Central And Eastern United States Research Articles

The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States

We update the ground-motion characterization for the 2023 National Seismic Hazard Model (NSHM) for the conterminous United States. The update includes the use of new ground-motion models (GMMs) in the Cascadia subduction zone; an adjustment to the central and eastern United States (CEUS) GMMs to reduce misfits with observed data; an updated boundary for the application of GMMs for shallow, crustal earthquakes in active tectonic regions (i.e. western United States (WUS)) and stable continental regions (i.e. CEUS); and the use of improved models for the site response of deep sedimentary basins in the WUS and CEUS. Site response updates include basin models for the California Great Valley and for the Portland and Tualatin basins, Oregon, as well as long-period basin effects from three-dimensional simulations in the Greater Los Angeles region and in the Seattle basin; in the CEUS, we introduce a broadband (0.01- to 10-s period) amplification model for the effects of the passive-margin basins of the Atlantic and Gulf Coastal Plains. In addition, we summarize progress on implementing rupture directivity models into seismic hazard models, although they are not incorporated in the 2023 NSHM. We implement the ground-motion characterization for the 2023 NSHM in the US Geological Survey’s code for probabilistic seismic hazard analysis, nshmp-haz-v2, and present the sensitivity of hazard to these changes. Hazard calculations indicate widespread effects from adjustments to the CEUS GMMs, from the incorporation of Coastal Plain amplification effects, and from the treatment of shallow-basin and out-of-basin sites in the San Francisco Bay Area and Los Angeles region, as well as locally important changes from subduction-zone GMMs, and from updated and new WUS basins.

Anomalous Crustal Stress in the Eastern Tennessee Seismic Zone

AbstractThe eastern Tennessee seismic zone (ETSZ) experiences the second highest rates of natural seismicity in the central and eastern United States (CEUS), following the New Madrid area, yet the cause of elevated earthquake rates is unknown. We probe the origin of ETSZ seismicity using geomechanically constrained stress inversions of earthquake focal mechanisms from 57 earthquakes, including 24 newly derived here and five from the recent events not used in the previous stress studies. Highly oblique northwest–southeast (NW–SE) extension that is unique in the CEUS dominates the ETSZ—central Alabama to southeastern Kentucky—and preferentially reactivates normal to strike-slip faults in the northeast (NE) and southwest (SW) quadrants (strikes 018°–086° or 196°–272° and dips 55°–90°). This extension cannot be explained by the compressive tectonic plate-boundary tractions that cause oblique NE–SW contraction elsewhere in the CEUS. Although our analyses do not uniquely determine the origin of the anomalous stress, we favor isostatic disequilibrium, due to anything from surface processes to crust–mantle interactions, as the possible cause. Increased long-term seismic hazard in the ETSZ may be controlled by and confined to the spatial extent of this anomalous seismotectonic state.

A seismological method for estimating the long-period transition periodTLin the seismic building code

Many changes have been made to the design response spectrum used in the ASCE 7 Standard in recent years. One parameter that has not been investigated or revisited since its first appearance in FEMA 450-1/2003 is the long-period transition period parameter, TL. The long-period transition period parameter was introduced and defined as the corner period that marks the transition from the constant velocity to the constant displacement segments of the design response spectrum. The long-period transition period parameter is primarily important for long-period structures such as high-rise buildings and bridges. The most current estimation of TLused in engineering design standards is loosely based on a correlation between modal magnitude Mwand TLthat does not account for stress drop Δ σ or the crustal velocity in the source region β. This study aims to include both Δ σ and β in its estimation of TL. Modal magnitude is obtained from disaggregation data from the 2018 National Seismic Hazard Model (NSHM) for the conterminous United States (CONUS) and from the 2021 NSHM for Hawaii (HI). The parameter β is determined from previous literature. Then, inversion of ground motion models for Central and Eastern United States (CEUS) is used to determine Δ σ for CEUS events, and published information is used to determine Δ σ for Western United States (WUS) events and HI events. Then, the definition of the corner period is used to determine TL. The results yield a generally more conservative (or longer) estimation of TLthan the estimation that is currently used in engineering design standards.

