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JDR Vol.21 No.1 pp. 236-248
(2026)
doi: 10.20965/jdr.2026.p0236

Paper:

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Transition Long-Period Map for the National Structural Code of the Philippines

Rhommel N. Grutas† ORCID Icon, Koreen G. Dorado ORCID Icon, Justine Anne O. Duka ORCID Icon, Miguel Antonio T. Magandi ORCID Icon, Rizza Micaela S. Padre ORCID Icon, John Edward A. Nachor ORCID Icon, Nicole P. Tenorio ORCID Icon, Nicole Ann B. Bersabe ORCID Icon, and Teresito C. Bacolcol

Department of Science and Technology, Philippine Institute of Volcanology and Seismology (DOST-PHIVOLCS)
PHIVOLCS Building, C.P. Garcia Avenue, UP Campus, Diliman, Quezon City 1101, Philippines

†Corresponding author

Received:
August 27, 2025
Accepted:
October 28, 2025
Published:
February 1, 2026
Creative Commons License
Keywords:
transition long-period map, design response spectra, disaggregation, seismic hazard, NSCP
Abstract

The National Structural Code of the Philippines is set to be updated to align with international standards through the adoption of the Minimum Design Loads and Associated Criteria for Buildings and Other Structures of the American Society of Civil Engineers 7-05. This development introduces new key parameters in the ground motion section, specifically the transition long-period (TL), which is essential for the long-period structure seismic design. To accurately represent ground motion at periods greater than 4 s, which are critical for the design of long-period structures, such as high-rise buildings, and to determine the TL values specific to the Philippines, data derived from the Seismic Hazard Assessment for the Design Earthquake of the Philippines Project, implemented by the Philippine Institute of Volcanology and Seismology, were utilized. Using this dataset, modal magnitude (Md) maps were developed through the disaggregation of the 2% probability of exceedance in 50 years for spectral acceleration (Sa) at T=2 seconds, which were then correlated with the corresponding corner period (Tc) values. The seismic source models were subdivided into fault, subduction, and area sources. Results indicate that, in areas located near fault sources, magnitudes are predominantly influenced by the crustal earthquake generators. However, subduction sources tend to dominate the earthquake magnitudes in regions farther from the crustal fault systems.

