A sanity check for earthquake recurrence models used in PSHA of slow deforming regions: the case of SW Iberia

Abstract. Probabilistic Seismic Hazard Assessment (PSHA) is the most common tool used to decide on the acceptable seismic risk and corresponding mitigation measures. We propose two consistency tests to address the variability of earthquake generation models found in PSHA studies: i) one rule-of-thumb test where the seismic moment release from the model is converted to an average slip on a typical fault and compared with known plate kinematics or GNSS deformation field; ii) using a neotectonic model, the computed deformation is converted into seismic moment release and to a synthetic earthquake catalogue. We apply these tests to the W and SW Iberia slow deforming region, where two earthquake source areas are investigated: 1) the Lower Tagus Valley, one of the largest seismic risk zones of Portugal; and 2) the offshore SW Iberia area, considered to be the source for the 1^st November 1755 event (M~8.7). Results show that some of the earthquake source models should be considered as suspicious, given their high/low moment release when compared to the expected values from GNSS observations or neotectonic modelling. In conclusion, PSHA studies in slow deforming regions should include a similar sanity check on their models' evaluation, downgrading the weight of poorly compliant models.