Sürdürülebilir Kalkınma Amaçları
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- ArticleYalnız künye2025Shear-wave velocity model of the Sivas City (inner eastern, Türkiye) using Rayleigh wave ellipticity inversion controlled by 2D microgravity modeling
Bektaş, Özcan; Büyüksaraç, Aydın; Sarıtepe, Halil Erdim; Önal, Kemal Mert; Canbaz, Oktay; Eyisüren, Onur; Pamuk, Eren; Akın, Özgenç; Akar, Fahriye; Koşaroğlu, Sinan
The change in duration, amplitude, and frequency content of the earthquake ground motion as it passes through the rock and ground environment is referred to as the local ground effect. Impedance differences between bedrock and soil, as well as the dynamic behavior of soils, can amplify this effect. The geometry of both dense and loose soil layers must be known to accurately define soil–structure interaction and properly assess how soil behavior affects a structure during an earthquake. Local ground effects are known to play a significant role in structural damage during earthquakes. In basin-like environments, however, studies based on foundation and sub-base depth often lack sufficient information, making it difficult to identify problems associated with basin effects. It is not appropriate to provide construction-related information, especially in environments with a basin structure like Sivas, without determining the bedrock or solid ground conditions. This study aimed at determining the bedrock/seismic foundation depth for the central settlement of Sivas and defining the basin structure, involved large-scale microgravity measurements. The study area was modeled in three dimensions using the gravity data obtained. Long-term microtremor measurements were also conducted, and one-dimensional depth–shear-wave (Vs) velocity models were generated using the Rayleigh ellipticity method. The bedrock/seismic foundation structure of the study area was defined using two different methods, and these definitions were combined into two-dimensional sections. A depth map of the study area was created, revealing that the thickness of the loose basin unit is approximately 90 m. Ambient noise was recorded at 35 points with a velocity seismometer, and S velocity (Vs) profiles were obtained from joint inversion of Rayleigh ellipticity data and dispersion curves from MASW and ReMi data. Furthermore, the Vs-depth structure of the basin was defined along the profiles cutting the basin in NW–SE and S–N directions, based on the Vs velocities in the 2D gravity model. The frequency range along these profiles was found to be 0.6 Hz in the deep parts of the basin and 2.5 Hz in the shallow parts.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2025Analysis of the recent regional stress field of Erzincan Basin (Türkiye) and its surroundings using small to moderate earthquakes
Akar, Fahriye; Hoskan, Nihan
The Erzincan Basin is one of the most actively deforming geologic features in Eastern Anatolia owing to the high seismic activity taking place in the surrounding area. In the last century, the 1939 Mw = 7.9 and the 1992 Mw = 6.8 earthquakes are the two largest events that devastated the city of Erzincan caused the loss of more than 33,000 and 600 lives, respectively. This study analyzes the seismicity in the vicinity of the Basin. The main trace of the North Anatolian Fault Zone (NAFZ) crossing the Erzincan Basin reveals relatively lower seismicity pattern in terms of small earthquakes. On the contrary, remarkable off-fault seismic activity occurs along the secondary segments. The segments located to the south of NAFZ are striking at high angles to the main trace. The potential of the secondary faults to generate Mw = 6.0 earthquakes was revealed by the 2003 Pülümür earthquakes, pointing out their significant contribution in shaping the Erzincan Basin. The fault segment ruptured by the Pülümür event is located to the east of the subparallel Ovacık fault showing left-lateral strike-slip sense of motion. Similar seismic lineaments exist to the west of the Ovacık fault. All these secondary segments are laying to the