Study On The Amplification Effect Of S Wave And Basin Induced Wave Of Basin Based On Strong Motion Records

The basin has a strong amplification effect on the seismic,and the focus of the body wave and the secondary surface wave in the basin are the two basic factors that cause the amplification of the ground motion.Due to the different amplification mechanisms of S waves and secondary waves in the basin,studying the relationship between amplification and basin depth plays an important role in understanding the amplification law of the basin.Based on the observation records of strong earthquakes in the Osaka Basin and the Kanto Basin in Japan,this paper studies the amplification effects of S waves and secondary waves in the basin,and the main conclusions are as follows:(1)Based on the 456 horizontal component records of 29 earthquakes in 14 stations in Osaka basin,the relationship between the amplification of S waves and basin-induced waves in the basin and the depth of the basin was studied by the traditional spectral ratio method and the seismic residual analysis method,and the results showed that the correlation between S wave amplification and basin depth in Osaka Basin was strong in short period(0.1-0.5s),but basically uncorrelated in long period(1-3s);basin-induced waves showed strong correlation in short and long periods.The amplification of S waves in the Osaka Basin is significantly larger than that of basin-induced waves in the short-term part,and in the long-term part,the amplification of basin-induced waves gradually approaches the S waves as the depth of the basin increases.The amplification of basin S waves and basin-induced waves caused by different locations of seismic sources is obviously different,the long-term basininduced wave amplification caused by shallow source earthquakes outside the basin has a weak correlation with the depth of the basin,and the amplification of long-term basininduced waves caused by earthquakes below the basin,deep source earthquakes outside the basin and distant earthquakes is obviously related to the depth of the basin;the short-term S wave amplification caused by earthquakes below the basin has a strong correlation with depth.The magnification of S waves and basin-induced waves in the basin calculated by the traditional spectral ratio method in the medium and long period(0.3s-3s)is higher than that of the residual analysis method.(2)Based on the 12,494 horizontal component records of 82 stations and 261 earthquakes in the Kanto Basin,the relationship between the amplification of S waves and basin-induced waves in the basin and the depth of the basin was studied by residual analysis method,as well as the amplification differences caused by the depth of the source,the moment magnitude,the distance of the source,and the location of the source.The results show that:(a)the amplification of S waves in the Kanto Basin as a whole shows a trend of decreasing first and then increasing with the period of growth,and the amplification of the period of 0.1s-3s is negatively correlated with the depth,and the positive correlation is higher when the period is greater than 3s.The magnification of the basin-induced wave is less than the amplification of the S wave in each period,and with the increase of the cycle,the amplification of the basin-induced wave is close to that of the S wave;when the period is 3s-5s,the deep correlation of the amplification of the basin-induced wave is higher than that of the S wave.The magnification of S waves in the Kanto Basin is greater than that of the Osaka Basin in each cycle,and the magnification of basin-induced waves in the basin is smaller than that of the Osaka Basin.(b)The amplification and depth correlation of S waves and basin-induced waves caused by shallow source earthquakes is significantly higher than that of deep source earthquakes.There is less difference in amplification between S waves caused by different magnitudes and basin-induced waves in basins.When the source distance is less than 100 km,the amplification of S waves in shallower basins is stronger,while when the source distance is greater than 100 km,the amplification of basin-induced waves is stronger at deeper depths in the basin.The S and basin-induced waves of the earthquake on the outer east side of the basin are amplified more strongly than the earthquake below the basin and the west side of the basin outside the basin.(3)For the Kanto Basin,the amplification effect of the basin caused by seismic waves of different angles of incidence varies greatly.(a)When the angle of incidence is less than 25°,the magnification within the period of 0.1s-5s decreases with the increase of the angle of incidence,and when the angle of incidence is greater than 25°,the difference in magnification with the angle of incidence is small(b)Compared with the Zhao06 seismic prediction model,when the angle of incidence is less than 20°,the seismic shock is significantly underestimated,and the average residual value of each cycle is about 0-0.6,especially for deep source earthquakes with an incident angle of less than 10°,and shallow source earthquakes with magnifications close to 0°-5°.At the period of 0.1s,the magnification of the angle of incidence less than 20° is negatively correlated with the depth of the basin;at the period of 0.3s,the correlation between the magnification and the depth of the basin is weak;with the growth of the cycle,the positive correlation between the magnification and the depth of the basin is strong at0.5s-5s.The depth correlation of magnifications for each cycle varies less with the angle of incidence.