Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Severity-Based Mapping of Land-Subsidence Hazard Zones and Critical Hotspots Using SBAS-InSAR and Spatial Statistics: The Konya Metropolitan Area, Turkey
Yalvac, Sefa; Bjelotomić Oršulić, Olga
Land subsidence induced by excessive groundwater withdrawal has become one of the most significant geohazards affecting the Konya Closed Basin, Turkey. Although previous studies have successfully monitored ground deformation using geodetic and remote sensing techniques, limited attention has been devoted to transforming deformation measurements into quantitative, spatially classified hazard information. This study presents a severity-based framework for delineating land-subsidence hazard zones and critical hotspots in the Konya metropolitan area by integrating SBAS-InSAR observations and spatial statistical analyses. A total of 82 Sentinel-1 SAR acquisitions (41 ascending and 41 descending images) acquired between January 2023 and May 2026 were processed using the Small Baseline Subset (SBAS) technique. Ascending and descending line-of-sight deformation measurements were combined to derive vertical deformation rates, which were integrated with spatial statistical indicators and a composite severity index to quantify deformation clustering and classify subsidence severity. Hazard zones and critical hotspot areas were delineated through severity-based classification and spatial connectivity analyses. The results reveal a continuous north–south-oriented subsidence deformation belt extending across the eastern Konya. Maximum vertical subsidence rates exceeded 230 mm/yr, while spatial statistical analyses confirmed strongly clustered and statistically significant deformation patterns. Severity-based hazard zonation identified four hazard classes and a continuous high-hazard corridor. Clustering analysis further identified a dominant hotspot belt covering approximately 160 km2, with mean subsidence rates of approximately 142 mm/yr. A sensitivity analysis of the composite severity index weighting scheme, the spatial statistical neighborhood distance, the DBSCAN clustering parameters, and the number of Jenks severity classes confirmed that the resulting hazard zones and critical hotspot belt are robust to reasonable parameter variations. The findings demonstrate that land subsidence in Konya is organized as a spatially continuous regional-scale deformation system rather than a collection of isolated subsidence centers. The proposed framework transforms InSAR-derived deformation measurements into quantitative, decision-support hazard information and provides a transferable methodology for land-subsidence hazard assessment in groundwater-stressed urban environments.
- DüzeltmeAçık Erişim202530 Ekim 2020 Mw:6.9 Sisam Depremi Sonrası İzmir ve Çevresinde Postsismik Deformasyonların İzlenmesi
Gezgin, Cemil; Solak, Halil Ibrahim; Tiryakioğlu, İbrahim; Ozener, Haluk; Aktug, Bahadir; Yalvac, Sefa; Eyübagil, Eda Esma; Yigit, Cemal Ozer; Demirelli, Ertuğrul; Çakanşimşek, Ece Bengünaz
Solak, H., Tiryakioğlu, İ., Yalvaç, S., Yiğit, C.Ö., Aktuğ, B., Özener, H., Dönmez, E., Demirelli, E., Eyübagil, E.E., Çakanşimşek, E.B., Gezgin, C., Şahiner, F., 2024. 30 Ekim 2020 Mw:6.9 Sisam Depremi Sonrası İzmir ve Çevresinde Postsismik Deformasyonların İzlenmesi, Afyon Kocatepe Üniversitesi, Fen ve Mühendislik Bilimleri Dergisi, 24 (6): 1442-1455. https://doi.org/10.35414/akufemubid.1465489 Yukarıda künye bilgileri verilen makale için yazar tarafından düzeltme talebinde bulunulmuştur. Makalenin kaynakça bölümünde yer alan “Çırmık, A., Pamukçu, O. and Gönenç, T., 2017. The Stress/Strain Analysis of Kinematic Structure at Gülbahce Fault and Uzunkuyu Intrusive (İzmir, Turkey). Pure and Applied Geophysics, 174, 1425- 1440. https://doi.org/10.1007/s00024-017-1474-5” kaynağının sehven hatalı olarak yazıldığı makale yayınından sonra tespit edilmiştir. Yazarın yazılı talebine istinaden ilgili kaynak aşağıda belirtilen şekliyle düzeltilmiştir. Okuyucuların ve kullanıcıların bilgisine sunarız.
