Browsing by Author "Bulbul, S."

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Citation - WoS: 2
Citation - Scopus: 2
Investigation of Tec Anomalies Possibly Caused by the 6 February 2023 Kahramanmaraş(turkey) Earthquakes With Space Weather Conditions
(Ist Nazionale Di Oceanografia E Di Geofisica, 2024) Bulbul, S.
This study investigates the Total Electron Content (TEC) variations associated with major earthquakes in Kahramanmara & scedil;(Turkey) on 6 February 2023, utilising Global Navigation Satellite System (GNSS) measurements and TEC values published by the Jet Propulsion Laboratory. Covering a 37-day period, including 18 pre/post-earthquake days, TEC values, originally from 15 CORS-TR stations in the earthquake region, were analysed in the gridded version. The study assesses pre/post-earthquake anomalies with the purpose of differentiating TEC changes caused by seismic events from those influenced by space weather conditions (SWCs). The examination of SWCs (disturbance storm time, geomagnetic storm index, GSM interplanetary magnetic field, solar wind speed, pressure, electric field, and proton density) reveals a general pre-earthquake quietness. Positive and negative TEC anomalies observed at the station locations during the study period indicate seismic events as potential precursors. Post-earthquake anomalies on 15 and 16 February 2023 are likely linked to SWCs and aftershocks. The study concludes that earthquake-induced TEC variations manifest approximately 16 days before the event, with positive anomalies, transitioning to both positive and negative anomalies approximately eight days before the earthquake. This suggests an eight-day period as a potential earthquake precursor, emphasising the potential for a future development of an early earthquake warning system through the integrated analysis of TEC variations and SWCs.
Citation - WoS: 1
Citation - Scopus: 1
Investigation Relationship Between Tec Anomalies and Space Weather Conditions: Morocco Earthquake Example
(Indian Assoc Cultivation Science, 2025) Basciftci, F.; Bulbul, S.; Bilgen, B.
The relationship between the ionosphere and earthquakes using total electron content (TEC) values has become a topic of interest, particularly since the 2000s. The idea behind this relationship is to investigate anomalies in TEC values occurring before or after earthquakes, if at all. Identifying precursors to earthquakes and aftershocks could minimize potential losses. This study examines the possible effect of the MW: 6.8 earthquake that occurred near Al Haouz, Morocco (31.058 degrees N - 8.385 degrees W) on the ionosphere. The TEC changes detected by the Center for Orbit Determination in Europe (CODE) are analyzed in conjunction with space weather conditions (solar activity index, Geomagnetic Storm and Geomagnetic Activity indices, magnetic field variation indices and Proton Density). Anomalies caused by TEC changes are analyzed using different statistical methods (1.34 sigma and Interquartile Range (IQR)). The aim of this study is to highlight differences in analyzing TEC anomalies caused by earthquakes with space weather conditions and to demonstrate that using the IQR statistical method can provide more accurate results for earthquakes with outlier TEC changes. It is one of the important points of the study that two different statistical analysis methods are used together to contribute to earthquake predictability with the help of Space Weather Conditions (SWCs).
Citation - WoS: 8
Citation - Scopus: 8
Statistical Analysis of the Regional and Global Ionosphere Model on Intense Geomagnetic Storm
(Indian Assoc Cultivation Science, 2023) Başçiftçi, F.; Bulbul, S.
This study evaluated an intense geomagnetic storm two days before, on the day of the magnetic storm (26 August 2018), and two days after, for a total of 5-daily global navigation satellite system (GNSS) measurements. The assessments were carried out for eight continuously operation reference stations-Turkey (CORS-TR) stations located in the province of Konya, Turkey. The change in the ionosphere layer caused by the geomagnetic storm was analyzed in terms of the total electron content (TEC) values. The analysis revealed that positive and negative anomalies had occurred on the day of the magnetic storm, the day before, and the day after. The statistic tests and correlation coefficient were calculated between regional and global ionosphere models. The global model that best fit the regional model was determined by comparing the regional values obtained from the GNSS measurements with the CODE, IRI-2016, and IRI-Plas. Besides, the geomagnetic storm, solar wind parameters (Bz, E, P, N, v), and geomagnetic activity indices (Dst, ap, Kp) were examined. As a result of the study, the global model that best fit the ionosphere model found using the regional TEC values was obtained using CODE TEC values. Moreover, the study demonstrated that magnetic storm-induced changes in the ionosphere could be detected using GNSS stations located in Turkey. Besides, the possible effects of the intense geomagnetic storm were propounded by the TEC anomalies.
Towards Geodetic-Level Accuracy in Low-Cost GNSS: Tectonic Velocity Determination Capabilities of the U-Blox ZED-F9P Over a Year Multi-GNSS PPP-AR Time Series
(Elsevier Ltd, 2025) Duman, H.; Ogutcu, S.; Alçay, S.; Ozdemir, B.N.; Atiz, O.F.; Bulbul, S.
The growing availability of low-cost dual-frequency GNSS receivers is enhancing their suitability for various kinds of geodetic applications. Geodetic monitoring of the continuous crustal deformation using GNSS time series analysis is one of the commonly used geodetic applications. To maintain the most accurate estimated parameters such as secular velocity, seasonal signal parameters and offsets, geodetic-grade GNSS receivers are commonly used in the GNSS time series analysis. However, due to the increasing availability of low-cost dual-frequency GNSS receivers and advancements in software and hardware, these receivers have now reached a level that supports the GNSS time series analysis. In this study, over a year of multi-GNSS PPP-AR time series of the u-blox ZED-F9P low-cost GNSS receiver are investigated by evaluating the accuracy of the estimated parameters, comparing them with data from a geodetic-grade GNSS receiver monumented on a building roof. The results show that the minimum detrended standard deviation obtained from White Noise (WN) estimation is achieved using GPS + GLONASS + Galileo PPP for both receivers. The computed annual velocity and amplitude differences obtained from the GNSS time series between the u-blox ZED-F9P and the geodetic-grade GNSS receivers using GPS + GLONASS + Galileo PPP-AR are found as 0.6 mm / 0.4 mm / 0.8 mm and 1.5 mm / 0.4 mm / 0.2 mm for north, east, and up components, respectively. © 2025 Elsevier B.V., All rights reserved.