Page 444 - Acquisition and Processing of Marine Seismic Data

9.2 VELOCITY DETERMINATION FROM SEISMIC DATA 435

FIG. 9.8 (A) An example semblance plot from a supergather of a 2D seismic line, (B) RMS velocity (dashed white line) and
interval velocity (solid black line) functions picked from the semblance plot. (C) A 2D RMS velocity field can be obtained by
mapping several velocity functions along the line, and (D) the interval velocity field can be computed from (C) using Eq. (9.9).

of the data, then the effective period of the seismic negative amplitudes associated with reflection
signal can be found as the inverse of the domi- hyperbolas in summation results in a better reso-
nant frequency. Since the absolute value of the lution in semblance plots. The effect of the proper
amplitudes is used in the summation in selection of time gate on the quality of semblance
Eq. (9.11), incorporating all the positive and plots is explained in Section 9.3.6.