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Modelling directivity effects of the October 21, 2002 (Mw = 5.7), Molise, Southern Italy, earthquake
Author(s)
Type
Conference paper
Language
English
Status
Unpublished
Issued date
September 2006
Conference Location
Geneva, Switzerland
Keywords
Abstract
Acceleration time series recorded by the Italian Strong Motion Network (RAN) during the
October 31, 2002 (Mw=5.8), Molise earthquake, are employed in order to investigate source
effects on the ground motion in the epicentral area. We consider two different seismogenic
sources: a fault model inferred from inversion of teleseismic, regional and local seismic signals
[Vallée and Di Luccio, 2005], and a fault model based on seismotectonic data [Basili and Vannoli,
2005].
Both source studies suggest a deep location of the earthquake fault plane (ranging from 6.0 to 20.1
km and from 12.0 to 19.9 km, respectively), however, with considerably different fault lengths
(5.2 and 10.5 km, respectively), and widths (14.2 and 8 km, respectively). Due to these
differences, only the second model allows for effective horizontal unilateral rupture propagation.
Finite fault effects are modelled by the Deterministic-Stochastic-Method (DSM) [Pacor et al.,
2005], and the Hybrid Integral-Composite source model (HIC) [Gallovic and Brokesova, 2006]. In
both methods k-square slip distributions on the faults are considered.
We simulate the October 31, 2002 earthquake considering: 1) Vallée and Di Luccio [2005]
faultwith a bilateral rupture propagation, and 2) Basili and Vannoli [2005] fault with unilateral
directions of the rupture propagation. The spectral attenuation is modelled using a regional
estimate of the quality factor [Castro et al., 2004] and k values estimated from acceleration
records. Comparison between synthetic and recorded data at nearby stations (hypocentral distances
< 60 km) performed in terms of frequency content and peak ground motion, favours the model
with unilateral propagation of the rupture.
Assuming the source model with unilateral rupture propagation, we utilize both asymptotic and
full wave field methods in order to simulate ground shaking scenarios for an area extending up to
150 km epicentral distance. These results are then subjected to comparison with peak ground
accelerations recorded in the far field.
October 31, 2002 (Mw=5.8), Molise earthquake, are employed in order to investigate source
effects on the ground motion in the epicentral area. We consider two different seismogenic
sources: a fault model inferred from inversion of teleseismic, regional and local seismic signals
[Vallée and Di Luccio, 2005], and a fault model based on seismotectonic data [Basili and Vannoli,
2005].
Both source studies suggest a deep location of the earthquake fault plane (ranging from 6.0 to 20.1
km and from 12.0 to 19.9 km, respectively), however, with considerably different fault lengths
(5.2 and 10.5 km, respectively), and widths (14.2 and 8 km, respectively). Due to these
differences, only the second model allows for effective horizontal unilateral rupture propagation.
Finite fault effects are modelled by the Deterministic-Stochastic-Method (DSM) [Pacor et al.,
2005], and the Hybrid Integral-Composite source model (HIC) [Gallovic and Brokesova, 2006]. In
both methods k-square slip distributions on the faults are considered.
We simulate the October 31, 2002 earthquake considering: 1) Vallée and Di Luccio [2005]
faultwith a bilateral rupture propagation, and 2) Basili and Vannoli [2005] fault with unilateral
directions of the rupture propagation. The spectral attenuation is modelled using a regional
estimate of the quality factor [Castro et al., 2004] and k values estimated from acceleration
records. Comparison between synthetic and recorded data at nearby stations (hypocentral distances
< 60 km) performed in terms of frequency content and peak ground motion, favours the model
with unilateral propagation of the rupture.
Assuming the source model with unilateral rupture propagation, we utilize both asymptotic and
full wave field methods in order to simulate ground shaking scenarios for an area extending up to
150 km epicentral distance. These results are then subjected to comparison with peak ground
accelerations recorded in the far field.
References
Anderson, J.G. and Hough, S. (1984), A model for the shape of Fourier amplitude spectrum of acceleration at
high frequencies, Bull. Seism. Soc. Am., 74, 1969-1994.
