Local effects disturbing the monitoring of tectonic movements of the Mecsekalja fault by shallow deep borehole tiltmeters in Hungary

Abstract

In autumn of 1997 two borehole tiltmeters, type AppliedGeomechanics, A722 were installed for monitoring recentmovements of the Mecsekalja fault in Southwest Hungary. Beside the continuous tilt measurements a geodetic network for GPS and electronic distance measurements (EDM) and a levelling line crossing the fault were established. The borehole tiltmeters are continuously recording and the geodetic measurements (GPS, EDM, precision levelling) are repeated twice in a year, in spring and in autumn. This paper presents experiences and results of the tiltmeter measurements and analyses the disturbing effects e.g. earth tide, tilt caused by ground water level variations, precipitation of the surrounding vegetation, etc. superposed to the tilt signal. The paper shows some of these effects which can use to prove the goodness of the coupling between the instrument and the ground.