It often happens that the location of oil is controlled by faulting. But the dominating effect of stratified reflectors may overwhelm the weak diffraction evidence of faulting. A cosmetic process could weaken the zero and small dips, accentuating dips in the range of 10 to 60,and then suppress the wide angles and evanescent energy. As with frequency filtering, sharp cutoffs are not desirable because of the implied long (and in space, wide) impulse response.