Late Quaternary activity of slow-slip intraplate Mariánské Lázně fault as revealed by trenching and shallow geophysical survey; Bohemian Massif (Czech Republic, central Europe)
Abstrakt
The NNW-SSE trending Mariánské Lázně Fault (MLF) zone is situated in the western part of the Bohemian Massif (Czech Republic, central Europe) where it intersects NE-trending Cenozoic Eger rift. The northern segment of the MLF controls the morphologically pronounced mountain front of Krušné hory Mts. and eastern limit of Cenozoic Cheb basin, which is famous for earthquake swarms (max.
ML=4.6) and CO2 emanation. We performed 2D and 3D geophysical survey (electric resistivity tomography, ground penetration radar) and 3D trenching to look for large surface-rupturing prehistoric earthquake responsible for pronounced moutain range front.
Seven excavated and six hand-dug trenches revealed a complex geology and deformation at the study site probably as a result of right-lateral transpression during Late Quaternary. Two Holocene earthquakes 1150-590 BC and 780-1000 AD were inferred from 14C dating of faulted Holocene colluvium with corresponding magnitudes Mw=6.7-7.0.
The latter one is the youngest documented surface-rupturing event in central Europe.