Seismic Design in Western Kentucky: Issues and Alternatives

Seismic hazard and risk are two very important concepts in engineering design and other policy considerations. Although seismic hazard and risk have often been used interchangeably, they are fundamentally different. Furthermore, seismic risk is more important in engineering design and other policy considerations. Seismic hazard assessment is an effort by earth scientists to quantify seismic hazard and its associated uncertainty in time and space and to provide seismic hazard estimates for seismic risk assessment and other applications. Although seismic hazard assessment is more a scientific issue, it deserves special attention because of its significant implication to society. Two approaches, probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA), are commonly used for seismic hazard assessment. Although PSHA has been proclaimed as the best approach for seismic hazard assessment, it is scientifically flawed (i.e., the physics and mathematics that PSHA is based on are not valid). Use of PSHA could lead to either unsafe or overly conservative engineering design or public policy, each of which has dire consequences to society. On the other hand, DSHA is a viable approach for seismic hazard assessment even though it has been labeled as unreliable. The biggest drawback of DSHA is that the temporal characteristics (i.e., earthquake frequency of occurrence and the associated uncertainty) are often neglected. An alternative, seismic hazard analysis (SHA), utilizes earthquake science and statistics directly and provides a seismic hazard estimate that can be readily used for seismic risk assessment and other applications.

Finland, which is characterized by very low seismicity, does not have a national seismic hazard map. However, site specific Probabilistic Seismic Hazard Assessments (PSHAs) for critical infrastructure, including nuclear power plants (NPPs), have been conducted. The sophisticated 2020 European Seismic Hazard Model (ESHM20) offers several advancements that could influence seismic hazard work in stable continental regions like Finland.  As part of the SEISMIC RISK collaborative project involving the University of Helsinki, VTT Technical Research Centre of Finland, and the Geological Survey of Finland, a national PSHA model has been developed. The model is based on a Fennoscandian earthquake catalogue – FENCAT, compiled from Nordic national catalogues based on the observations from the national seismic networks. This allows for calculation of the recurrence parameters with lower magnitudes than the ESHM20. Although a preliminary comparison reveals only minor local differences at hazard levels, a more detailed examination at critical infrastructure sites is necessary. We have compared the regional hazard results obtained within the SEISMIC RISK project and hazard values of the ESHM20 at two NPP sites in Finland. Four criteria from the literature, compiled by Douglas et al. (2023), were employed for assessing the differences between the seismic hazard models. To this end, the mean, median, and 16th and 84th fractiles for the ESHM20 were obtained from the European Facilities for Earthquake Hazard and Risk (EFEHR) database hosted by EPOS–Seismology. A visual inspection of the hazard curves initially indicated consistently higher mean hazards from the Finnish model at the NPP sites compared to ESHM20. The lognormal distributions of the hazard models were estimated, and the differences were assessed for the return periods of 106, 104, 5000, 2475, and 475 years using the four criteria. The distributions revealed a significantly smaller standard deviation for the Finnish model than for the ESHM20. When comparing the two models, the mean Annual Frequency of Exceedance (AFE) changed by over 25% for the ground-motions corresponding to AEFs ≤ 10-4 and by more than 35% for ground-motions corresponding to 10-6 AFE. These findings underline the significant differences between the models.  In summary, a minimum of two out of the four criteria are met at one of the NPP sites, and at the other NPP site, three out of four criteria are satisfied. This further highlights the significance of the differences between the ESHM20 and the Finnish hazard model. Nevertheless, while the observed change in hazard between the Finnish hazard model and the ESHM20 can be deemed substantial, it does not justify the use of the Finnish hazard model for the longer return periods. Further investigations, such as site-specific hazard assessments, are necessary for the return periods relevant to NPPs.        Douglas, J., Crowley, H., Silva, V., Marzocchi, W., Danciu, L., & Pinho, R. (2023). Methods for evaluating the significance and importance of differences amongst probabilistic seismic hazard results for engineering and risk analyses: A review and insights. EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-991 

Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study.

