Analysis of surface waves in shallow water environment of the Persian Gulf using S and tfk transform

2010 SEG. Strong surface wave occurrence and its dispersion create severe problems for seismic data analysis in the shallow water environment of the Persian Gulf where the average water depth is about 10-15m. Common techniques for surface wave analysis are frequency, f-k or velocity filtering based on exploiting low frequency and high amplitude characteristics. However, spatial aliasing of surface waves due to under-sampling presents unique challenges to these methods. Considering that seismic signals are non-stationary and surface waves have various spectrums over time, we in this paper explore the difference in time-frequency variations of different seismic events to analyze and attenuate Scholte waves and other P-related surface waves. In this study, we utilize the S transform instead of Fourier transform to build a t-f-k filter which provides a convenient way to analyze surface waves on separate f-k panels at different times. The velocity of Scholte waves ranges from 450 m/s to about 2100 m/s depending upon the spatial variation of seabed shear wave velocity. The P-related surface waves usually have a velocity ranging from 1300 m/s to 3500 m/s, which are more severely aliased than other waves in the seismic record. Analysis indicates that the proposed S-t-f-k transform is effective to attenuate these surface waves in this area and improve reflection signal quality, which may be applicable in other similar ultra shallow water environment.

Analysis of surface waves in shallow water environment of the Persian Gulf using S and tfk transform Conference Paper