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Seismic Response Study Around the Bridge of the Lions, Chapultepec Forest, México City

2025; National Institute of Geophysics and Volcanology; Volume: 68; Linguagem: Inglês

10.4401/ag-9126

2037-416X

Martín Cárdenas‐Soto, David Escobedo‐Zenil, Jesús Sánchez-Gónzalez, Martín Carlos Vidal‐García,

Botany and Geology in Latin America and Caribbean

The Bridge of the Lions, with its straps resting on two artificial slopes, serves as a pedestrian walkway for hundreds of Mexico City residents who visit the Chapultepec Forest daily. Ambient seismic noise results let us explain the bridge deterioration, a direct result of the local terrain subsidence. The site frequency, measured in the free field (1.14 Hz), matches the estimate on the bridge straps, indicating that the strap depth does not reach the firm layer. At 1.72 Hz, the bridge vibrates more vertically. This frequency is close to site frequency, suggesting soil-structure interaction effects. Also, the rotating analysis of HVSR functions in the bridge straps revealed a second peak of 1.64 Hz caused by vibration from the Av. Circuito Interior vehicle flow. The spectral analysis of virtual source sections obtained by the seismic Interferometry technique reveals that superficial materials have velocities similar to soft clays in the lake area (Vs < 150 m/s). A second layer of poorly consolidated clays (Vs 350 m/s) with significant lateral variation indicates that subsidence around the bridge is causing significant damage to the structure. According to this study, soil‑structure interaction effects are present, as the bridge foundations likely do not penetrate the most competent deep strata. This suggests that additional inquiry is necessary to assess the static and seismic response of the bridge.