Andrews, D. J. (1980), A stochastic fault model, 1. Static case, J. Geophys. Res., 85, 3867-3877.
Bernard, P. and Madariaga, R. (1984), A new asymptotic method for the modeling of near field accelerograms,
Bull. Seism. Soc. Am., 74, 539-558.
Bouchon, M. (1981), A simple method to calculate Green's functions for elastic layered media, Bull. Seism. Soc.
Am., 71, 959-971.
Castro, R. R., Gallipoli, M. R. and Mucciarelli, M. (2004), An attenuation study in Southern Italy using local and
regional earthquakes recorded by seismic network of Basilicata, Ann .Geophys ., 47, 1597-1608.
Gallovic, F. and Brokesova, J. (2006), Hybrid k-squared Source Model for Strong Ground Motion Simulations:
an Introduction, submitted to Physics .Earth. Planet. Int. (http://geo.mff.cuni.cz/~gallovic)
Chiarabba, C, De Gori, P., Chiaraluce, L. Bordoni, P., Cattaneo, M., De Martin, M., Frepoli, A., Michelini, A.,
Monachesi, G., Moretti, M., Augliera, P., D’Alema, E., Frapiccini, M., Gassi, A., Marzorati, S., Di
Bartolomeo, P., Gentile, S., Govoni, A., Lovisa, L., Romanelli, M., Ferretti, G., Pasta, M., Spallarossa, D.
and Zunino, E. (2005), Mainshocks and aftershocks of the 2002 molise seismic sequenze, southern Italy,
J. Seismol., 9, 487-494.
Basili, R., and Vannoli, P. (2005). Source ITGG052 San Giuliano di Puglia and Source ITGG053 Ripabottoni.
In: DISS Working Group, Database of Individual Seismogenic Sources (DISS), Version 3.0.1: A
compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas.
http://www.ingv.it/DISS/ - Istituto Nazionale di Geofisica e Vulcanologia.
Maffei, J. and Bazzurro, P. (2004), The 2002 Molise, Italy, Earthquake, Earthquake Spectra, 20-S1, S1-S22.
Nuti, C., Santini, S. and Vanzi, I. (2004), Damage, Vulnerability and Retrofitting Strategies for the Molise
Hospital System Following the 2002 Molise, Italy, Earthquake, Earthquake Spectra, 20-S1, S285-S299.
Pacor, F., Cultrera, G., Mendez, A. and Cocco, M. (2005), Finite Fault Modeling of Strong Motion Using a
Hybrid Deterministic-Stochastic Approach, Bull. Seism. Soc. Am., 95, 225-240.
Satoh, T. (2002), Empirical Frequency-Dependent Radiation Pattern of the 1998 Miyagiken-Nanbu Earthquake
in Japan, Bull. Seism. Soc. Am., 92, 1032-1039.
Spudich, P. and Frazer, L.N. (1984), Use of ray theory to calculate high frequency radiation from earthquake
sources having spatially variable rupture velocity and stress drop, Bull. Seism. Soc. Am., 74, 2061-2082.
SSN – Dipartimento della Protezione Civile – Ufficio Servizio Sismico Nazionale – Servizio Sistemi di
Monitoraggio (2004), The Strong Motion Records of Molise Sequence (October 2002 – December 2003),
CD-ROM, Rome, 2004.
Valensise, G., Pantosti, D. and Basili, R. (2004), Seismology and Tectonic Setting of the 2002 Molise, Italy,
Earthquake, Earthquake Spectra, 20-S1, S23-S37.
Vallée, M. and Di Luccio, F. (2005), Source analysis of the 2002 Molise, southern Italy, twin earthquakes (10/31
and 11/01), Geophys. Res. Lett., 32, L12309.
Wells, D.L. and Coppersmith, K.J. (1994), New Empirical Relationships among Magnitude, Rupture Length,
Rupture Width, Rupture Area, and Surface Displacement, Bull. Seism. Soc. Am., 84, 974-1002.
Zeng, Y., Anderson, J. G. and Yu, G. (1994), A composite source model for computing realistic synthetic strong
ground motions, Geophys. Res. Lett., 21, 725-728.
high frequencies, Bull. Seism. Soc. Am., 74, 1969-1994.
