Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

456 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E PATA Days 2024 K E Y W O R D S Mariánské Lázně fault, paleoseismic trenching, morphometric analysis, tectonic activity, Bohemian Massif (1) Institute of Rock Structure and Mechanics, Czech Academy of Sciences, V Holešovičkách 41, 18209, Prague 8, Czech Republic *Email: stepancikova@irsm.cas.cz Štěpančíková, Petra (1) Flašar, Jan (1) Rockwell, Thomas (1) Stemberk, Jakub (1) Tábořík, Petr (1) Goswami, Chandreyee (1) Hartvich, Filip (1) Sana, Hamid (1) VARIABILITY OF LATE CENOZOIC ACTIVITY ALONG-STRIKE THE MARIÁNSKÉ LÁZNĚ FAULT (BOHEMIAN MASSIF, CZECH REPUBLIC) A B S T R A C T The Mariánské Lázně fault (MLF) is a 150 km long NW-SE- striking structure within the western Bohemian Massif (Czech Republic). It delineates the eastern boundary of the Cheb- Domažlice graben and controls the pronounced fault escarpment for over 100 kilometers. We studied its neotectonic activity along- strike by analyzing the faults scarp, longitudinal river profiles and river network and by using morphometric indices (mountain front sinuosity, basin asymmetry, and SL index). Moreover, we carried out paleoseismic trenching survey on three sites, two of them in the northern portion where the NW-SE striking MLF borders the Cheb basin and one in the southern portion where the strike is N-S and more favorably oriented towards the current horizontal maximum stress being NW-SE to NNW-SSE. All the geological and geomorphological results confirm the segmentation of the MLF and the variability of the age and rate of its activity, while the Cheb basin portion is the youngest (with Holocene surface- rupturing earthquakes) and most active (present-day earthquake swarms in the area). I N T R O D U C T I O N A N D T E C T O N I C S E T T I N G The Mariánské Lázně Fault (MLF) is a 150 km long NNW -SSE trending tectonic structure controlling the eastern limit of the Cheb- Domažlice Graben, located in the western part of the Bohemian Massif in the Czech Republic. MLF delineates several geological units that have undergonedifferent geological processes.The fault itselfwas formedduring Variscan orogeny 380 - 300Ma as a normal fault with dextral component (Pitra et al., 1999) and it separates main geological units building the Bohemian Massif – Moldanubian, Saxothuringian and Teplá-Barrandian