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Microgravity applications in environmental and engineering geology
by
Vratislav Blecha
Charles University, Dept. of Applied Geophysics, Albertov 6, CZ-128 43 Prague, Czech Republic
Application of the gravity method in environmental and engineering geology requires highly accurate measurement and processing, since surveyed targets are often small-scale heterogeneities generating low-amplitude anomalies. Potential of the gravity method was substantially increased by usage of digital all-in-one gravimeters with resolution of 1 µGal. Resulting accuracy is influenced not only by resolution but also by all on-line corrections (tides, long-term drift, tilt, noise spikes) made by inner software of gravimeters. Typical mean square error of measurement with these types of instruments is ±3 µGal and sources with amplitudes of about 10 µGal are reliable detectable.
One of the most important factors influencing overall quality of microgravity data are corrections for residual tides and drift registered at the base station. According to the field test of different types of gravimeters the optimal method for residual time corrections is approximation of base station readings by smooth algebraic curve.
They are given three examples of the near-surface microgravity applications when sources show only subtle amplitudes of anomalies: prospecting of an undermined area, localization of underground voids caused by flooding and survey of the karst cave entirely filled by sediments. In all cases gravity interpretations where verified by subsequent drilling.
Date received: July 13, 2004
Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caon-08.