Several scientists from different disciplines have studied earthquakes for many years. As a resul... more Several scientists from different disciplines have studied earthquakes for many years. As a result of these studies, it has been proposed that some changes take place in the ionosphere layer before, during or after earthquakes, and the ionosphere should be monitored in earthquake prediction studies. This study investigates the changes in the ionosphere created by the earthquake with magnitude of Mw=7.2 in the northwest of the Lake Erçek which is located to the north of the province of Van in Turkey on 23 October 2011 and at 1.41 pm local time (-3 UT) with the epicenter of 38.758° N, 43.360° E using the TEC values obtained by the Global Ionosphere Models (GIM) created by IONOLAB-TEC and CODE. In order to see whether the ionospheric changes obtained by the study in question were caused by the earthquake or not, the ionospheric conditions were studied by utilizing indices providing information on solar and geomagnetic activities (F10.7 cm, Kp, Dst). As a result of the statistical test on the TEC values obtained from the both models, positive and negative anomalies were obtained for the times before, on the day of and after the earthquake, and the reasons for these anomalies are discussed in detail in the last section of the study. As the ionospheric conditions in the analyzed days were highly vibrant, it was thought that the anomalies were caused by geomagnetic effects, solar activity and the earthquake. The authors believe that interdisciplinary studies are needed to distinguish the earthquake-related part of the anomalies in question.
Journal of civil structural health monitoring, Apr 16, 2024
This study aims to assess the future structural performance of the Kozlu-Ulutan clay core rockfil... more This study aims to assess the future structural performance of the Kozlu-Ulutan clay core rockfill (CCR) dam, one of the most significant water structures in the Black Sea region of Turkey, by utilizing 35 years of levelling measurements and 3D finitedifference analyses. Settlement measurements were obtained from five different points on the dam surface every 6 months. Subsequently, a three-dimensional (3D) model of the dam was created using the finite-difference method. Time-dependent creep analyses and seismic analyses were conducted sequentially, employing the Burger-Creep and Mohr-Coulomb material models, respectively. Non-reflecting boundary conditions were defined for the boundaries of the dam model. The 3D numerical analysis results were found to be highly compatible with the 35 years of levelling measurements. Additionally, the future seepage and settlement behaviors of the dam over a 100-year period (2023-2123) were analyzed, considering special time functions. Current and future seismic analyses were performed, taking into account the settlement results of the dam in 2023 and 2123. For seismic analyses, data from ten various earthquakes that occurred in Kahramanmaraş, Hatay, Malatya, and Gaziantep in Turkey in 2023 were utilized. The seismic analysis results provided significant information about the future seismic behavior of the Kozlu-Ulutan Dam, revealing notable differences between the current and future earthquake behaviors of the dam. Moreover, it was concluded that the clay core is the most crucial section concerning the current and future seismic behaviors of CCR dams. The study results emphasized the importance of continuous monitoring and periodic seismic evaluations for the safe operation of CCR dams.
Ionospheric total electron content (TEC) variations estimated from dual-frequency receivers of gl... more Ionospheric total electron content (TEC) variations estimated from dual-frequency receivers of global positioning systems (GPS) can be used as a tool to detect possible seismo-ionospheric anomalies before strong earthquakes. In this study, possible seismoionospheric anomalies before the 2018 Papua New Guinea earthquake (6.0684°S, 142.7678°E, February 25, 2018, 00:44:43 UTC, Mw = 7.5) was investigated by using GPS-TEC variations from four International GNSS Service (IGS) stations (KAT1, TOW2, SOLO and ALIC) near the epicenter and four IGS station (USUD, SHAO, WIND and ZAMB) outside of the EPZ. The earthquake (EQ) is a local phenomenon and space weather conditions (SWCs) are a global phenomenon so that we selected four IGS stations away from the earthquake epicenter, which is at the same latitude and the same longitude with the earthquake to figure out a clear SWCs' effects on the GPS-TEC anomalies. In order to see these effects on ionospheric TEC variations, 10 different SWC indices were used. An analysis of occurrence time and duration of the following conclusions was made: both positive and negative anomalies are ensuing, and earthquake-related ionospheric anomalies revealed that they occurred 1 to 7 days before the associated earthquake. At the end of the study, the potential causes of these results were examined. Analysis results revealed that anomalies occurred, and the possible ionospheric GPS-TEC anomalies may be the earthquake precursors obtained 4 to 9 days before the Papua New Guinea earthquake. The increase in scientific research to analyze the seismo-ionospheric anomalies that occur before earthquakes will become an important warning tool to alert people to the devastating environmental effects of earthquakes.
