Quantitative Tsunami Risk Assessment in Terms of Building Replacement Cost Based on Tsunami Modelling and GIS Methods: The Case of Crete Isl., Hellenic Arc I. TRIANTAFYLLOU, 1 T. NOVIKOVA, 1 M. CHARALAMPAKIS, 1 A. FOKAEFS, 1 and G. A. PAPADOPOULOS 1 Abstract—Tsunami risk assessment is an important component of the planning for risk reduction. We considered tsunami risk as a convolution of tsunami hazard, vulnerability of the assets at risk (e.g. buildings) and the economic value exposed. For testing the model, a coastal segment at the west of Heraklion, capital city of Crete Isl., Greece, was selected. Heraklion was hit in the past by strong tectonic and volcanic tsunamis, generated along the Hellenic Arc in the Mediterranean region. The Minoan tsunami produced by pyroclastic flows during the LBA (17th century BC) great eruption of Thera (Santorini) was selected as an extreme tsunami scenario for the hazard (inundation) zone determination through numerical simulation based on Boussinesq equations for fully non-linear waves. It was found that the wave penetrates inland up to * 1.2 km, while the maximum water depth is * 14 m. The building stock was obtained from the 2011 national census data and vali- dated with the use of orthophotomaps, field inspection and Google Maps. Building vulnerability was determined with the use of the empirical GIS tool DAMASCHE which is based on 2004 Indian Ocean tsunami building damage data and produces damage level by combining water depth and building construction types. The damage level was translated to absolute monetary loss on the basis of cost flat rates determined officially for building replacement, i.e., either reparation or reconstruction, after the destructive earthquakes in Greece during 2014. The method is applicable in other parts of the Mediterranean and beyond provided that appropriate data are available. Key words: Tsunami risk, Minoan tsunami, numerical simu- lation, GIS mapping, building vulnerability, monetary loss. 1. Introduction Large tsunamis are low-probability but high-im- pact natural events causing physical and economic destruction as well as social disruption in coastal communities. After the devastating mega tsunamis of 26th December 2004 in the Indian Ocean and of 11th March 2011 in NE Japan, the issue of preparedness against, and management of, the tsunami threat attracted great interest around the globe. The interest is multifold and includes hazard, vulnerability and risk assessment, building-up and operation of tsunami warning systems as well as the development of a series of risk mitigation actions including risk man- agement plans, training and education, exercises and public awareness. Critical elements in the destruc- tiveness of tsunamis are, among others, the impact on buildings, critical facilities and infrastructures as well as on population, such as loss of life, injury, or other health impacts. Therefore, the estimation of expected impacts from future tsunamis is of particular value for risk assessment and emergency planning. 1.1. Definitions Definitions of the term risk related to earthquakes, as originally defined by UNESCO in 1978 (Alger- missen et al. 1979; Fournier d’ Albe 1982), considers it as a multidisciplinary issue mathematically expressed by the convolution of hazard, vulnerability, and value exposed to the hazard: Risk ¼ hazard H vulnerability H value ð1Þ This definition was generalised to other kinds of risks (e.g. Smith 1992) and adopted for tsunami risk as well (e.g. Papadopoulos and Dermentzopoulos 1998; Curtis and Pelinovski 1999), which is consis- tent with definitions of relevant terms and glossaries (UNISDR 2009; EC-Working Paper 2010; IOC 2013). We adopted such a discrimination between hazard, which is a potentially damaging or destruc- tive natural process or phenomenon, and risk as an expression of the natural event’s impact. On the other 1 Institute of Geodynamics, National Observatory of Athens, Athens, Greece. E-mail: ioannatriantafyllou@yahoo.gr Pure Appl. Geophys. Ó 2018 Springer Nature Switzerland AG https://doi.org/10.1007/s00024-018-1984-9 Pure and Applied Geophysics