south of the NAFZ main trace. In this study, the stress tensor analysis of the Erzincan Basin was conducted using the azimuths and plunges of the P- and T-axes obtained from the focal mechanism solutions of the earthquakes that occurred in the region. The focal mechanisms of the events around those segments have P- and T-axes oriented close to N–S and E–W, respectively. On the contrary, to the north of NAFZ prominent seismic activity takes place only along a segment striking almost E–W accommodating events mostly showing right-lateral strike-slip faulting. These facts indicate a complex stress field acting around the Erzincan Basin.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Geotechnical and Structural Damages Caused by the 2023 Kahramanmaraş Earthquakes in Gölbaşı (Adıyaman)
Akar, Fahriye; Işık, Ercan; Avcil, Fatih; Büyüksaraç, Aydın; Arkan, Enes; İzol, Rabia
On 6 February 2023, two independent earthquake pairs on the East Anatolian Fault Zone, with epicenters in Pazarcık (Mw = 7.7) and Elbistan (Mw = 7.6) districts of Kahramanmaraş province, caused great destruction. Adıyaman and Gölbaşı districts of this city are among the settlements most affected by the earthquake. Especially in the district where geotechnical damages are most observed, the destructive effects of earthquakes have been clearly observed in buildings with different structural systems. In this study, information is given about the earthquakes that hit the region and the fault zone where the earthquakes occur. Geotechnical and structural damages occurring in the villages and center of the district were evaluated within the scope of earthquakes and structural engineering. It can be stated that damages observed in the district center are generally caused by soil–structure interaction problems. The fact that masonry structures, which are widely used in rural areas, do not benefit from any engineering services has an impact on the level of damage. The main reason for the damages occurring in the reinforced concrete structures in the district is the reinforced concrete system that is not designed properly or not built in accordance with the design. This case study demonstrated the importance of earthquake–soil–structure interactions in line with earthquake-resistant building design principles.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024The upper crustal thermal structure of the Cameli Basin and its surroundings (SW Anatolia, Türkiye) by using the fractal-based centroid method of aeromagnetic data and its relationship with earthquakes occurring in the region
Akar, Fahriye
The Cameli Basin and its surroundings are located in southwestern Anatolia, Türkiye, and are one of the tectonically active regions in western Türkiye. The Curie point depth of continental crust can help us to determine the regional tectonic and geothermal structures. The aeromagnetic magnetic data of the study region were used to determine the Curie Point Depth estimates. The fractal-based centroid method is used for this purpose. The fractal approach removes the effect of fractal magnetization in the power spectrum. The depth to the bottom of the deepest magnetic sources in the study region ranges between 6.9 and 14.05. The estimated thermal gradient varies from 41.28°C/km to 89.23°C/km and the average value is 58.59°C/km (580°C for magnetite). The distributions of earthquakes are compatible with NW-SE trending estimated Curie depth anomalies. Interpretation indicates that the depth to the Curie isotherm is considerably shallower than the Moho depth.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Spatio-temporal changes in b-value associated with the 2023 Türkiye earthquake
Akar, Fahriye