Abstract Global Navigation Satellite Systems record the total electron content via their receiver... more Abstract Global Navigation Satellite Systems record the total electron content via their receivers, and total electron content measurements have become popular with the requirement for capturing any ionospheric abnormalities prior to earthquake. Based on space weather conditions, the solar activity and geomagnetic activity indices are critical to monitor the total electron contents in the ionosphere. This study aimed to investigate the ionospheric variations induced by six sequential earthquakes in Nepal in 2015 with magnitude higher than 6.0, examine the total electron content data from Global Ionosphere Maps and Global Positioning Systems and analyze the contributing factors to the abnormal total electron content levels affected by space environment and geomagnetic activity status. We performed moving median analysis for 15 days to determine the pre- and post-earthquake abnormalities. With the static and dynamic time analysis, we concluded that there was likelihood for positive or negative anomalies, earthquake-induced ionospheric anomalies occurred on the previous day or up to six days earlier and even had potentiality for successive earthquakes. Furthermore, the data used in the analysis can be divided into two groups: Global Ionosphere Maps Total Electron Content and Global Positioning System Total Electron Content variations. LHAZ International Global Navigation Satellite System Service station from which we obtained these was close to the earthquakes’ epicenter. We studied three indices, such as geomagnetic storm index (K-planetary), geomagnetic activity index, and solar activity index, depending on space climate and discussed what factors can be influential in this disaster. Hence, we suggest that the earthquake may account for a typical variation in Global Ionosphere Maps Total Electron Content data as well as Global Positioning System Total Electron Content as solar activities and geomagnetic storms leading to abnormalities in the ionosphere.
The potential of the soil to hold plant nutrients is governed by cation exchange capacity (CEC) o... more The potential of the soil to hold plant nutrients is governed by cation exchange capacity (CEC) of any soil. Estimating soil CEC aids in conventional soil management practices to replenish the soil solution that supports plant growth. In the present study, a multiple model integration scheme driven by hybrid GANN (MM-GANN) was developed and employed to predict the accuracy of soil CEC in Tabriz plain, an arid region of Iran. The standalone models (i.e., artificial neural network (ANN) and extreme learning machine (ELM)) were implemented for incorporating in the MM-GANN. In addition, it was tested to enhance the prediction accuracy of the standalone models. The soil parameters such as clay, silt, pH, carbonate, calcium equivalent (CCE), and soil organic matter (OM) were used as model inputs to predict soil CEC. By the use of several evaluation criteria, the results showed that the MM-GANN model involving the predictions of ELM and ANN models calibrated by considering all the soil par...
Bu çalışma, 24. güneş döngüsünde meydana gelen 01 Şubat 2017 (DsT-45 nT) zayıf jeomanyetik fırtın... more Bu çalışma, 24. güneş döngüsünde meydana gelen 01 Şubat 2017 (DsT-45 nT) zayıf jeomanyetik fırtınasının matematiksel analizini amaçlamaktadır. NASA'dan alınan güneş rüzgarı parametreleri (Bz, E, P, N, v, T), zonal jeomanyetik indeksleri (Dst, ap, AE) ve nedensonuç ilişkisini göz önünde bulundurarak Şubat fırtınasının matematiksel modeli ortaya çıkarılmıştır. Makalede fırtına titizlikle analiz edilir ve nedensellik ilkesinin yönettiği modellerle özellikleri ortaya çıkarılmaya çalışılır. Bu çalışmada değişkenlerin değer aralığı ve standart sapmaları tanımlayıcı analiz ile tanımlanır, verilerin binary ilişkileri kovaryans matrisi ile gösterilir ve yine verilerin hiyerarşik kümeleri dendrogram ile tanıtılır. Faktör analizi, verilerin normal dağılımları yardımıyla gerçekleştirilir ve fenomenin gizemi lineernonlineer modellerle tartışılmaya çalışılır. Değişkenlerin ikili görünümleri grafikler ile okuyucuya sunularak fırtınaya görsellik kazandırılır. Bu çalışma, literatürde sınırlı sayıda çalışma bulunan zayıf seviyede manyetik fırtınanın modellenmesi konusuna katkı sağlamaktadır.
