Empirical Earth Rotation Model: a Consistent Way to Evaluate Earth Orientation Parameters
It is customary to perform analysis of the Earth’s rotation in two steps: first, to present results of estimation of the Earth orientation parameters in the form of time series based on a simplified model of variations of the Earth’s rotation for a short period of time, and then to process this time series of adjustmentsby applying smoothing, re-sampling and other numerical algorithms. This approach suffers from self-inconsistency: the total set of Earth orientation parameters depends on a subjective choice of the apriori Earth orientation model, crosscorrelations between points of the time series are lost, and results of an operational analysis per se have a limited use for end users. Here, an alternative approach of direct estimation of the coefficients of expansion of Euler angle perturbations into basis functions is developed. These coefficients describe the Earth’s rotation over the entire period of observations and are evaluated simultaneously with stationpositions, source coordinates and other parameters in a single LSQ solution. In the framework of this approach considerably larger errors in apriori EOP model are tolerated. This approachgives a significant conceptual simplification of representation and estimation of the Earth’s rotation.
Erratum: Correction to ``Geodesy by Radio Interferometry: Studies of the forced nutations of the Earth, 1, Data Analysis''
The analysis of 235 very long baseline interferometry observing sessions carried out between July 1980 and December 1984 has yielded estimates of corrections to the seven largest nutation series coefficients (with periods ≤1 year) in the Wahr nutation series, the most complete such model available at this time. The largest correction is to the amplitude of the retrograde annual nutation: −1.80±0.18 - i(0.42±0.18) milliarc seconds (mas), where the estimated standard deviations contain contributions from the effects of systematic as well as random errors. We interpret this correction as being due to an incompleteness in the model of the core-mantle coupling used by Wahr. We have also examined our results for evidence of any “free core nutation” and can place an upper bound of 1.0 mas (99.5% confidence interval) on its amplitude.
Facies and microfacies of slope deposits
Abstract This paper reviews the facies and microfacies of the main types of slope deposits. Lamination and sorting, when preserved, are good evidence for overland flow. Features due to deformation (folds, boudins, coatings and tails due to the rotation of clasts) are associated with the early stages of deformation in earth slides. Other mass-movements such as debris flows, rock avalanches, earth flows, and to a certain extent, dry grain flows may be characterised by similar microscopic facies, typically a poorly sorted, porphyric material. Porosity gives evidence for both liquefaction (debris flows) and frost-induced mass-movement (solifluction). However, this criterion is thought to be irrelevant for fossil deposits owing to the rapidity and scale of post-depositional changes (wetting and drying, freezing and thawing, bioturbation). At present, only a detailed analysis of both the macro- and micromorphological characteristics of the deposits allows an accurate identification of past slope dynamics.