Geophysical Images of the North Anatolian Fault Zone in the Erzincan Basin, Eastern Turkey, and their Tectonic Implications

Üm It Avşar; Erşan Türkoǧlu; Martyn Unsworth; Ilyas Çaǧlar; Bülent Kaypak

doi:10.1007/s00024-012-0521-5

Geophysical Images of the North Anatolian Fault Zone in the Erzincan Basin, Eastern Turkey, and their Tectonic Implications

Üm It Avşar^*, Erşan Türkoǧlu, Martyn Unsworth, Ilyas Çaǧlar, Bülent Kaypak

^*Corresponding author for this work

Department of Geophysical Engineering

Research output: Contribution to journal › Article › peer-review

9 Citations (Scopus)

Abstract

The collision between the Arabian and Eurasian plates in eastern Turkey causes the Anatolian block to move westward. The North Anatolian Fault (NAF) is a major strike-slip fault that forms the northern boundary of the Anatolian block, and the Erzincan Basin is the largest sedimentary basin on the NAF. In the last century, two large earthquakes have ruptured the NAF within the Erzincan Basin and caused major damage (M_s = 8. 0 in 1939 and M_s = 6. 8 in 1992). The seismic hazard in Erzincan from future earthquakes on the NAF is significant because the unconsolidated sedimentary basin can amplify the ground motion during an earthquake. The amount of amplification depends on the thickness and geometry of the basin. Geophysical constraints can be used to image basin depth and predict the amount of seismic amplification. In this study, the basin geometry and fault zone structure were investigated using broadband magnetotelluric (MT) data collected on two profiles crossing the Erzincan Basin. A total of 24 broadband MT stations were acquired with 1-2 km spacing in 2005. Inversion of the MT data with 1D, 2D and 3D algorithms showed that the maximum thickness of the unconsolidated sediments is ~3 km in the Erzincan Basin. The MT resistivity models show that the northern flanks of the basin have a steeper dip than the southern flanks, and the basin deepens towards the east where it has a depth of 3. 5 km. The MT models also show that the structure of the NAF may vary from east to west along the Erzincan Basin.

Original language	English
Pages (from-to)	409-431
Number of pages	23
Journal	Pure and Applied Geophysics
Volume	170
Issue number	3
DOIs	https://doi.org/10.1007/s00024-012-0521-5
Publication status	Published - Mar 2013

Funding

This research was funded by grants from NSERC and the Alberta Ingenuity Fund to Martyn Unsworth. It was also supported by a grant to İlyas C¸ ag˘lar from the Scientific and Research Council of Turkey (TUBI-TAK-CAYDAG 105Y022). Phoenix Geophysics (Toronto) is thanked for the loan of a broadband MT system. Alan Jones and Gary McNeice are thanked for the use of their tensor decomposition code. Ümit Avs¸ar thanks the Tinc¸el cultural foundation for funding his research visit to the University of Alberta. We thank Eylem Türkog˘lu, Bülent Tank of Bog˘azic¸i University, Ahmet S¸ener and Tunc¸ Demir of Istanbul Technical University for assistance during data collection. We also thank Erzincan Sugar Factory for assistance and accommodation. Lastly, we would like to thank two anonymous reviewers for their helpful comments. Topography maps were created using the generic mapping tools (GMT) software of Wessel and Smith, (1991).

Funders	Funder number
Scientific and Research Council of Turkey	TUBI-TAK-CAYDAG 105Y022
Tinc¸el cultural foundation
Natural Sciences and Engineering Research Council of Canada
University of Alberta
Alberta Ingenuity

Keywords

Eastern Turkey
Erzincan Basin
Magnetotellurics
electrical resistivity
fault zone conductor

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10.1007/s00024-012-0521-5

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abstract = "The collision between the Arabian and Eurasian plates in eastern Turkey causes the Anatolian block to move westward. The North Anatolian Fault (NAF) is a major strike-slip fault that forms the northern boundary of the Anatolian block, and the Erzincan Basin is the largest sedimentary basin on the NAF. In the last century, two large earthquakes have ruptured the NAF within the Erzincan Basin and caused major damage (Ms = 8. 0 in 1939 and Ms = 6. 8 in 1992). The seismic hazard in Erzincan from future earthquakes on the NAF is significant because the unconsolidated sedimentary basin can amplify the ground motion during an earthquake. The amount of amplification depends on the thickness and geometry of the basin. Geophysical constraints can be used to image basin depth and predict the amount of seismic amplification. In this study, the basin geometry and fault zone structure were investigated using broadband magnetotelluric (MT) data collected on two profiles crossing the Erzincan Basin. A total of 24 broadband MT stations were acquired with 1-2 km spacing in 2005. Inversion of the MT data with 1D, 2D and 3D algorithms showed that the maximum thickness of the unconsolidated sediments is ~3 km in the Erzincan Basin. The MT resistivity models show that the northern flanks of the basin have a steeper dip than the southern flanks, and the basin deepens towards the east where it has a depth of 3. 5 km. The MT models also show that the structure of the NAF may vary from east to west along the Erzincan Basin.",

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Geophysical Images of the North Anatolian Fault Zone in the Erzincan Basin, Eastern Turkey, and their Tectonic Implications

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