<p&amp... more <p>The last two decades a significant effort has been invested in order to understand and interpret the link between seismic activity and ionospheric perturbations. Since not any individual seismo-ionospheric precursor can be used as an accurate stand alone for earthquake prediction it is required to integrate different kinds of precursors and analysis techniques.</p> <p>To this context, the aim of this study is to investigate pre-earthquake ionospheric anomalies that occurred prior to large 6.4 Mw earthquake in Albania (26<sup>th</sup> November 2019), following a multi-instrument and multi-technique approach, using subionospheric radio VLF/LF signals obtained from the Romanian receivers of the INFREP European network and Total Electron Content (TEC) observations from GNSS global network.</p> <p>To identify possible ionospheric anomalies before the earthquakes we applied the terminator time and nighttime fluctuation methods on the amplitude of subionospheric LF radio signals and spectral analysis on diurnal TEC variations several days prior the seismic event. It was found that sunrise terminator times are delayed approximately 20-40 min few days before and during the earthquake day. Intensified wave-like TEC oscillations with periods around 20 min were also revealed up to 5 days prior to the earthquake shocks in all cases that could be interpreted as possible ionospheric precursors of the impending earthquakes.      </p>
Son yıllarda internet üzerinden çevrim içi GNSS değerlendirme servisleri konum elde etmede önemli... more Son yıllarda internet üzerinden çevrim içi GNSS değerlendirme servisleri konum elde etmede önemli bir araç olarak kullanılmaktadır. Bu sistemlerin en önemli özelliği GNSS verilerinin değerlendirilmesi konusunda yeterli bilgiye sahip olmayan kişilerin veriyi rahatlıkla değerlendirebilmesine olanak sunması ve ücretsiz olmasından dolayı ticari veya bilimsel yazılımın alınmasına gerek duyulmamasıdır. Bu çalışmada ANRK, ANTL, IZMI, SINP ve VAN1 istasyonlarına ait RINEX gözlemleri 1, 4, 8, 12, 16, 20 ve 24 saatlik dilimlere ayrılarak CSRS-PPP ve Trimble-RTX servislerine gönderilmiş ve elde edilen koordinatların doğruluk araştırması yapılmıştır. Çalışma sonucunda CSRS-PPP servisinden elde edilen konum verisinin referans veriye daha yakın olduğu anlaşılmıştır.
The analysis of the unexpected ionospheric phases before large earthquakes is one of the cutting-... more The analysis of the unexpected ionospheric phases before large earthquakes is one of the cutting-edge issues in earthquake prediction studies. In this study, the total electron content (TEC) data from seven International GNSS Service (IGS) stations and the global ionosphere maps (GIMs) were used. Short-time Fourier transform (STFT) and a running median process were applied to the TEC time series to detect abnormalities before the M w 7.3 Iran-Iraq border earthquake on 12 November 2017. The analyses showed positive anomalies 8-9 d before the earthquake and some positive and negative anomalies 1-6 d before the earthquake. These anomalies were cross-checked using the Kp, Dst, F10.7, B z component of the interplanetary magnetic field (IMF B z), electric field (E y), and plasma speed (V SW) space weather indices. The results showed that the anomalies 1-6 d before the earthquake were caused by a moderate magnetic storm. Moreover, the positive anomalies 8-9 d before the earthquake were likely related to the Iran-Iraq border earthquake due to quiet space weather, local dispersion, and the proximity to the epicenter.
Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 2020
Öz 08.09.2017 tarihinde gerçekleşen manyetik fırtınanın iyonosfer tabakasında sebep olduğu değişi... more Öz 08.09.2017 tarihinde gerçekleşen manyetik fırtınanın iyonosfer tabakasında sebep olduğu değişim, GNSS ölçüleri kullanılarak elde edilen TEC değerleri üzerinden analiz edilmiştir. Kuzey ve güney yarımkürede, iyonosferin farklı bölgelerinde bulunan GNSS istasyonlarına ait RINEX gözlemlerinden TEC değerleri elde edilmiştir. Manyetik fırtına kaynaklı TEC değişiminin ortaya çıkarılabilmesi için manyetik fırtına öncesi 10 gün, manyetik fırtına günü ve sonrası 1 gün olmak üzere her istasyona ilişkin toplam 12 günlük veri değerlendirilmiştir. Yapılan analiz sonucunda manyetik fırtınanın olduğu gün, öncesi ve sonrasında pozitif ve negatif anomaliler elde edilmiştir. Bu çalışma sonucunda Türkiye'de bulunan GNSS istasyonları kullanılarak manyetik fırtına kaynaklı iyonosfer değişimlerinin tespit edilebileceği gösterilmiştir.
