Publication Date:
2018-09-01
Description:
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 Mw = 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. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
2169-9313
Electronic ISSN:
2169-9356
Topics:
Geosciences
,
Physics
