Admittance, Coherency and Coherence

Abstract

The estimation of effective elastic thickness from gravity and topography data using spectral methods requires the computation of the admittance and coherence between those data sets. The admittance is a frequency-domain transfer function—a filter—from topography to gravity. The coherence is derived from the coherency which provides the degree of correlation between gravity and topography as a function of the wavelength of features within the signals. Both are complex-valued quantities, and their imaginary parts provide useful information about certain types of noise. This chapter covers the estimation of admittance and coherency using both multitaper and wavelet methods, and discusses two methods to obtain their errors.