Dynamic Behavior of the Colonial 17th Century Church La Merced in the Historic Center of Cusco, Perú

This research focuses on the dynamic characterization of the Church of La Merced, a colonial building located in the Historic Center of Cusco (Perú), supported by an integrated 3D geometric survey. Built in the mid-17th century and composed of stone and brick masonry, the church features a 26-meter-high eccentric bell tower, covers an area of approximately 1,470 m² and is part of a larger architectural complex known as the Temple and Convent of La Merced. Throughout its history, this building suffered significant seismic damage. It was rebuilt after the historical earthquake of 1650 (M ~7.1; IMM = VIII–IX). The subsequent earthquakes of 1950 (M ~ 6.0; IMM = VII) and 1986 (Ms = 5.3; IMM = VI) mainly affected the tower, vaults, domes, and principal walls of the reconstructed temple. The dynamic characterization was conducted using an integrated experimental campaign combining velocimeters and accelerometers for the structural dynamic identification, and a velocimeter-based ambient noise recording for soil characterization through HVSR analysis. For the bell tower, fundamental frequencies of approximately 3.1–3.2 Hz (transverse) and 3.7 Hz (longitudinal) were identified. A global mode involving the nave walls was identified at approximately 2.7 Hz. A mode at approximately 6.9 Hz was also identified, involving the nave walls, the dome region, and the bell tower, where the dome exhibits predominantly longitudinal motion while the tower zone responds in the transverse direction, reflecting the influence of the existing structural configuration on the coupled dynamic response. The soil fundamental frequency was estimated at 0.8 Hz from the HVSR analysis, relatively far from the structural frequencies of the monument. The results from the Operational Modal Analysis revealed a frequency-dependent coupling behavior among the main structural elements, with different structural components exhibiting contrasting directional behavior depending on the frequency range considered. This study provides a reliable geometric and experimental basis for the calibration of a finite element model aimed at the ongoing structural assessment of the building under different seismic excitations.