Far-field ground motion characteristics of the 2025 Mw 7.7 Myanmar earthquake and implications for tall buildings

The impact of far-field long-period ground motions (LPGMs) on tall buildings has become increasingly significant. On March 28, 2025, the Mw 7.7 Myanmar earthquake provided a valuable dataset, with numerous ground motion records collected by the China Earthquake Early Warning Network. Tall buildings in Yunnan Province experienced strong shaking induced by far-field LPGMs. To further investigate the characteristics of far-field LPGMs and the effects on tall buildings, this study conducts a comparative analysis based on extensive ground motion data. Differences in amplitude ratios, durations, and spectral characteristics of the ground motions are examined. The Empirical Mode Decomposition (EMD) method is employed to extract and analyze the various Intrinsic Mode Functions (IMFs) contained in the seismic records. Furthermore, a tall building model was developed using the OpenSees software to analyze the impact of IMF components on long-period Building. The study also evaluated the perception and intensity of shaking experienced by tall buildings during the earthquake. The results indicate that far-field ground motions are characterized by relatively low intensity but prolonged duration and enriched low-frequency components, which pose potential threats to long-period buildings. The IMFs within the long-period range account for a considerable proportion of the total ground motion. Removing the IMF5 component, whose period closely matches the natural vibration period of the structure, can significantly reduce the response of tall buildings by up to 28.76%. Compared with the MMNGU station located 128 km from the epicenter, the YN.N0203 station in Ruili City at a distance of 283 km recorded ground motion exceeding the seismic design spectrum at intensity 8, suggesting that tall buildings may face increased risks under far-field large earthquakes. In particular, under LPGMs, the liquid sloshing-induced instability of rooftop water tanks further exacerbated the structural risk. Tall buildings in western Yunnan, particularly in Ruili City, experienced strong shaking during this earthquake, reaching LPGM Level 3 and Violent shaking. However, the current Chinese Seismic Intensity Scale fails to fully reflect the actual shaking intensity experienced by tall buildings, leading to underestimation.