The prediction of vertical movements of the earth's crust from 1st and 2nd order repeated levelling for the territory of the GDR

Abstract

Derived from the collocation of least squares, a technique has been developed to detect vertical movements of the earth's crust based on repeated 1st and 2nd-order levelling in the national levelling network which is characterised by the following features: • - Division of the territory of the GDR into sections (1st-order loops) with corresponding overlapping zones. • - Geological-geomorphological examination of the levelling control points, delimitation of points and areas with nontectonic movements. • - Consideration of the functional areas within each section in the form of zero-th grade trends (simple arithmetic means). • - Detection of random localised signals by means of trend differentiation for the control points. • - Prediction of the movements in elementary areas as the sum of trends and signals, including a significance test within each region. • - Construction of isobases using predicted elementary areas and geological aspects with an isobase interval of 0.5 mm/year. This technique produced the following results: • - The mean error of the movements predicted in the elementary areas came to an average of 0.08 mm/year. The significant percentage of these movements varied between 24 and 94% in the individual areas. • - Using an isobase interval of 0.5 mm/year, the fine structure of the vertical movement of the earth's crust in the territory of the GDR was statistically established. • - By making maximum use of the information obtained from repeated 1st and 2nd order levelling, this technique gives statistically significant data on relatively slight movements of the earth's crust in the GDR. A comparable result cannot be obtained with trend polynomials or conventional techniques alone.