El Salvador’s seismic design code has remained unchanged for over 28 years, and neither a geophysical nor a soil-column database has been developed. For that sake, the horizontal-to-vertical spectral ratios (HVSR) were computed from 383 microtremor records collected across the western districts of San Salvador City and an adjacent municipality. The results were compared to the theoretical HVSR and transfer functions derived from multichannel analysis of surface waves data provided by the Ministry of Public Works of El Salvador. Subsequently, maps of HVSR amplitude, predominant period, and fundamental (first) period were generated using the Kriging interpolation technique. This approach was selected for its ability to more accurately reflect the spatial variability of geological conditions, particularly those associated with the Plan de la Laguna extinct caldera.

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