The destructive tsunami on 22 December 2018 due to the flank collapse of the Anak Krakatau volcano was a bitter reminder of large tsunami risks and of the shortcomings of the existing tsunami warning systems for atypical sources (tsunamis generated by non-seismic and complex sources). In the Mediterranean, several tsunamis were generated by landslides associated with volcanic systems in the past.The volcanic unrest experienced in 2011–2012 on the Santorini volcanic island in the Southern Aegean Sea pointed out the need to identify and quantify tsunami hazard and risk due to possible flank instability which may be triggered as a result of volcanic unrest or nearby seismotectonic activities. Inspired from this need, in this study we examined three possible landslide scenarios in Santorini Island with tsunamigenic potential. The results show that the scenarios considered in our study are able to generate significant local tsunamis impacting Santorini and the nearby islands, as well as producing significant impact along the coasts of the Southern Aegean Sea. While maximum tsunami amplitudes/arrival time ranges are 1.2 m/30-90 min for locations in the Greek-Turkish coasts in the far field, they are in the order of ≈60 m/1-2 min for some locations at the Santorini Island. The extreme tsunami amplitudes and short arrival times for locations inside the Santorini Island is a major challenge in terms of tsunami hazard warning and mitigation. As an effort to address this challenge, a discussion on the requirements for local tsunami warning system addressing atypical sources in the context of multi-hazard disaster risk reduction is also provided.

On January 15, 2022, the Hunga Tonga-Hunga Ha'apai volcano's huge eruption generated tsunami waves globally due to an unusual source in this unique event: fast-traveling air pressure disturbances originated from the explosion of the volcano. Here we investigate the global propagation of the pressure waves (first cycle) and the consequent ocean waves. The analysis of the measured air pressure waves shows that the speed of air pressure linearly increases with time. The peak and trough amplitudes of the pressure wave exponentially decrease with the traveled distance until half the overall distance; then, it restarts to increase, reaching a peak towards the apogee. Two different modeling approaches are followed to solve the air pressure waves and the resulting ocean waves: i) a synthetic pressure forcing model based on barometric measurements and ii) a numerical model based on nonlinear shallow water theory using an initial disturbance at the volcano. We forced the hydrodynamic model by the produced pressure fields to compute the resulting tsunami waves globally. We present the modeling results, discussing the possible sea level amplification mechanisms and affecting factors. Fairly well agreement between the computed and measured air pressure waves and sea levels around the globe is promising.

Historical records with recent events reveal that tsunamis are threatening the western coast of Turkey due to the intensely active seismicity of the Eastern Mediterranean Sea. The most recent tsunami events in the region (30 October 2020 Izmir-Samos and 20 July 2017 Bodrum-Kos) restated that the cities located near the Eastern Mediterranean and connected seas should also consider tsunami events in their disaster mitigation plans. Bodrum is one of the most critical coastal districts vulnerable to marine hazards, with popular hotels, numerous coastal facilities, long and famous beaches, cultural, historical and touristic places. Tsunami evacuation planning is required for Bodrum district to mitigate the damage caused by destructive tsunami waves inundating on land. This study calculates the geospatial distribution of pedestrian evacuation time, based on selected credible worst-case scenarios. A widely used anisotropic least-cost distance model is applied via the Pedestrian Evacuation Analyst Tool to calculate the required time for a pedestrian to evacuate the region under tsunami threat based on the selected scenarios. The model includes landscape properties that affect the walking pace of pedestrians during an evacuation, such as elevation, slope, land cover, and land use types (beach, road, bushes, water bodies, and barriers). The resultant pedestrian evacuation time maps show that the maximum time needed for a pedestrian is 8, 6, 5, 4, and 3 min for highly populated coastal settlements of Bodrum, which are Central Bodrum, Yahsi, Akyarlar-Karaincir-Aspat Bays, Bitez, and Gumbet Bays, respectively.

Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead as population and risk exposure continue to increase in coastal areas.Through the last decades, tsunamis have caught coastal populations off-guard, providing evidence of lack of preparedness. Recent tsunamis, such as the Indian Ocean Tsunami in 2004, 2011 Tohoku and 2018 Palu, have shaped the way tsunami risk is perceived and acted upon.Based on lessons learned from a selection of past tsunami events, this paper aims to review the existing body of knowledge and the current challenges in tsunami risk communication, and to identify the gaps in the tsunami risk management methodologies. The important lessons provided by the past events call for strengthening community resilience and improvement in risk-informed actions and policy measures.This paper shows that research efforts related to tsunami risk communication remain fragmented. The analysis of tsunami risk together with a thorough understanding of risk communication gaps and challenges is indispensable towards developing and deploying comprehensive disaster risk reduction measures. Moving from a broad and interdisciplinary perspective, the paper suggests that probabilistic hazard and risk assessments could potentially contribute towards better science communication and improved planning and implementation of risk mitigation measures.

