Tidal Sea Load Tilt of the Crust, and its Application to the Study of Crustal and Upper Mantle Structure

Abstract

Summary Tilt measurements with the Askania borehole pendulum in Northern Germany (station Kiel-Rehmsberg, AE = 9”59’13”, q5,+. = 54O18’51”) have been analysed for tilts of the Earth’s surface caused by sea tides, mainly those of the North Sea and the Baltic Sea. Using the Boussinesq solution for the homogeneous half space, the effective moduli of rigidity of the Earth’s crust and upper mantle have been determined from load tilts in the main tidal waves Mz, N,, Sz and 0,. The results are consistent with knowledge of crustal and upper mantle elasticity from seismology. Beyond that, models for normalized tilt Green’s functions-which attempt to represent regional crustal and upper mantle structure in detail-have been determined, such that the calculated theoretical amplitudes and phases of the M, load tilt for these models are in good agreement with the measured ones. The comparison of the experimental normalized tilt Green’s functions with theoretical ones as, given by Farrell for realistic Earth‘s crust and mantle models shows that the indirect effect of sea tides in tidal tilt measurements is capable of providing detailed information on the crustal and upper mantle structure.