Abstract In this study, we investigated the behavior of equatorial plasma bubble irregularities u... more Abstract In this study, we investigated the behavior of equatorial plasma bubble irregularities under different geomagnetic conditions during March 2015 and September 2017. It was used Total Electron Content (TEC) data obtained from SGOC (6,89 oN, 79,87 oE), IISC (12,94 oN, 77,57 oE) and HYDE (17,40 oN, 78,50 oE) receiver stations which located between the trough and the crest of the equatorial ionization anomaly (EIA). We used the Rate of TEC change (ROT) and Rate of TEC change index (ROTI) to represent plasma bubbles irregularities. These indices are a well proxy for the ionospheric fluctuations and can be used to describe features of plasma bubbles irregularities. The equatorial plasma bubble irregularities for all stations were observed between 13 UT and 20 UT (during postsunset period) during equinoxes. The intensity level of ROTI during postsunset periods was greater than 1 TECU min−1. Also, the values of mean ROTI (ROTIave) between 13 UT and 20 UT have values greater than 0,4 TECU min−1 while the values of ROTIave at the other hours have values less than 0,4 TECU min−1. The geomagnetic activity has a significant effect on the occurrence of equatorial plasma bubbles irregularities. The occurrence rate of equatorial plasma bubble irregularities observed during postsunset hours increased as geomagnetic activity increases. It also was observed that the main phases of geomagnetic storms have the triggering effect of storms on equatorial plasma bubble irregularities observed at postsunset hours while the recovery phases of geomagnetic storms have the suppression effect of storms on equatorial plasma bubble irregularities. Asymmetry between two equinoxes was observed. The occurrence rate of equatorial plasma bubble irregularities in the March equinox was much larger than that of the September equinox. The occurrence probability of equatorial plasma bubbles for March Equinox was maximum with 45,1% at 17 UT while the occurrence probability of equatorial plasma bubbles for September Equinox was maximum with 11,5% at 16 UT. The enhancements and reductions in the latitudinal gradient of VTEC show similar behaviors with the occurrence of equatorial plasma irregularities. The EIA during postsunset hours contributes significantly to the occurrence of equatorial plasma bubbles irregularities.
Many scientists from different disciplines have studied earthquakes for many years. As a result o... more Many scientists from different disciplines have studied earthquakes for many years. As a result of these studies, it has been proposed that some changes take place in the ionosphere layer before, during or after earthquakes, and the ionosphere should be monitored in earthquake prediction studies. This study investigates the changes in the ionosphere created by the earthquake with magnitude of Mw=7.2 in the northwest of the Lake Erçek which is located to the north of the province of Van in Turkey on 23 October 2011 and at 1.41 pm local time (-3 UT) with the epicenter of 38.75° N, 43.36° E using the TEC values obtained by the Global Ionosphere Models (GIM) created by IONOLAB-TEC and CODE. In order to see whether the ionospheric changes obtained by the study in question were caused by the earthquake or not, the ionospheric conditions were studied by utilizing indices providing information on solar and geomagnetic activities (F10.7 cm, Kp, Dst). One of the results of the statistical test on the TEC values obtained from the both models, positive and negative anomalies were obtained for the times before, on the day of and after the earthquake, and the reasons for these anomalies are discussed in detail in the last section of the study. As the ionospheric conditions in the analyzed days were highly variable, it was thought that the anomalies were caused by geomagnetic effects, solar activity and the earthquake.
Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 2021
Öz Hassas ve güvenilir hız bilgilerinin elde edilmesi ve konum doğruluğu GNSS bazlı çok sayıda ça... more Öz Hassas ve güvenilir hız bilgilerinin elde edilmesi ve konum doğruluğu GNSS bazlı çok sayıda çalışma için önem arz etmektedir. Bu sebeple, nokta hızlarının kullanılabilirliği için gereken optimum sürenin belirlenmesi gerekmektedir. İç Anadolu Bölgesinin güneyinde yer alan ve deprem riskinin en az olduğu illerden biri olan Karaman ilinde bulunan TUSAGA-Aktif istasyonlarından biri olan KAMN istasyonuna ait 24 saatlik RINEX verileri 8 adet IGS istasyonuna dayalı olarak İsviçre'nin Bern üniversitesi tarafından geliştirilen Bernese v5.2 bilimsel GNSS yazılımı ile değerlendirilmiştir.
The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and ... more The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hou...