Tarihsel çalışmaların yanısıra 21 Temmuz 2017 Mw 6.6 Bodrum-Kos ve 30 Ekim 2020 Mw 6.9 Doğu Ege depremlerinin neden olduğu tsunamiler ve etkileri, ülkemizin tsunami tehlikesine açık olduğunu karşı konulamaz bir şekilde ortaya koymuş bulunmaktadır. Özellikle kıyı şeritlerindeki kentsel ve turistik yerleşimler ile endüstriyel yapılaşmaların artması, çevre ve iç denizlerimizde yaşanabilecek herhangi bir tsunaminin ülkemize olan etkileri üzerinde dikkatle durulmasını gerektirmektedir. Olası bir tsunaminin oluşması durumunda mümkün olan en kısa sürede afet acil durum yönetimi bileşenlerine ve halka erken uyarı mesajını gönderebilmek kritik önem taşımaktadır. 2015-2030 Sendai Afet Risk Azaltma Çerçevesi, afet risk yönetiminde özellikle afet riskinin anlaşılması için ulusal ve uluslararası iş birliği mekanizmalarının güçlendirilmesi adına yol gösterici bir özellik taşımakta ve yeni risklerin önlenmesini, mevcut risklerin azaltılmasını ve afetlere karşı dirençliliğin artırılmasını hedeflemektedir. Bu kapsamda belirlenen 7 küresel hedeften birisi çoklu tehlike erken uyarı sistemlerinin, afet risk bilgisinin ve değerlendirmelerinin kullanımını ve bunların toplum tarafından ulaşılabilirliğinin 2030 yılına kadar önemli ölçüde arttırılması olarak tanımlanmıştır. Bu çalışma, bir deprem ülkesi olan ülkemizde bu yaklaşım doğrultusunda Türkiye'de deprem kaynaklı tsunami erken uyarısı ve tsunami riskinin azaltılmasına ilişkin sorunlara ve önerilere odaklanmaktadır.

Tsunamis constitute a significant hazard for European coastal populations, and the impact of tsunami events worldwide can extend well beyond the coastal regions directly affected. Understanding the complex mechanisms of tsunami generation, propagation, and inundation, as well as managing the tsunami risk, requires multidisciplinary research and infrastructures that cross national boundaries. Recent decades have seen both great advances in tsunami science and consolidation of the European tsunami research community. A recurring theme has been the need for a sustainable platform for coordinated tsunami community activities and a hub for tsunami services. Following about three years of preparation, in July 2021, the European tsunami community attained the status of Candidate Thematic Core Service (cTCS) within the European Plate Observing System (EPOS) Research Infrastructure. Within a transition period of three years, the Tsunami candidate TCS is anticipated to develop into a fully operational EPOS TCS. We here outline the path taken to reach this point, and the envisaged form of the future EPOS TCS Tsunami. Our cTCS is planned to be organised within four thematic pillars: (1) Support to Tsunami Service Providers, (2) Tsunami Data, (3) Numerical Models, and (4) Hazard and Risk Products. We outline how identified needs in tsunami science and tsunami risk mitigation will be addressed within this structure and how participation within EPOS will become an integration point for community development.

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.

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.

Recent tsunami disasters revealed severe gaps between the anticipated level of hazard and the true extent of the event, with resulting loss of life and property. The severe consequences were underestimated in part due to the lack of rigorous and accepted hazard analysis methods and large uncertainty in forecasting the tsunami source mechanism and strength. Uncertainty and underestimation of the hazard and risk resulted in insufficient preparedness measures. While there is no absolute protection against disasters of the scale of mega tsunamis, a more accurate analysis of the potential risk can help to minimize losses from tsunami. After the major events in 2004 and 2011 many new initiatives originated novel methods for tsunami hazard and risk analysis. However, rigorous performance assessment and evaluation – with respect to guiding principles in tsunami hazard and risk analysis – has not been conducted. In particular, comprehensive uncertainty assessments and related standards are required in order to implement more robust and reliable hazard analysis strategies and, ultimately, better mitigate tsunami impact. This is the core challenge of the proposed COST Action Accelerating Global science In Tsunami HAzard and Risk analysis (AGITHAR). In our presentation we will demonstrate first results of the Action, assessing research gaps, open questions, and a very coarse roadmap for future research.

