Effects of the internal shear wave window: Comparison with anisotropy induced splitting

Conference · Tue Jul 10 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

OSTI ID:5316007

Liu, Enru; Crampin, S ^[1]

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1. British Geological Survey, Edinburgh (Scotland) Univ of Edinburgh (Scotland)

In the absence of anisotropy, the observed polarizations of shear waves should be those radiated from the source, modified only by interaction with internal interfaces and free surface topography. It has been suggested that shear wave polarizations may be systematically distorted by internal interfaces, which could lead to difficulties in interpreting anisotropy-induced shear wave splitting. Since the literature now reports many investigations of shear wave splitting, possible complications caused by internal interfaces would be important and need to be assessed. In this paper, the authors investigate the polarization of shear waves in full-wave synthetic seismograms incident from a point source at an isotropic-to-isotropic interface, over a range of angles of incidence. Particle motion due to plane and curved wave fronts has different characteristics. Internal shear wave windows can be defined, analogous to the shear wave window at the free surface. Within the innermost window, the polarizations at subsurface geophones (as in vertical seismic profiles) are recorded with little distortion, but outside this window the waveforms become increasingly distorted for larger angles of incidence. This is similar to the behavior of shear waves with respect to the shear wave window at the free surface, except that the behavior at internal interfaces is more complicated because of additional critical angles, and additional windows. The authors conclude that the interaction of shear waves with internal interfaces is only a serious difficulty when interpretating wide offset vertical seismic profiles, wide angle reflections, and cross-hole data.

• OSTI ID: 5316007
• Report Number(s): CONF-880531--
• Conference Information: Journal Name: Journal of Geophysical Research; (United States) Journal Volume: 95:B7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ANISOTROPY
BIREFRINGENCE
CONSTRAINTS
CORRELATIONS
DATA ANALYSIS
GEOPHYSICAL SURVEYS
INCIDENCE ANGLE
INTERFACES
MEASURING INSTRUMENTS
POLARIZATION
REFRACTION
SEISMIC ARRAYS
SEISMIC DETECTORS
SEISMIC S WAVES
SEISMIC SURVEYS
SEISMIC WAVES
SEISMOGRAPHS
SIMULATION
SURVEYS
WAVE FORMS
WAVE PROPAGATION