# MCPSHA: A New Tool for Probabilistic Seismic Hazard Analysis Based on Monte Carlo Simulation
## 4 Results and Analyses
### Estimation of the Probability of an Earthquake Intensity  
Using the method described in this paper, 1,000,000 groups of simulated earthquake catalogs over the next 50 years are generated. Figure 10 shows the distribution of earthquake epicenters (\(5.0\leq\mathrm{M}\leq 8.5\)) in 1 group of simulated earthquake catalogues in the next 50 years.  
Figure 10: The distribution of earthquake epicenters (\(5.0\leq\mathrm{M}\leq 8.5\)) in 1 group of simulated earthquake catalogues in the next 50 years. (**a**) Distribution of research area scope. (**b**) The distribution of earthquake epicenters in 1 group and spatial distribution maps of seismic zones.  
Figure 9: Parameter test of the simulated earthquake catalogue ((**a**) \(b\)-value distribution of each simulated earthquake catalogue in different seismic belts, (**b**) \(V_{h}\) distribution of each simulated earthquake catalogue in different seismic belts).  
Using a grid size of 0.05\({}^{\circ}\)\(\times\) 0.05\({}^{\circ}\), we compute the seismic intensity for the Baoji area at a specific hazard level. Macro-seismic intensity uncertainty is randomly drawn from a distribution with a mean of zero and a standard deviation of 0.574, truncated at two standard deviations. Figure 11 illustrates the mean intensity incidence rates for VI, VII, and VIII sites in the region over 50 years based on Equation (18). The results reveal the lowest incidence rate in the northeast and the highest in the northwest. One contributing factor may be the presence of more tectonic feature zones with a \(m_{uz}\) greater than 7.5 in the northwest, as compared to the northeast and southeast of Baoji city.  
Figure 12 displays the variation in intensity with the probability of occurrence and exceedance over 50 years in the region, calculated using our program. Notably, the difference between the two probabilities is more pronounced at intensity levels VI-VII, whereas at intensity level VIII, the difference is smaller.  
Figure 13 illustrates a comparison of the mean curves for the two probabilities (VI, VII, and VIII) in the region. The results reveal that as the intensity value increases, the disparity between the two gradually diminishes. Baoji is categorized as a moderate earthquake area, where occurrences of intensity above VIII are infrequent, and the occurrence probability of the intensity aligns closely with the extreme probability of the intensity value. However, in seismic loss estimation, specific regions necessitate individualized analysis owing to their diverse tectonic environments to determine their fundamental consistency. Despite minor distinctions, these differences may still introduce deviations in the evaluation results. Therefore, in the context of general seismic damage loss estimation, the exceedance probability of intensity cannot substitute for the occurrence probability of intensity.  
Figure 11: The mean activity rate of intensity equals VI, VII, and VIII in the region in 50 years. ((**a**) the mean activity rate of intensity equals VI; (**b**) the mean activity rate of intensity equals VII; (**c**) the mean activity rate of intensity equals VIII).  
Figure 12: Different intensity with probability in 50 years. (**a–c**) show the intensity VI, VII, and VIII with the probability of occurrence in the region; (**d–f**) display the intensity VI, VII, and VIII with the probability of exceedance in the region.  
Figure 13: Comparison of the two probabilities for each intensity in the region.