DOI: 10.17798/bitlisfen.1869499 ISSN: 2147-3129

Seismicity Parameters of the Westernmost Part of the North Anatolian Fault Zone (NAFZ)

Burçin Didem Tamtaş
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This study characterizes seismicity and stress regime in the westernmost part of the North Anatolian Fault Zone (NAFZ), focusing on the Saros segment, where dextral strike-slip deformation transitions into the transtensional northern Aegean domain. Unlike previous regional studies that combine Marmara and broader Aegean datasets or focus on individual rupture sequences, this study isolates a coordinate-bounded transition window to quantify the intrinsic seismic behavior of the terminal NAFZ–North Aegean Trough (NAT) linkage zone within a completeness-controlled framework. A December 1917–September 2025 earthquake catalog was compiled and homogenized to local magnitude (ML). Completeness analysis yields a reference Mc ≈ 3.2, consistent with Gutenberg–Richter statistics. Recurrence and annual probability metrics were evaluated for 1917–2025, 1985–2025, and 2010–2025 to assess temporal stability and completeness-related effects in seismic productivity. Recurrence and frequency–magnitude characteristics of the non-declustered and declustered catalogs were compared to assess aftershock effects on seismic rates. For events with M ≥ Mc, the estimated parameters are b = 0.91 ± 0.05 and a = 5.392 indicate moderate seismic productivity. Focal mechanisms and stress tensor inversion indicate a dominant dextral strike-slip regime with subordinate N–S extension, confirming a transtensional stress field linking the Saros region to the northern Aegean. Integrated completeness-controlled seismicity statistics and stress-tensor inversion show that the Saros segment functions as a transform–transtensional linkage corridor rather than a discrete tectonic boundary, refining the seismotectonic framework of the Marmara–Saros–North Aegean transition zone and providing robust parameters for seismic hazard and fault-segmentation analyses.

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