Several scientists from different disciplines have studied earthquakes for many years. As a resul... more Several scientists from different disciplines have studied earthquakes for many years. As a result of these studies, it has been proposed that some changes take place in the ionosphere layer before, during or after earthquakes, and the ionosphere should be monitored in earthquake prediction studies. This study investigates the changes in the ionosphere created by the earthquake with magnitude of Mw=7.2 in the northwest of the Lake Erçek which is located to the north of the province of Van in Turkey on 23 October 2011 and at 1.41 pm local time (-3 UT) with the epicenter of 38.758° N, 43.360° E using the TEC values obtained by the Global Ionosphere Models (GIM) created by IONOLAB-TEC and CODE. In order to see whether the ionospheric changes obtained by the study in question were caused by the earthquake or not, the ionospheric conditions were studied by utilizing indices providing information on solar and geomagnetic activities (F10.7 cm, Kp, Dst). As a result of the statistical test on the TEC values obtained from the both models, positive and negative anomalies were obtained for the times before, on the day of and after the earthquake, and the reasons for these anomalies are discussed in detail in the last section of the study. As the ionospheric conditions in the analyzed days were highly vibrant, it was thought that the anomalies were caused by geomagnetic effects, solar activity and the earthquake. The authors believe that interdisciplinary studies are needed to distinguish the earthquake-related part of the anomalies in question.
Journal of civil structural health monitoring, Apr 16, 2024
This study aims to assess the future structural performance of the Kozlu-Ulutan clay core rockfil... more This study aims to assess the future structural performance of the Kozlu-Ulutan clay core rockfill (CCR) dam, one of the most significant water structures in the Black Sea region of Turkey, by utilizing 35 years of levelling measurements and 3D finitedifference analyses. Settlement measurements were obtained from five different points on the dam surface every 6 months. Subsequently, a three-dimensional (3D) model of the dam was created using the finite-difference method. Time-dependent creep analyses and seismic analyses were conducted sequentially, employing the Burger-Creep and Mohr-Coulomb material models, respectively. Non-reflecting boundary conditions were defined for the boundaries of the dam model. The 3D numerical analysis results were found to be highly compatible with the 35 years of levelling measurements. Additionally, the future seepage and settlement behaviors of the dam over a 100-year period (2023-2123) were analyzed, considering special time functions. Current and future seismic analyses were performed, taking into account the settlement results of the dam in 2023 and 2123. For seismic analyses, data from ten various earthquakes that occurred in Kahramanmaraş, Hatay, Malatya, and Gaziantep in Turkey in 2023 were utilized. The seismic analysis results provided significant information about the future seismic behavior of the Kozlu-Ulutan Dam, revealing notable differences between the current and future earthquake behaviors of the dam. Moreover, it was concluded that the clay core is the most crucial section concerning the current and future seismic behaviors of CCR dams. The study results emphasized the importance of continuous monitoring and periodic seismic evaluations for the safe operation of CCR dams.
Ionospheric total electron content (TEC) variations estimated from dual-frequency receivers of gl... more Ionospheric total electron content (TEC) variations estimated from dual-frequency receivers of global positioning systems (GPS) can be used as a tool to detect possible seismo-ionospheric anomalies before strong earthquakes. In this study, possible seismoionospheric anomalies before the 2018 Papua New Guinea earthquake (6.0684°S, 142.7678°E, February 25, 2018, 00:44:43 UTC, Mw = 7.5) was investigated by using GPS-TEC variations from four International GNSS Service (IGS) stations (KAT1, TOW2, SOLO and ALIC) near the epicenter and four IGS station (USUD, SHAO, WIND and ZAMB) outside of the EPZ. The earthquake (EQ) is a local phenomenon and space weather conditions (SWCs) are a global phenomenon so that we selected four IGS stations away from the earthquake epicenter, which is at the same latitude and the same longitude with the earthquake to figure out a clear SWCs' effects on the GPS-TEC anomalies. In order to see these effects on ionospheric TEC variations, 10 different SWC indices were used. An analysis of occurrence time and duration of the following conclusions was made: both positive and negative anomalies are ensuing, and earthquake-related ionospheric anomalies revealed that they occurred 1 to 7 days before the associated earthquake. At the end of the study, the potential causes of these results were examined. Analysis results revealed that anomalies occurred, and the possible ionospheric GPS-TEC anomalies may be the earthquake precursors obtained 4 to 9 days before the Papua New Guinea earthquake. The increase in scientific research to analyze the seismo-ionospheric anomalies that occur before earthquakes will become an important warning tool to alert people to the devastating environmental effects of earthquakes.
