Traveltime picking of the first arrival

The common receiver gather used in this example was recorded in a marine Walk-cross survey, in which, a receiver was loaded down into a bore-hole. The receiver records the waves generated by the shots along the surface. If the medium above the receiver were homogeneous, the first arrival on the common receiver gather would follow a hyperbola. We fitted a hyperbola to the first arrival on this gather and performed the moveout corrections. Figure shows the first arrival after the moveout corrections. The event is not flattened because the actual medium is not homogeneous. The residual time shifts of the event can be used to estimate the velocity anomalies of the media. We then applied our algorithm to estimate the residual shifts. The result is superposed on the event. Figure compares the wavelets of the event before and after residual shift corrections. The wavelets do not line up perfectly at a point because their waveforms are distorted from one another.

 

vsppick
Figure 6 Picked residual shifts of the first arrival.

 

vspcor
Figure 7 Wavelets before (left) and after (right) the residual shift corrections.