Estimation of seabottom reflection characteristics and source signature from seabed reflected waves

Abstract

We describe a procedure for modeling the primary and multiple reflected seabed pulses as a function of distance. The assumption is made that the registered pulse can be constructed as a sum of elementary pulses, that is, the time and relative size of the arrivals are calculated for each source‐receiver position. This is done using both angle‐dependent and angle‐independent reflection coefficients at the seabottom. For each receiver channel on the cable, the predicted seismogram is calculated as the sum of the registrations in each hydrophone included in that channel. It is demonstrated first how the shape of the seabottom reflections changes with the sea depth and source‐receiver distance because of geometry effects, and because of the extended sources and receivers applied in marine seismic exploration. Next, We show that angle‐dependent reflection coefficients do introduce additional and sometimes quite drastic variations in the shape of the different pulses. Finally, we demonstrate that the predicted pulses can be matched quite well to observed data from the North Sea. This gives a possibility to estimate the geophysical characteristics of the seabed.