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Relation Between Near‐Fault Ground Motion Impulsive Signals and Source Parameters
Author(s) -
Scala A.,
Festa G.,
Del Gaudio S.
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2018jb015635
Subject(s) - hypocenter , seismology , seismogram , directivity , geology , amplitude , fault (geology) , geodesy , pulse (music) , physics , induced seismicity , engineering , optics , telecommunications , detector , antenna (radio)
Near‐fault ground motion records often present impulsive signals, characterized by a large amplitude in the velocity wavefield and by the energy concentrated in a short time window as compared to the total earthquake duration. This pulse‐like behavior is ascribed to the directivity of the seismic rupture, and it requires a stronger demand to the buildings not predicted by the classical design spectra. In this work we investigate the pulse occurrence and duration in near‐fault synthetic seismograms generated from an ensemble of k −2 source models. We exploited the fault geometry of the M w = 6.3, 2009 L'Aquila earthquake, which represents a typical example of normal‐fault earthquake for which several records in the fault vicinity are available for comparison with synthetics. We show that impulsive records are sensitive to the rupture velocity, to the hypocenter depth, and to the station location, whether it is on the hanging wall or on the footwall. The pulse duration was also shown to be proportional to the risetime, and it scales with the source‐receiver distance and inversely with the rupture velocity. We model these results as an effect of the coupled along‐strike and updip directivity.