Cite this article as:
R. Grutas, K. Dorado, J. Duka, M. Magandi, R. Padre, J. Nachor, N. Tenorio, N. Bersabe, and T. Bacolcol, “Transition Long-Period Map for the National Structural Code of the Philippines,” J. Disaster Res., Vol.21 No.1, pp. 236-248, 2026.
Data files:
References
  1. [1] World Bank, “Philippines urbanization review: Fostering competitive, sustainable and inclusive cities,” Report No.114088, 1997. https://doi.org/10.1596/27667
  2. [2] M. A. Aurelio, “Shear partitioning in the Philippines: Constraints from Philippine Fault and global positioning system data,” Island Arc, Vol.9, No.4, pp. 584-597, 2000. https://doi.org/10.1111/j.1440-1738.2000.00304.x
  3. [3] “Chapter 11: Seismic design criteria,” American Society of Civil Engineers, “Minimum Design Loads for Buildings and Other Structures,” ASCE/SEI 7-05, pp. 115-116, 2006.
  4. [4] C. Crouse, E. V. Leyendecker, P. G. Somerville, M. Power, and W. J. Silva, “Development of seismic ground-motion criteria for the ASCE 7 standard,” 8th US National Conf. on Earthquake Engineering 2006, pp. 46-53, 2006.
  5. [5] C. Assadollahi, S. Pezeshk, and K. Campbell, “A seismological method for estimating the long-period transition period TL in the seismic building code,” Earthquake Spectra, Vol.39, No.2, pp. 1037-1057, 2023. https://doi.org/10.1177/87552930231153673
  6. [6] Y. Chen, L. Xu, X. Zhu, and H. Liu, “A multi-objective ground motion selection approach matching the acceleration and displacement response spectra,” Sustainability, Vol.10, Issue 12, Article No.4659, 2018. https://doi.org/10.3390/su10124659
  7. [7] “Uniform building code,” Int. Conf. of Building Officials, 1997.
  8. [8] I. Takewaki, K. Fujita, and S. Yoshitomi, “Uncertainties in long-period ground motion and its impact on building structural design: case study of the 2011 Tohoku (Japan) earthquake,” Engineering Structures, Vol.49, pp. 119-134, 2013. https://doi.org/10.1016/j.engstruct.2012.10.038
  9. [9] J. J. Bommer, A. S. Elnashai, and A. G. Weir, “Compatible acceleration and displacement spectra for seismic design codes,” Proc. of the 12th World Conf. on Earthquake Engineering, Vol.8, Article No.0207, 2000.
  10. [10] C. A. Cornell, “Engineering seismic risk analysis,” Bulletin of the Seismological Society of America, Vol.58, No.5, pp. 1583-1606, 1968.
  11. [11] K. Vipin, P. Anbazhagan, and T. Sitharam, “Estimation of peak ground acceleration and spectral acceleration for South India with local site effects: Probabilistic approach,” Natural Hazards and Earth System Science, Vol.9, Issue 3, pp. 865-878, 2009. https://doi.org/10.5194/nhess-9-865-2009
  12. [12] P. Anbazhagan, J. Vinod, and T. Sitharam, “Probabilistic seismic hazard analysis for Bangalore,” Natural Hazards, Vol.48, No.2, pp. 145-166, 2008. https://doi.org/10.1007/s11069-008-9253-3
  13. [13] N. Jayaram and J. Baker, “Efficient sampling and data reduction techniques for probabilistic seismic lifeline risk assessment,” Earthquake Engineering & Structural Dynamics, Vol.39, No.10, pp. 1109-1131, 2010. https://doi.org/10.1002/eqe.988
  14. [14] S. L. Kramer, “Geotechnical Earthquake Engineering, Chapter 4, Section 4,” Prentice Hall, pp. 117-137, 1996.
  15. [15] M. Pagani, D. Monelli, G. Weatherill, L. Danciu, H. Crowley, V. Silva, P. Henshaw, L. Butler, M. Nastasi, L. Panzeri, M. Simionato, and D. Vigano, “OpenQuake engine: An open hazard (and risk) software for the global earthquake model,” Seismological Research Letters, Vol.85, No.3, pp. 692-702, 2014. https://doi.org/10.1785/0220130087
  16. [16] V. Silva, H. Crowley, M. Pagani, D. Monelli, and R. Pinho, “Development of the OpenQuake engine, the Global Earthquake Model’s open-source software for seismic risk assessment,” Natural Hazards, Vol.72, pp. 1409-1427, 2014. https://doi.org/10.1007/s11069-013-0618-x
  17. [17] J. F. Pacheco and L. R. Sykes, “Seismic moment catalog of large shallow earthquakes, 1900 to 1989,” Bulletin of the Seismological Society of America, Vol.82, No.3, pp. 1306-1349, 1992. https://doi.org/10.1785/BSSA0820031306
  18. [18] M. L. Bautista and K. Oike, “Estimation of the magnitudes and epicenters of Philippine historical earthquakes,” Tectonophysics, Vol.317, Nos.1-2, pp. 137-169, 2000. https://doi.org/10.1016/S0040-1951(99)00272-3
