ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

1aAO7. Double monopole resonance of a gas-filled cavity in a sediment.

Steven G. Kargl

Kevin L. Williams

Appl. Phys. Lab., Univ. of Washington, 1013 N.E. 40th St., Seattle, WA 98105

Raymond Lim

Coastal Systems Station, Panama City, FL 32407-7001

The monopole response of a gas-filled, spherical cavity in a sediment is investigated. The sediment is a saturated, poroelastic medium and we assume that its dynamical behavior satisfies a homogeneous Biot theory. Our method entails the scattering of an incident, (fast) longitudinal field that preferentially excites a monopole response of the cavity. Our main result demonstrates that a gas-filled, spherical cavity in a saturated, poroelastic medium exhibits two distinct monopole resonances. These resonances arise from the two distinct longitudinal modes of propagation in saturated, poroelastic medium as described by Biot's theory. The sensitivity of these resonances to various environmental parameters (such as permeability and porosity) will be presented and discussed. [Work supported by ONR.]