Comparison of Seismic Hazard Assessments Obtained with the Probabilistic and Probabilistic-Deterministic Approaches for the Territory of Uzbekistan

The study compares seismic hazard assessments of the territory of Uzbekistan, obtained with the same input parameters, but using different methodological approaches: the Riznichenko approach based on the theory of macroseismic and spectral-time shaking and the classical Cornell probabilistic approach based on the full probability theorem. As seismic source models, linearly extended sources (seismogenic zones) and area sources (quasi-uniform seismological provinces) were considered. The authors used a number of their own damping dependences, established from analysis of isoseismic earthquake patterns in Central Asia, when assessing the seismic hazard of the study area in terms of macroseismic intensity, along with the Shebalin dependence, obtained from global data (I = 1.5M – 3.5 log R + 3). To estimate seismic hazard in engineering seismic indicators, the dependences built into the R-CRISIS software package, developed over the past 10–12 years for shallow active crust and stable regions, were used as the ground motion equation. For a 50-year seismic impact nonexceedance probability P = 0.90, the maximum differences in seismic hazard assessments using the two considered approaches for the entire seismically active part of the study area are ∆I = 0.39; for P = 0.95, ∆I = 0.54; for P = 0.98, ∆I = 0.61; and for P = 0.99, ∆I = 0.76. A similar comparison of seismic hazard assessments in the values of maximum ground motion accelerations leads to the following figures: for P = 0.90, ∆a_max = 75 cm/s²; for P = 0.95, ∆a_max = 111 cm/s²; for P = 0.98, ∆a_max = 167 cm/s²; for P = 0.99, ∆a_max = 273 cm/s².