Identification of velocity pulses in 2023 Türkiye earthquakes records and impact on single degree of freedom systems

Near fault ground motions which are generally characterized by their high energy and long period velocity pulses can impose significant seismic demands on structures especially with longer natural periods. Structures located near active fault regions are most vulnerable to such pulse-like ground motion records. Therefore, precise identification and a comprehensive understanding of pulse-like ground motions are of extreme importance for the enhancemet of seismic design methodologies and ensurance of a safer built environment. The 6 February 2023 Türkiye earthquakes highlighted the destructive potential of such motions. Owing to the dense network of seismic station in the affected region, numerous ground motion records were obtained, particularly from the near-fault sites. This thesis aims to identify and characterize pulse-like ground motions from the 2023 Türkiye earthquakes and investigate their effects on structures using single-degree-of-freedom (SDOF) systems. For this purpose, a total of 41 ground motion records from 2023 Türkiye earthquakes are analyzed for the identification and extraction of velocity pulses using Continuous Wavelet Transform (CWT) and Ensemble Empirical Mode Decomposition (EEMD). Pulse period (Tp), a critical pulse parameter, is also estimated by using five different methods: wavelet-based analysis, spectral velocity (Sv) analysis, the product of spectral velocity and spectral displacement (Sv × Sd), the peak point method, and an empirical formula based on earthquake magnitude and rupture distance. A comparison of pulse extraction results shows the superior sensitivity of the Hilbert-Huang Transform (HHT) in detecting pulse-like characteristics within complex signals. A comparison of pulse period (Tp) showed variation in pulse period values with the wavelet-based method showing slightly higher values compared to other methods. The Sv method yielded lower values, while empirical formulas provided a single representative Tp value, lacking the sensitivity needed for site-specific assessments. Additionally, the study of structure response via single degree of freedom systems shows that structures with longer periods are particularly vulnerable to amplified displacement demands when subjected to pulse-like motions. These findings underscore the importance of accurately identifying and incorporating pulse-like effects into seismic hazard analysis and structural design to improve the resilience of buildings especially in near-fault regions.