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Fluctuations in Plates-coupling Strength Suggested by Episodic Triggering of Shallow Earthquakes at the Carpathians BendNormal access

Authors: H. Mitrofan, M.A. Anghelache, M. Visan and F. Chitea
Event name: 8th Congress of the Balkan Geophysical Society
Session: Seismology & Lithosphere I
Publication date: 05 October 2015
DOI: 10.3997/2214-4609.201414228
Organisations: BGS, EAGE
Language: English
Info: Extended abstract, PDF ( 802.54Kb )
Price: € 20

There has been analyzed the 1965-2015 time-series of shallow (<60 km) earthquakes recorded next to the SE Carpathians bend, at the contact between the Moesian and East-European tectonic plates. It seems that each of the major (Mw6.9) Vrancea earthquakes having occurred nearby, at intermediate-depths (>60 km), during the 1977-1990 time interval, succeeded to trigger a subsequent enhancement of that shallow seismicity: presumably, by episodically unblocking channels along which high-pressure/ultra-high-pressure rocks were ascending, in a discontinuous process of exhumation, by the present time. Yet even in periods when only moderate shocks (Mw<6) occurred at intermediate-depth in Vrancea region, focal mechanisms of shallow earthquakes, as well as vertical GPS displacements, were still consistent with an ongoing up-flow of exhuming material; consequently, by taking into account that no waves generated by a strong earthquake could have been then involved in unblocking exhumation channels, it was suggested that in those periods, the exhuming material ascent should have proceeded more unrestricted. Overall considered, since the hypothesized exhuming pathways presumably followed the contacts between the tectonic plates which are juxtaposed in that region, such distinctions noticed in terms of shallow earthquakes generation could be related to the strength of the coupling between the involved plates.

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