Novel depiction of love wave dispersion and inversion for inversely dispersive medium by full SH-wavefield reflectivity method – part I: numerical example

Abstract

Recently, Love wave applications on geological and geophysical problems have been frequently reported by numerous authors. Unlike Rayleigh wave, Love wave modelling has a simpler algorithm since depends only on three earth properties: SH-wave velocity, density, and thickness of layers. The fewer the parameters more stable the inversion result. There are several tasks, however, that have not been reported related to the modelling and inversion of Love wave data. The tasks are to give answer to several following questions: (a) can Love wave propagate in an inversely dispersive medium of the earth? (b) what is the method recommended to use for explaining appropriate Love wave dispersion curve for the inversely dispersive medium? (c) is that possible to have ‘effective’ Love wave dispersion curve for the inversely dispersive medium and to utilize it in the inversion process? Numerical simulations show that modal matrix method cannot prepare appropriate Love wave dispersion for such a medium. The resulting Love wave dispersion curve still shows high phase velocities at low frequencies, which is not as desired. Full SH-waveform method, in the other hand, successful simulates appropriate Love wave dispersion for such a medium. By this method, an effective Love wave dispersion curve is also introduced. Inversion of the effective dispersion curve can excellently estimate the shear-wave velocity.