Consideration of near-fault effects in New Zealand seismic hazard analysis and design spectra

12. An Introduction to Probabilistic Seismic Hazard Analysis

One dimensional seismic response analysis on the ground surface of the Non-Commercial Power Reactor (RDNK) site based on the mean uniform hazard spectrum (UHS) and disaggregation analysis has been conducted. The study’s objective was to perform an analysis on site-specific response spectra on the ground surface based on existing mean UHS and disaggregation data of the site that correspond to a 1,000 and 10,000 year return period of earthquakes in compliance with the national nuclear regulatory body requirements of Indonesia. Detailed site characterization was defined based on secondary data of a geotechnical drill-hole, seismic cross-hole, downhole data, and microtremor array data. The dynamic site characteristic analysis was presented along with strong motion selection and processing using two types of strong motion datasets. An investigation of strong motion selection, spectral matching, and scaling has been presented as an essential step in ground motion processing. One-dimensional equivalent linear analysis simulation was performed by computing the processed ground motions. A seismic design spectrum and ground surface response spectra from the two datasets of strong motion, both corresponding to a 10,000 and 1,000 year return period, are presented at the end of this study. This study has shown that in order to establish the appropriate seismic response design spectrum, site-specific data and seismic hazard analysis must be immensely considered.

<p>The Emilia earthquakes of May 20, 2012 (Ml 5.9, INGV; Mw 6.11, http://www.bo.ingv.it/RCMT/) and May 29, 2012 (Ml 5.8, INGV; Mw 5.96, http://www.bo.ingv.it/RCMT/) struck an area that in the national reference seismic hazard model [MPS04; http://zonesismiche.mi.ingv.it, and Stucchi et al. 2011] is characterized by expected horizontal peak ground acceleration (PGA) with a 10% probability of exceedance in 50 years that ranges between 0.10 g and 0.15 g (Figure 1), which is a medium level of seismic hazard in Italy. The strong impact of the earthquakes on a region that is not included among the most hazardous areas of Italy, and the ground motion data recorded by accelerometric networks, have given the impression to the population and the media that the current seismic hazard map is not correct, and thus needs to be updated. Since the MPS04 seismic hazard model was adopted by the current Italian building code [Norme Tecniche per le Costruzioni 2008, hereafter termed NTC08; http://www.cslp.it/cslp/] as the basis to define seismic action (the design spectra), any modification to the seismic hazard model would also affect the building code. The aim of this paper is to briefly present the data that support the seismic hazard model in the area, and to perform some comparisons between recorded ground motion with seismic hazard estimates and design spectra. All of the comparisons presented in this study are for the horizontal components only, as the Italian hazard model did not perform any estimates for the vertical component. […]</p><br />

The uniform hazard response spectrum only considers the seismic hazard of a site, without taking into account the seismic fragility of the structure. As a result, structures designed based on this spectrum may exhibit varying levels of collapse risk under earthquakes in different regions. To this end, first, various cases are employed to determine a first-order approximation of the seismic hazard function H(x), followed by a validation of its rationality. Subsequently, with the objective of achieving uniform collapse risk, considering both seismic hazard and structural fragility, single anchor point, double anchor points, and multiple anchor points methods are proposed to construct the risk-targeted seismic design spectra for frequent earthquake (FE), design basis earthquake (DBE), maximum considered earthquake (MCE), and very rare earthquake (VRE). Furthermore, a comprehensive study is conducted to analyze the risk-targeted seismic design spectra corresponding to different seismic design levels, site classes, and characteristic periods constructed using the multiple anchor points method. In addition, a comparative analysis is conducted on the risk-targeted seismic design spectra constructed using different methods. The study indicates that determining H(x) based on DBE and VRE is reasonable, and the relative difference between the risk-targeted ground motion (RTGM) derived from this case and the RTGM obtained by determining H(x) based on probabilistic seismic hazard analysis is within 4%. The risk-targeted seismic design spectra constructed using three different methods show overall similarity. The single anchor point method offers simplicity in calculations and ensures that the uniform risk seismic design spectrum aligns with the uniform hazard seismic design spectrum in terms of spectral shape. Although the multiple anchor points method involves increased computational effort, it allows for the consideration of seismic hazard at multiple periods.

