Identification of the main ground motion parameters influencing the significant duration on rock sites in Türkiye

The significant duration ( D 5 , 95 ) is an important parameter in geotechnical earthquake engineering, directly influencing the number of cycles in effective stress analyses and playing a pivotal role in evaluating soil liquefaction potential. Liquefaction susceptibility is dependent on the number of cycles, which is inherently related to the duration of the earthquake and the response of the soil. In dynamic site response analyses, ground motions recorded on rock sites are essential because they serve as the excitation input, minimizing site-specific effects such as amplification or valley influences. Consequently, the significant duration of these rock-based ground motions becomes a fundamental parameter in evaluating liquefaction and selecting ground motions for site response analyses. However, existing duration models are predominantly regression-based ground motion prediction equation (GMPE) formulations calibrated on mixed site conditions, and predictors trained exclusively on rock-station recordings using artificial neural networks (ANNs) remain scarce. In this regard, the relationships among significant duration ( D 5 , 95 ) and key seismological and intensity measures were investigated within an ANN framework using a rock-site dataset compiled from Türkiye Strong Ground Motion Database (1208 records from 143 earthquakes with moment magnitudes ( M w ) ≥ 4.5) recorded at 59 stations established on rock units (NEHRP class B or harder rock, V s , 30 ≥ 760 m/s) (AFAD, 2023). Two complementary models were developed: a baseline ANN using ( M w , rupture distance ( R rup ), and V s , 30 )and an enhanced ANN additionally incorporating peak ground acceleration (PGA) and cumulative absolute velocity (CAV). The enhanced model yields improved predictive performance and tighter residual dispersion relative to the baseline model. Sensitivity analysis indicates that CAV is the most influential predictor of D 5 , 95 , followed by R rup and PGA, highlighting the dominant role of cumulative/energy-related measures under rock-reference conditions. These results provide a practical two-tier framework for estimating rock-site significant duration in Türkiye, supporting duration-aware motion selection and nonlinear geotechnical analyses.