Research Of Kanto Basin Amplification Effect Based On Residual Analysis Of Ground-motion Recordings

The irregular geological topography of the basinusually leads to the excitation of surface waves in the basin,which significantly increases the amplitude of the spectrum and prolongs the duration of seismic motion,aggravating the seismic damage of the engineering structure in the basin.This is accomplished using analyses of strong-motion data sets,and the following works had been done in this thesis:?1?In this research,the Kanto basin in Japan was selected as the research object,and 3254 groups of strong-motion recordings collected from 111 K-NET stations in the Kanto basin with its adjacent areas in 75 shallow source earthquakes?Mw 4.5⁶.5?were used,based on the residual analysis of observation recordings of Zhao06 ground-motion prediction equation model,we obtained the period-depend basin amplification functions of spectral acceleration.Amplification model of spectral accelerations at different period in the Kanto basin is given by tensor spline interpolation method,there are significant amplifications near north of Tokyo in central basin.Amplification of ground motion response spectrum of acceleration decreases approximately with the increasing characteristic period,which may be related to the unique topography of the Kanto basin.The Kanto basin model of Japan was constructed by the surface elevation data of NASA and the shear wave velocity model of underground structure published by the Headquarters for Earthquake Research Promotion.?2?We analyzed the effects of moment magnitude,hypocenter distance,shallow and deep site characteristic parameters,different positions in the basin of station,and the azimuth angle of epicenter systematically.The results indicate that the effect of moment magnitude on amplification is not obvious;Based on the residual analysis of the recordings with small hypocenter distance,the basin amplification effect is generally smaller than that of the recordings with large hypocenter distance.The basin amplification effect decreases monotonically with VS30 value;The basin amplification effect is not consistent with the distribution of the depth to the 1.0 km/sec,1.5 km/s,2.0km/s shear-wave isosurface,which is denoted Z_1.0,Z_1.5,and Z_2.0.The maximum site amplification effect does not occur in the region with the maximum overburden thickness,but in the region with a larger overburden thickness?Z1.0>600m?,the amplification effect is more obvious.The basin edge amplification effect is not distinct,which may be related to the fact that the open structure on the east-southeast side of the Kanto basin that is not easy to generate edge-excited surface waves.The amplification effect of the basin based on the residual analysis of seismic observation recordings at the northeast side of the basin is distinctly higher than that at the southwest side.The amplification effect of the Kanto basin is related to its unique topographic structure.The distance,Z_1.0 and V_S30 and seismic orientation have a key influence on the amplification effect of the Kanto basin,which provides a foundation for the construction of the amplification effect model of the Kanto basin.?3?A simple model of basin amplification factor for the Kanto basin is established.The residual analysis between the predicted and measured values of amplification effect is obtained by model calculation,the good fit between the model and observed strong-motion recordings suggests that the new model is reasonably robust.Due to the unique topography of the Kanto basin and the limited influence factors taken into account by the model,the distribution of the basin amplification factor obtained by the model is somewhat different from that of other models.