Observation of local tectonic movements by a quartz-tube extensometer in the Sopronbánfalva Geodynamic Observatory, in Hungary–Validation of extensometric data by tidal analysis and simultaneous radon concentration measurements

摘要

In 1990 a quartz tube extensometer was installed in the Sopronbánfalva GeodynamicudObservatory (SGO) of the Geodetic and Geophysical Research Institute of the HungarianudAcademy of Sciences. On the basis of the 20 year data series, an average strain rate of -5.36udμstr/y was determined. Because the instrumental drift can also cause a slow change in theudoutput signal of the sensor similar to the tectonic movements, a lot of efforts were made touddetermine the drift of the extensometer. The instrument has no detectable drift according toudthe instrumental calibrations (regular calibration, parallel recording by more displacementudsensors, etc.). Since autumn of 2008, the radon concentration has been continuouslyudmonitored by an AlfaGuard instrument in the SGO. The investigation of the relationshipudbetween strain and radon concentration also showed the absence of instrumental drift, so theudinstrument measures real tectonic movements. The results of the extensometric measurementsudshow that the rate of tectonic movement is not constant. During the period 1993-2001, theudstrain rate accelerated to a maximum of -8.6 μstr/y in 2001, and then decelerated againudbetween 2002-2010 to approx. -2.5 μstr/y in 2010.