Probabilistic Tsunami Hazard Analysis (PTHA) quantifies the likelihood of exceeding a specified measure of tsunami inundation at a given location within a given time interval. It provides scientific guidance for decision making regarding coastal engineering and evacuation planning. PTHA considers a discretization of the total hazard into many potential scenarios together with an evaluation of the probability of each scenario. Site-specific PTHA, with an adequate discretization of source scenarios, combined with high-resolution inundation modelling, has been out of reach with existing models and computing capabilities with tens to hundreds of thousands of moderately intensive numerical simulations being required. In recent years, more efficient GPU-based High-Performance Computing (HPC) facilities, together with efficient GPU-optimized shallow water type models for simulating tsunami inundation, have made a regional and local long-term hazard assessment feasible. PTHA is Pilot Demonstrator 7 (PD7) in ChEESE. The PD7 workflow operates in three main stages: i) site-specific source selection and discretization, ii) efficient numerical inundation simulation for each scenario using the GPU-based Tsunami-HySEA numerical tsunami propagation model, and iii) hazard aggregation. The PD7 workflow enables integration of large batches of tsunami simulations (typically tens to hundreds of thousands) carried out on Tier-0 systems, for quantifying probabilistic hazard. By aggregating the hazard, a much more fine-grained assessment compared to the previously available regional assessments can be produced. Through the PRACE project TsuHazAP, the capability of the PD7 workflow has been demonstrated on the Marconi100 Supercomputer.