Ufuk Hancilar

Vulnerability, understood as the conditions determined by physical, social, economic and environmental factors or processes that increase the potential for an individual, a community, assets or systems to be negatively affected by hazards, is a key component when assessing tsunami risk. Vulnerability can be affected by human interventions. Hence, the study of vulnerability is essential to support decision-making (e.g., land use planning and emergency planning) for more effective risk management. Vulnerability is most commonly represented through a vulnerability function that expresses the likelihood of achieving a value of a loss parameter for increasing values of a hazard intensity measure.

Empirical methods for the development of fragility functions employ observational damage data collected after an earthquake. Observations at various locations, which are graded based on a predefined damage scale, are correlated to a ground motion intensity measure and as a result of this statistical process fragility functions are generated. This procedure essentially requires characterization of corresponding ground motion intensity levels that the buildings in the damage data set have experienced. Ideally, recorded ground motion data across the surveyed areas would be used for intensity level assignments. However, due to the scarcity of ground motion recordings, ground motion intensity values over the geographical extent where the damaged buildings spread out are obtained, in practice, through ground motion prediction equations (GMPEs) or physics based ground motion simulations, which come with certain complexities and at additional computational cost. The estimated ground motions can then be further improved by the incorporation of the recorded values, if any available. After the Feb. 6, 2023 Kahramanmaraş-Türkiye earthquakes we derived fragility functions (Hancilar and Acikgoz, 2024a) using the official field based damage data (2023) and the rapid ground shaking estimations (Hancilar et al., 2023). We recently revisited our analyses for the computation of the spatial distributions of ground shaking intensities by incorporating different local site effect models, ground motion predictive models as well as by implementing bias adjustments on the ground motion estimations with the addition of more strong motion recording stations (Hancilar and Acikgoz, 2024b). This study deals with the re-derivation of fragility functions with different ground motion inputs while the building damage data kept unchanged. The resulting fragilities are compared and the effect of the ground motion uncertainty is examined.

When looking at the history of tsunami research, considering the early efforts, two trends can be observed. Academic tsunami research was carried out in diverse disciplines with boosts after large global events, such as the 1960 Chile event that lead to the creation of warning centers in the U.S. and Japan in the Pacific, or the 2004 Indian Ocean event that had a large impact on global tsunami preparedness efforts, supported by IOC UNESCO and other global organizations. On the other hand, the engineering community in particular in the United States created building codes and formalized such hazard prevention measures.Efforts were made to gather the scientific community and the well established series of tsunami sessions at AGU and EGU meetings is just one indication for this. The IUGG Joint Tsunami Commission formalized some of the community effort in tsunami research, and the Tsunami Society International with its International Journal Science of Tsunami Hazards has been instrumental to gather important information and progress in tsunami science.Around 2015 it became clear that there is demand for a formal approach to an integration of scientific progress and transfer into stakeholder groups, involving social sciences, geosciences, engineering, and computational sciences. Adopting some of the probabilistic approaches from seismic hazard assessment, covering uncertainty quantification, and developing multi-scale approaches to hazard and risk analysis, communicating and applying these topics was outside of the purely scientific agenda.The idea for a Global Tsunami Model (GTM) entity was born, borrowed from the Global Earthquake Model (GEM) foundation. Further discussions within the community at several international meetings finally led to the idea of applying for a COST Action, funded through the European Cooperation in Science and Technology (COST). The COST Action AGITHAR was then instrumental in further developing and forming a basis for an entity supporting the ideas mentioned before. Accompanied by successful European Research Council funded projects related to tsunami hazard and risk assessment a portfolio of products and services could be developed. A further one-year funding from COST for sustaining the efforts of AGITHAR, finally led to the inauguration of the Global Tsunami Model Association, a registered association under German legislation.In this presentation we announce GTM Association and invite the global community to become part of this initiative. The presentation will give a brief overview of the history of GTM, will introduce the vision and mission of the association, as well as outline the governing structure. We present the assets as well as our ideas on a sustained business model with a variety of development paths open to the community. While much of the development took place in the European context so far due to funding opportunities, GTM is global and will extend internationally. GTM is committed to serve the scientific community, stakeholder groups as well as the general society by coordination, knowledge transfer, and scientific progress as a non-for-profit organization.

