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The 2023 February 6 Mw 7.8 earthquake was the first one of a doublet which shook Türkiye and Syria causing, as per the estimates at the time of writing of this abstract, more than 45,000 casualties.The current standard operating procedures of the NEAMTWS (Tsunami Warning System in the North-Eastern Atlantic, the Mediterranean and connected seas, coordinated by UNESCO/IOC) for the initial tsunami warning message following an earthquake are based on a Decision Matrix (DM), whose input parameters are hypocentre and magnitude of the earthquake. Since the epicentre of this earthquake was located at a depth between 15-35 km at almost 100 km from the coast, both KOERI (Türkiye) and INGV (Italy) Tsunami Service Providers (TSPs) of the NEAMTWS issued a Tsunami Watch message (i.e., runup expected to exceed 1 m) for the whole Mediterranean Sea. NOA (Greece) did not issue any alert, because its initial location was more than 100 km from the coast.In response to the tsunami warning, trains were stopped in different locations in Southern Italy for several hours, and evacuation of some coastal areas was enforced. However, only a relatively small tsunami was recorded by Turkish close-by tide-gauges in the Eastern Mediterranean, with a maximum recorded amplitude of less than 50 cm. Based on these measurements and on others showing little to no tsunami at increasing distances, the alert was then ended after 5 and 9 hours by INGV and KOERI, respectively, based on the available tide-gauge recordings and interaction with Civil Protection Officers.This event has highlighted that NEAMTWS is an asset for the coastal communities. It can provide rapid alerts, which can save lives if the last-mile of the procedures is in place and the communities are “Tsunami Ready”, that is aware and prepared to respond with evacuations and other appropriate countermeasures. On the other hand, while it is reasonable – and dutiful based on current standard operation procedures – to issue a basin-wide, or at least a local alert, for an inland earthquake of unknown mechanism and of such a large magnitude, it is perhaps possible to improve the DM, which is totally heuristic and characterized by hard-thresholds, with consideration of numerical tsunami simulations and quantitative uncertainty treatment with more continuous variations. Moreover, there is no procedure currently in place to differentiate among locations where the expected time of arrival differs by many hours across the Mediterranean basin, nor a sufficient instrumental coverage that could make cancellation/ending faster due to a more solid observational basis.We will discuss some of the scientific and operational aspects with the aim of identifying which lessons can be learned to improve the NEAMTWS efficiency. We will also compare the DM-based alerts with those that would be produced with the recently introduced Probabilistic Tsunami Forecasting (PTF, Selva et al., 2021, Nature Communications), presently in pre-operational testing at INGV.

SUMMARYWe investigate active tectonics in southwestern Turkey along the trend between Fethiye, near the eastern end of the Hellenic subduction zone, and Burdur, on the Anatolian plateau. Previously, regional GNSS velocities have been used to propose either (1) a NE-trending zone of strike-slip faulting coined the Fethiye–Burdur Fault Zone, or (2) a mix of uniaxial and radial extension accommodated by normal faults with diverse orientations. We test these models against the available earthquake data, updated in light of recent earthquakes at Arıcılar (24 November 2017, Mw 5.3), Acıpayam (20 March 2019, Mw 5.6) and Bozkurt (8 August 2019, Mw 5.9), the largest in this region in the last two decades. Using Sentinel-1 InSAR and seismic waveforms and arrival times, we show that the Arıcılar, Acıpayam and Bozkurt earthquakes were partially or fully buried ruptures on pure normal faults with subtle or indistinct topographic expressions. By exploiting ray paths shared with these well-recorded modern events, we relocate earlier instrumental seismicity throughout southwestern Turkey and incorporate these improved hypocentres in an updated focal mechanism compilation. The southwestern Fethiye–Burdur trend is dominated by ESE–WNW trending normal faulting, even though most faults evident in the topography strike NE–SW. This hints at a recent change in regional strain, perhaps related to eastward propagation of the Gökova graben into the area or to rapid subsidence of the Rhodes basin. The northeastern Fethiye–Burdur trend is characterized by orthogonal normal faulting, consistent with radial extension and likely responsible for the distinct physiography of Turkey’s Lake District. We find that the 1971 Mw 6.0 Burdur earthquake likely ruptured a NW-dipping normal fault in an area of indistinct geomorphology near Salda Lake, contradicting earlier studies that place it on well-expressed faults bounding the Burdur basin, and further highlighting how damaging earthquakes are possible on faults that would prove difficult to identify beforehand. Overall, our results support GNSS-derived kinematic models that depict a mix of uniaxial and radial extension throughout southwestern Turkey, with no evidence from focal mechanisms for major, active strike-slip faults anywhere along the Fethiye–Burdur trend. Normal faulting orientations are consistent with a stress field driven primarily by contrasts in gravitational potential energy between the elevated Anatolian plateau and the low-lying Rhodes and Antalya basins.

