A specially shaped (candlestick shape, high, slim and more or less cylindrical), intact and vulnerable stalagmite (IVSTM) in the Plavecká priepast' cave has been examined. This IVSTM is suitable for estimating the upper limit for horizontal peak ground acceleration (HPGA) generated by prehistoric and paleoearthquakes. These long-term information about size of earthquakes can be important taking into account that historical earthquake catalogues are only 1-2 thousand years long in Central Europe. The method of our investigation is: - the density, Young's modulus and tensile failure stress of broken stalagmite samples (lying at the same hall of the Plavecká priepast' cave, as the stalagmite we investigated) have been measured in mechanical laboratory; - the height and the diameters of the IVSTM have been determined in situ, and its vibration was measured in the cave as well; - theoretical calculations, based on in situ measurements, produce the value of horizontal ground acceleration resulting in failure, as well as the theoretical natural frequency and harmonic oscillations of the IVSTM; - core samples were taken from a column dripstone standing in the same hall as the investigated stalagmite to obtain the age of the stalagmite, by Multi Collector - Inductively Coupled Plasma Mass Spectrometry analysis (MC-ICP MS). The HPGA values as a function of time going backward into the past determined from the stalagmite we investigated were presented on a figure. The figure shows that for example at the time of Jóko event the HPGA value could not be higher than 1.02 m/s2, and at the time of the assumed Carnuntum event (∼340 A.D.) it could not be higher than 1.34 m/s2. This technique can yield important new constraints on seismic hazard as well, as geological structures close to Plavecka priepast' cave did not generate strong paleoearthquakes in the last few thousand years, which would have produced horizontal ground acceleration larger than the upper acceleration threshold that we determine from the IVSTM. These results have to be taken into account, when calculating the seismic potential of faults near to the Plavecka priepast' cave as well as faults in Vienna basin (Markgrafneusiedler and Lassee faults). A particular importance of this study results from the seismic hazard of two close-by capitals Vienna and Bratislava.
|Translated title of the contribution||Constraints on long-term seismic hazard from vulnerable stalagmite in Plavecká priepast' cave, Slovakia|
|Number of pages||16|
|State||Published - 2017|