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• MakaleAçık Erişim2026/r/gumushane/10585
  Modeling Long-Term Postseismic Deformation Following the 2020 Mw 7.0 Samos Earthquake Using Campaign and Continuous GNSS Observations

  Solak, Halil Ibrahim; Tiryakioglu, Ibrahim; Gezgin, Cemil; Aladogan, Kayhan; Yalvaç, Sefa; Aktug, Bahadir; Yigit, Cemal Ozer; Dönmez, Ergin; Demirelli, Ertugrul; Eyübagil, Eda Esma

  Highlights What are the main findings? What are the implications of the main findings?Highlights What are the main findings? What are the implications of the main findings?Abstract 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.

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• MakaleAçık Erişim2026/r/gumushane/13897
  Severity-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.

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• DüzeltmeAçık Erişim2025/r/gumushane/19797
  30 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.

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• MakaleAçık Erişim2025/r/gumushane/13823
  The 2023 Mw 7.8–7.7 Kahramanmaraş earthquakes were loosely slip-predictable

  Vavra, Ellis; Fialko, Yuri; Bulut, Fatih; Garagon, Aslı; Yalvaç, Sefa; Yaltırak, Cenk

  Understanding the behavior of large earthquakes over multiple seismic cycles is limited by short time spans of observations compared to recurrence intervals. Most of large instrumentally-recorded earthquakes have occurred on faults lacking well-documented histories of past events. The 2023 Mw 7.8–7.7 Kahramanmaraş earthquake doublet is exceptional as it ruptured multiple segments of the East Anatolian Fault (EAF) system, where historical records of devastating earthquakes span over two millennia. Here, we use historical earthquake records, measurements of interseismic deformation, and published slip models of the 2023 events to evaluate the recurrence patterns of large earthquakes. We compare slip deficit that accrued on each fault segment since the respective penultimate events to the average coseismic slip of the 2023 doublet. We find that the coseismic slip equaled to or exceeded the accumulated slip deficit, suggesting that the slip-predictable recurrence model applies as a lower bound on strain release during the Kahramanmaraş earthquakes.

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• MakaleAçık Erişim2024/r/gumushane/19893
  Monitoring 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.

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• MakaleAçık Erişim2024/r/gumushane/13960
  Monitoring Surface Deformations in a Fossil Landslide Zone and Identifying Potential Failure Mechanisms: A Case Study of Gümüşhane State Hospital

  Alemdag, Selçuk; Yalvaç, Sefa; Bjelotomić Oršulić, Olga; Kara, Osman; Zeybek, Halil İbrahim; Bostanci, Hasan Tahsin; Markovinović, Danko

  The escalating occurrence of landslides has drawn increasing attention from the scientific community, primarily driven by a combination of natural phenomena such as unpredictable seismic events, intensified precipitation, and rapid snowmelt attributable to climate fluctuations, compounded by inadequacies in engineering practices during site selection. Within the scope of this investigation, contemporary geodetic techniques using the GNSS were employed to monitor structural and surface deformations in and around a hospital edifice situated within an ancient fossil landslide region. Additionally, inclinometer measurements facilitated the determination of slip circle parameters. A subsequent analysis integrated these datasets to scrutinize both the hospital structure and its surrounding slopes. In addition to the finite element method, four different limit equilibrium methods (Bishop, GLE–Morgenstern–Price, Spencer, and Janbu) were used in the evaluation of stability. Since the safety number determined in all analyses was <1, it was determined that the slope containing the hospital building was unstable. The movement has occurred again due to the additional load created by the hospital building built on the currently stable slope, the effect of surface and groundwater, and the improperly designed road route. As a result of geodetic monitoring, it was determined that the sliding speed on the surface was in the N-E direction and was approximately 3 cm, and this situation almost coincided with inclinometer measurements.

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• MakaleAçık Erişim2024/r/gumushane/12688
  Seismic 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.

