Speaker
Dr
Katalin Gribovszki
(Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences)
Description
Earthquakes hit urban centers in Europe infrequently, but occasionally with disastrous effects. Obtaining an unbiased view of seismic hazard (and risk) is therefore very important.
In principle, the best way to test Probabilistic Seismic Hazard Assessments (PSHA) is to compare them with observations that are entirely independent of the procedure used to produce PSHA models. Arguably, the most valuable information in this context should be information on long-term hazard, namely maximum intensities (or magnitudes) occurring over time intervals that are at least as long as a seismic cycle. The new observations can provide information of maximum intensity (or magnitude) for long time scale as an input data for PSHA studies as well.
Long-term information can be gained from intact stalagmites in natural caves. These formations survived all earthquakes that have occurred over thousands of years, depending on the age of the stalagmite. Their “survival” requires that the horizontal ground acceleration (HGA) has never exceeded a certain critical value within that time period.
Here we present such a stalagmite-based case study from the Little Carpathians of Slovakia. A specially-shaped, intact and vulnerable stalagmite in Plavecká priepast cave was examined in 2013. This stalagmite is suitable for estimating the upper limit of horizontal peak ground acceleration generated by prehistoric earthquakes.
The critical HGA values as a function of time going back into the past determined from the stalagmite that we investigated are presented. E.g. at the time of Jókő event (1906) the critical HGA value cannot have been higher than 1 m/s^2, and 1.3 m/s^2 at the time of the assumed Carnuntum event (~340 A.D.), and 3 thousand years ago it must have been lower than 1.7 m/s^2.
We claimed that the effect of Jókő earthquake (1906) on the location of the Plavecká priepast cave is consistent with the critical HGA value provided by the stalagmite we investigated.
The approach used in this study yields significant new constraints on the seismic hazard, as tectonic structures close to Plavecká priepast cave did not generate strong earthquakes in the last few thousand years. The results of this study are highly relevant given that the two capitals, Vienna and Bratislava are located within 40 and 70 km of the cave, respectively.
Primary author
Dr
Katalin Gribovszki
(Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences)
Co-authors
Prof.
Goetz Bokelmann
(Department of Meteorology and Geophysics, University of Vienna)
Dr
Marketa Lednicka
(Institute of Geonics, Academy of Sciences of the Czech Republic)
Dr
Moseley Gina
(Department of Earth Sciences, University of Minnesota, Minneapolis, USA)
Péter Mónus
(Geodetic and Geophysical Institute, CSFK, Hungarian Academy of Sciences)