Seismic resistance design requires the estimation of futuristic seismic force to the structure in terms of spectral acceleration/velocity/displacement at the corresponding natural period of the structure. These expected seismic forces are defined based on detailed seismic hazard analysis and design spectrums from recorded earthquakes in the region. In this study, we have presented seismic design criteria in the Indian Seismic Code IS 1893 since its development, state-of-the-art procedure for the seismic hazard estimation, and the development of seismic design spectrum at the Indian Rock Site from North India and South India seismic data separately. The first Indian seismic code of IS 1893 was released in 1962 based on the studies of the Geological Survey of India on past earthquakes. IS 1893 was frequently revised soon after major earthquakes in different parts of the country and the currently available version is IS 1893 (2016). The seismic zonation map of India is based on past earthquake intensities and not on systematic futuristic seismic hazard estimation accounting for probable location and size of earthquakes. The different natural period of structural design requires respective design spectral amplitude. The previous versions of IS 1893 have given seismic coefficients for seismic zones and spectral amplitude for the different periods based on earthquakes recorded in US at an epicentral distances of 50–70 km, with multiplication factors. A recent version of IS 1893 adopted a design spectrum from the Uniform Building Code, again without considering regional data. After discussing these points, a modern smoothened, and normalized way of developing the design spectrum using regional data is explained. Further, rock site seismic records from the southern and northern parts of India were collated and used to create the design spectrum. The derived design spectra presented are applicable at the rock sites for 5% damping based on inter- and intraplate regions. Our study shows North and South Indian spectrums are different from the IS 1893 spectrum and the signature of each seismotectonic region is reflected in the proposed new spectral shape.

We present a detailed discussion on the needs of hazard assessment for different applications of earthquake engineering and risk assessment. This discussion includes design and risk assessment issues. We define the requested information from seismic hazard analysis as an input to a meaningful and economical engineering analysis. This provides the basis for a detailed review of the main methods of contemporary seismic hazard analysis: (1) traditional Probabilistic Seismic Hazard Analysis (PSHA) as used in building codes of many countries, (2) scenario-based seismic hazard analysis or neo-deterministic seismic hazard analysis (NDSHA) as the principal alternative, and (3) the state of the art physics-based deterministic method. We demonstrate that only the physics- and scenario-based seismic hazard analysis method that combines (a) contemporary seismic waveform modelling, (b) an in-depth geological and seismo-tectonic analysis of the region of interest, and (c) empirical information is able to provide the complete set of input information for economical earthquake engineering analysis that allows to combine improved seismic performance of both the structures and components with reasonable design costs. We show that the scenario-based seismic hazard method can easily be adapted/extended for risk assessment as required in assurance applications by developing state of the art probabilistic data models that are in compliance with observational data assembled in earthquake catalogues. The paper includes a practical example of the scenario-based approach for the development of the design basis of a critical infrastructure and the risk assessment for a seismically induced production loss of a nuclear power plant located in Switzerland. We recommend that DSHA and NDSHA must be used for engineering design. When/if PSHA is required based on national regulations, it is highly

Seismic damage hazard analysis for requalification of nuclear power plant structures: methodology and application

The calculation of design spectra for building sites threatened by seismic ground motion is approached by considering the maximum responses of linearly elastic oscillators as indicators of ground motion intensity. Attenuation functions describing the distribution of response as a function of earthquake magnitude and distance are derived using 68 components of recorded ground motion as data. With a seismic hazard analysis for several hypothetical building sites, the distributions of maximum oscillator responses to earthquakes of random magnitude and location are calculated, and spectra are drawn to indicate the maximum responses associated with specified probability levels. These spectra are compared to design spectra calculated from published methods of amplifying peak ground motion parameters. The latter spectra are found to be inconsistent in terms of risk for building sites very close and very far from faults. A ground motion parameter defined to be proportional to the maximum response of a 1 Hz, 2 per cent damped linearly elastic oscillator is investigated; this parameter, in conjunction with peak ground acceleration, is found to lead to risk‐consistent design spectra. Through these two parameters, a design earthquake magnitude and design hypocentral distance are defined, for a specified building site and risk level. The use of these parameters in the seismic hazard mapping of a region is illustrated.

