Abstract: The M_S4.8 earthquake occurred on May 28,2012, at the junction area of Guye and Luanxian, Tangshan, Hebei Province. Acceleration records were obtained by 94 digital strong motion stations installed in Hebei province, Tianjin and Beijing. In this paper, the distribution of strong motion stations recording the earthquake is shown, subsequently the count of records within different epicenter distances are analyzed, and the acceleration time history of three typical strong motion records are emphatically displayed within small epicentral distance. Accordingly, the peak ground acceleration contour map is drawn, and the T=0.2 s, 2.0 s response spectrum contours maps are also displayed. By comparing the differences of the three contours maps, it is found that the extreme distribution has obvious regional features, which may be due to the distinct amplification of thick sedimentary layer to the long-period ground motion. The peak ground acceleration also with the T=0.2 s, 2.0 s response spectrum attenuation characteristics are studied by comparing the observed data with the three attenuation relationships applied to this region. The T=2.0 s response spectrum attenuation characteristics with the epicenter distanceis consistent to the attenuation relationship in this region, however, between the epicentral distance of 100 to 130 km, where concentrated by thick sedimentary layers, the response spectrum are larger than the attenuation relationship, which is also because of the distinct amplification of the thick sedimentary layer to the long-period ground motion. In this paper, the characteristic periods of response spectra is also studied by analyzing strong motion recordings on different types of site soil and deposit layers with the similar epicenter distances. Compared response spectra recorded on bedrock stations and on soil stations, it is found that the soft soil site layer at the soil stations has an amplified effect on the ground motion, and it will cause the amplified long-period ground motion. Compared response spectra recorded on thin sedimentary layer stations and on thick sedimentary layer stations, it is found that the thick sediments have amplification effect on the ground motion, as well as make the characteristic periods of response spectra to become larger.

Key words: Strong motion records, Peak ground acceleration, Response spectrum, Attenuation relationship, Characteristic period