Estimation of Vs30 values by topography in the Mérida Metropolitan Area as a contribution to the seismic microzonation of the region

SEISMIC THREAT

Abstract

The Metropolitan Area of Mérida is situated within the Bocono fault¿ system, a region characterized by high seismic hazard with estimated ground accelerations ranging from 0.21g to 0.36g. Locally, the area rests on Quaternary deposits (terraces and alluvial fans) which amplify seismic shaking (site effect), thereby increasing the risk to infrastructure and the population. Previous research has mainly concentrated on the urban centers of the Campo Elias, Libertador, and Santos Marquina municipalities, without characterizing the surrounding areas within these municipalities. This limitation holds particular significance given that earthquake-resistant regulations are enforced at the municipal level, making complete territorial coverage crucial for their effective implementation. The aim of this study is to address these limitations by employing the Allen and Wald (2009) methodology for Vs30 estimation via topographic data, thus allowing for the characterization of site effects throughout the municipality. The results revealed three primary zones: low-velocity zones (300-400 m/s), characterized by sedimentary deposits; intermediate
zones (400-650 m/s), characterized by transitions between geological units; and high-velocity zones (≥650 m/s), characterized by consolidated rocky slopes. The methodology demonstrated its particular utility in extrapolating information to areas lacking direct data, while maintaining coherence with field measurements. This investigation establishes the first comprehensive technical foundation for the development of municipal seismic-resistant codes that encompass the entire territory, including areas not previously taken into account. This methodological approach offers a cost-effective solution for managing seismic risk in data-scarce regions.