Verification of correctness of using real part of complex root as Rayleighwave phase velocity with synthetic data
Pan, Y.; Xia, J.; Zeng, C.
Abstract:
Highfrequency (≥ 2 Hz) Rayleighwave phase velocities have been utilized to determine shearwave velocities in nearsurface geophysics since the early 1980s. One of the key steps is to calculate theoretical dispersion curves of an earth model. When the earth model contains a lowvelocity halfspace, however, some roots of the dispersion equation turn out to be complex numbers, which makes phase velocities disappear at some frequencies. When encountering this situation, the common practice is to append an additional high velocity layer as the halfspace to the model to make the roots real or use the real parts of complex roots as Rayleighwave phase velocities. The correctness of the first method has been verified. The correctness of the second method, however, remains to be unproved. We use synthetic data generated by numerical modeling of the wave equation to verify the correctness of the second method. In this paper, we firstly discuss the reasons that only complex numbers of the dispersion equation exist at some frequencies when an earth model contains a low velocity halfspace. Then we discuss how the nearest offset affects a synthetic model and recommend an optimal nearest offset in generating synthetic data that are close to realworld situations. Several synthetic models are used to verify correctness of using real parts of complex roots as Rayleighwave phase velocities when an earth model contains a low velocity layer as the halfspace.
Zugehörige Institution(en) am KIT 
Geophysikalisches Institut (GPI)

Publikationstyp 
Zeitschriftenaufsatz 
Jahr 
2013 
Sprache 
Englisch 
Identifikator 
DOI: 10.1016/j.jappgeo.2012.09.012
ISSN: 09269851, 18791859
KITopen ID: 1000059100 
Erschienen in 
Journal of applied geophysics 
Band 
88 
Seiten 
94100 