Source of Analytical Data on Main Faults and Faulted Areas with Seismic Potential
Structure ID: DBF
Fault Section IDs: DF_1-10; BF_1-17; WEI_1-3
Related terms: Diendorf fault (ger: Diendorfer Störung), Boskovice Graben fault (cze: okrajový zlom boskovické brázdy), Weitzendorf fault (ger: Weitzendorfer Störung; cze: weitzendorfský zlom)
Editor: Petr Špaček
First published: Aug 2019 | Last update: 29. 5. 2024
Diendorf-Boskovice fault system (DBF) is more than 200 km long fault structure running in the general NE-SW direction from the Alpine thrust front in Austria to the transverse faults of the Haná fault zone in the Czech Republic. It is formed by two major faults: the Diendorf fault (DF) to the south and the eastern marginal fault of the Boskovice half-graben, here termed the Boskovice Graben fault (BF), to the north (Fig. 1). Physical linking of both faults in the flat area of the Alpine molasse/Carpathian foredeep basins is strongly supported by geophysical data (see Špaček at el. 2018). Here, the formal border between DF and BF is located in the external part of the Carpathian foredeep basin. Southwestward continuation of DF beneath the Alpine nappes is unclear. To the north-northeast the BF is terminated by cross-cutting faults with apparently younger slip (the Haná Fault Zone). The parallel Weitzendorf fault and some minor faults (not necessarily included in the database) are formally assigned to DBF.
At shallow levels the fault is always steep, dipping either due W or E or vertical in both BF and DF. At general scale the BF is expected to be steeply inclined to WNW. The azimuth of the fault trace ranges between <20° and >45°.
The fault core, where observed, is often built by several meter wide mélange with fragments or bodies of limestones and greywackes (sections BF_2 through BF_14; Špaček et al. 2002) locally containing dark coloured clays. Surface observations near Zöbing (vineyards north of Kammern) suggest that the strongly deformed zone may be >10 m broad there. Similar width is expected elsewhere in Permian and crystalline rocks. In trench near Hostěradice, a 5-6 m wide zone of strong shearing and additional >5 m wide damage zone with dense small-scale faults is exposed in Lower Miocene clays and sands. The former contains frequent small fragments of weathered crystalline rocks.
A <20 to 250 m wide damage zone of the main fault is documented in Early Miocene sediments across a large part of BF_1 section by EM conductivity mapping (Fojt and Špaček, unpublished) and by observations in aerial photographs.
Parallel fault sections (splays of primary fault) are indicated by geological mapping and relief morphology in some parts of DF and BF, in a zone up to 800 m wide. Multiple parallel and oblique faults (observed and assumed) located in a broader zone (within up to 10 km to both sides of the BF and DF) indicate distributed faulting reflecting the complexity of long term evolution in different stress fields.
Cross structures, mostly of general NW-SE strike, traverse the DBF at multiple places, preferentially at its northern, Czech part. These are mainly (from north to south):
Fig.1. Schematic map of DBF with some basic features mentioned in text: Acronyms alphabetically: bb – Boskovice graben, BF – Boskovice graben marginal fault, BG – Blansko graben, DF – Diendorf fault, HFZ – Haná fault zone, mh – Miroslav horst, SCH – scarp near Schönbühel, SF – Slup fault, TZ – Tišnov—Kuřim zone, VG – Valchov graben, WEI – weitzendorf fault.
Surface morphology at the fault trace varies significantly, largely due to different degree of differential erosion at contacts of rocks with similar vs. contrasting mechanical properties.
This section will be revisited after completion of earthquake catalogue (submitted deliverable of Prachař and Pazdírková for WP1)! It is now based on review in Lenhardt et al. (2007) and preliminary compilations of ZAMG Vienna and IPE Brno (Pazdírková, unpublished) - see Fig. 2.
Following evidence is considered in the assessment of Quaternary activity:
Basing on this local evidence the fault activity is currently evaluated in a following way:
On a theoretical basis, the evaluation of similarly oriented sections of DBF by different activity ranks may be justified by:
(See layer Local evidence in the map. The sites are listed in south-to-north order.)
evi_ID: SCHO_A
fsec_IDs: DF_1, DF_1a, DF_9
editor: Petr Špaček
evi_ID: LIM_A
fsec_ID: DF_4
editor: Petr Špaček
evi_ID: TAS_A
fsec_ID: DF_7
editor: Petr Špaček Ivan Prachař
evi_ID: LECH_A
fsec_ID: BF_1
editor: Petr Špaček
evi_ID: STOS_A
fsec_ID: BF_1
editor: Petr Špaček
evi_ID: HOS_A
fsec_ID: BF_1
editor: Petr Špaček
Hostěradice profile with ERT, interpreted geology and position of the trench. Note vertical exaggeration. From Špaček et al. 2017.
evi_ID: KAD_A
fsec_ID: BF_2
editor: Petr Špaček
Profile Kadov with ERT, interpreted geology and position of the trench. Note the vertical exaggeration. From Špaček et al. 2017.
evi_ID: LES_A
fsec_ID: BF_3
editor: Petr Špaček
evi_ID: BUD_A
fsec_ID: BF_4
editor: Petr Špaček
Geological maps and explaining texts:
Geophysics:
Other:
Ongoing research and possible future work to be done: