INVERSE Q-FILTERING. A SPECTRAL BALANCING TECHNIQUE*

Inverse Q-filtering (IQF) is a technique designed to correct for transmission losses due to inelastic attenuation. It is based on the constant-Q model and is derived from a Taylor series solution of a standard convolutional-trace model (primaries only). To avoid a non-causal solution, the attenuation is assumed to be minimum-phase. Band limitation is introduced to make IQF a stable process in the presence of noise. The main features of IQF are demonstrated using both synthetic and field data.     

PULSE DISTORTION IN CAUSTIC REGIONS1

It is well known that there is a phase shift of π associated with the propagation of a seismic pulse through a focus. But this simple behaviour is true only if the two points at which the pulse is observed lie sufficiently far from the focus, one on either side. Near the focus matters are more complicated and the shape of the pulse may be severely distorted because of diffraction. To examine this problem we consider a pulse generated by a point source and focused by a spherical reflector. Using a general combined method of ray tracing and diffraction, we compute seismograms for receivers lying both inside and outside the focal region, and determine how the shape of the pulse changes on propagation through the focus. To assist the physical interpretation of the numerical results, we also present relevant exact and asymptotic results for comparison.