Velocity Analysis by Residual Moveout
Technical rept. for 1 Jan 1991-30 Sep 1992
COLORADO SCHOOL OF MINES GOLDEN CENTER FOR WAVE PHENOMENA
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Velocity analysis by normal moveout encounters problems in handling dipping reflectors or lateral variation of velocity. Prestack migration provides a powerful tool to do velocity analysis, which is based on the following principle the imaged depths at a common location are independent of source- receiver offset when the correct velocity is used. Conventional approaches, such as depth focusing analysis, generally involve iteration, which requires repeated prestack migration. In this paper, a residual moveout method for velocity analysis on multi-offset data is presented that needs only a single prestack migration. A number of theoretical problems in this method are studied. When the velocity has a lateral anomaly, we derive a formula to calculate the interval velocity from the stacking velocity by perturbation theory. A suggested data processing technique based on our method is composed of prestack migration with a constant velocity, velocity analysis, residual moveout, stacking, velocity conversion, and poststack residual migration.