Bangkok Basin's Long-Period Ground Motion: A Love Wave Story

This study analyzes horizontal elastic response spectra of earthquake ground motion in the Bangkok basin. It finds significant amplification of spectral energy at long periods (0.5-2s) within the basin, linked to surface wave arrivals. Analysis of different parts of accelerograms confirms that long-period energy is associated with surface wave propagation, not source effects. HVSR analysis reveals predominant frequencies between 5.1-5.5s for basin stations, consistent with elastic spectra. Analysis of the 2008 Mw 7.9 event shows that low-frequency ground motion (0.1-0.3Hz) in the basin is influenced by locally generated surface waves, particularly Love waves. Further research is recommended, including large-array observations with reliable low-frequency seismometers and 2D/3D basin-structure ground motion modeling.