Seismic Waves—Numerical Investigations
Numerical studies can point the way for experiments and indicate the sort of data that analysts of field data should be expecting. One explanation for anisotropy in sedimentary sections arises directly out of the effects of layering on long wavelength seismic signals. This theory can be extended to predict the shapes of transmitted wavefronts in transversely isotropic media, as was shown in the 1982 paper, ‘Computed waveforms in transversely isotropic media.’ Attenuation again receives special attention in ‘Computing seismic speeds and attenuation in rocks with partial gas saturation’ (1975), which notes that shear-wave amplitudes are less affected by partial gas saturation than are P-waves. This observation has been the driving force in the popularity of 4-C offshore surveys to see beneath gas cloud ‘wipe-out’ zones on regular P-wave seismic sections by exploiting the ability of mode-converted waves (P-down, S-up) to propagate successfully through zones that would severely attenuate P-waves.
Figures & Tables
Seismic Wave Propagation: Collected Works of J. E. White
This first chapter sets the stage for the later technical development of Dr. Whit’s career in applied seismics. Experiments, f’wst at the Acoustics Laboratory of the Massachusetts Institute of Technology and later at Mobil Oil and Marathon Oil, provided insight into the general problems of impedance measurements, transduction, filtering, and attenuation. These papers also serve as a bridge to show geophysicists how theft own experiments in seismology naturally interface with (indeed, arose out of) the larger world of sound measurements in air and water. These experiments demonstrate the power of geometrically constrained experiments to allow verification of approximate (and in some cases, exact) theories of sound.