ISSN:
1420-9136
Keywords:
Surface waves
;
scattering
;
layered media
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Malin's (1980) first-order single scattering theory has been extended to study the scattering of surface waves as well as body waves by distributed point scatterers in a layered medium. The scattered waveform itself is generated and examined instead of its energy envelope. The theory used allows 1) mode conversion, 2) wave type conversion, 3) finite scatterer distribution, and 4) the effect of attenuation from scattering as well as intrinsic absorption. The cases studied are for elastic or slightly attenuative media with any kind of source and receiver at any place in the layered structure. This direct calculation of coda waves provides us an immediate description of the relation of coda and scattering. The objectives are to find 1) the effect of layering on scattering, 2) the effect of scatterer distribution on recorded vertical and horizontal motion, 3) the relation of scatteringQ to intrinsicQ, 4) the scattering behavior of surface and body waves, and 5) the superposition of scattering waves to form the coda. The generation of body waves by ‘locked mode’ approximation, which makes the body-wave scattering a subset of the ‘surface-wave’, scattering. Preliminary results explain some observed coda behavior surprisingly well. We find a larger geometrical spreading for near scatterers, which is caused by mode conversion or wave type conversion because of the wide angle scattering. This makes the speading correction higher for early part of coda which may account for the lowQ observed in early coda of regional earthquakes. This study is of practical value as an effort to understand the complicated coda phases.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01772588
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