Fragility curves are useful tools for presenting the risk of structural damage from earthquakes as a function of a ground-motion parameter. Seismic hazard analysis for an area precedes the fragility analysis for structures built in that area. Many studies are available in the literature regarding probabilistic seismic hazard analysis (PSHA) and fragility estimation. However, a practical approach to integrate the hazard curve from PSHA and using the ground motion of that level to estimate fragility can be an area to explore further. In this study, an effort has been made to obtain peak ground acceleration (PGA) level at design-based earthquake (DBE) from PSHA. Based on this PGA value obtained, a fragility assessment has been performed. This study aims to obtain a fragility curve for a midrise RC frame building for DBE hazard level using PSHA. Three 6-story RC frame buildings are considered in this study for a seismically active zone in India. The buildings have been designed with the following performance objectives: (1) immediate occupancy (IO) with 1% drift, (2) life safety (LS) with 2% drift, and (3) collapse prevention (CP) with 3% drift. Incremental dynamic analysis (IDA) is performed using 22 numbers of far-field ground motions as prescribed by a strong ground-motion database to obtain the capacity of exceeding the respective drift limit states. Fragility curves for the three buildings are generated based on those capacities. The present study is a practical approach to capture the consequence of seismic hazard for an area and predicting the seismic risk.

Surat, the financial capital of Gujarat, India, is a mega city with a population exceeding five millions. The city falls under Zone III of the Seismic Zoning Map of India. After the devastating 2001 Bhuj earthquake of Mw 7.7, much attention is paid towards the seismic microzonation activity in the state of Gujarat. In this work, an attempt has been made to evaluate the seismic hazard for Surat City (21.170 N, 72.830 E) based on the probabilistic and deterministic seismic hazard analysis. After collecting a catalogue of historical earthquakes in a 350 km radius around the city and after analyzing a database statistically, deterministic analysis has been carried out considering known tectonic sources; a further recurrence relationship for the control region is found out. Probabilistic seismic hazard analyses were then carried out for the Surat region considering five seismotectonic sources selected from a deterministic approach. The final results of the present investigations are presented in the form of peak ground acceleration and response spectra at bed rock level considering the local site conditions. Rock level Peak Ground Acceleration (PGA) and spectral acceleration values at 0.01 s and 1.0 s corresponding to 10% and 2% probability of exceedance in 50 years have been calculated. Further Uniform Hazard Response Spectrum (UHRS) at rock level for 5% damping, and 10% and 2% probability of exceedance in 50 years, were also developed for the city considering all site classes. These results can be directly used by engineers as basic inputs in earthquake-resistant design of structures in and around the city.