As the earliest institute in Turkey dedicated to locating, recording, and archiving earthquakes in the region, the Kandilli Observatory and Earthquake Research Institute (KOERI) has a long history in seismic observation, which dates back to the installation of its first seismometers soon after the devastating Istanbul earthquake of 10 July 1894. For over a century, since the deployment of its first seismometer, the KOERI seismic network has grown steadily in time. In this article, we present the KOERI seismic network facilities as a data center for the seismological community, providing data and services through the European Integrated Data Archive (EIDA) and the Rapid Raw Strong-Motion (RRSM) database, both integrated in the Observatories and Research Facilities for European Seismology (ORFEUS). The objective of this article is to provide an overview of the KOERI seismic services within ORFEUS and to introduce some of the procedures that allow to check the health of the seismic network and the quality of the data recorded at KOERI seismic stations, which are shared through EIDA and RRSM.

Aktif fay zonları boyunca asimetrik olarak dağılmış olan mikro çatlaklar bu zonlardaki depremlerin tekrarlı oluşumları nedeniyle meydana gelmektedir. Aynı bölgede sürekli tekrarlanan depremler, elastik olarak farklı olan malzemeleri ayırarak iki-malzemeli arayüzeyler meydana getirir ve deprem davranışını etkileyen önemli sonuçlar doğurur. Kuzey Anadolu Fay Zonu üzerinde kurulan DANA (Dense Array of Northern Anatolia) sismik ağı Kuzey Anadolu Fay Zonu’nun Sakarya ve Sapanca segmentleri üzerinde iki malzemeli arayüzeyin incelenmesi için elverişli veri sağlamaktadır. Bu çalışmanın amacı, yoğun sismik dizilim bulunan Kuzey Anadolu Fay Zonu’nun (KAFZ) batı ucunda Sakarya ve Sapanca segmentleri arasında, deprem dalgası çapraz ilişki analizleri kullanarak, iki malzemeli arayüzey geçişindeki hız değişimlerini belirlemektir. Araştırma kapsamında 2012-2013 yıllarında, çalışma alanında faaliyet gösteren DANA geçici sismik ağına ait 73 adet sismik istasyondan, 109 adet uzak deprem kaydı kullanılarak 50.000'den fazla dalga formu derlenmiştir. Uzak deprem dalgalarının, sismik kayıtçılara varışları arasındaki zaman farkları, fayın karşılıklı bölümlerinde kabuktaki hız kontrastını tespit etmek ve fark değerini ölçmek için kullanılmıştır. Elde edilen bulgular KAFZ kuzey kolunun kuzeybatısında düşük, kollar arası Armutlu-Ovacık bloğu altında yüksek hızlara işaret etmektedir. Referans kayıtçıların analizinde, hız oranlarında lokal değişimler hesaplanmış olsa da, bölge geneline bakıldığında KAFZ kuzey kolunun kuzeyi ile, yine KAFZ kuzey kolunun doğusu ve güney doğusu arasında görece büyük hız farkları elde edilmiştir. Sonuçlar, KAFZ kuzey ve güney kollarındaki hız değişimlerini ve genel tektonik ortamla ilişkilendirilen özellikleri ortaya koymaktadır.

KOERI has a long history of earthquake seismology, beginning its observations right after the devastating earthquake on 10 July 1894 in Istanbul, by deploying the first seismograph in the region. Naturally, its seismic network and earthquake catalog evolved since that time, in harmony with the progress in the science of seismology. Currently, the seismic network consists of 242 stations that record approximately 1500 earthquakes per month during periods of regular seismicity. Magnitude is one of the most critical parameters in determining the size of an earthquake, especially in seismic hazard assessment studies. The objective of this study is to homogenize the magnitudes of the KOERI catalog between 2008 and 2018. For this aim, we computed the Magnitude of Completeness (Mc) for two different time periods between 2008–2011 and 2012–2018 by taking into account the duration magnitude (Md) and local magnitude (Ml), where these parameters might not be available jointly for the both time periods considered. As a result, we present a relationship of Md and Ml magnitudes derived from and applicable to KOERI's earthquake catalogs.

Seismicity catalogs are the most important product of seismic network operating centers, especially for the earthquake hazard studies. Understanding the nature of regional catalogues has primary importance in shedding light on statistical parameters of the seismicity behavior of that given region. It is a well-known truth that man made inhomogeneties and artificial facts exist in the catalogs due to the change of infrastructure with time. Precisely determined earthquake parameters are important not only for understanding the seismicity and seismotectonics of a region but also for providing an accurate estimation of seismic hazard and risk parameters. In this study, we present an evaluation of Kandilli Observatory and Earthquake Research Institute (KOERI) - Regional Earthquake Tsunami Monitoring Center (RETMC) seismicity catalog for the time duration of 2013 – 2017. We mapped the magnitude of completeness, Mc, for Turkey for the RETMC catalog. We compared the results with the Mc values of different local earthquake sequences in the region, by also considering the variations of Mc with time. Results of the study will be a reference guide for researchers who benefit from RETMC-KOERI data.

