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Complexity of theMw6.3 2009 L’Aquila (central Italy) earthquake: 2. Broadband strong motion modeling
Language
English
Obiettivo Specifico
4.1. Metodologie sismologiche per l'ingegneria sismica
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/117(2012)
ISSN
0148-0227
Electronic ISSN
2156–2202
Publisher
American Geophysical Union
Pages (printed)
B0438
Issued date
April 21, 2012
Keywords
Abstract
Near-fault strong-ground motions (0.1–10 Hz) recorded during the Mw 6.3 2009
L’Aquila earthquake exhibit great spatial variability. Modeling the observed seismograms
allows linking distinct features of the observed wavefield to particular source and
propagation effects and provides insights on strong motion complexity from this moderate
magnitude event. We utilize a hybrid integral-composite approach based on a k-square
kinematic rupture model, combining low-frequency coherent and high-frequency
incoherent source radiation and providing omega-squared source spectral decay. Several
source model features, proven to be stable by means of an uncertainty analysis in the
preceding low-frequency (<0.2 Hz) multiple finite-extent source inversion (Paper 1), were
constrained. Synthetic Green’s functions are calculated in a 1D-layered crustal model
including 1D soil profiles to account for site-specific response (where available). The
results show that although the local site effects improve the modeling, the spatial
broadband ground-motion variability is to large extent controlled by the rupture
kinematics. The modeling thus confirms and further constraints the source model features,
including the position and slip amount of the two main asperities, the largest asperity time
delay and the rupture velocity distribution on the fault. Furthermore, we demonstrate
that the crossover frequency dividing the coherent and incoherent wavefield, often
considered independent on the station position, has to be variable in order to adequately
reproduce both near and far station recordings. This suggests that the incoherency of the
radiated wavefield is controlled by the wave-propagation phenomena and/or the initial
updip rupture propagation was very smooth (coherent) up to relatively high frequencies
(>2 Hz)
L’Aquila earthquake exhibit great spatial variability. Modeling the observed seismograms
allows linking distinct features of the observed wavefield to particular source and
propagation effects and provides insights on strong motion complexity from this moderate
magnitude event. We utilize a hybrid integral-composite approach based on a k-square
kinematic rupture model, combining low-frequency coherent and high-frequency
incoherent source radiation and providing omega-squared source spectral decay. Several
source model features, proven to be stable by means of an uncertainty analysis in the
preceding low-frequency (<0.2 Hz) multiple finite-extent source inversion (Paper 1), were
constrained. Synthetic Green’s functions are calculated in a 1D-layered crustal model
including 1D soil profiles to account for site-specific response (where available). The
results show that although the local site effects improve the modeling, the spatial
broadband ground-motion variability is to large extent controlled by the rupture
kinematics. The modeling thus confirms and further constraints the source model features,
including the position and slip amount of the two main asperities, the largest asperity time
delay and the rupture velocity distribution on the fault. Furthermore, we demonstrate
that the crossover frequency dividing the coherent and incoherent wavefield, often
considered independent on the station position, has to be variable in order to adequately
reproduce both near and far station recordings. This suggests that the incoherency of the
radiated wavefield is controlled by the wave-propagation phenomena and/or the initial
updip rupture propagation was very smooth (coherent) up to relatively high frequencies
(>2 Hz)
Type
article
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