Finite Difference Modeling of Infrasound Propagation to Local and Regional Distances
Abstract
The finite difference (FD) method yields the solution to a discretized version of the full acoustic wave equation for arbitrarily complex media. It is a full spectrum approach and is thus reliable at all angles of propagation, including backscatter. This offers an advantage over other standard propagation methods in wide use, as it allows for accurate computation of acoustic energy levels in the case where significant scattering can occur near the source, such as may happen for an explosion near the surface, or underground. This fits in with nuclear monitoring goals, in that it allows for an improved understanding of the generation and propagation of infrasound energy from arbitrary sources, including underground and near-surface explosions. Two types of FD methods of solving the acoustic wave equation are presented in this paper. The first is a finite difference frequency domain (FDFD) method, applied in cylindrical coordinates to simulate the effects of a point source in an azimuthally symmetric medium. The second is a finite difference time domain (FDTD) approach including the effects of both gravity and wind, applied in two-dimensional Cartesian coordinates. In this paper equations are developed for the FDTD approach where both wind and gravity effects are considered. It is shown that the FD approach can be used to solve for sound intensities in arbitrarily complex models that may include high material contrasts and arbitrary topography. In this paper, results of FDTD and FDFD approaches are compared for the case of a shallow underground source, for a boundary with significant topography. The effects of wind and gravity on the solution are examined.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2007
- Accession Number
- ADA519378
Entities
People
- Catherine De Groot-hedlin
Organizations
- Scripps Institution of Oceanography