A comparison of the seismic risk assessment for the Lake Baikal railway system based on standard probabilistic and neo-deterministic approaches

Abstract

Seismic hazard assessment (SHA) and evaluation of seismic risks (SRs) require an adequate understanding of the actual distribution of earthquakes over magnitude, space, and time ranges. The standard probabilistic seismic hazard analysis (PSHA) has never been subjected to unbiased scrutiny before publication of the final maps, which are misleading to unacceptable human and economic losses; this has been proven on many occasions, including the most recent cases – 6 February 2023 (Turkey), 8 September 2023 (Morocco), and 1 January 2024 (Japan).  Neo-deterministic seismic hazard assessment (NDSHA) methodologies have been developed to improve the reliability and accuracy of reproducible seismic hazard maps. In the last decade, the application of NDSHA in many regions of the world has confirmed the availability of reliable and effective input for mitigating earthquake risks (Panza et al., 2021). NDSHA results have passed intensive testing by historical evidence and realistic modelling of scenario earthquakes. We used two agents of the NDSHA synergy, i.e. Unified Scaling Law for Earthquakes (USLE) and anisotropic propagation of seismic effect, to evaluate SRs for the Lake Baikal regional railroad system on the basis of seismic hazard maps of maximum macroseismic intensity expected in 50 years with 10%, 5%, and 1% chance of exceedance. Specifically, we employed the regional layers from the widely used crowdsourced dataset, Open Street Map, which features global coverage. These layers include infrastructure elements such as tracks, bridges, and tunnels. We have extended our analysis of seismic risk assessment for the Lake Baikal Region railway system presented earlier (Nekrasova et al., 2024) and compare our results with the SR evaluations based on the General Seismic Zonation 2016 and Global Earthquake Model 2018 final hazard maps at identical levels of probability of exceedance. A comparison of PSHA and NDSHA approaches in application to the Lake Baikal railway system disclose significant overestimation of the reconstruction costs for expected state of extreme damage (Hazus state standard ds5 - Complete) due to earthquakes, if GSZ2016 or GEM2018 and not USLE modelling is used. In particular, the significant discrepancy in the area of expected ground shaking of macroseismic intensity VIII or higher that may damage the railroad tracks, bridges, and tunnels leads to a dramatic difference in the seismic risk values measured in arbitrary units of currency. Our results are presented for academic purposes only. Evidently, more adequate though significantly more complex procedures involving more complicated procedures of convolution of seismic hazard, exposures, and their vulnerability are required when addressing realistic and practical assessment of seismic risks. Such assessments should involve experts in seismology, earthquake engineering, social sciences, and economics.