- MakaleAçık Erişim2024Monitoring Postseismic Deformations in Izmir and Its Surroundings After the 30 October 2020 Mw:6.9 Samos Earthquake
Gezgin, Cemil; Solak, Halil Ibrahim; Tiryakioğlu, İbrahim; Ozener, Haluk; Aktug, Bahadir; Yalvac, Sefa; Eyübagil, Eda Esma; Yigit, Cemal Ozer; Demirelli, Ertuğrul; Çakanşimşek, Ece Bengünaz
A devastating (Mw: 6.9) earthquake occurred in the north of Samos island on October 30, 2020. This earthquake caused loss of life and property in Izmir city center and some districts. After the earthquake, studies conducted in Izmir and its south showed that there was a horizontal displacement of 4-14 cm in Izmir and its south, the largest of which was in Seferihisar. In this region, there are many active faults with the potential to produce earthquakes between Mw:6.1 and Mw:6.9. A 27-site GNSS network has been established to monitor the postseismic deformation in this region since an earthquake can affect the earthquakes that may be caused by other surrounding faults. 4 GNSS campaign measurements were conducted over 6-month periods between 2020 and 2022 in this network. Eurasian fixed velocities of all sites were obtained using GNSS data. The results obtained show that the differences between both the current velocities and the pre-earthquake velocities in the network have reached 6 mm, and accordingly, the postseismic deformation continues in the region.
- MakaleAçık Erişim2024Seismic Disturbances and Geodetic Effects: Unraveling the Impact of the Mw = 6.2 Petrinja Earthquake on the Croatian Positioning System CROPOS
Bjelotomić Oršulić, Olga; Varga, Matej; Yalvac, Sefa
A destructive Mw = 6.2 earthquake struck NW Croatia on 29 December 2020, ranking among the most hazardous events in the country in the last century. This study assesses the impact of the earthquake on the permanent geodetic stations of the Croatian national positioning system. Using a novel approach, we combined positioning station data with satellite radar data for the first time in a geodynamic study across Croatia. The analysis involved collecting daily solutions data from 11 nearby network stations as well as multi-temporal satellite images before and after the earthquake. The results reveal a significant co-seismic shift, with the Sisak reference station experiencing the largest displacement of 5 cm to the southeast. Stations up to 100 km from the epicenter exhibited horizontal shifts between 1 and 2.5 cm and vertical shifts between 2 and 4 cm. Satellite images confirmed the co-seismic effects on the permanent stations. The study establishes a strong correlation between geodetic and geological findings, suggesting that vertical displacements result from superficial deposit consolidation in the river plains due to the earthquake shaking, while positional displacement reflects tectonic block movements along the activated strike-slip fault system. The late 2020 earthquake may have further relaxed the accumulated strain on the Mt. Medvednica thrust fault system, which had ruptured in early 2020 with a lower magnitude than expected.
- MakaleAçık Erişim2022İzmit Körfezi ve Çevresinde Bina Yoğunluk ve Sıvılaşma Yayılımının Mekânsal Analizi
Şentürk, Erman; Üstün, Aydın; Comut, Fatma Canaslan; Kaya, Efdal; Aşcı, Metin; Nehbit, Pakize Küreç; Konak, Haluk; Irmak, Tahir Serkan; Yalvac, Sefa; Erener, Arzu
2017 yılı Aralık ayından itibaren KOÜ Harita Mühendisliği Bölümü’nün yürütücülüğü ve Kocaeli Büyükşehir Belediyesi’nin desteği ile “Çok Bandlı InSAR ve GNSS Tekniği ile Doğu Marmara (İzmit Körfezi) Düşey Yönlü Yer Değiştirmelerin İzlenmesi, Zemin Çökmeleri ile Bina Yoğunluğu ve Sıvılaşma İlişkisinin Araştırılması” başlıklı ve 117Y155 numaralı TÜBİTAK projesi kapsamında İzmit körfez bölgesinde risklerin tespiti için çalışmalara başlanmıştır. Bu bağlamda, proje kapsamında yapılan bina yoğunluk analizleri ve sıvılaşmanın körfez bölgesi çevresindeki mekânsal dağılımı CBS ortamında bütünleşik olarak ele alınarak mekânsal dağılımları incelenmiştir. Zemindeki yüke ait bilgi çıkarımı için binaların 3. boyutu dikkate alınarak bina katlarının mekânsal dağılımları mekânsal otokorelasyon çalışmaları ile irdelenmiştir. Mekansal otokorelasyon analizlerinden Lokal Moran’s I istatistikleri dikkate alınmıştır. Ayrıca körfez ve çevresinde görülen sıvılaşma potansiyeli 0-3 m, 3-6 m, 6-9 m, 9-12m’den 33-35 m derinlikleri için oluşturulmuştur. Sıvılaşma potansiyel eşiklerine göre, farklı derinlikler için, sıvılaşma değerleri kategorize edilerek sıvılaşma alanları ve riskli bölgeler tanımlanmıştır. Sonuç olarak sıvılaşma risk alanlarında bulunan bina tespitleri yapılmıştır. Çalışma; ileriye yönelik doğal afetlere karşı sürdürülebilir önlemlerin alınması, yapılaşma hızı ve yoğunluğu için önlem planlarının hazırlanması, Gölcük ve İzmit Körfez çevresinde bina ve zemin sıvılaşmalarının mevcut durumunun belirlenmesi, risk taşıyan alanlarda mühendislik tedbirlerinin alınarak yapı ve can güvenliğinin sağlanması ve afet değerlendirmelerinde altlık oluşturması açısından önem arz etmektedir.
