ISSN:
1420-9136
Keywords:
Wave scattering
;
free surface
;
heterogeneity
;
body
;
Rayleigh
;
and Love waves
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract The seismic coda is usually thought to be composed of waves scattered from the heterogeneities in the earth. Three classes of scattering mechanisms have been recognized: repeated specular reflection of primary waves in a uniformly layered structure, volume scattering of primary waves from localized volume heterogeneities, and scattering of primary waves from irregularities in an otherwise generally layered structure. The presence of the earth's surface complicates the description of all these scattering phenomena whenever the scattering obstacles are near or at the surface. In this paper I review work which demonstrates the effects of scattering near the earth's surface, emphasizing three general areas of investigation: scattering of body waves from an irregular free surface, scattering of body waves in irregular layers, and propagation of surface waves across irregular topography or in irregular wave guides. Most of the effects of importance have been recognized in model studies of idealized geometries. Observational evidence in support of the model studies exists, but is often inferred. Few controlled experiments to measure scattering have been performed. Topography can focus or defocus incident body waves and can convert body waves to surface waves and vice versa. Irregular surface layers can amplify incident body waves, couple body and surface waves, and produce resonances in spatially limited low velocity valley structures and highly irregular layers. Love wave propagation is highly sensitive to irregularities in a wave guide. Love wave dispersion measured over irregularly layered media can be quite different from the dispersion of the mean plane layered structure beneath the receiver array. Rayleigh wave dispersion is far less sensitive to smooth irregularities in a wave guide and is usually representative of the mean structure beneath the receiving array.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00874356