Over the past two decades, seismic hazard modeling has advanced along two complementary frontiers: empirical probabilistic frameworks, which systematically capture uncertainty through statistical inference, and physics-based simulation platforms, which directly compute ground motions from the governing equations of wave propagation. This project seeks to unify these two worlds by developing an end-to-end integration between OpenQuake and CyberShake, thereby creating a new generation of seismic hazard models that are globally extensible, probabilistically complete, and physically consistent. CyberShake has been under active development for more than a decade, demonstrating its robustness and scientific maturity through extensive implementations in California. It performs a physics-based probabilistic seismic hazard analysis (PSHA), replacing traditional empirical Ground Motion Prediction Equations (GMPEs) with full 3D numerical simulations of seismic wave propagation. Built upon the UCERF2/3 Earthquake Rupture Forecasts, CyberShake computes hazard curves directly from synthetic seismograms generated via Strain Green’s Tensors and thousands of stochastic rupture variations. This approach enables non-ergodic, site-specific hazard estimation and has set a global benchmark for high-fidelity hazard computation. However, its application has remained geographically limited: both the ERF and 3D velocity models were designed specifically for California, requiring extensive datasets that are rarely available elsewhere. Conversely, OpenQuake, developed by the Global Earthquake Model (GEM) Foundation, provides a fully open-source, Python-based framework for probabilistic seismic hazard and risk analysis. It serves as the computational backbone of large-scale hazard models such as the European Seismic Hazard Model 2020 (ESHM20), which integrates decades of regional expertise into a unified and statistical representation. OpenQuake provides a complete probabilistic framework to build Earthquake Rupture Forecasts (ERFs) that combine declustered catalogs, background seismicity, and multi-branch logic trees, ensuring a balanced and uncertainty-aware representation of regional tectonics. Furthermore, its ecosystem extends seamlessly to vulnerability and exposure modules, enabling the translation of hazard into actionable risk assessments and resilience planning.This project will establish a direct pipeline from OpenQuake’s event-based results to the generation of an ERF compatible with CyberShake’s simulation framework, ensuring moment–rate consistency. By doing so, it will enable CyberShake simulations to be performed for regions beyond California, extending its use to Europe based on the knowledge contained in the ESHM20. The first pilot region is Istanbul, Turkey, a densely populated metropolis located near the western termination of the North Anatolian Fault. Our initial results show that the workflow is already functioning at the prototype level: we have developed a unified 3D velocity model for the Istanbul region by combining available tomographic models with local datasets; generated preliminary event-based rupture catalogs from ESHM20 using OpenQuake; and demonstrated early convergence behavior in hazard curves, indicating that the rupture sampling strategy is statistically robust. These initial results demonstrate the feasibility of the integration approach and indicate that the essential elements needed for a CyberShake-ready ERF are already in place.

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.ReferencesNekrasova A, Kossobokov V, Podolskaia E (2024) Regional seismic risk assessment based on the Unified Scaling Law for Earthquakes: The Lake Baikal railway system. Soil Dynamics and Earthquake Engineering 177, 108402. https://doi.org/10.1016/j.soildyn.2023.108402Panza G, Kossobokov V, De Vivo B, Laor E (Eds) (2021) Earthquakes and Sustainable Infrastructure: neo-deterministic (NDSHA) approach guarantees prevention rather than cure. Elsevier. Paperback ISBN: 9780128235034, eBook ISBN: 9780128235416, xxv, 672 p. https://doi.org/10.1016/C2020-0-00052-

The site-wide probabilistic seismic hazard analysis (PSHA) of the Hanford Site (hereafter Hanford PSHA) in southeastern Washington State was undertaken by Pacific Northwest National Laboratory (PNNL) and its contractors for the U.S. Department of Energy (DOE) Office of River Protection (ORP), DOE Richland Operations Office (RL), and Energy Northwest to provide a detailed characterization of the vibratory ground motion hazard at the Hanford Site from potential future earthquakes. The study was conducted to fulfill the requirements for DOE facilities as well as those for commercial nuclear power plants, through a collaboration and joint sponsorship between DOE and Energy Northwest. The study fulfills the requirement to develop an update to the PSHA as required by DOE Order. In addition, the study fulfills the requirement from the U.S. Nuclear Regulatory Commission (NRC) that Energy Northwest conduct a PSHA using Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 procedures for the Columbia Generating Station. Because the Hanford Site includes several facility sites, the PSHA has been conducted such that seismic hazard is calculated at five sites that are located across the Hanford Site.

To quantify the annual probability of earthquake ground motion (GM) exceeding a given threshold, the extensively used method named by probabilistic seismic hazard analysis (PSHA) can be adopted. The PSHA software made this method more effortless for estimating earthquake hazards for a seismic site. The main motivation of the PSHRisk-tool is to evaluate the PSHA by a user-friendly graphical interface as well as identify the intensities of GM, which will contribute to the most vulnerable condition for the infrastructure. This python-code based tool can demonstrate the source identification, probability distribution plot of magnitude and distance, formulate the hazard curve according to almost all ground motion prediction equations (GMPEs). The deaggregation for each intensity measure (IM) and the effect of seismic parameters in each GMPE can also be determined. Alongside this, the combination of the failure frequency and the hazard analysis for identifying risk assessment separates this tool from the other existing PSHA software. Accurate verification with analytical and existing test models and a case study inspires its acceptance rate. However, with the quickest and easiest way users can determine the seismic hazard analysis for any location. Failure risk analysis can be evaluated simply based on the structural failure parameters.

