Crustal constraints on the origin of mantle seismicity in the Vrancea Zone, Romania: The case for active continental lithospheric delamination

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• 作者：James H. Knapp ; Camelia C. Knapp ; Victor Raileanu ; Liviu Matenco ; Victor Mocanu and Cornel Dinu
• 关键词：Delamination ; Vrancea zone ; Romania ; Tectonics ; Carpathians
• 刊名：Tectonophysics
• 出版年：2005
• 出版时间：9 December 2005
• 年：2005
• 卷：410
• 期：1-4
• 页码：311-323
• 全文大小：940 K

文摘

The Vrancea zone of Romania constitutes one of the most active seismic zones in Europe, where intermediate-depth (70–200 km) earthquakes of magnitude in excess of M_w = 7.0 occur with relative frequency in a geographically restricted area within the 110° bend region of the southeastern Carpathian orogen. Geologically, the Vrancea zone is characterized by (a) a laterally restricted, steeply NW-dipping seismogenic volume (30 × 70 × 200 km), situated beneath (b) thickened continental crust within the highly arcuate bend region of the Carpathian orocline, and (c) miscorrelation of hypocenters with the position of known or inferred suture zones in the Carpathian orogenic system. Geologic data from petroleum exploration in the Eastern Carpathians, published palinspastic reconstructions, and reprocessing of industry seismic data from the Carpathian foreland indicate that (1) crust of continental affinity extends significantly westward beneath the external thrust nappes (Sub-Carpathian, Marginal Folds, and Tarcau) of the Eastern Carpathians, (2) Cretaceous to Miocene strata of continental affinity can be reconstructed westward to a position now occupied by the Transylvanian basin, and (3) geologic structure in the Carpathian foreland (including the Moho) is sub-horizontal directly to the east and above the Vrancea seismogenic zone. Taken together, these geologic relationships imply that the Vrancea zone occupies a region overlain by continental crust and upper mantle, and does not appear to originate from a subducted oceanic slab along the length of the Carpathian orogen. Accordingly, the Vrancea zone appears to potentially be an important place to establish evidence for active lithospheric delamination.