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Etude volcano-structurale du volcan Nemrut (Anatolie de l'Est, Turquie) et risques naturels associés

Abstract : Active Mt. Nemrut volcano, situated at the west of Lake Van, is one of the most important volcanoes of the Eastern Anatolia. It has a summit caldera with 8.5×7 km diameter. Volcanic activity of Mt. Nemrut started ~1 Ma ago and has continued in historical times. The most recent eruptions of the volcano were in 1441, 1597 and 1692 A.D. Amongst the Eastern Anatolian volcanoes; Mt. Nemrut is the most hazardous volcano for its vicinity, threatening 135,000 habitants living nearby. The present volcanic activities are represented by hydrothermal and fumarolic output within the caldera. Structural evolution of the volcano is mainly investigated in two stages (precaldera and post-caldera) separated by catastrophic caldera collapse. Pre-caldera products are dominated by felsic lava flows and domes. Nemrut and Kantaşı ignimbrite series represent the caldera forming activity, of which sequences are comprised of plinian units and ignimbrite flows. Post-caldera activity is represented by bimodal basaltic - rhyolitic effusive and explosive hydrovolcanic activity concentrated in the caldera and on Nemrut rift zone. Hydrothermal fluid circulation paths in Nemrut caldera and the structure of the caldera have been revealed using self-potential surveys, bathymetry data, derivatives of DEMs, Landsat and ASTER images. It is proposed that the caldera consists of three main blocks and has collapsed in a piecemeal manner. Boundaries delimiting these blocks and the main structural boundary of the caldera control the intra-caldera hydrothermal activities. Initiation of compressional-extensional tectonic regime in Pliocene structurally rooted and triggered the volcanism of Mt. Nemrut. Addition of strike-slip component to the pre-existing structures has led localized extensions where Nemrut volcanic system has been preferentially emplaced. To monitor the Nemrut volcano, three seismometers were installed. This is the first volcano-seismic monitoring network around a Turkish volcano and real-time data are being collected since October 2003. Hydrothermal signature as well as acquired volcanic signals clearly refer to an active magma chamber emplaced around 4-5 km depth. Long term monitoring of this active-quiescent volcano is vital and will yield more knowledge about this volcano.
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  • HAL Id : tel-00730602, version 1

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Inan Ulusoy. Etude volcano-structurale du volcan Nemrut (Anatolie de l'Est, Turquie) et risques naturels associés. Volcanologie. Université Blaise Pascal - Clermont-Ferrand II, 2008. Français. ⟨NNT : 2008CLF21855⟩. ⟨tel-00730602⟩

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