Operational damage misclassification in scenario-based ShakeMaps: evidence from station-updated ground-motion fields in a deep-basin urban environment

Abstract. Near-real-time ShakeMap-based damage assessments are widely used to support rapid post-earthquake decision-making. However, their operational reliability depends on how accurately ground-motion fields represent local site and basin effects. This study investigates the potential for operational damage misclassification arising from purely scenario-based ShakeMap representations in deep-basin urban environments.

The 30 October 2020 Samos earthquake was analysed for the Mansuroğlu Neighborhood (Bayraklı District, Izmir, Türkiye) using a two-stage framework: (i) a scenario-based rapid damage estimation and (ii) a station-updated near-real-time configuration incorporating strong-motion recordings from Disaster and Emergency Management Authority of Türkiye (AFAD) stations located within a 3 km radius.

Results show that the scenario-based configuration systematically underestimates intermediate-period spectral demand (T = 0.6–1.0 s), which governs the response of the predominantly mid-rise reinforced concrete building stock. These discrepancies propagate into cumulative damage exceedance probability estimates. While the scenario-based approach largely confines the {Moderate + Extensive + Collapse} exceedance probability to the 0–10 % range, station-based updating increases this range to approximately 15–30 % in critical zones.

This shift represents a transition across an operationally meaningful threshold with direct implications for response categorization and resource prioritization during the early post-earthquake phase. The findings demonstrate that misclassification risk in rapid damage assessment arises not only from modelling uncertainty but also from threshold-sensitive distortions in exceedance estimation.

Even a limited number of spatially proximal strong-motion stations can substantially enhance the robustness of ground-motion representation. The study therefore highlights ShakeMap calibration as a governance-relevant intervention in seismic risk management rather than merely a technical refinement.