The Eynali mountain range, a prominent natural and cultural heritage site in Tabriz, faces significant geological challenges regarding the structural stability of its historic access routes. This study aims to conduct a comprehensive assessment of the structural stability at the field scale (1:10,000) and seismic response at the tectonic scale (1:25,000) for the two primary hiking and access paths leading to the Eynali site. Given the site’s proximity to the North Tabriz Fault (NTF), understanding the seismic susceptibility and structural integrity of these paths is crucial for developing effective mitigation, structural reinforcement strategies, or identifying safer alternative routes to preserve the site’s heritage.

To achieve this, the research employs a multi-faceted methodological framework. Initially, a detailed identification of structural components—including fault geometries and fracture networks—was conducted along both access routes. A critical component of this data acquisition involved the Ultrasonic Pulse Velocity (UPV) Test, which provided reliable quantitative indicators of the physical and mechanical properties of rock masses along the paths. These laboratory-derived metrics were integrated with spatial geostatistical analyses, specifically utilizing variogram analysis of recent seismic event data. These datasets were subsequently normalized based on the tectonic scale of the study area to ensure consistency.

The structural measurements covered in-situ rock blocks located in the walls and along the path floors to develop a high-resolution map of the structural positioning. This field-based qualitative validation approach was designed to bridge the gap between sparse data points and large-scale structural interpretations, significantly reducing the time and costs associated with extensive field surveys while ensuring the reliability of the seismic response models.

The final analysis of structural and seismic instability reveals significant variations between the two routes. The results indicate that the highest risk of instability for Route 1 is primarily concentrated in the middle segments. In contrast, Route 2 exhibits the highest risk of instability in both the initial and middle segments. These findings are strongly correlated with the kinematics of active transverse fault zones associated with the North Tabriz Fault (NTF) system and the presence of loose rock blocks that are susceptible to displacement under seismic loading.

The outcomes of this research provide a robust evidence-based foundation for decision-makers and urban planners. By identifying specific high-risk segments, the study advocates for targeted structural reinforcements or realignment of the access paths. Ultimately, this approach not only enhances the safety of visitors and the integrity of the Eynali heritage site but also provides a scalable model for seismic risk assessment in similar mountainous terrain situated in seismically active regions.