Seismic Anisotropy Tomography and Mantle Dynamics of Central‐Eastern USA

AbstractWe present high‐resolution 3‐D tomographic models of isotropic P‐wave velocity (Vp), azimuthal anisotropy, and radial anisotropy down to 1,300 km depth beneath the central and eastern United States (CEUS), which are obtained by inverting a great number of local and teleseismic data and making a whole‐mantle correction to teleseismic travel‐time data recorded by the USArray. Trade‐offs between azimuthal and radial anisotropies occur due to the correlation between the azimuthal and incidence angles of seismic rays, but the use of uniform and crisscrossing rays can reduce the trade‐off effect. Our tomographic images reveal the North American Craton with layered anisotropy and strong anisotropies in the lower mantle related to the deeply subducted Farallon slab and passage of the Bermuda hotspot. In the upper mantle, low‐velocity anomalies with significant seismic anisotropy are revealed beneath three intraplate seismic zones in New Madrid, East Tennessee, and South Carolina, suggesting that hot and wet mantle upwelling occurs under the seismic zones, and the related fluids affect the earthquake generation. The most important dynamic processes in the mantle beneath the CEUS are the deep subduction of the Farallon plate and the passage of the Bermuda hotspot, which have caused strong structural heterogeneities, seismic anisotropy, as well as thermal anomalies and fluids that contributed to the formation of intraplate seismic zones in the CEUS.

Revised Earthquake Geology Inputs for the Central and Eastern United States and Southeast Canada for the 2023 National Seismic Hazard Model

AbstractIt has been about a decade since updates to seismic and fault sources in the central and eastern United States (CEUS) were last assessed for the 2012 Central and Eastern United States Seismic Source Characterization for nuclear facilities (CEUS-SSCn) and 2014 U.S. Geological Survey National Seismic Hazard Model (NSHM) for the conterminous United States. In advance of the 2023 NSHM update, we created three related geospatial databases to summarize and characterize new fault source information for the CEUS. These include fault section, fault-zone polygon, and earthquake geology (fault slip rate, earthquake recurrence intervals) databases that document updates to fault parameters used in the prior seismic hazard models in this region. The 2012 CEUS-SSCn and 2014 NSHM fault models served as a foundation, as we revised and added fault sources where new published studies documented significant changes to our understanding of fault location, geometry, or activity. We added nine new fault sections that meet the criteria of (1) a length ≥7 km, (2) evidence of recurrent Quaternary tectonic activity, and (3) documentation that is publicly available in a peer-reviewed source. The prior CEUS models only included six fault sections (sources) and 10 fault-zone polygons (previously called repeating large-magnitude earthquake [RLME] polygons). The revised databases include 15 fault sections and 12 fault-zone polygons. Updates to the faults constitute a 150% increase in fault sections, and two additional fault-zone polygons, although some fault-zone polygons differ from RLME polygons used in the prior models. No faults were removed from the past models. Several seismic zones and suspected faults were evaluated but not included in this update due to a lack of information about fault location, geometry, or recurrent Quaternary activity. These updates to the fault sections, fault-zone polygons, and earthquake geology databases will inform fault geometry and activity rates of CEUS sources during the 2023 NSHM implementation.

Crustal Seismic Attenuation of the Central United States and Intermountain West

AbstractSeismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) attenuation tomography across a region that stretches from the CEUS across the Rocky Mountains to the Basin and Range using a total of 115,870 amplitude measurements from 106 earthquakes recorded on 544 stations across five frequency bands spanning 0.5–16 Hz. Similar to previous studies, we find higher attenuation in the WUS (Q0 ∼ 190) than the nominally CEUS (Q0 ∼ 250) and comparatively high attenuation on the Gulf Coast (Q0 ∼ 175). Our models defy simple east versus west regionalization, however. Heterogeneity within the Rocky Mountain region—low attenuation in the Colorado Plateau interior and Wyoming Craton (Q0 ∼ 230) compared to high attenuation in the southern Rockies (Q0 ∼ 110)—exceeds the gross differences between the CEUS and western United States. These province‐scale patterns are readily interpreted in terms of intrinsic attenuation. The boundary between the Colorado Plateau and Basin and Range hosts the highest attenuation imaged in the study area (Q0 ∼ 90), consistent with localized scattering across contrasting crustal structure. Focused high attenuation in the southern Rockies may represent the effects of represent in situ partial crustal melt. Within the CEUS, second‐order bands of comparatively high attenuation align with the Proterozoic Yavapai‐Mazatzal suture zone and Midcontinent Rift. This complex attenuation structure defies broad regionalization and suggests a need for path‐specific models near these boundaries and for critical infrastructure.

