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

near Lázně Kynžvart. Towards the both ends the fault became less morphologically distinct. The character of the fault escarpment also varies along the MLF, which is expressed by different grades of facets evolution, water stream erosion etc. This could have been a result of complicated tectonic history and possible differences in age and rate of the tectonic movements along the particular segments of the MLF. The MLF could be divided into several segments (as many as 17, see Flašar, Štěpančíková 2022) based on varying fault orientation and geology, natural breaks in the trace of the fault slope, in agreement with results of morphometric analysis such as mountain front sinuosity index (Smf), basin asymmetry, and longitudinal profiles. These morphometric parameters showed different river network evolution including river captures and supports the hypothesis of variable tectonic activity along the MLF (Flašar, Štěpančíková 2022). The results of morphometric analysis also indicated that the activity of the MLF could have been younger than Miocene-Pliocene, so possibly Pleistocene, while most intensive in the central part of the MLF. M E T H O D S In this paper we summarize the results from literature and from our previous studies which were published (morphometric analysis of the MLF - Flašar, Štěpančíková 2022, fluvial terraces in Cheb basin - Balatka et al. 2019), and from our paleoseismic trenching published (Štěpančíková et al. 2019) or not yet published to compare the varying Quaternary activity of the MLF. The paleoseismic survey was focused on the northern portion of the MLF – often called here as Eastern border fault of the Cheb basin (e.g. Špičáková et al. 2000), where two trenching sites Kopanina and Horka were explored (Fig. 2). The results of one 100m long trench in Kopanina site (in 2010)(Štěpančíková et al. 2019) are here combined with results of following 3D trenching in Kopanina site (in 2017), and of Horka site, where 2 trenches were excavated (in 2022) to confirm the Holocene surface-breaking earthquakes. To compare and asses the activity in the southern portion of the MLF, N-S trending segment at Nová Hospoda site was excavated by 2 trenches (in 2023). All the trenching survey was preceded and accompanied by our multiple geophysical survey such electric resistivity tomography, ground penetrating radar, DEMP, seismic refraction at Kopanina site, gravimetry, and magnetotellurics (see also Fischer et al. 2012, Blecha et al. 2018). Quaternary activity along-strike The MLF is morphologically pronounced for as long as 120 km by a well-expressed escarpment with triangular and trapezoidal facets, which varies from 50 to 400 m of height (Fischer et al., 2012). The highest fault scarp can be found in the central part of the fault, near Lázně Kynžvart and its height became less morphologically distinct towards both ends, near Plauen (in Germany) in the NW and near Horšovský Týn in the SE. Northern portion of the MLF Late Cenozoic activity along the northern portion of the MLF is expressed by the subsidence of the half- graben of Cheb basin controlled by the MLF. So, the thickest part of the basin infill, up to 400m of Plio- Pleistocene Vildštejn Formation occurs next to the MLF (Špičáková et al., 2000). Pleistocene activity is also reflected in discrepancies in Pleistocene fluvial terraces of the Eger (Ohře) river, which crosses the MLF and flows antecedently eastward into the elevated relief. The oldest terraces from Tiglian stage are 15 m vertically offset (Ambrož 1958, Balatka et al. 2019). Pleistocene to Holocene activity was proved by displaced and deformed deposits within the MLF at Kopanina trenching site, situated on the foothill of the Krušné hory Mts and Cheb basin infill limit (Štěpančíková et al. 2019). The trenching discovered Pleistocene and Holocene surface-breaking earthquakes, the youngest one resulting from right- lateral motion within the MLF and deforming the relief (Fischer et al. 2012, Štěpančíková et al. 2019). As the kinematics of the movements were inferred as dominantly strike-slip during the youngest periods,