Conditional Ground-Motion Model for Damaging Characteristics of Near-Fault Ground Motions Based on Instantaneous Power

The velocity pulse in near-fault ground motions has been used as a key characteristic of damaging ground motions. Characterization of the velocity pulse involves three parameters: presence of the pulse, period of the pulse, and amplitude of the pulse. The basic concept behind the velocity pulse is that a large amount of seismic energy is packed into a short time, leading to larger demands on the structure. An intensity measure for near-fault ground motions, which is a direct measure of the amount of energy arriving in short time, called instantaneous power (IP (T-1)), is defined as the maximum power of the bandpassfiltered velocity time series measured over a time interval of 0.5 T-1, in which T-1 is the fundamental period of the structure. The records are bandpass filtered in the period band (0.2 T-1-3 T-1) to remove the frequencies that are not expected to excite the structure. Zerin and Abrahamson (2020) showed that the drift is better correlated with the IP (T-1) than with the velocity pulse parameters for records scaled to the same spectral acceleration at T-1. A conditional ground-motion model (GMM) for the root IP is developed based on the 5%-damped spectral acceleration at T-1, the earthquake magnitude, and the rupture distance. This conditional GMM can be used for record selection for near-fault ground motions that captures the key features of velocity pulses and can lead to a better representation of the median and variability of the maximum interstory drift. The conditional GMM can also be used in a vector hazard analysis for spectral acceleration (T-1) and IP (T-1) that can be used for more accurate estimation of drift hazard and seismic risk.