- MakaleAçık Erişim2021Land subsidence and its relations with sinkhole activity in karapınar region, turkey: A multi-sensor insar time series study
Orhan, Osman; Oliver-Cabrera, Talib; Wdowinski, Shimon; Yalvac, Sefa; Yakar, Murat
The Karapinar basin, located in the Central Anatolian part of Turkey, is subjected to land subsidence and sinkhole activity due to extensive groundwater withdrawal that began in the early 2000s. In this study, we use Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and groundwater level data to monitor and better understand the relations between groundwater extraction, land subsidence, and sinkhole formation in the Karapinar basin. The main observations used in the study are InSAR-derived subsidence velocity maps calculated from both Sentinel-1 (2014–2018) and COSMO-SkyMed (2016–2017) SAR data. Our analysis reveals broad areas of subsidence with rates exceeding 70 mm/yr. The InSAR-derived subsidence was compared with GNSS data acquired by a continuously operating GNSS station located in the study area, which show a similar rate of subsidence. The temporal characteristic of both InSAR and GNSS time series indicate a long-term subsidence signal superimposed by seasonal variability, which follows the overall groundwater level changes, with over 80% cross-correlation consistency. Our results also indicate that sinkhole activity is limited to slow subsidence areas, reflecting strong cohesion of near-surface rock layers that resist subsidence but yield to collapse in response to aquifer system deformation induced by groundwater extraction.
- MakaleYalnız künye2021Investigating the historical development of accuracy and precision of Galileo by means of relative GNSS analysis technique
Yalvac, Sefa
Galileo navigation system has significantly expanded satellite constellation over the last few years and now serves with 22 satellites in three orbital planes. The development of the Galileo is not only limited to the number of satellites in the space segment, but also the quality of the IGS MGEX products produced by different Analysis Centers has increased gradually and brought up the topic of investigation of the accuracy and precision of the Galileo-only positioning. However, almost all of the studies on Galileo-only positioning in the literature have been performed with Precise Point Positioning method and comprehensive studies with the relative positioning technique are quite a few. In this study, the development of the accuracy and precision of the Galileo from 2016 to the end of 2019 (4 years) has been investigated for the first time by means of relative positioning technique. For this purpose, data of eight GNSS stations selected from the IGS MGEX network were obtained and analyzed with GAMIT/GLOBK software as GPS-only and Galileo-only, separately. Using the daily solutions obtained from both navigation systems, time series were produced and the differences between them were compared in order to reveal the Galileo accuracy. According to the results, the accuracy of the Galileo was variable during the experiment and it could be examined in three periods. The averages of 3D positioning error in the first period (2016-2017) is 14.92 mm and improved by 56%, and decreased to 6.55 mm in the second period (2017-2018), and then improvement at 23% in the third period (2018 to the end of 2019) and decrescent to level of 5.13 mm on average for all stations. Similarly, standard deviations obtained from Galileo increased during the experiment and during the 3rd period it was closed to a few mm with GPS. It was concluded that the accuracy and precision of the Galileo showed parallel development and the development was directly related to the number of satellites in the Galileo constellation, and as a result, nowadays, Galileo-derived coordinates are close to the coordinates obtained from the GPS by a few mm.