The 2020 Mw 6.8 Elazig earthquake was the largest along the Eastern Anatolian Fault (EAF) in over a century and so provides valuable insights into its rupture behavior. Because the EAF is of low-to...

A tsunami warning system providing services in the Eastern Mediterranean, Aegean, Marmara and Black Seas under the UNESCO Intergovernmental Oceanographic Commission (IOC)—Intergovernmental Coordination Group (ICG) for the Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean and Connected Seas (NEAMTWS) framework was established in Turkey by the Kandilli Observatory and Earthquake Research Institute (KOERI) (Özel et al., 2011). KOERI’s Regional Earthquake and Tsunami Monitoring Center (RETMC) was established on the foundations of the legacy KOERI National Earthquake Monitoring Center (NEMC) by adding observation, analysis and operational capability related to tsunami early warnings after an extensive preparatory period during 2009 and 2011. The center initiated its test-mode 7/24 operational status as a national tsunami warning center in 2011, and after a one year period it became operational as a candidate tsunami warning center for NEAMTWS on 1 July 2012, together with CENALT (Centre d’Alerte aux Tsunamis—France) and followed by the NOA (National Observatory of Athens—Greece) on 28 August 2012, INGV (Instituto Nazionale di Geofisica e Vulcanologia—Italy) on 1 October 2014 and IPMA (Instituto Português do Mar e da Atmosfera—Portugal) on 1 February 2018, completing full coverage of the tsunami-prone regions monitored by NEAMTWS. In this paper, an overview of the progress and continuous improvement of KOERI’s tsunami early warning system will be presented, together with lessons learned from important tsunamigenic events, such as the 20 July 2017 Bodrum–Kos Mw 6.6 and 30 October 2020 Samos–Izmir Mw 6.9 earthquakes. Gaps preventing the completion of an effective tsunami warning cycle and areas for future improvement are also addressed.

Turkey is located in a seismically active region with a complex tectonic history. In order to perform seismic risk assessment precisely, major fault zones (North Anatolian Fault Zone and East Anatolian Fault Zone) that are well defined are monitored continuously. It is a widely known fact that intraplate settings, such as Anatolian Plate, in which devastating earthquakes may occur, need to be observed densely. In this study, we investigate the seismotectonics of Malatya Fault within the Malatya Ovacık Fault Zone (MOFZ), which is one of the major agents responsible for internal deformation acting on Anatolian Plate. Recent geological and paleoseismological studies underline the necessity of comprehending the seismicity and latency of a major earthquake in this fault zone.We applied traditional techniques to investigate data of such a region. Earthquakes that occured in the vicinity of Malatya Fault between the years 2011 and mid-2019 are employed in a detailed analysis. The results of this study are constrained by the distribution of sensor networks in the region, yet allowing to define an active structure which is not included in the active fault map of Turkey, therefore, making a significant contribution to seismic hazard estimation.

Turkey and its surrounding regions are tectonically active and have high‐seismicity rates. The seismicity in the region is observed by the national networks of the Kandilli Observatory and Earthquake Research Institute (KOERI) and the Disaster and Emergency Management Presidency Earthquake Department (AFAD). The quality and quantity of seismic stations improved significantly after the 17 August 1999 M w 7.4 Izmit earthquake. In the meantime, a number of focal mechanism catalogs were produced, covering different time periods. However, a homogeneous long‐term catalog of moment tensor (MT) solutions with increased data amount and quality was not available for the region. In this article, we perform a systematic MT inversion of 133 M ≥4.5 earthquakes within Turkey between 2008 and 2015, using the dense seismic networks of KOERI and AFAD. The use of combined networks and site‐specific velocity models for the computation of MT inversion results in high‐quality solutions of focal mechanisms. This homogeneous focal mechanism catalog provides important new information on the seismotectonics in this region.

The North Anatolian Fault Zone is (NAFZ), which is one of the world’s most active seismic structures, runs along the northern part of Turkey. Seismic velocity structure of the crust in the seismically active regions such as NAFZ plays an important role not only in the accurate hypocenter location and characterization of earthquakes but also in the determination of source mechanism and fault properties. We investigated the Moment Tensor (MT) solutions of earthquakes with respect to different crustal velocity models. MT solutions of earthquakes (M > 4.0) occurred in Yedisu segment, which is located near the intersection of North Anatolian Fault Zone and East Anatolian Fault Zone were examined in the study. MT solutions were calculated by full waveform inversion using the software package ISOLA. Different crustal velocity models and hypocenter location parameters were tested during the computation of MT solutions. All observations are very well justified in terms of moment tensor resolvability (a well-posed problem with a low condition number), satisfactory fit between observed and synthetic waveforms, and large doublecouple percentages. Obtained results provide valuable information in understanding the seismotectonic behaviour of one of the most seismically active regions along the NAFZ.