Overview of TS 1170.5:2025 and changes from NZS 1170.5:2004
DOI:
https://doi.org/10.5459/bnzsee.1695Abstract
This paper provides the background and overview of the development of Technical Specification (TS) 1170.5, released for public comment in February 2024 and published in 2025. The paper also serves as an introduction to the second of two special issues of the Bulletin of the New Zealand Society for Earthquake Engineering, including a total of eight papers providing supporting technical background for changes to NZS 1170.5:2004 and other considerations during the development of TS1170.5:2025. This is the first major update to NZS 1170.5 since 2004. These special issues are expected to be of interest to practicing engineers and researchers wanting an in depth understanding of the basis for the changes found in TS 1170.5 and future standards development committees. The paper concludes with a brief introduction to ongoing efforts under Stage 2 of the Seismic Risk Work Programme.
References
Standards New Zealand (2024). "Draft Technical Specification DZ TS1170.5: Structural Design Actions. Part 5: Earthquake Actions ‐ New Zealand”. Standards New Zealand, Wellington, NZ, 126pp.
Standards New Zealand (2025). "TS1170.5: Structural Design Actions. Part 5: Earthquake Actions ‐ New Zealand”. Standards New Zealand, Wellington, NZ.
Standards New Zealand (2004). "NZS1170.5: Structural Design Actions. Part 5: Earthquake Actions ‐ New Zealand”. Standards New Zealand, Wellington, NZ, 76pp.
Standards New Zealand (2016). "NZS1170.5: Structural Design Actions. Part 5: Earthquake Actions ‐ New Zealand. Amendment No. 1”. Standards New Zealand, Wellington, NZ, 88pp.
Francis TC, Sullivan TJ, Hulsey AM and Elwood KJ (2025). “Recommendations for the shape of the design response spectrum in the New Zealand seismic loadings technical specification”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(2): 83-97. https://doi.org/10.5459/bnzsee.1692
de la Torre C, Cubrinovski M, Bradley BA and Bora SS (2025). “PGA adjustment factors for nonlinear site-response effects on soft soil sites: Application to TS1170.5”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(2): 98-108. https://doi.org/10.5459/bnzsee.1727. DOI: https://doi.org/10.5459/bnzsee.1727
Bradley BA and Weatherill G (2025). “Consideration of near-fault effects in New Zealand seismic hazard analysis and design spectra”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(2): 109-118. https://doi.org/10.5459/bnzsee.1743
Hulsey AM, Elwood KJ, Horspool N, Gerstenberger MC and Sullivan TJ (2025). “Assessing the life-safety risk for the proposed Technical Specification (TS) 1170.5”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(2): 119-133. https://doi.org/10.5459/bnzsee.1690
Francis TC and Sullivan TJ (2025). “Simplified relationships between inelastic and elastic spectral acceleration demands for seismic design in New Zealand”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(2): 134-148. https://doi.org/10.5459/bnzsee.1664
Lee RL, Cubrinovski M and Bradley BA (2025). “Site classification methodology for TS 1170.5 design spectra”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(1): 11-39. https://doi.org/10.5459/bnzsee.1686 DOI: https://doi.org/10.5459/bnzsee.1686
Millen MDL and Hare HJ (2025). “Development of provisions for simplified design of rocking foundations”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(1): 40-51. https://doi.org/10.5459/bnzsee.1659 DOI: https://doi.org/10.5459/bnzsee.1659
Haymes K, Sullivan TJ and Hare HJ (2025). “Recommendations for the revision of the approach for seismic design of parts and components in New Zealand design standards”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(1): 52-72. https://doi.org/10.5459/bnzsee.1661 DOI: https://doi.org/10.5459/bnzsee.1661
Bradley BA (2025). “Seismic hazard with deterministic maximum limits: Considerations in a New Zealand-specific context”. Bulletin of the New Zealand Society for Earthquake Engineering, 58(1): 1-10. https://doi.org/10.5459/bnzsee.1692 DOI: https://doi.org/10.5459/bnzsee.1706
MBIE (2023) “Acceptable Solutions and Verification Methods for New Zealand Building Code Clause B1 Structure”. New Zealand Government, Wellington, 95pp. https://www.building.govt.nz/assets/Uploads/building-code-compliance/b-stability/b1-structure/asvm/b1-structure-1st-edition-amendment-21.pdf
Standards New Zealand (2011). "AS/NZS 1170.0:2002 Structural Design Actions. Part 0: General Principles: Amendment 5”. Standards Australia / Standards New Zealand, Wellington, NZ, 40 pp.
