Bulletin of the Seismological Society of America; August 2006; v. 96; no. 4A;
p. 1359-1374; DOI: 10.1785/0120040138
© 2006 Seismological Society of America
Multiple Scattering of Elastic Waves by Subsurface Fractures and Cavities
A. Rodríguez-Castellanos1,
F. J. Sánchez-Sesma2,
F. Luzón3 and
R. Martin4
1 Instituto Mexicano del
Petróleo
Eje Central L. Cárdenas 152
CP 07730, México
D.F.
México
arcastel{at}imp.mx
(A.R.-C.)
2 Instituto de
Ingeniería
Universidad Nacional Autónoma de
México
Cd. Universitaria, Coyoacán
CP 04510, México
D.F.
México
sesma{at}servidor.unam.mx
(F.J.S.-S.)
3 Departamento de Física
Aplicada
Universidad de Almería
Cañada de San Urbano
s/n.
04120, Almería,
Spain
fluzon{at}ual.es
(F.L.)
4 Laboratory of Modeling and Imaging in
Geosciences
CNRS UMR 5212 and INRIA Futurs Magique 3D
University of Pau,
64013 Pau cedex,
France
roland.martin{at}univ-pau.fr
(R.M.)
Comprehensive studies in geophysics and seismology have dealt with scattering
phenomena in unbounded elastic domains containing fractures or cavities. Other
studies have been carried out to investigate scattering by discontinuities
located near a free surface. In this last case, the presence of fractures and
cavities significantly affects wave motion and, in some cases, large resonant
peaks may appear. To study these resonant peaks and describe how they can be
affected by the presence of other near-free-surface fractures or cavities we
propose the use of the indirect boundary element method to simulate 2D
scattering of elastic P and SV waves. The geometries
considered are planar and elliptic cracks and cavities. This method establishes
a system of integral equations that allows us to compute the diffracted
displacement and traction fields. We present our results in both frequency and
time domains. In the planar cracks located near the free surface, we validate
the method by comparing results with those of a previously published study. We
develop several examples of various fractures and cavities to show resonance
effects and total scattered displacement fields, where one can observe
conspicuous peaks in the frequency domain and important wave interactions in the
time domain. Finally, we show how our dimensionless graphs can be used to deal
with materials like clay, sand, or gravel and compare the response with
finite-element analysis of elastic beams.
Copyright © 2009 by Seismological Society of America