Analysis on site effect of ground motion in Beijing urban area revealed by strong-motion records in M5.1 Guye，Tangshan earthquake on 12^th July，2020

Ground motion characteristics are significantly affected by local site conditions, as spectral acceleraiongs at medium-to-long periods would be obviously amplified on thick and soft sites as a result of seismic site effects. The statistical results of strong-motion records obtained in M5.1 Guye, Tangshan earthquake on 12^th July, 2020 by spectral ratio method indicated that, the seismic site effects in Beijing urban area were remarkable as the spectral acceleraiongs were evidently amplified by thick and soft soil layers, and the amplification factor could reach 4.0 at period T=1.2 s in this earthquake. In addition, the consistency between the ground motions which the soft soil sites suffered and the ground motions on reference bedrock sites was found to be the critical factor which restricted the reliability of statistical results by spectral ratio method.