A strong earthquake occurred on November 12, 2017, in Sarpol-e Zahab city, western Iran, with the moment magnitude ( $$M_{{\text{w}}}$$ ) of 7.3 and a focal depth of 18 km. The maximum horizontal peak ground acceleration of 0.69 g was recorded at the Sarpol-e Zahab station. Significant damages were observed in frame and masonry buildings, while the damage distribution was non-uniform throughout this small city. The preliminary site reconnaissance revealed that numerous engineering structures collapsed or considerably damaged in some regions, contrary with those non-structural masonry buildings in other regions which remained intact during earthquake. This paper represents a preliminary reconnaissance report prepared through the site visit done by the authors, a few days following the earthquake occurrence. Then, the data recorded by the strong ground motion stations in the affected city and the surrounding regions together with the geotechnical data gathered from the available boreholes in Sarpol-e Zahab are incorporated for probabilistic seismic hazard and local site effect analyses. The observed response spectra at two stations and distance-dependency of ground acceleration are compared with those predicted by some attenuation models. The results of probabilistic seismic hazard analysis in the return periods of 475 and 2475 years are compared with the observed ground response and the design spectra recommended by the Iranian seismic code (for site classes Types I and II). Several geotechnical boreholes from the previous works in the affected area were analyzed through the equivalent-linear site response approach in order to obtain the seismic response at the soil surface. The results are then compared with the code design spectra for the site classes of Types III and IV. It is demonstrated that the calculated response spectra are generally larger than those recommended by the Iranian seismic code, especially for the 4–7 stories buildings.

A probabilistic seismic hazard analysis (PSHA) determines the probability rate of exceeding of various levels of ground motion in a specified period of time, in a given area. On the other hand, the neo-deterministic seismic hazard assessment (NDSHA) is based on modeling techniques, developed from physical knowledge of the seismic source process and of the propagation of seismic waves, which can realistically simulate the ground motion due to an earthquake by means of synthetic seismograms. The NDSHA confirms that peak ground acceleration values are larger than those given by the PSHA in areas where large earthquakes are observed and in areas identified as prone to large earthquakes, such as in the case of the city of Catania (Italy). The city of Catania, located on the eastern part of Sicily, is one of the most seismically active areas of Italy. The Val di Noto earthquake of January 11, 1693 is considered one of the biggest earthquakes which occurred in Italy. Site response analyses have been developed for a group of 3 test sites in the city of Catania (Italy). On the sites are localised some strategic buildings to upgrade against seismic risk. The analysis of seismic ground response at the sites was conducted using a numerical method, which is developed in three main phases: the definition of the geometric, geological and geotechnical model of the subsurface, the definition of the seismic input (synthetic or recorded), the choice of one or more computer codes to use and process the results. The reconstruction of the geological and geotechnical model of the subsurface has highlighted a morphology quite irregular especially with regard to the covers. One-dimensional local site response analyses have been performed assuming that all geologic boundaries are horizontal and the response of soil deposits is predominantly caused by waves propagating vertically from the underlying bedrock. Equivalent linear analysis using EERA code has been performed in this study. One of the targets of the paper is the development of measures for the seismic retrofitting of buildings.Seismic retrofitting and/or improving have to be definitely considered a multidisciplinary subject, which depends in fact on many factors, such as: local site effects and the dynamic interaction between the foundation soil and the structure. The accurate investigation on the structure and the surrounding soil is the first fundamental step for a realistic evaluation of the structure seismic performance.

