Seismic Microzonation of the City of Cuenca (Ecuador) Based on the Dynamic Characterization of the Soil

Seismic microzonation is an essential tool for risk management and structural design, as it enables the identification of homogeneous zones according to the dynamic response of the soil. In Ecuador, existing seismic microzonation studies are limited and do not consider other dynamic parameters relevant to local seismic response. This study presents a seismic microzonation proposal for the city of Cuenca (Ecuador) based on the dynamic characterization of the soil using the fundamental frequency (f0) and the average shear-wave velocity of the upper 30 meters (Vs30). A total of 530 ambient vibration measurements were carried out using the HVSR method, together with 85 geophysical surveys (MASW and MAM). The obtained f0 values range from 1.06 to 17.43 Hz, while Vs30 varies between 292 and 628.5 m/s, indicating a predominance of soil types C and D, in accordance with the Ecuadorian Construction Code. From the recorded data, a local empirical correlation between f0 and Vs30 was established, consistent with models developed in other regions. The results show that variations in subsurface stiffness, associated with local geology and the distribution of alluvial, colluvial, and volcanic deposits, control the seismic response of the ground. Furthermore, the findings highlight the need to revise the Vs30 ranges and soil classification criteria in the Ecuadorian code, by integrating fundamental frequency (f0) as an additional parameter and adopting soil-type ranges similar to those in ASCE (2022). This study provides an updated technical basis for seismic-resistant design and urban planning in the city of Cuenca.