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• MakaleYalnız künye2023/r/gumushane/11493
  Excessive groundwater withdrawal and resultant land subsidence in the Küçük Menderes River Basin, Turkey as estimated from InSAR-SBAS and GNSS measurements

  Yalvaç, Sefa; Alemdağ, Selçuk; Zeybek, Halil İbrahim; Yalvaç, Murat

  Küçük Menderes River Basin (KMRB) is located in the western part of Turkey in the city of İzmir. The basin hosts about half a million people and 90% of the population makes their living from farming and animal husbandry. Most of the water needs for agricultural irrigation, animal husbandry, and drinking are met from groundwater resources in the basin. Since the water pumped from the aquifers cannot be naturally recharged by surface waters and precipitation, the groundwater level is rapidly receding and a decrease of up to 150 meters has been observed in the historical groundwater level time series since the 1990s. For this reason, land subsidence occurred in the basin and as a result of this, crustal surface cracks have formed and infrastructure and superstructure facilities have been endangered. To prevent loss of life and property that may occur in the future, it has become necessary to estimate the magnitude and the expansion zone of the land subsidence by carrying out geodetic monitoring studies in the region. In this study, the analyzes performed by Interferometric Synthetic Aperture Radar-Small Baseline Subset (InSAR-SBAS) and Global Navigation Satellite System (GNSS) methods to monitor land subsidence in the KMRB are presented. For this purpose, monthly 74 SAR images from 2017 to the end of 2022 were evaluated according to the SBAS procedure in the GMTSAR academic analysis software. In order to, both validate the InSAR-SBAS results and convert the deformation rate in the Line of Sight (LOS) to the ellipsoid normal direction, 3 periods of GNSS campaign were performed between 2021 and 2023 in 5 different GNSS stations and evaluated with the GAMIT/GLOBK software. According to the analyses, the land subsidence rate of up to −165 mm/year has been estimated in the KMRB, especially in the district centers of Bayındır and Ödemiş. In addition, unlike many studies, different rates and propagation of subsidence were determined in different parts of the basin depending on the aquifer type and precipitation. Monthly time series of the deformations were created and the behavior of the deformations and its relationship with the groundwater withdrawal and the lithological structure in the region was scrutinized. Thus, the spatio-temporal behaviour of the land subsidence and the associated geological factors were revealed.

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• MakaleAçık Erişim2022/r/gumushane/17109
  İzmit 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.

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• MakaleAçık Erişim2021/r/gumushane/14872
  Anatomy of october 30, 2020, samos (Sisam) –kuşadası earthquake (mw 6.92) and its influence on aegean earthquake hazard

  Bulut, Fatih; Doğru, Aslı; Yaltirak, Cenk; Yalvaç, Sefa; Elge, Murat

  We investigated rupture geometry, size, and slip distribution of October 30, 2020, Samos (Sisam)–Kuşadası earthquake combining seismographs, GPS measurements, and SAR analysis. Right after the earthquake, we measured 13 additional campaign-based GPS sites to intensify the available GPS network consisting of 10 continuous stations. We combined all available seismographs to have the best possible accuracy for mainshock and aftershock hypocenter locations. We compiled all available seismic profiles and integrated them using high-resolution bathymetry to map seismically active faults. The mainshock hypocenter is located at 37.913 ± 0.009 N° and 26.768 ± 0.017 E° and a depth of 12.3 ± 1.7 km. Our fault plane solution shows that the mainshock has almost a pure normal-type mechanism. Based on accurate aftershock locations as well as InSAR results, the mainshock rupture is subsegmented with two north-dipping rupture planes. The rupture probably starts on a low angle plane generating 1.1 m average slip between the depths of 9–14 km. It merges to a steep plane at 9 km depth where it generates 1.2 m average slip extending towards the surface near the shoreline of Samos (Sisam) Island. Total size of the two rupture planes and their average slips determine that the magnitude of the mainshock is (Mw ) 6.92 ± 0.02. The mainshock has substantially increased Coulomb stress on several fault segments near the towns Kuşadası and Söke, which have the potentials to generate strong earthquakes. It also nonnegligibly increased Coulomb stress on several fault segments south of İzmir giving a warning for increased earthquake hazard in this highly inhabited area.

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