Understanding the seismic response of electrical equipment subjected to high–frequency ground motions

Ground motion studies in Central and Eastern United States (CEUS) show that the ground motion response spectra exceeds design spectrum of nuclear power plants in high–frequency range. To ensure safe shutdown of nuclear power plants in events where design spectrum is exceeded, the safety–related digital control systems and electrical equipment such as relays must be seismically qualified for high–frequency ground motions. Conventionally, uncoupled linear analysis of building and electrical cabinet is conducted and then seismic demands on equipment are evaluated. The conventional analysis ignores effects of various factors such as geometric nonlinearities, mass interaction between primary (building) and secondary (electrical cabinet) systems, etc. Ignoring such factors leads to unnecessarily high seismic demands on equipment. In this study, the seismic demands on equipment are evaluated by conducting both coupled and uncoupled analysis of linear primary system and linear as well as nonlinear secondary system. Various cases are analyzed where at least one mode of primary system is tuned with one mode of secondary systems. Each case is subjected to both low–frequency and high–frequency ground motions to compare the difference in response to each ground motion. The seismic demands on equipment are compared for coupled and uncoupled analysis as well as for linear and nonlinear systems. The results show reduction in seismic demands on electrical equipment for various nonlinear coupled analysis cases. The high seismic demands evaluated from linear uncoupled analysis may lead to exclusion of some electrical equipment which can be avoided by conducting coupled nonlinear analysis of primary–secondary systems and obtaining the realistic seismic demands on equipment.

Seismic risk assessment for the CEUS nuclear power plant fleet based on the NGA-East ground motion model

Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical fields. This presents challenges to stability and decision-making concerning safety that require effective assessment tools. Updated mean hazard estimates were developed at nuclear power plant (NPP) sites in Central and Eastern United States (CEUS) using the Next Generation Attenuation (NGA)-East ground motion model (GMM) and the latest available site amplification data. These estimates indicated that seismic hazard increases at several CEUS NPP sites, especially for spectral frequencies below 5 Hz. To assess the safety implications, updated mean seismic core damage frequency (SCDF) estimates were developed for the CEUS NPP fleet using the updated mean hazard estimates and updated plant-level fragilities (PLFs). The PLFs were developed from plant-specific information compiled by the U.S. Nuclear Regulatory Commission (USNRC) and recent seismic probabilistic risk assessments (SPRAs) completed by some NPPs. The SCDF quantification followed a method defined by the USNRC to combine risk contributions from different spectral frequencies. While not intended to provide a precise quantification of risk, such as that provided by a full SPRA, when the results are compared against other estimates using the same approach, this process provides valuable insight into the overall change in risk as the understanding of hazard changes. The assessment indicated no significant change in estimated risk for the majority of the CEUS fleet compared to the 2010 USNRC estimates—about 90% of the fleet risk distribution was lower, equal, or slightly higher. A few NPPs had SCDF estimates significantly larger than the 2010 estimates. The SCDF increases at these few NPPs have larger contributions from updated PLFs than updated hazard estimates. The majority of these NPPs have recently completed detailed SPRAs and have tools to develop more accurate estimates of the updated risk than can be achieved in this fleet-level study.

