Importance sampling of seismic tsunami sources with near-field emphasis for inundation PTHA: benchmarking with complete ensembles

• DOI: 10.1093/gji/ggaf034
• Publication Date: 2025-01-28T01:10:12Z
• Authors: A Abbate; G Davies; S Lorito; N Kalligeris; F Romano; R Tonini; M Volpe
• Keywords: Benchmarking; Emphasis (telecommunications)

Summary Site-specific Probabilistic Tsunami Hazard Assessment (PTHA) is a powerful tool for coastal planning against tsunami risk. However, its typically high computational demands led to the introduction of Monte Carlo Stratified Importance Sampling (SIS) approach, which selects representative subset scenarios numerical inundation simulations. We here empirically validate this sampling first time our knowledge, using an existing extensive dataset simulations two sites in Mediterranean Sea (Catania and Siracusa, both located Sicily, Italy). Moreover, we propose modified importance function prioritise seismic based on their arrival at offshore point near target site, addition wave amplitude occurrence rate as leveraged previous work. This applied separately each earthquake magnitude bin, allows denser near-field earthquakes whose variations tsunamis are very sensitive. compare confidence intervals PTHA estimates obtained with new original functions. Then, benchmark onshore functions calculated full set scenarios. also test assumption that random errors follow normal distribution, found previously case. As result benchmarks, find SIS approach works satisfactorily. Introducing additional factor enhances precision mean percentiles considered. With modification it possible deal efficiently heterogeneous sources involving deformation Catania regional crustal subduction sources. By comparing model (epistemic) uncertainty, optimal trade-off between number employed uncertainty can be found, even such complex situation. A relatively small scenarios, order few thousand, sufficient perform site-specific practical applications. These numbers correspond 4–8% already reduced ensembles used assessments same sites.