Analysis of the Long-Period Ground Motion Duration Directionality and Characteristics of Seismic Damage to the Transportation System in the Noto Peninsula Earthquake

The directional effects of near-fault ground motions significantly influence the severity and damage patterns of transportation infrastructure. However, the directional characteristics of ground motion duration, particularly for long-period motions, remain unclear. This study investigates the response spectra and duration spectra of near-fault long-period ground motions recorded during the Noto Peninsula earthquake on January 1, 2014. A novel method, called the omnidirectional duration spectrum, is proposed to investigate the characteristics of long-period ground motion duration. This approach provides an intuitive visualization of the relationships among duration, period, and direction. When combined with omnidirectional response spectra, this method is applied to analyze ground motion records from five stations near the fault during the earthquake, examining the relationship between ground motion directionality and fault strike. The study further details the damage characteristics observed in railway and highway systems during the earthquake. A statistical analysis is conducted to evaluate the damage across different intensity zones, highlighting the correlation between damage patterns and the directionality of strong ground motion records near fault. Finally, the seismic design of transportation structures in the hanging wall region of reverse faults is discussed. The results reveal that uniform duration spectra effectively capture the dominant directional characteristics of ground motion duration, whereas significant duration spectra lack clear directionality for longer periods. The Noto Peninsula earthquake exhibited prominent directional characteristics in near-fault long-period ground motions, with maximum directionality aligned with the reverse fault rupture direction on the fault slip plane. The dominant period range for these motions was 1.6–8[Formula: see text]s, closely matching the damage patterns of long-period structures such as railways and highways in the strong motion region. The settlement of bridge abutments and the design of landslide protections along highways should comprehensively account for the characteristics of potential seismogenic faults, and corresponding seismic measures should be implemented.