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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.

Subduction zones are the most seismically active regions in the world and hosted many great tsunamigenic earthquakes in the past, often with destructive coastal consequences. Hence, an accurate estimate of the tsunami forecast is crucial in Tsunami Early Warning Systems (TEWS) framework. However, the inherent uncertainties associated with the tsunami source estimation in real-time make tsunami forecasting challenging. In this study, we consider the South American subduction zone, where in the last 15 years occurred, three M8+ tsunamigenic earthquakes; in particular, we focus on the 2014 Mw 8.1 Iquique event.Here, we evaluate the variability of the tsunami forecasting for the Chilean coast as resulting i) from the coseismic slip model obtained by geophysical data inversion and ii) from an expeditious method for the tsunami source estimation, based on an extension of the well-known spectral approach. In the former method, we estimate the slip distribution of the 2014 Iquique earthquake by jointly inverting tsunami (DARTs and tide-gauges) and GPS data; we adopt a 3D fault geometry and Green’s functions approach.On the other hand, a set of stochastic slip models in the latter is generated through a Phase Variation Method (PVM), where realizations are obtained from both the wavenumber and phase spectra of the source.In the analysis, we also evaluate how the different physics complexity included in the tsunami modelling (e.g. by including dispersion or not) can be mapped into the tsunami forecasting uncertainty. Finally, as an independent check, we compare the predicted deformation field from the slip models (inverted or by PVM) with the RADARSAT-2 InSAR data.

The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has the primary responsibility for the seismic surveillance service of the Italian territory and the tsunami alert in the Mediterranean Sea.The activities in the monitoring room at the INGV National Earthquake Observatory headquarters in Rome (hereafter INGV-Rome), are carried on by two seismologists, one tsunami specialist and one technician/engineer who work in three shifts a day to provide monitoring service on a 24/7 basis. They calculate, as rapidly and accurately as possible, the location and size of all Italian earthquakes with M2.5+ and swiftly disseminate such information to emergency authorities, to government agencies, to the public and the media by different platforms (email, text message, and via Facebook and Twitter). Starting with hypocentral and magnitude parameters, the moment tensors, the historical seismicity map and the shakemaps are also published in (near) real time.In addition, the INGV-Rome monitoring room hosts the Italian Tsunami Alert Center (CAT-INGV). CAT-INGV is one of the Tsunami Service Providers acting in the North-eastern Atlantic, the Mediterranean and connected sea (NEAM) region of the Intergovernmental Oceanographic Commission (IOC)/UNESCO and is responsible for monitoring the seismicity of the Mediterranean Sea and disseminating tsunami alert messages to member States and EU agencies subscribing its services. The operation and the performance of the INGV monitoring system is ensured by a dedicated research and IT staff who facilitate real-time waveform acquisition and distribution, develop real-time seismic processing systems and new processing algorithms., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The accurate estimate of the tsunami forecast is crucial in Tsunami Early Warning Systems (TEWS) framework. However, the inherent uncertainties associated with the tsunami source estimation in real-time make tsunami forecasting challenging.In this study, we consider the South American subduction zone, one of the most seismically active regions in the world, where in the last 15 years occurred, three M8+ tsunamigenic earthquakes; in particular, we focus on the 2014 Mw 8.1 Iquique event.Here, we compare the tsunami forecasting for the Chilean coast as resultingi)from the coseismic slip model obtained by geophysical data inversion andii)from an expeditious method for the tsunami source estimation, based on an extension of the well-known spectral approach.In the former method, we estimate the slip distribution of the 2014 Iquique earthquake by jointly inverting tsunami waveforms and GPS data; on the other hand, a set of stochastic slip models in the latter is generated through a Phase Variation Method (PVM), where realizations are obtained from both the wavenumber and phase spectra of the source.We also evaluate how the different physics complexity included in the tsunami modelling (e.g. by including dispersion or not) can be mapped into the tsunami forecasting uncertainty. Finally, as an independent check, we compare the predicted deformation field from the slip models (inverted or by PVM) with the RADARSAT-2 InSAR data., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)