Probabilistic Seismic Hazard Assessment (Psha) for the Territory of Uzbekistan

The research aims to contribute to the development of a more accurate and reliable local seismic hazard map that aligns with international standards. The assessment follows the probabilistic approach to evaluate ground motion levels at various observation sites within a study region, focusing on the probability of exceeding specific intensities over a given period (50 years). The process assumes each seismic source is independent and that earthquake occurrences follow a Poisson process. Each source is characterized by its geometric properties (size, location, orientation) and its temporal occurrence behavior (e.g., maximum magnitude, Gutenberg-Richter parameters). Geometric properties are derived from earthquake records, geological and tectonic data while temporal behaviors are calibrated from past seismicity using a comprehensive earthquake catalog. The maximum acceleration value across the map for the design return period, approximately 0.5g, was observed in the Gazli area, which is significantly higher than previous results. The maximum difference between the two alternative methods (classical integration and simulation-based) for the design return period was about 0.05g. The effect of the GMPEs (Ground Motion Prediction Equations) on the results is substantial, showing up to a 0.1g difference when they are changed. It is the first time that the seismic hazard for the region has been evaluated using a finer discretization of 5 km and employing various methodologies, including classical-integration and simulation-based approaches. Limited alternative version of models are used and therefore, the usage of the several alternative models and GMPEs would be beneficial to reduce epistemic uncertainty.