Ayça Çırmık

Bu çalışma, Batı Anadolu genişleme tektoniği içerisinde yer alan Datça Yarımadası’nın merkezindeki Datça grabeninin yeraltı yapısını mikrogravite ve mikrotremor verileri kullanarak belirlemeyi amaçlamaktadır. Datça grabeni, Gökova ve Hisarönü grabenlerini yaklaşık dik kesen konumuyla dikkat çekmekte olup, kuzeyinde yer alan Gökova Körfezi’nin yoğun sismik aktivitesinden tüm yarımada etkilenmektedir. Yarımada, yerleşim, tarım ve turizm açısından önemli bir bölge olduğundan, graben sisteminin yapısal özelliklerinin aydınlatılması hem tektonik hem de sismik tehlike açısından büyük önem taşımaktadır. Bu çalışma, Datça grabeni ve yakın çevresindeki ilk kez yapılmış olan mikrogravite ve mikrotremor çalışmalarını içermektedir. Mikrogravite verilerine uygulanan düzeltmeler sonucunda Bouguer gravite anomalisi elde edilmiş ve alansal güç spektrumu analiziyle ortalama tabaka derinlikleri belirlenmiştir. Mikrotremor verilerinden elde edilen Yatay/Düşey Spektral Oran (HVSR) eğrilerinin ters çözümünden 1B yeraltı S-dalgası hızı ve derinlik bulgusu elde edilmiştir. Her iki yöntem ile elde edilen derinlik bulguları birbirleriyle uyumlu çıkmıştır. Ayrıca, bu iki yöntemden elde edilen bulgular bir profil hattı boyunca birlikte değerlendirilerek Talwani modellemesi uygulanmış ve böylelikle Datça grabeni boyunca iki boyutlu (2B) yeraltı modeli ilk kez bu çalışma ile oluşturulmuş ve üç farklı yoğunluk ile tanımlanan bir yeraltı yapısı ortaya konmuştur.

On February 6, 2023, two major earthquakes (Mw 7.7 and Mw 7.6) struck Kahramanmaraş, significantly affecting Eastern Anatolia. The tectonic structure of Malatya and its surroundings, including the East Anatolian Fault Zone (EAFZ) and the Malatya Fault, plays a crucial role in the region's seismicity. Following the Kahramanmaraş earthquakes, two moderate earthquakes (Mw 5.3 and Mw 5.0) occurred in Malatya in August 2023, causing panic among the locals. GNSS data from Continuously Operating Reference Stations-Turkey (CORS-TR) were analyzed in this study to investigate the tectonic activity in and around Malatya and assess how the stress accumulated after the February 2023 earthquakes may have influenced this region. Firstly, the displacements in Eastern Anatolia between January 1 and March 1, 2023, were calculated to evaluate the immediate effects of the February 6 earthquakes. Then, GNSS data from March 2 to December 31, 2023, were processed to examine the ongoing tectonic behavior. Additionally, seismic activity during the same period was analyzed, revealing the occurrence of several moderate earthquakes potentially linked to the February 6, 2023 Kahramanmaraş earthquakes. The GNSS results indicate that most stations show continued tectonic motion, suggesting that stress changes induced by the Kahramanmaraş earthquakes still influence the region. Furthermore, the lack of stabilization at the stations highlights the persistence of postseismic deformation. The spatial correlation between observed seismicity and displacement vectors emphasizes that the Malatya segment of the EAFZ remains a significant zone of strain accumulation and release. Stations such as MLY1 (Malatya), APK1 (Arapgir, Malatya), and ADY1 (Adıyaman) continued to move in the same direction observed during the mainshock, pointing to ongoing afterslip. Moreover, stations farther from the rupture zone (e.g., SUF1 (Sanlıurfa), HAT2 (Hatay), GURU (Gürün, Sivas)) exhibited consistent displacement patterns, indicating that postseismic deformation extended across a broad area, including the Arabian Plate and the back-arc region north of the fault. These findings underline the long-term impact of the February 6, 2023, earthquakes on regional seismic activity and demonstrate the importance of integrating geodetic and seismic data for ongoing hazard assessment in Eastern Anatolia.

In this study, geodynamic processes in the Western Anatolia Region were analyzed using Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite Systems (GNSS) data, incorporating wavelet transformation of InSAR time series based on GNSS observations. InSAR data were processed over a six-year period to produce line of sight (LOS) displacement maps. Ascending and descending track data were merged to derive information on both horizontal and vertical displacements. The InSAR-derived displacements were then compared with GNSS station data from the region to assess variations in the east and up components obtained by both techniques. Significant horizontal and vertical displacements were detected. While the Menemen Plain experienced a subsidence of up to 15 centimeters over a six-year period, the island of Samos experienced a rise of 29 centimeters. The performance of InSAR results was evaluated against GNSS data using Root Mean Square Error (RMSE). The RMSE values significantly decreased after applying corrections to the InSAR processing, indicating improved accuracy. For the DEUG station, the RMSE between InSAR and GNSS time series improved to 1.93% in the east component and 5.29% in the vertical component after wavelet-based noise removal. At the IZMI station, the RMSE was reduced to 2.62% (east) and 6.00% (vertical). Finally, at the CES1 station, the RMSE was reduced to 2.71% for the east component and 5.84% for the vertical component, all after correction.