A ground-motion prediction model for small-to-moderate induced earthquakes for Central and Eastern United States

This study presents a new ground motion model (GMM) for small-to-moderate potentially induced earthquakes for Central and Eastern United States (CEUS). We used a hybrid empirical model as the base model, which was developed and calibrated for tectonic events in Central and Eastern North America (CENA) as part of the Next-generation Attenuation-East (NGA-East) project. We calibrated the base model using a comprehensive database of potentially induced ground motions with smaller magnitudes and shallower depths than tectonic earthquakes, excluding all earthquake events and stations within the Gulf Coast region. We determined the model functional form coefficients using a mixed-effect regression procedure. The proposed GMM is derived for the peak ground acceleration and response-spectral ordinates at periods ranging from 0.01 to 10.0s, moment magnitudes ranging from 3.0 to 5.8, and hypocentral distances up to 200km. The performance of the proposed GMM is evaluated through a set of comprehensive residual analyses. Furthermore, we compared the proposed GMM with recently published GMMs with the observed data for CEUS. The proposed GMM could apply in long-term and short-term US Geological Survey National Seismic Hazard Maps and for the hazard evaluation of induced seismicity.

NGA-East ground-motion characterization model Part II: Implementation and hazard implications

As a companion article to Goulet et al., we describe implementation of the NGA-East ground motion characterization (GMC) model in probabilistic seismic hazard analysis (PSHA) for sites in the Central and Eastern United States (CEUS). We present extensions to the EPRI/DOE/NRC seismic source characterization (SSC) model for the CEUS needed for full implementation of NGA-East. Comparisons are presented to the EPRI GMC, the currently accepted model by the U.S. Nuclear Regulatory Commission for hazard assessment at nuclear facilities. Comparisons are presented both in terms of GMC model components and in the resulting seismic hazard assessments for a range of site locations in the CEUS. Illustrations of the effect of various components of the NGA-East GMC on seismic hazard results are also presented. Finally, we present recommendations for application of the NGA-East GMC in PSHA.

The 2018 update of the US National Seismic Hazard Model: Ground motion models in the western US

The U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous U.S. NSHM includes significant changes to the underlying ground motion models (GMMs), most of which are necessary to enable the new multi-period response spectra (MPRS) requirements of seismic design regulations that use hazard results for 22 spectral periods and eight site classes. This article focuses on the GMMs used in the western United States (WUS) and is a companion to a recent article on the GMMs used in the central and eastern United States (CEUS). In the WUS, for crustal and subduction earthquakes, two models used in previous versions of the NSHM are excluded to provide consistency over all considered periods and site classes. To more accurately estimate ground motions at long periods in the vicinity of Los Angeles, San Francisco, Salt Lake City, and Seattle, the 2018 NSHM incorporates deep sedimentary basin depth from local seismic velocity models. The subduction GMMs considered lack basin depth terms and are modified to include an additional scale factor to account for this. This article documents the WUS GMMs used in the 2018 NSHM update and provides detail on the changes to GMM medians, aleatory variability, epistemic uncertainty, and site-effect models. It compares each of these components with those considered in prior NSHMs and discusses their total effect on hazard.

Simplified methods to estimate mean hazard due to updated ground motion model: Application to nuclear power plants in CEUS

Two methods were developed to estimate updated mean seismic hazard for existing probabilistic seismic hazard analyses (PSHAs) due to a change in the ground motion model (GMM). Both methods were used to estimate updated hazard at nuclear power plant (NPP) sites in the Central and Eastern United States (CEUS) for a change from the Electric Power Research Institute (EPRI) 2013 GMM to the Next Generation Attenuation (NGA)-East GMM. These methods present efficient tools to inform decisions on whether to perform a full PSHA revision or other detailed evaluations, especially when a large number of sites must be analyzed. A Simplified Hazard (SiHaz) method was developed to estimate mean hazard explicitly using a reduced PSHA logic tree that incorporates the updated GMM and potential changes in the site response model. An alternative scaling method was independently developed to be applied directly to current CEUS NPP hazard. Both methods were validated using updated PSHA results at several sites. Estimates at 46 NPP sites using both methods showed good agreement for mean annual frequencies of exceedance between 1E-4 and 1E-5/yr.

