Near-fault seismic hazard effects on embankment dam response: sensitivity analysis of the Geyve Doğantepe Dam

This study investigates the seismic safety of the Geyve Doğantepe Dam, located approximately 700 m from the active Geyve Fault on the middle branch of the North Anatolian Fault Zone. Embankment dams in near-fault regions are exposed to strong ground motions, yet the combined effects of frequency content, material stiffness, and reservoir conditions remain insufficiently understood. To address this gap, nonlinear dynamic time-history analyses based on the finite element method were conducted using scaled records from the 1999 Kocaeli earthquake. The results show that the seismic response is concentrated within the short-period range (T ≈ 0.15–0.30 s), with peak spectral accelerations of 1.8–2.2 g at T ≈ 0.2 s. Maximum crest displacements range from ±0.10 to ±0.14 m, corresponding to amplification factors of 1.8–2.2 relative to bedrock motion. Sensitivity analyses reveal that stiffness-related parameters primarily control the seismic response, with the small-strain shear modulus having the greatest influence, followed by secant stiffness, while the effective internal friction angle has a smaller effect. Reservoir conditions reduce displacement demands by 10–20% due to hydrodynamic added-mass effects, emphasizing the importance of integrating period-dependent spectral evaluation, nonlinear time-history analysis, and parameter sensitivity analysis for reliable seismic assessment of near-fault embankment dams.