The insensitivity of reflected sh waves to anisotropy in an underlaying layered medium

Journal Article · Thu Oct 31 23:00:00 EST 1991 · Geophysical Prospecting; (United States)

DOI:https://doi.org/10.1111/j.1365-2478.1991.tb00355.x· OSTI ID:5574725

Schoenberg, M; Costa, J ^[1]

---

1. Univ. Federal do Para, Nucleo de Pesquisas e Pos-Graduacao em Geofisica de Petroleo, C.P. 308, 66050 Belem, Para (BR)

This paper reports on propagation in the plane of mirror symmetry of a monoclinic medium, with displacement normal to the plane which is the most general circumstance in anisotropic media for which pure shear-wave propagation can occur at all angles. Because the pure shear mode is uncoupled from the other two modes, its slowness surface in the plane is an ellipse. When the mirror symmetry plane is vertical the pure shear waves in this plane are SH waves and the elliptical SH sheet of the slowness surface is, in general, tilted with respect to the vertical axis. Consider a half-space of such a monoclinic medium, called medium M, overlain by a halfspace of isotropic medium I with plane SH waves incident on medium M propagating in the vertical symmetry plane of M. Contrary to the appearance of a lack of symmetry about the vertical axis due to the tilt of the SH-wave slowness ellipse, the reflection and transmission coefficients are symmetrical functions of the angle of incidence, and further, there exists an isotropic medium E with uniquely determined density and shear speed which gives exactly the same reflection and transmission coefficients underlying medium I as does monoclinic medium M. This means that the underlying monoclinic medium M can be replaced by isotropic medium E without changing the reflection and transmission coefficients for all values of the angle of incidence.

• OSTI ID: 5574725
• Journal Information: Geophysical Prospecting; (United States), Journal Name: Geophysical Prospecting; (United States) Vol. 39:8; ISSN 0016-8025; ISSN GPPRA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
29 ENERGY PLANNING, POLICY, AND ECONOMY
294000 -- Energy Planning & Policy-- Fossil Fuels
54 ENVIRONMENTAL SCIENCES
540250 -- Environment
Terrestrial-- Site Resource & Use Studies-- (1990-)
ANISOTROPY
CALCULATION METHODS
DATA PROCESSING
GEOLOGIC DEPOSITS
GEOPHYSICAL SURVEYS
MINERAL RESOURCES
OIL FIELDS
PETROLEUM DEPOSITS
PROCESSING
PROSPECTING
RESOURCES
SEISMIC SURVEYS
SEISMIC WAVES
SITE CHARACTERIZATION
SURVEYS
WAVE PROPAGATION