### ASA 125th Meeting Ottawa 1993 May

## 5aUW11. Free and forced vibrations in a floating ice sheet: Modeling and
comparison with data.

**T. C. Yang
**

**
**
*Naval Res. Lab., Washington, DC 20375
*

*
*
**T. Yates
**

**
**
*Vector Res. Co., Rockville, MD 20852
*

*
*
Time domain waveforms excited by an impulse, point force are modeled using
fluid-loaded thin plate theory and compared with measured data collected on
ice-implanted geophones. In the frequency domain, the solution, expressed as an
integral over wave number, can be expressed in terms of poles (free waves) and
branch cuts (forced waves). The time domain solution is obtained by taking a
Fourier transform of the frequency response of the plate, weighted by the
(measured) source spectrum. The modeled time domain waveform compared favorably
with the received time series data. A simple direct time domain solution for
the forced wave in a thin plate in air also approximates the data well. It is
shown that the forced wave solution produces the ``abnormal'' dispersion
relation observed in recent geophone data. The free-wave solutions, which have
been extensively studied before, also agree with the geophone data.