This study aims to provide a comparison and identify the key distinctions between the New Zealand Standard – Earthquake Actions (NZS 1170.5: 2004) seismic design spectra and the hysteresis-damped seismic demand spectra specified by either the New Zealand Society for Earthquake Engineering (NZSEE) “Assessment and Improvement of the Structural Performance of Buildings in Earthquakes” (AISPBE) Guidelines, or the “Displacement-Based Seismic Design of Structures” (DBSDS) textbook by Priestley et al. (2007). The damping provided by the draft document, “The Seismic Assessment of Existing Buildings” (TSAEB), was also briefly discussed. The seismic design spectrum was calculated for various levels of ductility using all three methods and compared against each other. This was performed for structural elastic periods from 0.1 to 4.5 seconds. For a given set of requirements based on the NZS 1170.5 parameters, a representative acceleration-displacement hysteresis loop has been generated. The equivalent viscous damping was then calculated based on the area under this hysteresis using the recommendations of either the AISPBE or through the damping equations based on the DBSDS. The final damped spectra were then compared with each other and against the NZS 1170.5 design spectrum. Results indicate good correlation between the NZS 1170.5 design spectra and the damped design spectra at low levels of ductility but show significant disparities at higher levels of ductility.

A better seismic design for building and other structures is the most effective way to reduce seismic risk and avoid earthquake disaster. Adoption and implementation of new seismic safety regulations and design standards have caused serious problems in many communities in the New Madrid region, including western Kentucky, however. The main reasons for these problems are (1) misunderstanding of the national seismic hazard maps and (2) confusion between seismic hazard and seismic risk. Both are caused by probabilistic seismic hazard analysis (PSHA). PSHA is a mathematical formulation derived from a probability analysis on the distribution of earthquake magnitudes, locations, and ground-motion attenuation. Some assumptions and distributions associated with PSHA have been found to be invalid in earth science, however. In addition, PSHA contains a mathematical error: equating a dimensionless quantity (the annual probability of exceedance – exceedance probability in one year) to a dimensional quantity (the annual frequency of exceedance with the unit of per year [1/yr]). Thus, PSHA is scientifically flawed and the resulting seismic hazard and seismic risk estimates are artifacts. The national seismic hazard curves and maps are artifacts because they were produced from PSHA, even though the inputs are scientifically sound. Although seismic hazard and seismic risk have often been used interchangeably, they are two fundamentally different concepts. Seismic hazard describes the natural phenomenon or property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. Seismic hazard and seismic risk play different roles in engineering design and other policy considerations. Furthermore, measures for seismic hazard mitigation are different from those for seismic risk reduction. The difficulties in the development of design ground motion for NEHRP provisions are caused by the use of the national seismic hazard maps which are neither seismic hazard nor seismic risk. The resulting design ground motions for building codes and other policy considerations are therefore problematic. California’s experience proves that deterministic/scenario seismic hazard analysis is an appropriate approach for seismic hazard assessment, seismic risk assessment, as well as *Kentucky Geological Survey, University of Kentucky, 504 Rose Street, Lexington, KY 40506; phone (859) 323-0564; fax (859)257-1147; e-mail: zmwang@uky.edu. 112 Seismic Hazard Design Issues in the Central United States engineering design and other policy considerations. Deterministic/scenario seismic hazard analysis is also appropriate for engineering design and other policy considerations in the New Madrid region, as well as other regions.

