ANALYSIS OF SURFACE WAVES FROM STRONG MOTION RECORDS

Abstract

Shallow focus earthquakes generate surface waves which dominates the seismogram; as they generally carry the greatest amplitude. The UD component of the accelerogram is studied which do not consider the contribution of Love waves , and only the Rayleigh wave component is analysed. Displacement spectrum is obtained by integrating the acclerogram twice. Multiple Filtering Technique is applied to find the group velocity dispersion curve from the displacement time series. The high frequency component of Rayleigh wave, that is in the period range of (1 to 5 sec) is used. The data is forward modelled using The Haskell method and Non Linear genetic Algorithms are used to invert the data. Velocity and density structure of the shallow subsurface is obtained as a result. The 1940 Imperial Valley Strong Motion Earthquake data is used for the purpose