The 6.1 magnitude earthquake in Aquila, Michoacán on January 12, 2025

On January 12, 2025, at 02:32:53 (UTC–06), a magnitude 6.1 M _W earthquake occurred with its epicenter at 18.496° N, 103.499° W (47 km SW of Coalcomán de Vázquez Pallares, Michoacán) and a hypocenter at a depth of 30 km. For structural response analysis, pseudo‑acceleration, pseudo‑velocity, and displacement spectra were generated for structural periods T from 0.0 to 5.0 s in 0.1 s increments, using a 5% critical damping ratio (ζ), based on accelerographic signals corrected and band‑pass filtered between 0.1 Hz and 10 Hz. Seismographs record ground motion along three orthogonal components: two horizontal (N–S and E–W) and one vertical. Although these axes facilitate global referencing, the maximum acceleration may occur at an intermediate direction θ, so that its projections onto the N–S and E–W axes (a cos θ and a sin θ) lie below the absolute value a. To capture the true horizontal peak, the two horizontal components are rotated and the RotD100 value is computed (the 100th percentile of the rotated amplitudes), since neither isolated component guarantees the absolute maximum. The greatest rotated acceleration in this seismic event was recorded at 29.86 km from the epicenter, with a value of 72.13 cm/s², and the maximum rotated pseudo‑acceleration reached 259.40 cm/s² at a structural period of 0.40 s. In Mexico City proper—within the area covered by the Accelerographic Network of the City of Mexico operated by the Centro de Instrumentación y Registro Sísmico A.C.—the peak rotated acceleration reached 7.17 cm/s², and the peak rotated pseudo‑acceleration was 46.14 cm/s² at a structural period of 2.1 s; both the PGA and PSA peaks occurred in the Cuauhtémoc borough, over geotechnical zone IIIc.