With the increasing rate of subduction along the Hellenic Arc in the Eastern Mediterranean, the seismic activities of the Aegean plate and Western Anatolia have markedly increased over the past decade. The increase in seismic activity is quite remarkable, starting from the coasts of Çanakkale in the north of Western Anatolia, including Lesbos Island, Samos Island, Kuşadası Bay and Datca. In this context, in order to determine the current deformation after the Samos Island earthquake that occurred on October 30, 2020, measurements were performed at six continuous GNSS stations in and around Izmir. This study is jointly managed by Dokuz Eylül University, with contributions from Konya Technical University and Atatürk University, focusing on both GNSS and seismological analyses. The preliminary results of this investigation include the evaluation of seismic impacts on the continuous GNSS stations from July 1st to December 31st, 2022.

Destructive earthquakes with high deformations have occurred in the Aegean region since the historical period. The most destructive of these earthquakes in recent years is the October 30, 2020 ( M _w = 6.9) Samos (Aegean Sea) earthquake. This earthquake affected a wide area and caused numerous losses of lives and property especially in Izmir city. For examining the effects of the earthquake, Global Navigation Satellite System (GNSS) data before, during, and after the earthquake were processed, and coseismic and postseismic displacement evaluations were made. Interferometric Synthetic Aperture Radar (InSAR) ascending, descending interferograms, line of sight velocity, and displacement maps were obtained for the earthquake-affected area. The GNSS and InSAR data were evaluated together, and the areas with subsidence and uplift were determined in conjunction with the fault zone. In addition, the horizontal displacements were analyzed by using Coulomb failure criteria, and peak ground displacements were obtained from the strong motion stations located in the study region. As a result, from all the displacement analyses, it was determined that high-amplitude energy was released, at the regional scale from Ayvalık in the North to Datça in the South after the earthquake, and this earthquake generated permanent deformation in the affected region.

Ground deformation monitoring of active volcanoes is used routinely to determine phases of vol-cano unrest and can provide insights in the evolving plumbing system of a volcano and the influence local tectonics structures have on the volcano tectonic evolution of the volcanic edifice. Volcanic deformation analysis can be performed using velocity and direction measurements of the ground surface using Global Navigation Satellite System (GNSS). In this study, we perform two-dimen-sional deformation analyses of pre-and post-eruptive phases with the scope of determining the strain before and after an eruptive phase at Mt. Etna Volcano (southern Italy) during 2004-2006. In order to do so, we analyse the GNSS displacement data from Mt. Etna between 2004-2005 and 2005-2006 using the dedicated SSPX software. The extention, dilation and rotation maps of the study area were determined. The contraction and volumetric decrease concomitant the 2004-2005 effusive eruptive period and extension and volumetric increase for the 2005-2006 data series were observed. The deformation on the northeast part of Mt. Etna Volcano, which showed different characteristics with respect to its surroundings, was thought to be conditioned by the dynamic of the Pernicana fault system. Additionally, Complete Spherical Bouguer (CSB) gravity anomaly and the gravity gradient tensors were calculated giving insight on the subsurface structures of Mt. Etna Volcano and its surroundings.

Tectonic forces formed in the continental crust, cause permanent changes in stress, compression and deformation. The amplitudes of earthquake waves vary with the stress/strain distribution in the crust. In this study, the change of stress/strain and regional absorption coefficient, which is effective in tectonic forces caused by elastic deformation energy accumulating in the brittle crust over time, was investigated. The study area is the middle part of the North Anatolian Fault Zone and the area formed by Ezinepazari fault zone and Merzifon fault zone. In this area, Coulomb stress analysis was carried out by using the focal mechanism solution values of the earthquake that occurred in Yoldere - Erbaa, Tokat on October 9, 2015 (M-L=5.1). In order to examine the deformation caused by this earthquake in and around the study area, Global Navigation Satellite System (GNSS) data were evaluated and the velocities of these stations were calculated using GNSS data of these stations for the years 2013-2014-2015-2016. Also, regional absorption coefficients were determined by using earthquake data. As a result, Coulomb stress analysis results, velocity values distribution obtained from GNSS data and absorption findings obtained from seismological study were evaluated together.