Standards New Zealand (1992). "NZS 4203:1992 General Structural Design and Design Loadings for Buildings”. Standards New Zealand, Wellington, NZ.
Matuschka T, Berryman KR, O'leary AJ, McVerry GH, Mulholland WM and Skinner RI (1985). “New Zealand seismic hazard analysis”. Bulletin of the New Zealand Society for Earthquake Engineering, 18(4): 313-322. https://doi.org/10.5459/bnzsee.18.4.313-322 DOI: https://doi.org/10.5459/bnzsee.18.4.313-322
Stirling MW, Wesnousky SG and Berryman KR (1998). “Probabilistic seismic hazard analysis of New Zealand”. New Zealand Journal of Geology and Geophysics, 41(4): 355-375. DOI: https://doi.org/10.1080/00288306.1998.9514816
McVerry GH, Zhao JX, Abrahamson NA and Somerville PG (2006). “New Zealand acceleration response spectrum attenuation relations for crustal and subduction zone earthquakes”. Bulletin of the New Zealand Society for Earthquake Engineering, 39(1): 1-58. https://doi.org/10.5459/bnzsee.39.1.1-58 DOI: https://doi.org/10.5459/bnzsee.39.1.1-58
Stirling MW, McVerry GH and Berryman KR (2002). “A new seismic hazard model of New Zealand.” Bulletin of the Seismological Society of America, 92: 1878–1903. DOI: https://doi.org/10.1785/0120010156
Stirling M, McVerry G, Gerstenberger M, Litchfield N, Dissen R, Berryman K, Barnes P, Wallace L and Villamor P (2012). “National seismic hazard model for New Zealand: 2010 Update.” Bulletin of the Seismological Society of America, 102(4): 1514–42. https://doi.org/10.1785/0120110170 DOI: https://doi.org/10.1785/0120110170
McVerry GH (2003). “From hazard maps to code spectra for New Zealand”. Pacific Conference on Earthquake Engineering, 9p.
Kaiser A, Holden C, Beavan J, Beetham D, Benites R, Celentano A, Collett D, Cousins J, Cubrinovski M, Dellow G and Denys P (2012). “The Mw 6.2 Christchurch earthquake of February 2011: Preliminary report”. New Zealand Journal of Geology and Geophysics, 55(1): 67-90. DOI: https://doi.org/10.1080/00288306.2011.641182
Hamling IJ, Hreinsdóttir S, Clark K, Elliott J, Liang C, Fielding E, Litchfield N, Villamor P, Wallace L, Wright TJ and D’Anastasio E (2017). “Complex multifault rupture during the 2016 M w 7.8 Kaikōura earthquake, New Zealand”. Science, 356(6334): 7194. DOI: https://doi.org/10.1126/science.aam7194
Budnitz RJ, Apostolakis G and Boore DM (1997). “Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts (No. NUREG/CR-6372-Vol. 1; UCRL-ID-122160)”. US Nuclear Regulatory Commission (NRC), Washington, DC. Division of Engineering Technology; Lawrence Livermore National Laboratory (LLNL), Livermore, CA. Electric Power Research Institute (EPRI), Palo Alto, CA. US Department of Energy (USDOE), Washington DC, USA. DOI: https://doi.org/10.2172/479072
Cowan H, Jordan J, Johnson L, Marzocchi W, Petersen M and Renwick J (2022). “National Seismic Hazard Model Revision: Project Assurance and ‘Lessons’ Review”. (https://nshm-static-reports.gns.cri.nz/NSHM/ScienceReports/NSHM%20Project%20Assurance_FINAL%20DRAFT_28Jul22.pdf)
