Earth tide strains at a particular site are affected by the internal structure of the solid earth, ocean loads, local inhomogeneities in elastic constants due to geologic structure, topography near the observation site, and the cavity in which the measuring instrument is situated. All of these influences have been estimated quantitatively for the Poorman site for a diurnal (01) and a semidiurnal (MPd2) tide. The predicted strains agree with those observed to within 5% for M2 and 10% for O1 whereas without the topographic and geologic corrections there is an amplitude discrepancy of about 25%. The phase discrepancy is reduced from -15¿ to -6¿ for 01. The residuals can be reduced further by using terms quadratic in the applied potential, which may imply a breakdown of linear tide theory, a deficiency in classical tidal calculations, or a local effect that modulates the tidal transfer function of our site.

Although the general features of strain tides are well understood, a quantitative comparison between theory and experiment has never, to our knowledge, yielded the sort of agreement obtained for gravity tides.

In this paper we show that by considering local topography and local inhomogeneities in the elastic constant, much of the discrepancy between classical tide theory and observations can be removed, at least for the M2 and O1 components. Although we have not analyzed the other minor tidal components, we are confident that the same sort of agreement would result from such an analysis.