The purpose of this study was to conduct seismic hazard analysis for Al-Tajiat and Al-Zawraa stadiums using probabilistic and deterministic approaches. The stadiums of Al-Tajiat and Al-Zawraa are located at latitude of \({33^{\circ}}\)25ʹ25.80ʺN, longitude of \({44^{\circ}}\)17ʹ9.28ʺE and latitude of \({33^{\circ}}\)20ʹ39ʺN, longitude of \({44^{\circ}}\)22ʹ5.81ʺE, respectively. To assess the seismic hazard, the region was divided into five seismic sources, and the seismic parameters were calculated for each selected seismic source. According to the results obtained from probabilistic seismic hazard analysis, the maximum horizontal accelerations on bedrock for return periods of 75, 475, and 2,475 years are equal to 0.06, 0.12, and 0.21 g, respectively. The result of deterministic seismic hazard assessment proves that the maximum horizontal and vertical acceleration on bedrock are 0.31 and 0.16 g, respectively. In order to analyze the response of structures against calculated acceleration, studies related to response spectrum and design spectrum have been carried out based on statistical analysis of appropriate time histories. The computer program Equivalent linear Earthquake Response Analysis was used to process the selected records and to consider the effect of soil conditions. Design spectrum has also been presented based on the response spectrum of the selected time histories and then was compared with the corresponding ones in UBC 1997 and ISIRI 2800 codes. The comparison shows that the presented design spectrum is more conservative than the results provided by the above codes.

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 Rehabilitation and reconstruction process for coastal area of city of Banda Aceh post Great Sumatra (Mw = 9.3) earthquake requires both seismic and tsunami hazards design criteria. A case study to develop design criteria of a coastal sub-district site in the effort of disaster mitigation is presented. The case study consists of probabilistic seismic and tsunami hazard analysis. The potential of both subduction and shallow crustal faults is considered in the seismic hazard analysis. The subduction source zones are considered as a seismic source for the tsunami hazard analysis. Some site-classification analyses were conducted to estimate level of ground surface acceleration. The analyses were based on collection of shear wave velocity data from a set of geotechnical subsurface exploration and spectral analysis of surface wave survey. Likewise, tsunami inundation maps generated from probabilistic tsunami hazard analysis was also developed. The maps were developed through tsunami and run-up numerical modeling associated with its earthquake probabilities. Both the seismic and tsunami hazard criteria are recommended as a basis for design criteria as part of the disaster mitigation effort in the currently undergoing rehabilitation and reconstruction process, as well as for long-term development of the case-study site.

Based on the seismic source model in the Fifth Generation Seismic Ground Motion Parameters Zonation Map of China (FGSGMPZMC), a new seismic fault model, the new zonation of seismic risk areas (SRAs), and the estimation of seismicity rates for 2021–2030, this study constructed a new time-dependent seismic source model of China’s mainland, and used the probabilistic seismic hazard analysis method to calculate seismic hazard by selecting the ground motion models (GMMs) suitable for seismic sources in China. It also provided the probabilities of China’s mainland being affected by earthquakes of modified Mercalli intensity (MMI) VI, VII, VIII, IX, and ≥ X in 2021–2030. The spatial pattern of seismic hazards presented in this article is similar to the pattern of the FGSGMPZMC, but shows more details. The seismic hazards in this study are higher than those in the FGSGMPZMC in the SRAs and fault zones that can produce large earthquakes. This indicates that the seismic source model construction in this study is scientific and reasonable. There are certain similarities between the results in this study and those of Rong et al. (2020) and Feng et al. (2020), but also disparities for specific sites due to differences in seismic source models, seismicity parameters, and GMMs. The results of seismic hazard may serve as parameter input for future seismic risk assessments. The hazard results can also be used as a basis for the formulation of earthquake prevention and mitigation policies for China’s mainland.

Simple method for probabilistic seismic landslide hazard analysis based on seismic hazard curve and incorporating uncertainty of strength parameters