Gerstenberger MC, Bora SS, Bradley BA, DiCaprio C, Kaiser AE, Manea EF, Nicol A, Rollins JC, Stirling MW, Thingbaijam KKS, Van Dissen RJ, Abbott ER, Atkinson GM, Chamberlain C, Christophersen A, Clark KJ, Coffey GL, de la Torre CA, Ellis SM, Fraser J, Graham K, Griffin J, Hamling IJ, Hill MP, Howell A, Hulsey A, Hutchinson J, Iturrieta P, Johnson KM, Jurgens VO, Kirkman R, Langridge RM, Lee RL, Litchfield NJ, Maurer J, Milner KR, Rastin SJ, Rattenbury MS, Rhoades DA, Ristau J, Schorlemmer D, Seebeck H, Shaw BE, Stafford PJ, Stolte AC, Townend J, Villamor P, Wallace LM, Weatherill G, Williams CA and Wotherspoon LM (2024). “The 2022 Aotearoa New Zealand national seismic hazard model: Process, overview, and results”. Bulletin of the Seismological Society of America, 114(1): 7-36. https:/doi.org/10.1785/0120230182 DOI: https://doi.org/10.1785/0120230182
Nicol A, Khajavi N, Humphrey J, Van Dissen R, Gerstenberger M and Stirling M (2022). “Geometries and slip of historical surface-rupturing earthquakes in New Zealand and their application to seismic hazard analysis”. (EQC Grant 16/718). EQC Biennial Report.
Bora SS, Bradley BA, Manea EF, Gerstenberger MC, Lee R, Stafford PJ, Atkinson GM, Kaiser AE, DiCaprio CJ and van Dissen RJ (2024). “Hazard sensitivities associated with ground-motion characterization modelling for the New Zealand national seismic hazard model revision 2022”. Bulletin of the Seismological Society of America, 114(1): 422-448. DOI: https://doi.org/10.1785/0120230167
Bradley BA, Bora SS, Lee RL, Manea EF, Gerstenberger MC, Stafford PJ, Atkinson GM, Weatherill G, Hutchinson J, de la Torre CA, Hulsey AM and Kaiser AE (2024). “The ground-motion characterization model for the 2022 New Zealand national seismic hazard model”. Bulletin of the Seismological Society of America, 114(1): 329-349. https:/doi.org/10.1785/0120230170 DOI: https://doi.org/10.1785/0120230170
Gerstenberger MC, Marzocchi W, Allen T, Pagani M, Adams J, Danciu L, Field EH, Fujiwara H, Luco N, Ma K-F, Meletti C and Petersen MD (2020). “Probabilistic seismic hazard analysis at regional and national scales: State of the art and future challenges”. Reviews of Geophysics, 58(2). https:/doi.org/10.1029/2019RG000653 DOI: https://doi.org/10.1029/2019RG000653
Baker J, Bradley B and Stafford P (2021). Seismic Hazard and Risk Analysis. Cambridge University Press. DOI: https://doi.org/10.1017/9781108425056
Boore DM, Stewart JP, Seyhan E and Atkinson GM (2014). “NGA-West2 equations for predicting PGA, PGV, and 5% damped PSA for shallow crustal earthquakes”. Earthquake Spectra, 30(3): 1057-1085. DOI: https://doi.org/10.1193/070113EQS184M
Bozorgnia Y, Abrahamson NA, Ahdi SK, Ancheta TD, Atik LA, Archuleta RJ, Atkinson GM, Boore DM, Campbell KW, Chiou SJ and Contreras V (2022). “NGA-Subduction research program”. Earthquake Spectra, 38(2): 783-798. DOI: https://doi.org/10.1177/87552930211056081
Atkinson GM (2024). “Backbone ground‐motion models for crustal, interface, and slab earthquakes in New Zealand from equivalent point‐source concepts”. Bulletin of the Seismological Society of America, 114(1): 350-372. DOI: https://doi.org/10.1785/0120230144
Stafford PJ (2022). “A model for the distribution of response spectral ordinates from New Zealand crustal earthquakes based upon adjustments to the Chiou and Youngs (2014) response spectral model”. GNS Science Report 2022/15. GNS Science, Lower Hutt, NZ, 97p. https://doi.org/10.21420/5098-0S19
