  Accurate and efficient tsunami modelling is essential for providing tsunami
forecasts and hazard assessments. Volna-OP2 is a finite volume solver of the
nonlinear shallow water equations and its capabilities of producing both faster
than real time ensembles and high resolution inundation studies are presented
here. The code is massively parallelised and can utilise various high
performance computing architectures. When an earthquake is detected there is
always some uncertainty on the source parameters. Generating a faster than real
time ensemble for maximum wave heights which captures this uncertainty would be
of great benefit to tsunami warning centres. The 2003 Boumerdes earthquake
(Algeria) acts as a test case for showing Volna-OP2's ability at rapidly
forecasting regional maximum wave heights. Drawing on various earthquake
sources proposed in the literature and scaling the magnitudes to mimic
uncertainty on the source, 20 separate earthquake realisations are simulated
for 4 hours real time in 97s on two Nvidia V100 GPUs. Further a reduced
ensemble of the Lisbon 1755 tsunami with an emphasis on the effects to the
Irish coastline is presented. Where again various earthquake sources have been
drawn from the literature and simulated on a regional scale. Finally, a pilot
study which builds upon the reduced ensemble results investigates the
inundation of a Lisbon tsunami on key sections of the Irish coastline. The
results of this pilot study highlight that the inundation is constrained to
low-lying areas with maximum run-up heights of $\approx 3.4m$ being found.
