Faults of the Bohemian Massif

Source of Analytical Data on Main Faults and Faulted Areas with Seismic Potential

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dbz:diendorf-boskovice_fault [2021/04/29 15:45]
petrs [Quaternary] 		dbz:diendorf-boskovice_fault [2021/04/29 16:42]
petrs [Quaternary]
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   ***//Seismicity and paleoseismicity//**   ***//Seismicity and paleoseismicity//**
-    * A cluster of epicentres of weak earthquakes between the towns of Langenlois, Gfohl, Ybbs an der Donau and Melk (see **[[dbz:diendorf-boskovice_fault#Observed seismicity]]**) suggest possible connection with southern Diendorf fault (sections DF_1, 2, 5 and 6). However, the causal links are unclear as the cluster shape (possibly affected by poor accuracy of location) allows for different conclusions. In the area of southern Bohemian Massif the increased seismicity seems to be characteristic. Some observations suggest that unmapped NW-SE striking faults may be responsible for at least part of these earthquakes (see site **[[dbz:diendorf-boskovice_fault#Schönbühel a.d. Donau: Cross-structure|Schönbühel a.d. Donau]]** as an example). The concerned sections of DF are admitted to take part in this deformation but activation of large segments by a single earthquake seems unlikely.+    * A cluster of epicentres of weak earthquakes between the towns of Langenlois, Gfohl, Ybbs an der Donau and Melk (see **[[dbz:diendorf-boskovice_fault#Observed seismicity]]**) suggest possible relation to southern Diendorf fault (sections DF_1, 2, 5 and 6). However, the causality is unclear as the cluster shape (possibly affected by poor accuracy of location) allows for different conclusions. In the area of southern Bohemian Massif the increased seismicity seems to be characteristic. Some observations suggest that unmapped NW-SE striking faults may be responsible for at least part of these earthquakes (see site **[[dbz:diendorf-boskovice_fault#Schönbühel a.d. Donau: Cross-structure|Schönbühel a.d. Donau]]** as an example). The concerned sections of DF are admitted to take part in this deformation but activation of large segments by a single earthquake seems unlikely.
     * To the north of Langenlois the low number and magnitude of historical and instrumental earthquakes and their low spatial correlation with fault line do not allow affiliation of seismicity to any known structures.     * To the north of Langenlois the low number and magnitude of historical and instrumental earthquakes and their low spatial correlation with fault line do not allow affiliation of seismicity to any known structures.
     * Rare local observations of soft sediment deformation structures are interpreted as due to paleoearthquakes with minimum intensity of 6-7° (sites **[[dbz:diendorf-boskovice_fault#Lechovice: Cross-structure and inferred paleoearthquake|Lechovice]]** and **[[dbz:diendorf-boskovice_fault#Tasovice: Observed sealing strata and inferred paleoearthquake|Tasovice]]**). The source of these hypothetical earthquakes is entirely unknown and they are not necessarily related to Diendorf fault. In case of epicentre located close to observation sites, the minimum magnitude of Mw=5 should be considered.     * Rare local observations of soft sediment deformation structures are interpreted as due to paleoearthquakes with minimum intensity of 6-7° (sites **[[dbz:diendorf-boskovice_fault#Lechovice: Cross-structure and inferred paleoearthquake|Lechovice]]** and **[[dbz:diendorf-boskovice_fault#Tasovice: Observed sealing strata and inferred paleoearthquake|Tasovice]]**). The source of these hypothetical earthquakes is entirely unknown and they are not necessarily related to Diendorf fault. In case of epicentre located close to observation sites, the minimum magnitude of Mw=5 should be considered.
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   *In the southern part of DBF, the sections DF_1 to BF_2 are ranked **class 3**, i.e. assumed or admitted to be active but without direct evidence. Quaternary slip rate at fault sections north of DF_3 is assumed very low (<0.01 mm/y). Southern sections may later be ranked class 1 (demonstrably active) when new earthquake data (better location, focal mechanism) bring clear evidence.   *In the southern part of DBF, the sections DF_1 to BF_2 are ranked **class 3**, i.e. assumed or admitted to be active but without direct evidence. Quaternary slip rate at fault sections north of DF_3 is assumed very low (<0.01 mm/y). Southern sections may later be ranked class 1 (demonstrably active) when new earthquake data (better location, focal mechanism) bring clear evidence.
   *In the northern part of DBF, the sections BF_3 to BF_ 17 are ranked **class 4**, i.e. assumed or demonstrated to be inactive.   *In the northern part of DBF, the sections BF_3 to BF_ 17 are ranked **class 4**, i.e. assumed or demonstrated to be inactive.
-On a theoretical basis, the evaluation of similarly oriented fault sections by different activity ranks may be justified by:+On a theoretical basis, the evaluation of similarly oriented sections of DBF by different activity ranks may be justified by:
   -expected northward decrease of rate of stress build-up (and hence crustal strain rate), and    -expected northward decrease of rate of stress build-up (and hence crustal strain rate), and 
   -expected northward decrease of slip potential due to rotation of stress orientation near junction of the Alpine and the West-European stress domains.   -expected northward decrease of slip potential due to rotation of stress orientation near junction of the Alpine and the West-European stress domains.
dbz/diendorf-boskovice_fault.txt · Last modified: 2024/05/29 16:39 by petrs

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