Abstract Global Navigation Satellite Systems record the total electron content via their receiver... more Abstract Global Navigation Satellite Systems record the total electron content via their receivers, and total electron content measurements have become popular with the requirement for capturing any ionospheric abnormalities prior to earthquake. Based on space weather conditions, the solar activity and geomagnetic activity indices are critical to monitor the total electron contents in the ionosphere. This study aimed to investigate the ionospheric variations induced by six sequential earthquakes in Nepal in 2015 with magnitude higher than 6.0, examine the total electron content data from Global Ionosphere Maps and Global Positioning Systems and analyze the contributing factors to the abnormal total electron content levels affected by space environment and geomagnetic activity status. We performed moving median analysis for 15 days to determine the pre- and post-earthquake abnormalities. With the static and dynamic time analysis, we concluded that there was likelihood for positive or negative anomalies, earthquake-induced ionospheric anomalies occurred on the previous day or up to six days earlier and even had potentiality for successive earthquakes. Furthermore, the data used in the analysis can be divided into two groups: Global Ionosphere Maps Total Electron Content and Global Positioning System Total Electron Content variations. LHAZ International Global Navigation Satellite System Service station from which we obtained these was close to the earthquakes’ epicenter. We studied three indices, such as geomagnetic storm index (K-planetary), geomagnetic activity index, and solar activity index, depending on space climate and discussed what factors can be influential in this disaster. Hence, we suggest that the earthquake may account for a typical variation in Global Ionosphere Maps Total Electron Content data as well as Global Positioning System Total Electron Content as solar activities and geomagnetic storms leading to abnormalities in the ionosphere.
The potential of the soil to hold plant nutrients is governed by cation exchange capacity (CEC) o... more The potential of the soil to hold plant nutrients is governed by cation exchange capacity (CEC) of any soil. Estimating soil CEC aids in conventional soil management practices to replenish the soil solution that supports plant growth. In the present study, a multiple model integration scheme driven by hybrid GANN (MM-GANN) was developed and employed to predict the accuracy of soil CEC in Tabriz plain, an arid region of Iran. The standalone models (i.e., artificial neural network (ANN) and extreme learning machine (ELM)) were implemented for incorporating in the MM-GANN. In addition, it was tested to enhance the prediction accuracy of the standalone models. The soil parameters such as clay, silt, pH, carbonate, calcium equivalent (CCE), and soil organic matter (OM) were used as model inputs to predict soil CEC. By the use of several evaluation criteria, the results showed that the MM-GANN model involving the predictions of ELM and ANN models calibrated by considering all the soil par...
Bu çalışma, 24. güneş döngüsünde meydana gelen 01 Şubat 2017 (DsT-45 nT) zayıf jeomanyetik fırtın... more Bu çalışma, 24. güneş döngüsünde meydana gelen 01 Şubat 2017 (DsT-45 nT) zayıf jeomanyetik fırtınasının matematiksel analizini amaçlamaktadır. NASA'dan alınan güneş rüzgarı parametreleri (Bz, E, P, N, v, T), zonal jeomanyetik indeksleri (Dst, ap, AE) ve nedensonuç ilişkisini göz önünde bulundurarak Şubat fırtınasının matematiksel modeli ortaya çıkarılmıştır. Makalede fırtına titizlikle analiz edilir ve nedensellik ilkesinin yönettiği modellerle özellikleri ortaya çıkarılmaya çalışılır. Bu çalışmada değişkenlerin değer aralığı ve standart sapmaları tanımlayıcı analiz ile tanımlanır, verilerin binary ilişkileri kovaryans matrisi ile gösterilir ve yine verilerin hiyerarşik kümeleri dendrogram ile tanıtılır. Faktör analizi, verilerin normal dağılımları yardımıyla gerçekleştirilir ve fenomenin gizemi lineernonlineer modellerle tartışılmaya çalışılır. Değişkenlerin ikili görünümleri grafikler ile okuyucuya sunularak fırtınaya görsellik kazandırılır. Bu çalışma, literatürde sınırlı sayıda çalışma bulunan zayıf seviyede manyetik fırtınanın modellenmesi konusuna katkı sağlamaktadır.
