Three large prehistoric earthquakes in the Eastern Alps evidenced by cave rupture and speleothem damage

0557129 - ÚSMH 2023 RIV NL eng J - Journal Article
Baroň, Ivo - Plan, L. - Grasemann, B. - Melichar, R. - Mitrović-Woodell, I. - Rowberry, Matthew David - Scholz, D.
Three large prehistoric earthquakes in the Eastern Alps evidenced by cave rupture and speleothem damage.
Geomorphology. Roč. 408, 1 July (2022), č. článku 108242. ISSN 0169-555X. E-ISSN 1872-695X
R&D Projects: GA ČR(CZ) GC22-24206J
Institutional support: RVO:67985891
Keywords : paleoearthquake * speleotectonics * speleoseismology * karst caves * active faults * speleothems * Eastern Alps
OECD category: Geology
Impact factor: 3.9, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0169555X22001350?via%3Dihub

Spectacular geomorphic evidence of recent tectonic activity and three potentially strong prehistoric earthquakes were discovered in Obir Caves in the Karawanken Mountains. This paper presents active fault structures, geomorphic features, and the age constraints attributed to particular seismotectonic events. The 1976 Mw 6.7 Friuli earthquake about 100 km from Obir Caves caused only local speleothem damage. The 100 km hypocentral distance enabled attenuation of the seismic waves so speleothem damage due to stalagmite resonance frequency was dampened. The documented dripstone column damage was rather caused by its sudden shortening due to passing elastic S-waves with estimated 3.5 (+8.2/−1.5) mm PGD amplitudes. At least three distinct seismotectonic events in the Late Pleistocene and Early to Middle Holocene were constrained by radiometric dating. The 40.6 cm sinistral fault slip occurred between 41.8 ± 1.3 ka and 18.7 ± 0.4 ka ago, the 2.6 cm dextral oblique reverse fault slip happened between 10.73 ± 0.23 and 8.61 ± 0.15 ka ago, and another speleothem damage event took place between 6.28 ± 0.24 ka and 5.7 ± 1.2 ka ago. These events were most probably accompanied by distinct destructive to very destructive paleoearthquakes with local intensities ranging from VIII to X on the ESI 2007 scale, significant rock weakening, and forming the large deep-seated gravitational slope deformation on the southeastern mountain slopes adjacent to Obir Caves.
Permanent Link: http://hdl.handle.net/11104/0331232