b-value analysis obtained using earthquake catalogues has been associated with stress accumulation for a very long time. In this study, the spatial and temporal distribution of the b-value, also known as the frequency magnitude distribution factor, was calculated and examined before and after the February 6, 2023, Kahramanmaraş earthquakes (Mw 7.7 and Mw 7.6). For this, all earthquakes that occurred between 1900 and the earthquakes of February 6, 2023, and all aftershocks that occurred until September 1, 2023, were used. A circular area with a radius of 300 km, including nearby active faults from the center of the first earthquake to the center of the second earthquake, was divided into grids of equal size. The b-value was calculated for each grid using the maximum likelihood method. Very low b values were detected in the area where the first earthquake occurred, and it was observed that the b-value decreased relatively in the area where the second earthquake occurred. From the change in b-value over time, it was determined that the b-value has decreased significantly in recent years. This situation is associated with stress accumulation in the area where both earthquakes occurred, especially the low b values of the region where the first earthquake occurred. The fact that b values obtained using aftershocks are still low suggests that stress in the region is not completely released, has not been completely relieved and aftershocks will continue for a long time.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2022Bodrum ve fethiye ilçeleri arasındaki bölgenin b-değerlerinin uzaysal analizi, güneybatı anadolu, türkiye
Akar, Fahriye; Akkoyunlu, Mehveş Feyza; Bilim, Funda
Herhangi bir bölgenin deprem veri setinde verilen bir büyüklüğün frekans dağılımı olan b-değerinin değişiminin tahmini, o bölgenin tektonik mekanizmasının yorumlanması ve sismik tehlike değerlendirmesi için önemli bir parametredir. Gerilme ile b-değeri arasında ters korelasyon bulunmaktadır. Magnitüd-frekans ilişkisi, iyi bilinen Gutenberg-Richter ilişkisi ile tanımlanır. Bu makalenin amacı, Bodrum ve Fethiye ilçeleri arasındaki bölgenin (GB Anadolu, Türkiye) yakın zamandaki sismisitesini araştırmaktır. Bu çalışmada 2004-2020 yılları arasında magnitüdü (Ml) 2'den büyük toplam 27357 deprem verisi kullanılmıştır Depremlerin büyük çoğunluğunun odak derinlikleri 0 ile 33 km arasında yoğunlaşmaktadır. Bu çalışmada, Gutenberg-Richter ilişkisindeki b-değeri, maksimum likelihood yöntemiyle hesaplanmıştır. Hesaplanan b-değerleri çalışma bölgesinde 0.5 ile 2 arasında değişmektedir. Daha düşük b değerleri (0.5-1) çalışma alanının GD'sunda (esas olarak Beydağları birimi) yer alırken, batı-doğu yönelimli yüksek değerler (1-2) fay zonları boyunca yer almaktadır. Çalışma alanındaki en yüksek b değerleri muhtemelen kırılgan alt-orta kabuk, termal rejim, normal faylar ve bu faylarla sınırlanan genç havzalarla ilgilidir.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye202121 Temmuz 2017 Mw 6.6 Bodrum-Kos depremi öncesi b-değerlerinin analizi
Akar, Fahriye
Bu Bu çalışmada 21 Temmuz 2017 tarihinde meydana gelen Bodrum-Kos depreminden (Mw 6.6) önce Bodrum ve civarındaki deprem aktivitesinin bölgesel ve zamana bağlı değişimlerinin istatiksel bir analizi yapılmış ve Gutenberg-Richter b-değeri değişimi incelenmiştir. Hesaplamalarda kullanılan deprem kataloğu Boğaziçi Üniversitesi, Kandilli Rasathanesi ve Deprem araştırma Enstitüsünden alınmıştır. Bu katalog 2004 yılı ile 21.07.2017 Bodrum-Kos depremine kadar olan zaman arasında M>2 olan 16947 depremi içerir. Bu depremler için tamamlılık magnitüdü 2.6 olarak hesaplanmıştır. b-değeri maksimum olasılık yöntemi kullanılarak 1.25+-0.01 olarak hesaplanmıştır. Tektonik depremlerin 0.5-1.5 arasında b-değerine sahip oldukları düşünülürse bu çalışmada Bodrum civarı için Gutenberg-Richter yasası ile elde edilen b-değerinin iyi uyum sağladığı görülmektedir. Ayrıca Bodrum-Kos depremi meydana gelmeden önce Bodrum’un kuzeyinde b-değerinin yüksek değerler aldığı gözlenmiştir. Bodrum’un güneydoğusunda ise düşük değerler gözlenmiştir. Bölge için b-değerleri ile gerilme birikimi ilişkilendirilmiştir.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2020Çameli Depremi (5.1) Artçı Şoklarının Çift Fark Algoritması İle İncelenmesi
Akar, Fahriye
