Tectonic geomorphology of the Yatağan Fault (Muğla, SW Turkey): implications for quantifying vertical slip rates along active normal faults

MEHRAN BASMENJI; TAYLAN SANÇAR; AYNUR DİKBAŞ; SARAH JEAN BOULTON; HÜSNÜ SERDAR AKYÜZ

Tectonic geomorphology of the Yatağan Fault (Muğla, SW Turkey): implications for quantifying vertical slip rates along active normal faults

Authors: MEHRAN BASMENJI, TAYLAN SANÇAR, AYNUR DİKBAŞ, SARAH JEAN BOULTON, HÜSNÜ SERDAR AKYÜZ

Abstract: South Western Anatolia is dominated by E-W and NW-SE trending active faults. The dip-slip Yatağan Fault is one of these active structures that trends in a NW direction for ~30 km. To assess the relative tectonic activity of the Yatağan Fault, two geomorphic segments were defined along the fault: the FS-1 (northern segment) and the FS-2 (southern segment). The vertical slip rate pattern of the fault was analyzed using steepness indexes, chi (χ) plots, and log-log slope area graphs. Results of the analyses indicate that the steepness of the streams draining the footwall reveal increasingly higher values downstream along the fault. All of the main basins contain at least one slope-break knickpoint associated with tectonic uplift. Facet morphology-based investigations using empirical methods along faceted spurs of the Yatağan Fault indicate vertical slip rates of 0.16 ± 0.05 mm/year and 0.3 ± 0.05 mm/year for the FS-1 and the FS-2, according to relationship of facet slope angle (R_sa). Additionally, using the facet basal height relationship (R_bh) we calculated slip rates of 0.24 mm/year and 0.36 mm/year for the FS-1 and the FS-2 segments, respectively. Mountain front sinuosity analysis yields values of 1.34 and 1.2, while the ratio of valley-floor width to valley height gives values of 0.64 and 0.24 for the FS-1 and the FS-2 respectively, indicating typical active mountain front where the uplift rates are ? 0.5 mm/year. Hypsometric analysis suggest a transition from mature to older stage for catchments along the Yatağan Fault. Comprehensive interpretation of the results from morphometric analysis, vertical slip rate calculations, and data based on field observations suggest preponderance of tectonic activity over erosional process along the Yatağan Fault. Our analyses reveal that the rate of the tectonic activity gradually increases from the FS-1 to the FS-2 along the fault.

Keywords: Tectonic geomorphology, normal fault, Yatağan Fault, slip rate, triangular facet, SW Anatolia

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