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Regional attenuation of amplitudes in a structurally complex crust at the orogenic front: case of Mw3.7 Alland 2016 earthquake

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ŠPAČEK Petr ZACHERLE Pavel MEURERS Rita PAZDÍRKOVÁ Jana BOKELMANN Götz SCHIPPKUS Sven

Rok publikování 2021
Druh Konferenční abstrakty
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Popis Unique set of dense instrumental and macroseismic records of ML4.2/Mw3.7 Alland 2016 earthquake (SW of Vienna) offers a possibility to study in detail the propagation of seismic waves in the tectonically complex junction region of the Alps, Carpathians, Alpine foreland and Pannonia. In this contribution we illustrate the contrasting amplitude decay in different tectonic domains and present its best fitting models as a function of geometrical spreading, anelastic attenuation and frequency-filtering structural barriers. We give possible explanation of the long-known and incompletely understood elongation of isoseismals from East Alpine earthquakes towards the Bohemian Massif in the Alpine foreland. In the latter, the slope of amplitude (and intensity) decay is reduced at near to middle distances, probably due to interference of Lg with waves reflected at rather shallow intracrustal reflectors and the Moho. Resemblance with observations in eastern North America is striking. On the contrary, high-frequency energy of the direct and guided waves passing towards the orogen is strongly attenuated at crustal barriers likely related to orogenic paleosuture. We emphasise the advantages of combining instrumental and macroseismic data which allows correct description of amplitude decay at local distances. We argue that similar locally-derived amplitude attenuation models based on few well-sampled earthquakes may give better input for regional SHA than those based on larger datasets and extrapolated from other regions.

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