Acceleration of Late Pleistocene activity of a Central European fault driven by ice loading

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Authors

ŠTĚPANČÍKOVÁ Petra ROCKWELL Thomas K. STEMBERK Jakub RHODES Edward J. HARTVICH Filip LUTTRELL Karen MYERS Madeline TÁBOŘÍK Petr ROOD Dylan H. WECHSLER Neta NÝVLT Daniel ORTUNO María HÓK Jozef

Year of publication 2022
Type Article in Periodical
Magazine / Source Earth and Planetary Science Letters
MU Faculty or unit

Faculty of Science

Citation
Web https://www.sciencedirect.com/science/article/pii/S0012821X22002321?via%3Dihub#!
Doi http://dx.doi.org/10.1016/j.epsl.2022.117596
Keywords paleoseismology; intraplate earthquakes; ice-loading; glacially triggered fault; Sudetic Marginal fault; Central Europe
Description We studied the southern part of the NW-SE trending Sudetic Marginal fault (SMF), situated at the northeastern limit of the Bohemian Massif in central Europe, to assess its Quaternary activity. Eighteen trenches and thirty-four electric resistivity profiles were performed at Bílá Voda to study the fault zone and 3-dimensional distribution of a beheaded alluvial fan on the NE side of the fault. We interpret a small drainage, located about 29–45 m to the SE of the fan apex, as the only plausible source channel implying a similar amount of left-lateral offset. The alluvial fan deposits' radiometric ages range between about 24 and 63 ka, but postglacial deposits younger than 11 ka are not displaced, indicating that all motion occurred in the late Pleistocene. The site lies ~150 km south of the late Pleistocene Weichselian maximum (~20 ka) ice sheet front. We model the effects of the ice load on lithospheric flexure and resolved fault stresses, and show that slip on the SMF was promoted by the presence of the ice sheet, resulting in a late Pleistocene slip rate of ~1.1+2.3/-0.6 mm/yr. As the most favorable time for glacial loading-induced slip would be during the glacial maximum between about 24 and 12 ka, it is doubtful that the slip rate remained constant during the entire period of activity, and if most slip occurred during this period, the short-term rate may have been even higher. Considering that the modern maximum principal stress (sigma(1)) is oriented nearly parallel to the Sudetic Marginal fault (NNW-SSE) and is thus unfavorable for fault motion, our observations suggest that the likelihood of continued motion and earthquake production is much lower in the absence of an ice sheet.
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