Date

2008-12-15

Author

Gans, Christine R.
Biryol, C. Berk
Beck, Susan L.
Zandt, George
Özacar, Atilla Arda
Tok, Hande
Turkelli, Niyazi
TAYMAZ, TUNCAY

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The 1400km-long North Anatolian Fault (NAF), located in northern Turkey, forms a transform boundary between the Anatolian and Eurasian plates, and is capable of large destructive earthquakes. Located in part on an old suture zone, continental basement material is found north of the NAF, while accretionary complexes are found to the south. The North Anatolian Fault Passive Seismic Experiment (2005-2008), a joint project between the University of Arizona, the Middle East Technical University, Istanbul Technical University and Bogazici University Kandilli Observatory, contained 39 broadband seismometers used to investigate the lithospheric structure of this region. Using 24 regional earthquakes located up to ~1000 km from the network, we have identified over 900 Pn phases in order to investigate the structure of the uppermost mantle. The Pn phase is a compressional wave that travels through the crust, refracts into the mantle, and then propagates through the mantle lid at mantle velocities. Using a tomography code developed by Hearn (1996), Pn travel time residuals were inverted for Pn wave velocity in northern Turkey. Results show no observable contrast in Pn velocity across the North Anatolian Fault. In general, large-scale velocity variations appear to be associated with older terrain features. We have imaged a strong transition, however, from slower (~7.7-7.9 km/s) to faster (8.0-8.1 km/s) Pn velocities from east to west across the Central Anatolian Fault Zone (CAFZ), which is associated with the paleotectonic Inner Tauride Suture (ITS). The slower velocities to the east, located beneath the Eastern Anatolian Accretionary Complex, may be associated with regions of partially molten to absent mantle lid, and potentially define the edge of a slab window in this region. Higher Pn velocities are often linked to areas having a stable mantle lid. A zone of fast velocities (>8.1 km/s) is found below the Cankiri and Safranbolu Basins, regions underlain by massifs. This zone appears to cross tectonic belts, the North Anatolian Fault, and the Intra-Pontide Suture. Finally, in the western part of our network, a region of slower Pn velocity (~7.9 km/s) appears to correspond to the location of the early Miocene Galatian volcanics.

URI

http://abstractsearch.agu.org/meetings/2008/FM/sections/T/sessions/T21A/abstracts/T21A-1918.html
https://hdl.handle.net/11511/94852

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Department of Geological Engineering, Conference / Seminar