Parabolic equation solutions for range-dependent seismo-acoustic propagation scenarios
Jon Collis, Assistant Professor
Department of Applied Mathematics and Statistics, Colorado School of Mines
Date and time:
Friday, September 6, 2013 - 3:00pm
Parabolic equation solutions are useful to accurately and efficiently model propagation in range-dependent ocean environments. Certain ocean acoustic environments (such as harbors or estuaries) can feature a seafloor interface consisting of partially consolidated sediments, which can be described as a transitional solid. These complex sediments are generally thin, with low-shear wave speeds, and can cause numerical instabilities to arise in parabolic equation solutions. These instabilities make it difficult to obtain accurate solutions. In the low-shear limit, the problem becomes singular, mathematically. In this talk, such an ocean environment is modeled as a water layer overlying a thin transitional solid sediment layer over an elastic basement. Solution approaches for the low-shear problem are discussed. Additionally, recent focus has been on seismic sources in ocean acoustic environments [S. D. Frank et al., J. Acoust. Soc. Am. 133]. These source fields generate parabolic equation solutions that can be used to study generation of oceanic T-phases via the process of downslope conversion. More general range-dependence has also been shown to scatter elastic wave energy into acoustic modes in the water column, which can then propagate as T-phases. This talk will discuss recent advances in elastic parabolic equation solutions. Results will be compared to and benchmarked against normal mode solutions.