Determination of layered structure parameters based on spectrum estimation techniques

Accurate estimation of the parameters associated with layered subsurface structures from wideband sounding is of great significance in many applications such as seismic exploration. In such applications, spectrum estimation techniques can be used to determine the locations of the interfaces between the layers. In this paper, the utility of multiple signal characterization (MUSIC), and the minimum variance distortionless response (MVDR) spectrum estimators will be applied to detect the interfaces in layered structures. We show that the MVDR estimator implementation is challenged by the fact that the boundary reflections are physically coherent, i.e., perfectly correlated, in most of the applications. Consequently, the sample covariance matrix of the measurements is singular. To overcome this, frequency smoothing is used over the measurement points. It is shown that such preprocessing of the measurements enhance the performance of the MVDR considerably. The performance, i.e., resolution, of these estimators is assessed via computer simulations as well as laboratory experiments.