Panel 5 focused on tsunami flooding with an emphasis on Probabilistic Tsunami Hazard
Analysis (PTHA) as derived from its counterpart, Probabilistic Seismic Hazard Analysis (PSHA)
that determines seismic ground-motion hazards. The Panel reviewed current practices in PTHA
and determined the viability of extending the analysis to extreme design probabilities (i.e., 10-4
to 10-6). In addition to earthquake sources for tsunamis, PTHA for extreme events necessitates
the inclusion of tsunamis generated by submarine landslides, and treatment of the large
attendant uncertainty in source characterization and recurrence rates. Tsunamis can be caused
by local and distant earthquakes, landslides, volcanism, and asteroid/meteorite impacts.
Coastal flooding caused by storm surges and seiches is covered in Panel 7. Tsunamis directly
tied to earthquakes, the similarities with (and path forward offered by) the PSHA approach for
PTHA, and especially submarine landslide tsunamis were a particular focus of Panel 5.