Strong ground motion characteristics of the M4.9 earthquake in Pingchuan District,Baiyin City,Gansu Province in 2023
The China Earthquake Early Warning Network recorded 197 sets of three-component ground motion acceleration data during the M4.9 earthquake in Pingchuan District,Baiyin City,Gansu Province.Among these,165 sets were recorded within 100 km of the epicenter,marking the first significant collection of near-fault strong motion observations near the Haiyuan fault zone.This paper delved into the strong ground motion characteristics of this earthquake by com-paring the acceleration response spectra at near-field stations with design spectra,contrasting ground motions of different periods with prediction models,and mapping the spatial impact field of the ground motions.The findings reveal that horizontal acceleration response spectra at six near-field stations exceed the design spectrum of 8-degree frequent earthquakes at the dominant period.Notably,the east-west response spectrum of station GS.D003E had a peak value excee-ding the design spectrum for an 8-degree fortification earthquake.However,its dominant period was lower than the natural period of typical urban and rural buildings in the area,resulting in minimal damage to buildings equipped with seismic measures nearby.Observed values of peak ground acceleration(PGA),peak ground velocity,Sa(0.2 s),Sa(0.5 s),and other short-period ground motions at the soil stations generally exceeded predicted values.Meanwhile,values for Sa(1.0 s),Sa(2.0 s),and other intermediate-period ground motions aligned with predictions,in-dicating a significant presence of high-frequency components during this earthquake.Further-more,observations from strong motion stations and intensity stations typically showed higher values than those from seismic stations.Spectral ratio analysis between adjacent soil and bedrock stations suggests that soil sites and topography amplify ground motion.PGA,Sa(0.2 s),and Sa(0.5 s)exhibited large amplitudes along the fault strike and on the southwest side of the epi-center,perpendicular to the fault.Conversely,Sa(1.0s),Sa(2.0s),and Sa(3.0s)demonstrated larger amplitudes solely on the southwest side of the epicenter,also perpendicular to the fault strike.This phenomenon may relate to the rupture characteristics of seismic sources and the in-fluence of station sites on ground motions.
earthquake early warning networkM4.9 earthquake in Pingchuan Districtresponse spectrumattenuation relationshipspatial distribution
万方数据
维普