An Mw 6.9 (Ml 6.6) earthquake occurred at an estimated focal depth of 12 km in the Aegean Sea on October 30th, 2020. 115 people died in Turkey in the devastating earthquake, it left more than one thousand people injured and several hundreds of families in need of a shelter. The strong ground shaking further amplified by local site effects caused building collapses and substantial damages throughout the city of Izmir (Turkey) as well as in Samos Island (Greece). In the aftermath of the event, an intensity-based damage analysis was conducted for the rapid estimation of number of damaged buildings at regional scale. For this purpose, first, spatial distributions of PGA, PGV values and instrumental intensities were computed by also incorporating the recorded ground motion data made available by several institutions. Numbers of damaged buildings at each EMS-98 damage grade were then estimated using the intensity-based, regionally adjusted structural vulnerability relationships. This paper presents the geographical distributions of rapid damage estimations and compares them to the observational damage data.

2008 yılında İstanbul Büyükşehir Belediyesi (İBB) tarafından cadde/sokak taramaları yoluyla derlenen İstanbul bina envanterinde yaklaşık 1,2 milyon bina bulunmaktadır. Bu binaların %15’i (180.000 civarı) 2000 yılı ve sonrasında inşa edilmiş, 5 ve üzeri katlı, betonarme çerçeve tipi yapılardır. Bu çalışmada, 2000 yılından sonra inşa edilen ve Afet Bölgelerinde Yapılacak Yapılar Hakkında Yönetmelik (1998)’e [ 1 ] göre tasarlandıkları varsayılan bu binalar için, tasarım depremi etkileri altında yapısal hasar ve yapısal hasar kaynaklı mali kayıp tahminleri sunulmaktadır. Bu amaçla, ELER (Earthquake Loss Estimation Routine) [ 2 ] yazılımının kapasite spektrumu yöntemini uygulayan Kentsel Deprem Kayıpları Tahmin Modülü (Hancılar vd., 2010) [ 3 ] kullanılmıştır. Spektral kapasite bazlı hasar analizlerinde deprem talebi %5 sönümlü elastik ivme spektrumu ile temsil edilirken bina yatay yük taşıyıcı sistemi kapasite eğrisi ile sunulur ve spektral yerdeğiştirmeler cinsinden kırılganlık fonksiyonları yoluyla farklı hasar seviyeleri için hasar olasılıkları hesaplanır. Analizlerde deprem etkileri 50 yılda %10 aşılma olasılığı (475 yıllık yinelenme süresi) için Şeşetyan vd. (2016) [ 4 ] tarafından verilen zemin bağımlı spektral ivmeler (0,2s ve 1.0s için) kullanılarak oluşturulan tasarım spektrumları ile dikkate alınmıştır. Hasar analizleri, bina kapasite eğrileri ve kırılganlık fonksiyonları için üç farklı model dikkate alınarak aynı deprem seviyesi altında gerçekleştirilmiştir: i) İstanbul Olası Deprem Kayıp Tahminleri (İBB-2009) [ 5 ] çalışmasında kullanılan, geçmiş analitik çalışmalara ve uzman görüşü/yorumuna dayanan yapısal kırılganlık fonksiyonları ile taşıyıcı sistem kapasite eğrileri; ii) Benzer bina sınıfları için HAZUS-MH MR4 (2004) Teknik Kılavuzu’nda [ 6 ] verilen kapasite eğrileri ve kırılganlık fonksiyonları; iii) Hancılar ve Çaktı (2015)’te [ 7 ] sunulan, yapısal analizlere dayalı kapasite eğrileri ve kırılganlık fonksiyonları. Üç modele ait sonuçlar hasarlı bina sayıları ve dağılımları ile yapısal hasar kaynaklı mali kayıplar cinsinden karşılaştırılmıştır.