Bradley BA (2013). “A New Zealand‐specific pseudospectral acceleration ground‐motion prediction equation for active shallow crustal earthquakes based on foreign models”. Bulletin of the Seismological Society of America, 103(3): 1801–1822. https://doi.org/10.1785/0120120021 DOI: https://doi.org/10.1785/0120120021
MBIE (2020). “Seismic Risk and Building Regulation in New Zealand”. Ministry for Business, Innovation, and Employment. (https://fl-nzgs-media.s3.amazonaws.com/uploads/2020/11/Seismic-Risk-and-Building-Regulation-in-NZ-For-Release.pdf)
MBIE (2021). “Module 1 - Overview of Earthquake Geotechnical Engineering Practice Guidelines”. Ministry for Business, Innovation and Employment, Wellington, NZ. https://www.building.govt.nz/building-code-compliance/b-stability/b1-structure/module-1-overview-guidelines
Stats NZ (2022). “Urban rural 2022 clipped (generalised)”. (https://datafinder.stats.govt.nz/layer/106703-urban-rural-2022-clipped-generalised)
Paulik R, Horspool N, Woods R, Griffiths N, Beale T, Magill C, Wild A, Popovich B, Walbran G and Garlick R (2023). “RiskScape: A flexible multi-hazard risk modelling engine”. Natural Hazards, 119(2): 1073-1090. https://doi.org/10.1007/s11069-022-05593-4 DOI: https://doi.org/10.1007/s11069-022-05593-4
Dong S, Sullivan TJ and Pettinga DJ (2025). “Investigating the impacts of design ductility values and importance levels on the performance of base-isolated buildings in New Zealand”. Bulletin of the New Zealand Society for Earthquake Engineering, Accepted for publication (Available online). https://doi.org/10.5459/bnzsee.1693
Bozorgnia Y and Campbell K (2003). ‘The vertical-to-horizontal response spectral ratio and tentative procedures for developing simplified V/H and vertical design spectra”. Journal of Earthquake Engineering, 5: 175–207. DOI: https://doi.org/10.1080/13632460409350486
Seebeck H, van Dissen R, Litchfield N, Barnes PM, Nicol A, Langridge R et al (2023). “The New Zealand Community Fault Model – Version 1.0: An improved geological foundation for seismic hazard modelling”. New Zealand Journal of Geology and Geophysics, 1–21. https://doi.org/10.1080/00288306.2023.2181362 DOI: https://doi.org/10.1080/00288306.2023.2181362
SESOC (2024). “TS 1170.5:2024 Evaluation Tool” https://sesoc.org.nz/static/apps/TS1170webtool.htm
ASCE (2022). “ASCE/SEI 7-22: Minimum Design Loads and Associated Criteria for Buildings and Other Structures”. American Society of Civil Engineers, Reston, Virginia. https:/doi.org/10.1061/9780784415788
Canadian Commission of Building and Fire Codes (2020). “National Building Code of Canada 2020”. National Research Council of Canada, Ottawa.
EN 1998-1 (2004). “Eurocode 8: Design of Structures for Earthquake Resistance – Part 1: General Rules, Seismic Actions and Rules for Buildings”. European Committee for Standardization, Brussels.
INN (2012). “NCh 433Of96 mod 2012, Earthquake Resistance of Buildings”. INN: Santiago, Chile.
Building Center of Japan (2016). “Building Standard Law of Japan”. Tokyo, Japan.