The 2018 update of the US National Seismic Hazard Model: Ground motion models in the central and eastern US

The United States Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous US NSHM includes major changes to the underlying ground motion models (GMMs). Most of the changes are motivated by the new multi-period response spectra requirements of seismic design regulations that use hazard results for 22 spectral periods and 8 site classes. In the central and eastern United States (CEUS), the 2018 NSHM incorporates 31 new GMMs for hard-rock site conditions [Formula: see text], including the Next Generation Attenuation (NGA)-East GMMs. New aleatory variability and site-effect models, both specific to the CEUS, are applied to all median hard-rock GMMs. This article documents the changes to the USGS GMM selection criteria and provides details on the new CEUS GMMs used in the 2018 NSHM update. The median GMMs, their weights, epistemic uncertainty, and aleatory variability are compared with those considered in prior NSHMs. This article further provides implementation details on the CEUS site-effect model, which allows conversion of hard-rock ground motions to other site conditions in the CEUS for the first time in NSHMs. Compared with the 2014 NSHM hard-rock ground motions, the weighted average of median GMMs increases for large magnitude events at middle to large distance range, epistemic uncertainty increases in almost all situations, but aleatory variability is not significantly different. Finally, the total effect on hazard is demonstrated for an assumed earthquake source model in the CEUS, which shows an increased ring of ground motions in the vicinity of the New Madrid seismic zone and decreased ground motions near the East Tennessee seismic zone.

Seismicity in the central and southeastern United States due to upper mantle heterogeneities

SUMMARYSources of stress responsible for earthquakes occurring in the Central and Eastern United States (CEUS) include not only far-field plate boundary forces but also various local contributions. In this study, we model stress fields due to heterogeneities in the upper mantle beneath the CEUS including a high-velocity feature identified as a lithospheric drip in a recent regional P-wave tomography study. We calculate velocity and stress distributions from numerical models for instantaneous 3-D mantle flow. Our models are driven by the heterogeneous density distribution based on a temperature field converted from the tomography study. The temperature field is utilized in a composite rheology, assumed for the numerical models. We compute several geodynamic quantities with our numerical models: dynamic topography, rate of dynamic topography, gravitational potential energy (GPE), differential stress, and Coulomb stress. We find that the GPE, representative of the density anomalies in the lithosphere, is an important factor for understanding the seismicity of the CEUS. When only the upper mantle heterogeneities are included in a model, differential and Coulomb stress for the observed fault geometries in the CEUS seismic zones acts as a good indicator to predict the seismicity distribution. Our modelling results suggest that the upper mantle heterogeneities and structure below the CEUS have stress concentration effects and are likely to promote earthquake generation at preexisting faults in the region’s seismic zones. Our results imply that the mantle flow due to the upper-mantle heterogeneities can cause stress perturbations, which could help explain the intraplate seismicity in this region.

Effects of High-Frequency Ground-Motion Spectra in the Seismic Response of Squat RC Walls

AbstractDue to the high-frequency content of ground motions in central and eastern United States (CEUS) sites, the US Nuclear Regulatory Commission has modified their regulatory guides to consider ...

Risk from Oklahoma’s Induced Earthquakes: The Cost of Declustering

ABSTRACTThe U.S. Geological Survey (USGS) has for each year 2016–2018 released a one-year seismic hazard map for the central and eastern United States (CEUS) to address the problem of induced and triggered seismicity (ITS) in the region. ITS in areas with historically low rates of earthquakes provides both challenges and opportunities to learn about crustal conditions, but few scientific studies have considered the financial risk implications of damage caused by ITS. We directly address this issue by modeling earthquake risk in the CEUS using the 1 yr hazard model from the USGS and the RiskLink software package developed by Risk Management Solutions, Inc. We explore the sensitivity of risk to declustering and b-value, and consider whether declustering methods developed for tectonic earthquakes are suitable for ITS. In particular, the Gardner and Knopoff (1974) declustering algorithm has been used in every USGS hazard forecast, including the recent 1 yr forecasts, but leads to the counterintuitive result that earthquake risk in Oklahoma is at its highest level in 2018, even though there were one-fifth as many earthquakes as occurred in 2016. Our analysis shows that this is a result of (1) the peculiar characteristics of the declustering algorithm with space-varying and time-varying seismicity rates, (2) the fact that the frequency–magnitude distribution of earthquakes in Oklahoma is not well described by a single b-value, and (3) at later times, seismicity is more spatially diffuse and seismicity rate increases are closer to more populated areas. ITS in Oklahoma may include a combination of swarm-like events with tectonic-style events, which have different frequency–magnitude and aftershock distributions. New algorithms for hazard estimation need to be developed to account for these unique characteristics of ITS.

