Damage spectra of global crustal seismic sequences considering scaling issues of aftershock ground motions

Recent studies and earthquakes have shown that the mainshock-aftershock (MSAS) sequences would induce significant cumulative damage, and it is urgent to incorporate the MSAS sequences into performance-based seismic design and resilience assessment. For this purpose, one of the key problems is how to accurately and quickly estimate the cumulative damage induced by MSAS sequences. This manuscript investigates the damage spectra of global crustal MSAS sequences and proposes a prediction equation of damage spectra as a tool to quantify the cumulative damage caused by MSAS sequences. The recorded MSAS ground motions from global crustal seismic sequences are collected. The structures are modeled by 4 different kinds of single degree of freedom systems with/without degradation and pinching behavior. The scaling indicator and scaling factor SF of aftershock ground motions are studied from the point of view of efficiency and accuracy. The results indicate that scaling aftershock ground motions with spectra acceleration S_a present the best efficiency. Applying the condition of SF smaller than or equal to 5.0 (ie, SF ≤ 5.0) can clearly reduce the bias induced by over-scaling and meanwhile has no change on the dispersion of results. Strong aftershocks (eg, relative S_a greater than 0.8) can increase the damage spectra by the minimum level of 20% for non-degrading systems, and quantitative effects of aftershocks strongly depend on the period of vibration, strength reduction factor, hysteretic behavior, and intensity of the aftershock ground motions. The proposed prediction equation shows high accuracy on the estimation of the cumulative damage induced by MSAS sequences.