PSI - Issue 78

Carla Grandón-Soliz et al. / Procedia Structural Integrity 78 (2026) 1505–1512

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4. Seismic Hazard of the area To enhance the knowledge of the Bridge in the context of Level 0 evaluations, the seismic hazard of the area was investigated by taking information by remote and available on web. The Fisculco Bridge, located within a tectonically active segment of the Bolivian Andes near Sucre, is exposed to significant seismic risk due to its proximity to deep and intermediate-focus seismic zones. Recent geospatial analyses reported in Figure 2a derived from USGS database show a concentration of seismic events at depths ranging from 150 km to over 500 km beneath this region, associated with the subduction of the Nazca Plate beneath the South American Plate (Lamb & Hoke, 1997; USGS, 2025). In contrast, shallow seismicity (depths <70 km) is more frequent in eastern Bolivia, particularly in Santa Cruz and northern La Paz, indicating varied seismotectonic mechanisms across the country (OSC, 2020). Historically, Bolivia lacked a unified seismic design standard for bridge infrastructure. Engineers typically relied on adaptations of the Bolivian Seismic Code NBC-2006, supplemented by international guidelines such as AASHTO LRFD and the Eurocodes. The recent approval of the Norma Boliviana de Diseño Sísmico (NBDS‑2023) represents a substantial advancement, offering a probabilistic seismic hazard map (Figure 2b) based on return periods of 475 years (10% probability of exceedance in 50 years), with peak ground acceleration (PGA) values that are critical for structural design. To further refine the seismic assessment of the Fisculco Bridge — particularly given its post-tensioned concrete box-girder design — a comparative framework is proposed using Italian Guidelines 2020 seismic code. The Guidelines offers performance-based classification of seismic risk, integrates condition-based inspections, and promotes long-term monitoring — features highly relevant for slender, high-risk structures like Fisculco. The integration of such methodologies within Bolivia's evolving regulatory environment, especially in conjunction with NBDS ‑ 2023, could significantly enhance seismic resilience. This would support better-informed risk management strategies, promote the durability of strategic infrastructures, and ensure the operational safety of critical transport links in a highly variable seismotectonic landscape. a) b)

Fig. 2 (a) Historical seismicity of Bolivia: Historic Earthquakes and Analysis of the Region (1950 – 2025) coming from Google Earth and USGS Data. (b) Probabilistic seismic hazard map for a 475-year return period, corresponding to a 10% probability of exceedance in 50 years, with indication of Peak Ground Accelerations (PGA), OSC (2019).