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

AbstractWe constructed a detailed map of the uppermost mantle seismic structure beneath the Central and Eastern United States (CEUS) using the International Seismological Centre Bulletin and seismic waveforms from USArray. Identical Pn and Sn travel time data sets were inverted to tomographically image the uppermost mantle P wave (Pn) velocity, S wave (Sn) velocity, and the velocity ratio (VPn/VSn). Furthermore, we modified the two‐station method in order to limit the contributions of site response and estimate the effective attenuation of Sn phase (Q−1Sn).Lower Q values generally correspond with lower velocities in terms of both Pn and Sn wave speeds (e.g., New England and the Mississippi Embayment), but some regions, including southern Georgia, eastern South Carolina, and the New Madrid Seismic Zone, show high velocity and low QSn values. This can be explained by scattering attenuation of the Sn phase. To estimate the uppermost mantle temperature, a constrained grid‐search algorithm was conducted using the observed VSn, VPn, and QSn with the calculated velocities of specific compositional models. The uppermost mantle temperature result shows ~300–500 °C beneath the northern midcontinent and 1100 °C beneath New England. Although our temperature results appear to be well resolved, we found that VPn, VSn, and QSn are not enough to constrain the detailed uppermost mantle composition model. Our results highlight significant temperature heterogeneity in the uppermost mantle across the CEUS and is consistent with there not being any melt within the uppermost mantle beneath the CEUS.

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform VS30maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.

Current Status and Future of Regional Seismic Network Monitoring in the Central and Eastern United States

AbstractThe central and eastern United States (CEUS) is an area of generally low-to-moderate seismic hazard with a number of large cities with high seismic risk, a history of occasional damaging earthquakes, and seismic activity induced by wastewater disposal. Seismic monitoring in the CEUS, which began at the beginning 1900s, has undergone many changes through time. Over the past two decades, broadband digital seismic stations connected by internet communications have become widespread. Modern data processing systems to automatically locate earthquakes and assign event magnitudes in near-real time have become the norm, and, since the inception of the Advanced National Seismic System in 2000, more than 10,000 earthquakes have been located and cataloged. Continuously recorded digital seismic data at 100 samples per second are allowing new avenues of research into earthquake source parameters, ground-motion excitation, and seismic wave propagation. Unfortunately, over the past two decades the number of regional seismic network (RSN) centers has diminished due to consolidations and terminations, as funding has tightened. Nevertheless, the public in different parts of the CEUS still looks to local experts for information when earthquakes take place or when they have questions about earthquakes and seismic hazard. The current RSNs must evolve to encompass the need for local seismic information centers and to serve the needs of present and future research into the causes and effects of CEUS earthquakes.

Seismic performance of emergency diesel generator for high frequency motions

Abstract The nuclear power plants in South Korea have been designed in accordance with the U.S. Regulatory Guide 1.60 (R.G 1.60) design spectrum of which the peak frequency range is 2–10 Hz. The characteristics of the earthquakes at the Korea nuclear power plant sites were observed to be closer to that of Central and Eastern United States (CEUS) than the R.G 1.60, which is a lower amplification in a low frequency range, and a higher amplification in a high frequency range. The possibility of failure for sensitive power plant components in the high frequency range has been considered and evaluated. In this study, in order to improve the reliability of nuclear plant and administrative control procedures, seismic tests of an emergency diesel generator (EDG) were conducted using a shaking table under both high and low frequency ranges. From the tests, oil/lubricant leaks from the bolt connections, the fuel filter and the fuel inlet were observed. Therefore, the check list of nuclear plant components after an earthquake should include bolt connections of EDG as well as anchor bolts.