11 research outputs found
Parabolic Radon transform and x-squared fk-transform - aliasing and efficiency
this paper the aliasing is studied by comparing the PRT with the Nonuniform Discrete Fourier Transform (NDFT). Although we find the same main principals, there are some differences. Moreover, the new points of view can provide a better understanding of the results found. The similarity between the PRT and the NDFT can also be used for the utilization of fast algorithms
Monitoring the Width of Hydraulic Fractures With Ultrasonic Measurements
Introduction During hydraulic fracturing experiments in the laboratory the opening of hydraulic fractures is monitored with ultrasonic transducers. The experiment closely resembles seismic monitoring surveys in the field [MEADOWS AND WIN- TERSTEIN 1994, WILLS ET AL. 1992]. The extraction of information out of these experiments is critically dependent on the understanding of the elastodynamic behaviour of the thin fluid filled fractures. The laboratory experiments provide useful information on what determines the seismic visibility of these fractures, both for compressional and shear waves. The role of the fracture thickness or width on the elastodynamic response and a new method for monitoring fracture opening is investigated. Most theoretical approaches postulate the use of the classical boundary conditions. The void boundary condition assumes a stress free surface. The "fluid-filled" fracture boundary conditio