Andrews, D. J. (1980), A stochastic fault model, 1. Static case, J. Geophys. Res., 85, 3867-3877.
Bernard, P. and Madariaga, R. (1984), A new asymptotic method for the modeling of near field accelerograms,
Bull. Seism. Soc. Am., 74, 539-558.
Bouchon, M. (1981), A simple method to calculate Green's functions for elastic layered media, Bull. Seism. Soc.
Am., 71, 959-971.
Castro, R. R., Gallipoli, M. R. and Mucciarelli, M. (2004), An attenuation study in Southern Italy using local and
regional earthquakes recorded by seismic network of Basilicata, Ann .Geophys ., 47, 1597-1608.
Gallovic, F. and Brokesova, J. (2006), Hybrid k-squared Source Model for Strong Ground Motion Simulations:
an Introduction, submitted to Physics .Earth. Planet. Int. (http://geo.mff.cuni.cz/~gallovic)
Chiarabba, C, De Gori, P., Chiaraluce, L. Bordoni, P., Cattaneo, M., De Martin, M., Frepoli, A., Michelini, A.,
Monachesi, G., Moretti, M., Augliera, P., D’Alema, E., Frapiccini, M., Gassi, A., Marzorati, S., Di
Bartolomeo, P., Gentile, S., Govoni, A., Lovisa, L., Romanelli, M., Ferretti, G., Pasta, M., Spallarossa, D.
and Zunino, E. (2005), Mainshocks and aftershocks of the 2002 molise seismic sequenze, southern Italy,
J. Seismol., 9, 487-494.
Basili, R., and Vannoli, P. (2005). Source ITGG052 San Giuliano di Puglia and Source ITGG053 Ripabottoni.
In: DISS Working Group, Database of Individual Seismogenic Sources (DISS), Version 3.0.1: A
compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas.
http://www.ingv.it/DISS/ - Istituto Nazionale di Geofisica e Vulcanologia.
Maffei, J. and Bazzurro, P. (2004), The 2002 Molise, Italy, Earthquake, Earthquake Spectra, 20-S1, S1-S22.
Nuti, C., Santini, S. and Vanzi, I. (2004), Damage, Vulnerability and Retrofitting Strategies for the Molise
Hospital System Following the 2002 Molise, Italy, Earthquake, Earthquake Spectra, 20-S1, S285-S299.
Pacor, F., Cultrera, G., Mendez, A. and Cocco, M. (2005), Finite Fault Modeling of Strong Motion Using a
Hybrid Deterministic-Stochastic Approach, Bull. Seism. Soc. Am., 95, 225-240.
Satoh, T. (2002), Empirical Frequency-Dependent Radiation Pattern of the 1998 Miyagiken-Nanbu Earthquake
in Japan, Bull. Seism. Soc. Am., 92, 1032-1039.
Spudich, P. and Frazer, L.N. (1984), Use of ray theory to calculate high frequency radiation from earthquake
sources having spatially variable rupture velocity and stress drop, Bull. Seism. Soc. Am., 74, 2061-2082.
SSN – Dipartimento della Protezione Civile – Ufficio Servizio Sismico Nazionale – Servizio Sistemi di
Monitoraggio (2004), The Strong Motion Records of Molise Sequence (October 2002 – December 2003),
CD-ROM, Rome, 2004.
Valensise, G., Pantosti, D. and Basili, R. (2004), Seismology and Tectonic Setting of the 2002 Molise, Italy,
Earthquake, Earthquake Spectra, 20-S1, S23-S37.
Vallée, M. and Di Luccio, F. (2005), Source analysis of the 2002 Molise, southern Italy, twin earthquakes (10/31
and 11/01), Geophys. Res. Lett., 32, L12309.
Wells, D.L. and Coppersmith, K.J. (1994), New Empirical Relationships among Magnitude, Rupture Length,
Rupture Width, Rupture Area, and Surface Displacement, Bull. Seism. Soc. Am., 84, 974-1002.
Zeng, Y., Anderson, J. G. and Yu, G. (1994), A composite source model for computing realistic synthetic strong
ground motions, Geophys. Res. Lett., 21, 725-728.
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