Time-dependent earthquake and tsunami hazard scenarios for the Adriatic region

During the last two decades, an operational procedure for time-dependent seismic hazard scenarios has been developed, which integrates fully formalized and validated earthquake forecasting information from pattern recognition analysis (e.g. by CN algorithm), with the realistic modelling of earthquake ground motion by the neo-deterministic approach (NDSHA). The proposed methodology permits to define, both at regional and local scale, a set of scenarios of ground motion for the time interval for the time interval in which a strong event is likely to occur within the alerted areas. When dealing with offshore large earthquakes occurrence, this integrated approach can be naturally extended to the definition of time-dependent tsunami scenarios, based on physical scenario models of tsunami waves.

CN forecasts for the Italian territory and its surroundings, as well as the corresponding time-dependent ground motion scenarios associated with the alarmed areas, are regularly updated since about two decades (Peresan, 2018, Geophysical Monograph Series, 234, pp. 149–172 and references therein). We review the results obtained so far by rigorous prospective testing of the developed procedure, including analysis of the statistical significance of issued forecasts. Special emphasis is placed on the recent earthquakes that occurred in the Adriatic region, which support validation of the applied methodologies, and evidence the opportunity of developing time-dependent tsunamis scenarios, by integrating forecast information with the modelling of tsunami waves propagation.

In this study, tsunami modelling is performed by the NAMI DANCE software (Yalciner et al., 2006, Middle East Technical University, Ankara, Turkey), which allows us accounting for seismic source properties, variable bathymetry, and non-linear effects in waves propagation. Urban scale hazard scenarios for selected coastal sites are developed considering different potential tsunamigenic sources of tectonic origin, located in the Central and Southern Adriatic Sea. The results from parametric studies accounting for possible sources related to historical events, as well as for yet unobserved extreme events, are considered for this purpose. Their verification against recent earthquakes, allows us assessing the relevance of space-time information and uncertainties on source parameters, and their possible operational contribution towards effective tsunami warning system for the Adriatic Sea and in the whole Mediterranean area.