- MakaleAçık Erişim2020Hassas Nokta Konumlama Yönteminin Kabuk Deformasyonu Belirleme Çalışmalarında Kullanılabilirliğinin Araştırılması
Yalvac, Sefa
Bu çalışmada, HNK (Hassas Nokta Konumlama) yönteminin kabuk deformasyonu belirleme çalışmalarındakullanılabilirliği, rölatif GNSS (Global Navigation Satellite System) analizleri eşliğinde araştırılmıştır. Bu amaçla,Kuzey Anadolu Fay (KAF) hattının kuzeyinde yer alan GIRS, SINP ve ZONG istasyonları ile söz konusu fay hattınıngüney kesiminde konumlanan RHIY, ANKR ve BILE TUSAGA-Aktif (Türkiye Ulusal Sabit GNSS Ağı-Aktif)istasyonlarının 2011-2018 (8 yıl) yılları arasındaki periyodik verileri elde edilerek analiz edilmiştir. Analizler, HNKyöntemi için CSRS PPP (Canadian Spatial Reference System Precise Point Positioning) çevrimiçi servisiyle, rölatifyöntem için ise GAMIT/GLOBK V10.7 akademik GNSS analiz yazılımı yardımıyla gerçekleştirilmiştir. Koordinatdeğerleri Kalman filtreleme tekniği yardımıyla analiz edilerek, her istasyona ait hız değerleri Avrasya plakasındakonumlanan ORID IGS (International GNSS Service) istasyonu sabit olarak Kuzey, Doğu ve Yukarı bileşenler için ayrıayrı kestirilmiştir. Her iki yöntemden elde edilen hız kestirim değerleri arasındaki farklardan hesaplanan üç boyutlukonum hatası değerlerinin 0.1 mm ile 2.4 mm seviyeleri arasında olduğu ve HNK yönteminin bilimsel kabukdeformasyonu belirleme çalışmalarında kullanılabileceği sonucuna varılmıştır.
- MakaleYalnız künye2020Validating InSAR-SBAS results by means of different GNSS analysis techniques in medium- and high-grade deformation areas
Yalvac, Sefa
This study aimed to validate the interferometric synthetic aperture radar (InSAR) method by using relative and absolute Global Navigation Satellite System (GNSS) techniques. In this context, two land subsidence areas, one high (Mexico City) and one medium (Aguascalientes), were monitored between 2014 and 2018 by using Sentinel 1A satellite data. The monitoring was carried out with the Small Baseline Subset (SBAS) technique using 46 images for Mexico City and 18 images for Aguascalientes. Concordantly, the GNSS Continuously Operating Reference Station (CORS) data in the regions were analyzed with relative and Precise Point Positioning (PPP) GNSS analysis techniques. The time series obtained from three different analyses were compared and the results were evaluated in light of statistical criteria. According to the results, it is determined that the InSAR-SBAS technique can vary up to ± 20 mm from the displacement values obtained from GNSS due to various noise sources. Such deviations were limited to a few samples, and in general the differentiations were reasonable in the range of 7–8 mm. The difference between the deformation velocity estimation results obtained from the three different methods varied between 3 and 10 mm/year. In this context, these findings suggest that the InSAR-SBAS technique is an effective method for monitoring land deformation with the accuracy of sub-centimeter decided. In addition, PPP which has become an increasingly popular technique showed fast and reliable results in the range of 5–10 mm for InSAR verification. Moreover, with this study, most current results for Mexico City, which is the world’s fastest subsiding metropole, were achieved. In the central region of the city, the detected 300 mm/year of subsidence rate was updated as 370 mm/year. In addition, Aguascalientes was monitored by using the Sentinel 1A satellite mission for the first time in this study. The 60 mm/year subsidence rate obtained for Aguascalientes in previous studies was updated and it was estimated that there are zones where this rate reaches up to − 115 mm/year levels. In this regard, it was concluded that the deformation rate has increased for both regions since the previous monitoring studies.
- MakaleAçık Erişim2019Investigating Accuracy of Precise Point Positioning Method in a Micro-Geodetic Network
Yalvac, Sefa
In this study, the accuracy of Precise Point Positioning (PPP) method was investigated. For this purpose, a microgeodetic network containing 5 stations was established and 8-hour GNSS Global Navigation Satellite System (GNSS) sessions for three consecutive days were performed. At the same time, the baselines between the stations in this network were measured by Electronic Distance Meter (EDM) and the height differences are measured by the geometric leveling method. The results obtained from classical terrestrial measurements, which are considered to be highly accurate (3 mm in horizontal and few mm invertical), were compared with the results of PPP and the relative GNSS methods. As a result of the comparisons, it was seen that the values obtained from the relative GNSS analysis approximated with the classical method with the levels of 1-6 mm in the horizontal and 10-20 mm in the vertical direction. For the PPP method, it was seen that the same values varied between 1-28 mm in horizontal and 5-8 cm in the vertical component. The standard deviation values of these changes were determined as ± 2.20 mm in horizontal and ± 16.46 mm in vertical for the relative positioning technique and ± 11.43 mm in the horizontal and ± 59.48 mm in vertical component for PPP method.