Abstract
Near-fault ground motion records often capture instances of pulse-like behavior, where a burst of energy is expressed as large wave amplitude that occur over short time. The pulse-like ground motion can cause serious damage to long-period structures. Using numerical simulations of near-fault ground motions, we analyze the mechanisms involved in the generation of velocity pulses in the 1994 Northridge Earthquake and the 1979 Imperial Valley Earthquake. The degree to which the asperities affect the pulse generation process is investigated by identifying individual velocity pulses from the superposition process of sub-fault ground motions. Pulse indicators Ep and PGVp represent pulse characteristics in the ground motions at the stations located near the epicenter (near-epicenter stations) and the stations located along the forward rupture propagation direction of the asperity (rupture-direction stations), respectively. To observe the effects of the asperities and the spatial relationship between the pulse-like ground motion stations and the asperities, we determine the contribution of the sub-fault motions to the pulse amplitude. Furthermore, we analyze the pulse indicators and the frequency components using simulated ground motions from two different slip distributions. The near-epicenter station ground motions, produced by homogeneous slip distribution, exhibit higher pulse amplitude and more concentrated low-frequency energy than those generated by the inhomogeneous slip distribution. The rupture-direction station ground motions, produced by inhomogeneous slip distribution, present higher pulse amplitude and more concentrated low-frequency energy than those generated by the homogeneous slip distribution. Our analysis reveals that during the fault rupture process, the pulse energy and the pulse amplitude are influenced by both the slip distribution on the fault plane and the spatial relationship between the seismic station and the asperity.
Highlights
Near-fault ground motions, which are distinctly different from far-field ground motions, are influenced by propagation media, site conditions, and the nature of seismic source
The rise time is positively correlated with the slip distribution in the seismic source model, which means that the rise time of the sub-faults at the asperity is longer
The Ep and PGVp results in the presence of these two types of slip distribution are shown in Figures 8, 9
Summary
Near-fault ground motions, which are distinctly different from far-field ground motions, are influenced by propagation media, site conditions, and the nature of seismic source. Poiata et al (2017) suggested that the seismic stations located in the forward fault rupture direction mainly affected the generation of pulse-like ground motions in the 2009 L’Aquila Earthquake (Italy). At the rupture-direction stations (Figure 8B), the Ep values from the inhomogeneous slip distribution simulation are higher than those from the homogeneous slip distribution simulation after the ground motions of the sub-faults at asperity are superimposed; these waveforms are affected by the rupture of asperity (Figure 8B).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