Turkey suffered from devastating earthquakes and faced with a considerable number of tsunamis in its past. Although, tsunamis occurred in Turkey are not catastrophic as the ones in Pacific Ocean, they may still cause substantial damage in highly populated and/or touristic coastal areas. On July 21, 2017 at 22.31 UTC, a strong earthquake in the Gulf of Gokova (Mediterranean Sea) with a magnitude (Mw) of 6.6 (KOERI) was recorded. The earthquake caused a tsunami that affected the southern coast of Bodrum, Turkey and the northern parts of Kos island, Greece. The largest tsunami run-up was about 1.9 m and observed at Gumbet Bay, Bodrum (Dogan et al., 2019). Fortunately, there were no causalities as tsunami occurred at night time when there were few people on the coast, despite summer season. However, if the same event had occurred during daytime, its impact to the coastal localities would be much higher and it would cause panic among more people. After the 2017 Bodrum-Kos tsunami, numerical simulations based on critical worst-case tsunami scenarios are performed with NAMI DANCE numerical model. According to the simulation results, a seismic scenario based on 1956-Amorgos earthquake and a combined scenario of Gokova fault and North Datca landslide scenario which is a possible submarine landslide assumed to be triggered by the seismic mechanism of Gokova scenario, give the maximum inundation distances and flow depth values at Southern coast of Bodrum Peninsula mainly in Central Bodrum town, Gumbet Bay, Bitez Bay, Yahsi Bay and Akyarlar-Karaincir-Aspat Bays where most of the settlements and touristic facilities are located. In this study, evacuation walk time maps are prepared for the coastal settlements at Southern Coastline of Bodrum Peninsula by using Pedestrian Evacuation Analyst Tool (PEAT) developed by Jones et al. (2014) based on the selected critical scenarios above mentioned. PEAT is a least-cost-distance (LCD) evacuation model that estimates evacuation times throughout hazard zone based on elevation, land cover, walking speed and direction of movement (Wood and Schmidtlein, 2012). The required data are gathered from international open source databases and data provided by Bodrum Municipality. The resultant pedestrian evacuation maps show time in minutes for pedestrian who aims to reach safety zone from shortest route. According to the maps, longest walk times to the safety are calculated to be 8 minutes for Central Bodrum, 3 minutes for Gumbet Bay, 4 minutes for Bitez Bay, 6 minutes for Yahsi Bay and 5 minutes for Akyarlar-Karaincir-Aspat Bays. The pedestrian evacuation times are also tested by onsite measurements. The results are compared and presented by discussions. The evacuation maps provide a base for emergency managers, planners and local decision makers during the planning of evacuation routes and preparation of emergency response plans. Acknowledgements: This study is partly supported by Turkey Tsunami Last Mile Project Analyses JRC/IPR/2018/E.1/0013/NC with contract number 936314-IPR-2018. Keywords: Tsunami evacuation, Least cost distance model, Pedestrian evacuation, Walk time maps

Abstract. 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 fact that artificial effects exist in the regional catalogues. 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 the seismic hazard and risk parameters. In this study, we present an evaluation of the 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.

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 fact that artificial effects exist in the regional catalogues. 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 the seismic hazard and risk parameters. In this study, we present an evaluation of the 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.

Abstract. This study presents the first tsunami scenario database in Marmara Sea, Turkey referring to 30 different earthquake scenarios obtained with the combinations of 32 possible fault segments. The fault mechanisms in Marmara Sea have been studied in detail within FP-7 MARSite project, which were derived from various databases and literature review. Tsunami simulations have been performed according to these defined 30 earthquake scenarios by tsunami numerical code NAMI DANCE (NAMIDANCE, 2011) which solves Nonlinear Shallow Water Equations (NLSWE) using leap-frog scheme. For each earthquake scenario, tsunami hydrodynamic parameters, mainly maximum water surface elevations, arrival time of first wave and maximum wave, and water level fluctuations were calculated at 1333 synthetic gauge points meticulously selected along the coasts of Marmara Sea. The overall simulation results indicate that maximum expected wave heights due to these earthquake scenarios are between 1 m and 2 m and even more than 2 m at some locations along Marmara coasts, such as Kadikoy, Halic and Silivri coasts in Istanbul and Bayramdere and Kursunlu districts along the coasts of Bursa province. The estimated maximum water levels at Bostanci, Pendik and Buyukada coasts in Istanbul, Cinarcik and Bandirma towns and at the entrance of Izmit Bay would reach up to 2 m. Tekirdag coasts and Buyuk Cekmece and Bakirkoy coasts in Istanbul and Yalova coasts would experience maximum tsunami wave amplitudes around 1.5 m. The waves reach up to 1 m at Izmit and Gemlik Bays, Erdek Peninsula and Marmara Island. The overwiew of the results reveal that higher historical tsunami wave heights observed in Marmara Sea cannot be explained by only earthquake-generated tsunamis. Therefore, there is strong agreement on considering submarine landslides as the primary tsunami hazard component in the Marmara Sea as experienced during history and expected in the future.

An Early Warning System or EWS is a core type of data driven IoT (Internet of Things) system used for environment disaster risk and effect management. The potential benefits of using a semantic type EWS include easier sensor and data source plug-and-play, simpler, richer and more dynamic metadatadriven data analysis and easier service interoperability and orchestration. The challenges faced during practical deployments of semantic EWS's are the need for scalable time-sensitive data exchange and processing (especially involving heterogeneous data sources) and the need for resilience to changing ICT resource constraints in crisis zones. We present a novel IoT EWS system framework that addresses these challenges, based upon a multisemantic representation model. We use 'lightweight' semantics for metadata to enhance rich sensor data acquisition. We use 'heavyweight' semantics for top level W3C OWL ontology models describing multi-levelled knowledge-bases and semanticallydriven decision support and workflow orchestration. This approach is validated through determining both system related metrics and a case study involving an advanced prototype system of the semantic EWS, integrated with a deployed EWS