Estimates of ground motion parameters of historical earthquakes in Lebanon based on the dynamic response of ancient free‐standing columns using numerical and theoretical modeling

Abstract

Lebanon has been devastated by large earthquakes over the last ten centuries, the last two major earthquakes hit Lebanon in 1202 and 1759. These earthquakes occurred in the pre‐instrumental era, where no seismic data was recorded. Therefore, the ground motion parameters used in the current seismic hazard assessment of the region may be unreliable. Studying the dynamic response of ancient, free‐standing structures subjected to ground excitations can serve in identifying the nature of the seismic event that caused damage to these structures. The dynamic response of the multi‐drum column at Baalbek and at Iaat was studied numerically using the 3DEC software that is based on the distinct element method. The columns were subjected to various near‐fault ground motions to investigate their dynamic behavior and display their mode of collapse. Critical accelerations required for a given period of the near‐fault ground excitations were identified. These results show good agreement with those obtained from a simple theoretical block overturning impulse. The results are also used to estimate the magnitude and intensity of historical earthquakes and compare them to previous estimates.