ISSN:
1420-9136
Keywords:
Curvature
;
amplitude
;
offset
;
P-waves
;
reflectors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract We analyze the effect of reflector curvature on the angular dependence of reflection amplitude using ray theory. Defining the curvature effect, CE, as the ratio of reflected amplitude from a curved boundary to that from a flat boundary at the same depth, we obtain 1/CE 2=(1+Z/a xcos2Θ)(1+Z/a y), where Θ is the angle of incidence,Z the depth of the boundary, anda x anda y are the principal radii of curvature of the reflector in the plane, of incidence and in the perpendicular plane, respectively. At Θ=0 this reduces to the formula given byHilterman (1975). The angular dependence ofCE involves onlya x, which appears to shorten at wider angles. This causes an augmentation of the dimming effect of an anticlinal geometry at far offsets. For synclinal structures, the amplitude increases with offset when |Z/ax|〈1 and decreases with offset when |Z/ax|〈1. In addition we examine the effects of wavefront curvature and of a layered overburden in modulating the curvature effect. We find that there is a significant difference in the curvature effect between plane waves and spherical waves impacting on a curved boundary. In addition results are given showing simple examples of the effect of layered overburden in distorting the curvature effect of a horizontal, but curved, reflector and, more interestingly, of a dipping, but planar, bed. These results strongly suggest that we still have but a rudimentary knowledge, in general, of the combined effects of wavefront curvature, reflector curvature and overburden layering in modulating and/or producing amplitude with offset behavior observed on seismic records.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00877739
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