The North Anatolian Fault Zone (NAFZ) in the north of Türkiye is considered one of the most active faults on earth and have caused many major earthquakes in the last century. Surface ruptures by those earthquakes indicate that this tectonic feature consists of many segments, which reveal different characteristics in terms of geometry and mechanism. NAFZ lies along between Bingöl in the eastern Turkey and Saros Gulf in the west. This study focuses on the central part of the NAFZ between Niksar and Ilgaz provinces. In addition to the main branch, the central section of the NAFZ also contains two sub-branches extending southward: Merzifon-Esençay and Sungurlu Faults. In the literature, there are several studies for the region, however a comprehensive study mainly focusing on the main branch of the NAFZ and its sub-branches along the central NAFZ has not been conducted yet, which would fully reveal the fault mechanism and seismic potential in the region. The aim of this study is to derive an up-to-date high-spa-tial-resolution Global Navigation Satellite Systems (GNSS) velocity field for the central NAFZ and to correlate with the strain accumulations along the faults. Based on this, a high-spatial-resolution GNSS network consisting of 60 sites was established enclosing the central NAFZ. The previously archived GNSS data for the same observation sites were collected from the different studies in the region and a new GNSS campaign measurement was conducted between October 2023 and February 2024. All GNSS data were processed using GAMIT/GLOBK software, and the results indicate the GNSS velocities ranging from 3-30 mm/year and their associated uncertainties of maximum ± 1.5 mm/year with respect to the Eurasian tectonic plate.

30 Ekim 2020 tarihinde Sisam adası kuzeyinde Mw:6.9 büyüklüğünde bir deprem meydana gelmiştir. Bu deprem İzmir şehir merkezinde ve bazı ilçelerinde can ve mal kayıplarına yol açmıştır. Deprem sonrası İzmir ve güneyinde yapılan çalışmalar, en büyüğü Seferihisar'da olmak üzere İzmir ve güneyinde 4-14 cm arasında değişen miktarlarda yatay atım meydana geldiğini göstermiştir. İzmir ve güneyinde ise Mw:6.1 ile Mw:6.9 arasında deprem üretme potansiyeline sahip olan diri faylar yer almaktadır. Meydana gelen bir depremin civardaki fayların neden olabileceği depremleri etkileyebilmesi nedeniyle bu bölgede postsismik deformasyonun takip edilmesi amacıyla 27 noktalık bir GNSS ağı kurulmuştur. Bu ağda 2020-2022 arasında 6 aylık periyotlar halinde 4 kampanya GNSS ölçümü gerçekleştirilmiştir. GNSS verileri kullanılarak tüm noktaların Avrasya sabit hızları elde edilmiştir. Elde edilen sonuçlar ağdaki noktaların hem deprem sonrasında kendi aralarındaki hem de deprem öncesi hızlarla aralarındaki farkların 6 mm'ye ulaştığını, buna bağlı olarak bölgede postsismik etkinin devam ettiğini göstermektedir.

30 Ekim 2020 tarihinde Sisam adası kuzeyinde Mw:6.9 büyüklüğünde bir deprem meydana gelmiştir. Bu deprem İzmir şehir merkezinde ve bazı ilçelerinde can ve mal kayıplarına yol açmıştır. Deprem sonrası İzmir ve güneyinde yapılan çalışmalar, en büyüğü Seferihisar'da olmak üzere İzmir ve güneyinde 4-14 cm arasında değişen miktarlarda yatay atım meydana geldiğini göstermiştir. İzmir ve güneyinde ise Mw:6.1 ile Mw:6.9 arasında deprem üretme potansiyeline sahip olan diri faylar yer almaktadır. Meydana gelen bir depremin civardaki fayların neden olabileceği depremleri etkileyebilmesi nedeniyle bu bölgede postsismik deformasyonun takip edilmesi amacıyla 27 noktalık bir GNSS ağı kurulmuştur. Bu ağda 2020-2022 arasında 6 aylık periyotlar halinde 4 kampanya GNSS ölçümü gerçekleştirilmiştir. GNSS verileri kullanılarak tüm noktaların Avrasya sabit hızları elde edilmiştir. Elde edilen sonuçlar ağdaki noktaların hem deprem sonrasında kendi aralarındaki hem de deprem öncesi hızlarla aralarındaki farkların 6 mm'ye ulaştığını, buna bağlı olarak bölgede postsismik etkinin devam ettiğini göstermektedir.

Postseismic deformation provides fundamental insights into earthquake-cycle processes, lithospheric rheology, and stress redistribution following large earthquakes. Although the 2020 Mw 7.0 Samos earthquake has been extensively investigated in terms of coseismic deformation and early postseismic behavior, the long-term evolution of deformation following the event remains poorly constrained. This study characterizes the long-term spatiotemporal evolution of postseismic deformation associated with the 2020 Mw 7.0 Samos earthquake using combined campaign and continuous GNSS observations. A total of 18 GNSS stations were analyzed over an approximately 4.5-year period following the earthquake. Pre-earthquake GNSS velocities were incorporated as prior constraints, while postseismic deformation was modeled using linear, logarithmic, exponential, and combined logarithmic–exponential functions. The preferred model for each station component was identified using the corrected Akaike Information Criterion (AICc), and model-selection robustness was evaluated through 1000 Monte Carlo observation–perturbation simulations. The results reveal a spatially heterogeneous postseismic deformation field with station-dependent temporal behavior. Among the nonlinear solutions passing the Monte Carlo and goodness-of-fit criteria, the seven single-process LOG and EXP solutions yielded characteristic relaxation times ranging from 182.6 to 730.5 days, with a median of 438.3 days. The two LOGEXP solutions additionally contained a logarithmic timescale of 109.6 days and exponential timescales of 292.2–438.3 days. These findings demonstrate that campaign GNSS observations, when integrated with continuous GNSS data and an objective statistical framework, can provide meaningful constraints on the long-term evolution of postseismic deformation despite sparse temporal sampling. More broadly, the results emphasize the strongly time-dependent nature of postseismic deformation and the critical role of observation timing in capturing its spatiotemporal evolution.

The North Anatolian Fault Zone (NAFZ) in the north of Türkiye is considered one of the most active faults on earth and have caused many major earthquakes in the last century. Surface ruptures by those earthquakes indicate that this tectonic feature consists of many segments, which reveal different characteristics in terms of geometry and mechanism. NAFZ lies along between Bingöl in the eastern Turkey and Saros Gulf in the west. This study focuses on the central part of the NAFZ between Niksar and Ilgaz provinces. In addition to the main branch, the central section of the NAFZ also contains two sub-branches extending southward: Merzifon-Esençay and Sungurlu Faults. In the literature, there are several studies for the region, however a comprehensive study mainly focusing on the main branch of the NAFZ and its sub-branches along the central NAFZ has not been conducted yet, which would fully reveal the fault mechanism and seismic potential in the region. The aim of this study is to derive an up-to-date high-spa-tial-resolution Global Navigation Satellite Systems (GNSS) velocity field for the central NAFZ and to correlate with the strain accumulations along the faults. Based on this, a high-spatial-resolution GNSS network consisting of 60 sites was established enclosing the central NAFZ. The previously archived GNSS data for the same observation sites were collected from the different studies in the region and a new GNSS campaign measurement was conducted between October 2023 and February 2024. All GNSS data were processed using GAMIT/GLOBK software, and the results indicate the GNSS velocities ranging from 3-30 mm/year and their associated uncertainties of maximum ± 1.5 mm/year with respect to the Eurasian tectonic plate.