Vollbrecht, Axel

[["dc.bibliographiccitation.firstpage","401"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Solid Earth"],["dc.bibliographiccitation.lastpage","414"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Krumbholz, Michael"],["dc.contributor.author","Bock, M."],["dc.contributor.author","Burchardt, S."],["dc.contributor.author","Kelka, U."],["dc.contributor.author","Vollbrecht, Axel"],["dc.date.accessioned","2018-11-07T09:14:31Z"],["dc.date.available","2018-11-07T09:14:31Z"],["dc.date.issued","2012"],["dc.description.abstract","In recent years, the electromagnetic radiation (EMR) method has been used to detect faults and to determine main horizontal stress directions from variations in intensities and directional properties of electromagnetic emissions, which are assumed to be generated during micro-cracking. Based on a large data set taken from an area of about 250 000 km(2) in Northern Germany, Denmark, and southern Sweden with repeated measurements at one location during a time span of about 1.5 yr, the method was systematically tested. Reproducible observations of temporary changes in the signal patterns, as well as a strongly concentric spatial pattern of the main directions of the magnetic component of the EMR point to very low frequency (VLF) transmitters as the main source and hence raise serious concerns about the applicability of the method to determine recent crustal stresses. We conclude that the EMR method, at its current stage of development, does not allow determination of the main horizontal stress directions."],["dc.description.sponsorship","University of Gottingen"],["dc.identifier.doi","10.5194/se-3-401-2012"],["dc.identifier.isi","000321443000005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/27435"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Copernicus Gesellschaft Mbh"],["dc.relation.issn","1869-9510"],["dc.title","A critical discussion of the electromagnetic radiation (EMR) method to determine stress orientations within the crust"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","33"],["dc.bibliographiccitation.journal","Journal of Structural Geology"],["dc.bibliographiccitation.lastpage","43"],["dc.bibliographiccitation.volume","65"],["dc.contributor.author","Krumbholz, Michael"],["dc.contributor.author","Vollbrecht, Axel"],["dc.contributor.author","Aschoff, Marius"],["dc.date.accessioned","2018-11-07T09:37:27Z"],["dc.date.available","2018-11-07T09:37:27Z"],["dc.date.issued","2014"],["dc.description.abstract","The strike direction of open intragranular microcracks in quartz and feldspar host grains was determined using optical transmission and reflection microscopy on eight oriented samples taken in two study areas in Precambrian basement rocks of southern and south-central Sweden. For an area of about 160 km(2) (SW of Vastervik) and two sample locations (W of Uppsala), the vast majority of open microcracks displays a strong preferred NW-SE strike direction. According to the common assumptions that natural cracks in crystalline rocks are predominantly extensional (mode I), and that open cracks belong to the latest microcrack generation, these strike directions should reflect the (sub-) recent main horizontal stress direction (sigma H) of the recent tectonic stress field. This conclusion is supported by corresponding directions known from in situ stress measurements and focal plane solutions in the vicinity of the study areas. It is remarkable that even in samples taken close (i.e. a few hundred metres) to recently active large scale faults the orientation of microcracks does not deviate from this common direction. This may point to slip on already softened faults, very local stress reorientations (e.g. m-scale) or that local stress relief was accomplished by other processes at microscale, e.g. mechanical twinning in favourably oriented feldspar crystals, or slip on grain boundaries. (C) 2014 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.jsg.2014.03.006"],["dc.identifier.isi","000337778800003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32844"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0191-8141"],["dc.relation.orgunit","Abteilung Strukturgeologie und Geodynamik"],["dc.title","Recent horizontal stress directions in basement rocks of southern Sweden deduced from open microcracks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]