Explosive events generate sudden shockwaves, dynamic pressure, and tensile forces that propagate through structures, posing critical risks to dam integrity. While historical incidents highlight the vulnerability of dams to explosive attacks, existing research predominantly focuses on concrete dams, with limited attention to earthen dams—despite their global prevalence, particularly in regions like Iran. This study addresses this gap by conducting a comprehensive numerical investigation of blast-induced deformation and stability in earthen dams using Abaqus/Explicit finite element software. A three-dimensional nonlinear dynamic model of the Alavian Dam in Maragheh, Iran, was developed to simulate surface explosions (500, 1000, and 1500 kg TNT equivalents) over a 2-second duration, accounting for soil-structure interaction and shockwave propagation through heterogeneous media (soil, water, and air). Key findings reveal significant mesh sensitivity in the simulations, emphasizing the necessity of refined meshing near the blast epicenter. Deformation patterns exhibited a direct correlation with explosive mass, peaking at the dam’s crown (maximum displacement: 1.2 m for 1500 kg) and diminishing toward the toe (0.3 m). The results underscore the critical role of localized material plasticity and energy dissipation mechanisms in mitigating blast effects. These insights provide actionable guidelines for enhancing blast resistance in earthen dam design, including optimized geometry, reinforcement strategies, and sensor placement for early threat detection. This work establishes a benchmark for future studies on geostructural resilience under extreme dynamic loading.