Probabilistic tsunami forecasting for earthquakes at global scale

Probabilistic Tsunami Forecasting (PTF) provides a rapid estimation of tsunami hazard intensity probabilities at given forecast points when a potentially tsunamigenic earthquake has occurred. According to predefined rules provided by the decision makers, PTF can also convert these values into uncertainty-informed alert levels that can be used in operational tsunami early warning or post-event actions for risk reduction (for example, evacuation). The PTF workflow is planned to become operational at the Italian Tsunami Warning Center (CAT-INGV) with a specific setting for delivering early warning messages in the Mediterranean area. Indeed, the PTF implemented for the CAT-INGV relies on the long-term hazard model NEAMTHM18 and on a large database of precomputed tsunami scenarios.

Here we present the first prototype of the PTF extension at global scale, where the ensemble of seismic scenarios is defined from scratch using real-time data (hypocenter and magnitude of the event) and moment tensor solutions provided by an ad hoc integrated tool and external agencies in quasi real time. Each source parameter is discretized within a given range of values around the provided solution and the corresponding uncertainties are assigned through weight distributions of these parametrizations. For each scenario, the initial sea floor displacement is computed based on a standard uniform rupture model. The corresponding tsunami impact is estimated using on-the-fly numerical simulations, requiring dedicated HPC resources.

This global-scale version of the PTF is here presented through the hindcast of two major megathrust events in the Pacific Ocean; the 2010 Mw 8.8 Maule, Chile and the 2011 Mw 9.1, Tohoku, Japan earthquakes and tsunamis.

This work was partially funded by the DT-GEO project (A Digital Twin for GEOphysical extremes, https://dtgeo.eu/) through the European Union’s Horizon Europe research and innovation programme under grant agreement nº 101058129.