Çameli bölgesi Burdur-Fethiye Fay Zonu’nun orta kesiminde bulunan aktif tektonik bölgelerden biridir. 2007-2008 yıllarında mikrodeprem aktivitesinde artış gözlenmiştir. Bu depremlerin en büyüğü 29 Ekim 2007 (ML=5.1)Çameli Depremidir. TÜBİTAK Yer ve Deniz Bilimleri Enstitüsü ile Afet İşleri Genel Müdürlüğü DepremAraştırma Dairesinin (AFAD) ortaklaşa yürüttükleri 'Deprem Sonrası Acil Gözlem Araştırmaları' projesikapsamında Çameli Bölgesinde kurulmuş olan 10 adet sismometre ağı ile Çameli Depremi sonrası 700 den fazladeprem kaydedilmiştir. Boğaziçi Üniversitesi Kandilli Rasathanesi, Deprem Araştırma Enstitüsü Ulusal Depremİzleme Merkezi (BDTİM) tarafından hazırlanan katalogdan Çameli Bölgesi’nde 2007-2008 yılında meydana gelen1206 adet deprem verisi derlenmiştir. Hem BDTİM’ den hem de TÜBİTAK’ tan alınan bu veriler incelenmiştir.Depremlerin doğru bir şekilde yeniden konumlandırılması yapılıp çalışma alanı için sismojenik kuşağın derinlikledeğişimi tespit edilmiştir. Çameli Depreminin meydana geldiği fayın geometrisi ve odak derinliğinin dağılımıortaya konulmuştur. Bunun için deprem çifti farkı yöntemi (hypoDD) kullanılmıştır. HypoDD yöntemininuygulanmasıyla her iki veri gurubu içindeki dağınık deprem konumları daha küçük kümelere daralmıştır. Dikeykesitlerden deprem odak derinliklerinin iyileştirilmesiyle sismojenik kabuğun sınırı net bir şekilde görülmüştür.Çameli depreminin artçı şokların 5 ile 15 km derinlikte meydana geldiği yüzeyde ise depremlerin KB-GD ve KDGB yönünde çizgisellik oluşturduğu gözlenmiştir.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2019REGIONAL GEOELECTRICAL DIMENSIONALITY OF THE NORTHWESTERN PART OF TURKEY FROM MAGNETOTELLURIC TENSOR INVARIANTS
Akar, Fahriye; Kaya, Cemal
In this study, measurements obtained through the first two profiles from the TÜBİTAK (The Scientific and Technological Research Council of Turkey) project titled “Research of the Crustal Structure of Northwestern Anatolia with Geophysical Methods” from 2007 were used. Magnetotelluric (MT) measurements were taken from 174 sites approximately every 3 km in the region between Zonguldak and Akşehir (Konya). Dimensionality analysis was conducted with the decomposition of the impedance tensor obtained through the measurement data from the two profiles. The relationship between the observed geo-electric behaviors, the geological structure of the area and the MT dimensionality changes were detected. Two-dimensional (2D) and three-dimensional (3D) structures were revealed as a result of the dimensionality analysis obtained through the MT data from the region located between Zonguldak and Akşehir. The dimensionality was observed to be complex in small periods due to the heterogeneous conductive materials close to the surface and 3D structures were observed to be predominant in high periods. Moreover, the dimensionality near the suture zones were observed to be more complex compared to other areas according to the dimensionality analysis results. The structures in the vicinity of the North Anatolian Fault were found out to be N-NE striking. This indicates the accuracy and reliability of the results.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Çameli bölgesi’ nin 3-BOYUTLU gravite ve manyetik yapısı ve depremsellikle ilişkisi
Özel, Oğuz; Akar, Fahriye
Çameli (Denizli) Bölgesi Güneybatı Anadolu’da bulunan aktif tektonik bölgelerden biridir. Bu çalışmada ÇameliBölgesi’ ndeki aktif deprem zonu, gravite ve manyetik yöntem kullanılarak 2- ve 3-boyutlu olarak modellenmiştir.Çalışma kapsamında Maden Tetkik ve Arama Genel Müdürlüğünden alınan gravite ve manyetik verilerine jeofizikanaliz yöntemleri uygulanmıştır. Son olarak, elde edilen gravite ve manyetik sonuçlarının birlikte yorumu ilebölgeye ait tektonik izler ortaya konmuş ve deprem oluşumu ile ilişkilendirilmiştir. Bu çalışmada her ne kadarbölgedeki akışkan varlığının deprem oluşumunda önemli bir etken olduğu ortaya çıkarılsa da genel olarak çalışmaalanının tektonik geçmişi, kabuktaki ve üst mantodaki malzemelerin litolojisi, akışkan içeriği, madde heterojenitesigibi tüm fiziksel ve mekanik özelliklerin bir arada deprem oluşumunu tetiklediği sonucuna ulaşılmıştır.
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