<p&amp... more <p>The last two decades a significant effort has been invested in order to understand and interpret the link between seismic activity and ionospheric perturbations. Since not any individual seismo-ionospheric precursor can be used as an accurate stand alone for earthquake prediction it is required to integrate different kinds of precursors and analysis techniques.</p> <p>To this context, the aim of this study is to investigate pre-earthquake ionospheric anomalies that occurred prior to large 6.4 Mw earthquake in Albania (26<sup>th</sup> November 2019), following a multi-instrument and multi-technique approach, using subionospheric radio VLF/LF signals obtained from the Romanian receivers of the INFREP European network and Total Electron Content (TEC) observations from GNSS global network.</p> <p>To identify possible ionospheric anomalies before the earthquakes we applied the terminator time and nighttime fluctuation methods on the amplitude of subionospheric LF radio signals and spectral analysis on diurnal TEC variations several days prior the seismic event. It was found that sunrise terminator times are delayed approximately 20-40 min few days before and during the earthquake day. Intensified wave-like TEC oscillations with periods around 20 min were also revealed up to 5 days prior to the earthquake shocks in all cases that could be interpreted as possible ionospheric precursors of the impending earthquakes.      </p>
Son yıllarda internet üzerinden çevrim içi GNSS değerlendirme servisleri konum elde etmede önemli... more Son yıllarda internet üzerinden çevrim içi GNSS değerlendirme servisleri konum elde etmede önemli bir araç olarak kullanılmaktadır. Bu sistemlerin en önemli özelliği GNSS verilerinin değerlendirilmesi konusunda yeterli bilgiye sahip olmayan kişilerin veriyi rahatlıkla değerlendirebilmesine olanak sunması ve ücretsiz olmasından dolayı ticari veya bilimsel yazılımın alınmasına gerek duyulmamasıdır. Bu çalışmada ANRK, ANTL, IZMI, SINP ve VAN1 istasyonlarına ait RINEX gözlemleri 1, 4, 8, 12, 16, 20 ve 24 saatlik dilimlere ayrılarak CSRS-PPP ve Trimble-RTX servislerine gönderilmiş ve elde edilen koordinatların doğruluk araştırması yapılmıştır. Çalışma sonucunda CSRS-PPP servisinden elde edilen konum verisinin referans veriye daha yakın olduğu anlaşılmıştır.
The analysis of the unexpected ionospheric phases before large earthquakes is one of the cutting-... more The analysis of the unexpected ionospheric phases before large earthquakes is one of the cutting-edge issues in earthquake prediction studies. In this study, the total electron content (TEC) data from seven International GNSS Service (IGS) stations and the global ionosphere maps (GIMs) were used. Short-time Fourier transform (STFT) and a running median process were applied to the TEC time series to detect abnormalities before the M w 7.3 Iran-Iraq border earthquake on 12 November 2017. The analyses showed positive anomalies 8-9 d before the earthquake and some positive and negative anomalies 1-6 d before the earthquake. These anomalies were cross-checked using the Kp, Dst, F10.7, B z component of the interplanetary magnetic field (IMF B z), electric field (E y), and plasma speed (V SW) space weather indices. The results showed that the anomalies 1-6 d before the earthquake were caused by a moderate magnetic storm. Moreover, the positive anomalies 8-9 d before the earthquake were likely related to the Iran-Iraq border earthquake due to quiet space weather, local dispersion, and the proximity to the epicenter.
Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 2020
Öz 08.09.2017 tarihinde gerçekleşen manyetik fırtınanın iyonosfer tabakasında sebep olduğu değişi... more Öz 08.09.2017 tarihinde gerçekleşen manyetik fırtınanın iyonosfer tabakasında sebep olduğu değişim, GNSS ölçüleri kullanılarak elde edilen TEC değerleri üzerinden analiz edilmiştir. Kuzey ve güney yarımkürede, iyonosferin farklı bölgelerinde bulunan GNSS istasyonlarına ait RINEX gözlemlerinden TEC değerleri elde edilmiştir. Manyetik fırtına kaynaklı TEC değişiminin ortaya çıkarılabilmesi için manyetik fırtına öncesi 10 gün, manyetik fırtına günü ve sonrası 1 gün olmak üzere her istasyona ilişkin toplam 12 günlük veri değerlendirilmiştir. Yapılan analiz sonucunda manyetik fırtınanın olduğu gün, öncesi ve sonrasında pozitif ve negatif anomaliler elde edilmiştir. Bu çalışma sonucunda Türkiye'de bulunan GNSS istasyonları kullanılarak manyetik fırtına kaynaklı iyonosfer değişimlerinin tespit edilebileceği gösterilmiştir.
