Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

302 PATA Days 2024 Combining the probability distributions, the surface rupture condition is calculated for all the W intersecting the ground surface, and the CPSR is computed as the combination of the probabilities satisfying the surface rupture condition. R E S U LT S A N D D I S C U S S I O N S Here we provide the results obtained for reverse faults in Japan. The most representative value obtained for the D90 in the study area is 10 km. Thus, to calculate the analytical curves in Figure 1, we considered a seismogenic depth of 10 km with an uncertainty of 2 km. For the average dip angle, we considered a mean value of 40° and an uncertainty of 5°. To compute the HDD we employed a normal distribution to model the frequencies of hypocentral depths, which resulted in a mean of 0.74 and a standard deviation of 0.20. The analytical curves were computed ranging from magnitude 5 to magnitude 8. The analytical curves exhibit low rupture probabilities for smaller magnitudes (i.e., before magnitude 6 in Figure 1) and higher rupture probabilities for larger magnitudes (i.e., above magnitude 7 in Figure 1). The transition zone between these two steps (i.e., in between magnitude 6 and 7 in Figure 1) corresponds to W values that equal the fault source. These W values are derived from the scaling relations used and are magnitude-dependent. Thus, as a primary outcome, the analytical curves exhibit different results depending on the magnitude scaling relation used. This difference is related to the different methodology used by the authors to derive the empirical regressions and the different uncertainties provided for the calculation of W. Both analytical curves reach seismogenic crust saturation around magnitude 6.5. We compared the above results with the empirical regression compiled by Takao et al (2013), developed exclusively for faults in Japan (blue line in Figure 1). We observe a good agreement between the observed data and the theoretical model, with the analytical curve closely tracking the empirical curve. We conducted sensitivity tests considering different dip angles, seismogenic depths and scaling relations. As expected, increasing the dip angle leads to higher probability of surface rupture, for a given magnitude. Conversely, increasing the seismogenic thickness results in lower surface rupture probability. But the variation in seismogenic thickness has a much greater impact on CPSR compared to the variation in dip angle.