.1. Metodologie sismologiche per l'ingegneria sismica
Status
Published
Issued date
August 23, 2011
Conference Location
Earth Research Institute, UCSB, Santa Barbara, CA 93106
Keywords
Abstract
We present velocity profiles obtained through surface-wave methods in the historical city of L’Aquila (Italy). The city suffered severe damage (VIII-IX EMS intensity) during the April 6th 2009 Mw 6.3 earthquake. The area is characterized by the deep (up to 300-400 meters) basin of the Aterno river valley filled by lacustrine sediments over limestone bedrock. In downtown L'Aquila an outcropping unit basically composed of stiff conglomerates (Breccia) is over-imposed to ancient lacustrine sediments with a possible velocity
inversion at a depth ranging from few tens up to one hundred meters. We deployed five 2-D arrays of seismic stations and 1-D array
of vertical geophones in the city center. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion and spatial autocorrelation curves, calculated using array methods, were inverted through a neighborhood algorithm jointly with the microtremor HVNSR ellipticity. We obtain shear-wave velocity profiles (Vs) representative of the southern and northern sector of downtown L'Aquila. The resulting Vs profiles are used to compare the 1-D transfer functions to
aftershock data results. We apply a convolution approach evaluating synthetic time-histories in sites where surface stratigraphy is known and comparing them to recorded strong-motion data.
inversion at a depth ranging from few tens up to one hundred meters. We deployed five 2-D arrays of seismic stations and 1-D array
of vertical geophones in the city center. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion and spatial autocorrelation curves, calculated using array methods, were inverted through a neighborhood algorithm jointly with the microtremor HVNSR ellipticity. We obtain shear-wave velocity profiles (Vs) representative of the southern and northern sector of downtown L'Aquila. The resulting Vs profiles are used to compare the 1-D transfer functions to
aftershock data results. We apply a convolution approach evaluating synthetic time-histories in sites where surface stratigraphy is known and comparing them to recorded strong-motion data.
References
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Modeling’’, Bull. Seism. Soc. Am., Vol. 95, No. 4, pp. 1469 - 1481.
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Milana, G., R. M. Azzara, E. Bertrand, P. Bordoni, F. Cara, R. Cogliano, G. Cultrera, G. Di Giulio, A.M. Duval and A. Fodarella, et
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soils’’, J. Geotech. Eng. Div., ASCE, Vol. 112 (GT11), pp. 1016-1032.
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shallow structure and consequences over Vs inversion’’, J. Seismol., Vol. 12, pp. 1-19.
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Dipartimento della Protezione Civile, pp. 1-796, in Italian.
Amoroso, S., F. Del Monaco, F. Di Eusebio, P. Monaco, B. Taddei, M. Tallini, F. Totani, and G. Totani [2010], “Campagna di
indagini geologiche, geotecniche e geofisiche per lo studio della risposta sismica locale della città dell'Aquila: la stratigrafia dei sondaggi (Giugno - Agosto 2010)’’, CERFIS Report n.1-2010, pp. 1-51, http://www.cerfis.it/it/attivita/microzonazione.html, in Italian.
Bardet, J. P., K. Ichii, and C. H. Lin [2000], ‘’EERA, a computer program for equivalent-linear earthquake site response analyses of layered soil deposits, University of Southern California, Department of Civil Engineering’’, http://gees.usc.edu/GEES/
Bettig, B., P. Y. Bard, F. Scherbaum, J. Riepl, F. Cotton, C. Cornou, and D. Hatzfeld [2001], “Analysis of dense array noise
measurements using the modified spatial autocorrelation method (SPAC). Application to the Grenoble area’’, Boll. Geof. Teor. Appl., Vol. 42, No. 3-4, pp. 281-304.
Capon, J. [1969], “High-resolution frequency-wavenumber spectrum analysis’’, Proc. of the IEEE, Vol. 57, No. 8, pp. 1408–1418.
Cardarelli, E., and M. Cercato [2010], “Relazione sulla campagna d'indagine geofisica per lo studio della risposta sismica locale della città dell'Aquila, Prova Crosshole Sondaggi S3-S4’’, DICEA Report, pp. 1-13, http://www.cerfis.it/it/attivita/microzonazione.html, in
Italian.
Çelebi, M., P. Bazzurro, L. Chiaraluce, P. Clemente, L. Decanini, A. DeSortis, W. Ellsworth, A. Gorini, E. Kalkan, S. Marcucci,
G. Milana, F. Mollaioli, M. Olivieri, R. Paolucci, D. Rinaldis, A. Rovelli, F. Sabetta, and C. Stephens [2010], “Recorded Motions of the 6 April 2009 Mw 6.3 L’Aquila, Italy, Earthquake and Implications for Building Structural Damage: Overview’’, Earthquake Spectra, Vol. 26, No. 3, pp. 651-684, doi:10.1193/1.3450317.
De Luca, G., S. Marcucci, G. Milana, and T. Sanò [2005], “Evidence of Low-Frequency Amplification in the City of L’Aquila,
Central Italy, through a Multidisciplinary Approach Including Strong- and Weak-Motion Data, Ambient Noise, and Numerical
Modeling’’, Bull. Seism. Soc. Am., Vol. 95, No. 4, pp. 1469 - 1481.
Lacoss, R. T., E. J. Kelly, and M. N. Toksoz [1969], “Estimation of seismic noise structure using arrays’’, Geophysics, Vol. 34, pp. 21-38.
Milana, G., R. M. Azzara, E. Bertrand, P. Bordoni, F. Cara, R. Cogliano, G. Cultrera, G. Di Giulio, A.M. Duval and A. Fodarella, et
al. [2011], “The contribution of seismic data in microzonation studies for downtown L’Aquila’’, Bull. Earthquake Eng., Vol. 9, No. 3, pp. 741-759, doi: 10.1007/s10518-011-9246-6.
Seed, H. B., R. T. Wong, I. M. Idriss, and K.Tokimatsu [1986], “Moduli and damping factors for dynamic analyses of cohesionless
soils’’, J. Geotech. Eng. Div., ASCE, Vol. 112 (GT11), pp. 1016-1032.
Vucetic, M. and R. Dobry [1991], “Effects of the soil plasticity on ciclyc response’’, J. Geotech. Eng. Div., ASCE, Vol. 117, No.1, pp.
898-907.
Wathelet, M. [2008], “An improved neighborhood algorithm: parameter conditions and dynamic scaling’’, Geophys. Res. Lett., Vol. 35, L09301, doi:10.1029/2008GL033256.
Wathelet, M., D. Jongmans, M. Ohrnberger, and S.Bonnefoy-Claudet [2008], “Array performances for ambient vibrations on a
shallow structure and consequences over Vs inversion’’, J. Seismol., Vol. 12, pp. 1-19.
Working Group MS-AQ [2010], “Microzonazione sismica per la ricostruzione dell’area aquilana’’, Ed. Regione Abruzzo-
Dipartimento della Protezione Civile, pp. 1-796, in Italian.
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