Abstract In this study, we investigated the behavior of equatorial plasma bubble irregularities u... more Abstract In this study, we investigated the behavior of equatorial plasma bubble irregularities under different geomagnetic conditions during March 2015 and September 2017. It was used Total Electron Content (TEC) data obtained from SGOC (6,89 oN, 79,87 oE), IISC (12,94 oN, 77,57 oE) and HYDE (17,40 oN, 78,50 oE) receiver stations which located between the trough and the crest of the equatorial ionization anomaly (EIA). We used the Rate of TEC change (ROT) and Rate of TEC change index (ROTI) to represent plasma bubbles irregularities. These indices are a well proxy for the ionospheric fluctuations and can be used to describe features of plasma bubbles irregularities. The equatorial plasma bubble irregularities for all stations were observed between 13 UT and 20 UT (during postsunset period) during equinoxes. The intensity level of ROTI during postsunset periods was greater than 1 TECU min−1. Also, the values of mean ROTI (ROTIave) between 13 UT and 20 UT have values greater than 0,4 TECU min−1 while the values of ROTIave at the other hours have values less than 0,4 TECU min−1. The geomagnetic activity has a significant effect on the occurrence of equatorial plasma bubbles irregularities. The occurrence rate of equatorial plasma bubble irregularities observed during postsunset hours increased as geomagnetic activity increases. It also was observed that the main phases of geomagnetic storms have the triggering effect of storms on equatorial plasma bubble irregularities observed at postsunset hours while the recovery phases of geomagnetic storms have the suppression effect of storms on equatorial plasma bubble irregularities. Asymmetry between two equinoxes was observed. The occurrence rate of equatorial plasma bubble irregularities in the March equinox was much larger than that of the September equinox. The occurrence probability of equatorial plasma bubbles for March Equinox was maximum with 45,1% at 17 UT while the occurrence probability of equatorial plasma bubbles for September Equinox was maximum with 11,5% at 16 UT. The enhancements and reductions in the latitudinal gradient of VTEC show similar behaviors with the occurrence of equatorial plasma irregularities. The EIA during postsunset hours contributes significantly to the occurrence of equatorial plasma bubbles irregularities.
Many scientists from different disciplines have studied earthquakes for many years. As a result o... more Many scientists from different disciplines have studied earthquakes for many years. As a result of these studies, it has been proposed that some changes take place in the ionosphere layer before, during or after earthquakes, and the ionosphere should be monitored in earthquake prediction studies. This study investigates the changes in the ionosphere created by the earthquake with magnitude of Mw=7.2 in the northwest of the Lake Erçek which is located to the north of the province of Van in Turkey on 23 October 2011 and at 1.41 pm local time (-3 UT) with the epicenter of 38.75° N, 43.36° E using the TEC values obtained by the Global Ionosphere Models (GIM) created by IONOLAB-TEC and CODE. In order to see whether the ionospheric changes obtained by the study in question were caused by the earthquake or not, the ionospheric conditions were studied by utilizing indices providing information on solar and geomagnetic activities (F10.7 cm, Kp, Dst). One of the results of the statistical test on the TEC values obtained from the both models, positive and negative anomalies were obtained for the times before, on the day of and after the earthquake, and the reasons for these anomalies are discussed in detail in the last section of the study. As the ionospheric conditions in the analyzed days were highly variable, it was thought that the anomalies were caused by geomagnetic effects, solar activity and the earthquake.
Bitlis Eren Üniversitesi Fen Bilimleri Dergisi, 2021
Öz Hassas ve güvenilir hız bilgilerinin elde edilmesi ve konum doğruluğu GNSS bazlı çok sayıda ça... more Öz Hassas ve güvenilir hız bilgilerinin elde edilmesi ve konum doğruluğu GNSS bazlı çok sayıda çalışma için önem arz etmektedir. Bu sebeple, nokta hızlarının kullanılabilirliği için gereken optimum sürenin belirlenmesi gerekmektedir. İç Anadolu Bölgesinin güneyinde yer alan ve deprem riskinin en az olduğu illerden biri olan Karaman ilinde bulunan TUSAGA-Aktif istasyonlarından biri olan KAMN istasyonuna ait 24 saatlik RINEX verileri 8 adet IGS istasyonuna dayalı olarak İsviçre'nin Bern üniversitesi tarafından geliştirilen Bernese v5.2 bilimsel GNSS yazılımı ile değerlendirilmiştir.
The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and ... more The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hou...
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Papers by Samed İnyurt