The Korea Atomic Energy Research Institute (KAERI) is conducting a five-year research project to develop a realistic seismic risk evaluation system which includes the consideration of aging of structures and components in nuclear power plants (NPPs). The KAERI research project includes three specific areas that are essential to seismic probabilistic risk assessment (PRA): (1) probabilistic seismic hazard analysis, (2) seismic fragility analysis including the effects of aging, and (3) a plant seismic risk analysis. Since 2007, Brookhaven National Laboratory (BNL) has entered into a collaboration agreement with KAERI to support its development of seismic capability evaluation technology for degraded structures and components. The collaborative research effort is intended to continue over a five year period. The goal of this collaboration endeavor is to assist KAERI to develop seismic fragility analysis methods that consider the potential effects of age-related degradation of structures, systems, and components (SSCs). The research results of this multi-year collaboration will be utilized as input to seismic PRAs. This report describes the research effort performed by BNL for the Year 4 scope of work. This report was developed as an update to the Year 3 report by incorporating a major supplement to the Year 3 fragility analysis. In the Year 4 research scope, an additional study was carried out to consider an additional degradation scenario, in which the three basic degradation scenarios, i.e., degraded tank shell, degraded anchor bolts, and cracked anchorage concrete, are combined in a non-perfect correlation manner. A representative operational water level is used for this effort. Building on the same CDFM procedure implemented for the Year 3 Tasks, a simulation method was applied using optimum Latin Hypercube samples to characterize the deterioration behavior of the fragility capacity as a function of age-related degradations. The results are summarized in Section 5 and Appendices G through I.

Gwadar City is located at the coastline of Pakistan. The city is currently in a phase of development, which is expected to become a future economic hub for Pakistan. This has led us to choose Gwadar for seismic hazard evaluation. Seismic hazard analysis for Gwadar is carried out using deterministic and probabilistic seismic hazard analysis techniques. The present study will help in sustainable development of a future large city and economic hub for Pakistan on ways of coping from a major threat of earthquake hazard. In deterministic seismic hazard analysis, line sources were identified close to Gwadar. Based on the analysis of maximum magnitude and closest distance (worse conditions), Makran subduction zone was identified out of all the line sources with earthquake potential of 8.2 at a distance of 30 km. This yielded a peak ground acceleration value of 0.38 g for Gwadar City. In second phase, probabilistic seismic hazard analysis technique with the area source modeling was adopted to acquire results at different return periods. For this purpose, seismic data were collected from the Pakistan Meteorological Department and International Seismological Center (2010) databases for development of a comprehensive data catalog. The a and b values were obtained using regression analysis for each source zone, and probabilistic analysis yielded the results of 0.34 g for a return period of 500 years. As per building codes of Pakistan, areas or cities with ground acceleration greater than 0.32 g are considered in seismic zone 4, and both deterministic and probabilistic hazard analysis place the city in seismic zone 4. These values correspond to rock site with shear wave velocity of 760 m/s.

Asymptotic behavior of seismic hazard curves

Chhattisgarh, located in Central India, has been carved out of Madhya Pradesh to become the 26th state of the Indian Union. North Chhattisgarh is addressed by the tribal population. In the current study, an endeavor has been made to carry out the seismic hazard analysis for the major district headquarters of north Chhattisgarh, considering the local site effects and developing a seismic zone map for north Chhattisgarh. Seismic hazard analysis has been done for major district headquarters Ambikapur, Baikunthpur [Koria], Korba, and Jashpurnagar of north Chhattisgarh, using seismotectonic information. All earthquake sources and past seismic events have been considered within a radius of 300 km for the headquarters, applying deterministic and probabilistic seismic hazard analysis approaches. The seismic parameters and peak ground acceleration at the bedrock level for the district headquarters of north Chhattisgarh have been estimated. Using probabilistic seismic hazard analysis, hazard curves have been developed for each district headquarters. Alternatively, for peak ground acceleration of 0.05 g, 0.1 g, and 0.15 g return periods have been estimated for the study area. The probabilities of exceedance for 2% and 10% for 50 years have also been estimated for the study area. The current study throws light on the design and construction of vital civil engineering structures near and around the seismically active headquarters in northern Chhattisgarh.