  19. [19] E. M. Scordilis, “Empirical global relations converting MS and mb to moment magnitude,” J. of Seismology, Vol.10, No.2, pp. 225-236, 2006. https://doi.org/10.1007/s10950-006-9012-4
  20. [20] B. Lolli, P. Gasperini, and G. Vannucci, “Empirical conversion between teleseismic magnitudes (mb and Ms) and moment magnitude (Mw) at the Global, Euro-Mediterranean and Italian scale,” Geophysical J. Int., Vol.199, No.2, pp. 805-828, 2014. https://doi.org/10.1093/gji/ggu264
  21. [21] G. A. Weatherill, M. Pagani, and J. Garcia, “Exploring earthquake databases for the creation of magnitude-homogeneous catalogues: Tools for application on a regional and global scale,” Geophysical J. Int., Vol.206, Issue 3, pp. 1652-1676, 2016. https://doi.org/10.1093/gji/ggw232
  22. [22] J. K. Gardner and L. Knopoff, “Is the sequence of earthquakes in Southern California, with aftershocks removed, Poissonian?” Bulletin of the Seismological Society of America, Vol.64, pp. 1363-1367, 1974. https://doi.org/10.1785/BSSA0640051363
  23. [23] O. Boyd, “A visitation of earthquake catalog declustering,” [Presentation slides], U.S. Geological Survey, USGS Seismic Hazard Workshop for CEUS Sources 2012, pp. 1-6, 2012.
  24. [24] R. E. Rimando and P. L. Knuepfer, “Neotectonics of the Marikina Valley fault system (MVFS) and tectonic framework of structures in northern and central Luzon, Philippines,” Tectonophysics, Vol.415, Nos.1-4, pp. 17-38, 2006. https://doi.org/10.1016/j.tecto.2005.11.009
  25. [25] H. Tsutsumi and J. S. Perez, “Large-scale active fault map of the Philippine fault based on aerial photograph interpretation,” Active Fault Research, Vol.2013, No.39, pp. 29-37, 2013. https://doi.org/10.11462/afr.2013.39_29
  26. [26] J. Perez, H. Tsutsumi, M. Cahulogan, D. Cabanlit, M. Abigania, and T. Nakata, “Fault distribution, segmentation and earthquake generation potential of the Philippine fault in eastern Mindanao, Philippines,” J. Disaster Res., Vol.10, No.1, pp. 74-82, 2015. https://doi.org/10.20965/jdr.2015.p0074
  27. [27] H. Tsutsumi, J. Perez, J. Marjes, K. Papiona, and N. Ramos, “Coseismic displacement and recurrence interval of the 1973 Ragay Gulf earthquake, southern Luzon, Philippines,” J. Disaster Res., Vol.10, No.1, pp. 83-90, 2015. https://doi.org/10.20965/jdr.2015.p0083
  28. [28] R. E. Rimando and J. M. Rimando, “Morphotectonic kinematic indicators along the Vigan-Aggao Fault: The western deformation front of the Philippine Fault Zone in Northern Luzon, the Philippines,” Geosciences, Vol.10, Issue 2, Article No.83, 2020. https://doi.org/10.3390/geosciences10020083
  29. [29] R. E. Rimando, J. M. Rimando, and R. B. Lim, “Complex shear partitioning involving the 6 February 2012 Mw 6.7 Negros Earthquake ground rupture in central Philippines,” Geosciences, Vol.10, Issue 11, Article No.460, 2020. https://doi.org/10.3390/geosciences10110460
  30. [30] J. S. Perez, D. C. E. Llamas, M. P. Dizon, D. J. L. Buhay, C. J. M. Legaspi, K. D. B. Lagunsad, R. C. C. Constantino, R. J. B. De Leon, M. M. Y. Quimson, R. N. Grutas, R. S. D. Pitapit, C. G. H. Rocamora, and M. G. G. Pedrosa, “Impacts and causative fault of the 2022 magnitude (Mw) 7.0 Northwestern Luzon earthquake, Philippines,” Frontiers in Earth Science, Vol.11, Article No.1091595, 2023. https://doi.org/10.3389/feart.2023.1091595
  31. [31] D. C. Llamas, B. J. Marfito, R. Dela Cruz, and M. A. Aurelio, “Surface rupture and fault characteristics associated with the 2020 magnitude (Mw) 6.6 Masbate earthquake, Masbate Island, Philippines,” Tectonics, Vol.43, Issue 9, Article No.e2023TC008106, 2024. https://doi.org/10.1029/2023TC008106
  32. [32] A. M. Dziewoński, T.-A. Chou, and J. H. Woodhouse, “Determination of earthquake source parameters from waveform data for studies of global and regional seismicity,” J. of Geophysical Research: Solid Earth, Vol.86, Issue B4, pp. 2825-2852, 1981. https://doi.org/10.1029/JB086iB04p02825
  33. [33] G. Ekström, M. Nettles, and A. M. Dziewoński, “The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes,” Physics of the Earth and Planetary Interiors, Vol.200, pp. 1-9, 2012. https://doi.org/10.1016/j.pepi.2012.04.002
  34. [34] J. Bonita, H. Kumagai, and M. Nakano, “Regional moment tensor analysis in the Philippines: CMT solutions in 2012–2013,” J. Disaster Res., Vol.10, No.1, pp. 18-24, 2015. https://doi.org/10.20965/jdr.2015.p0018
  35. [35] J. Salcedo, “Earthquake source parameters for subduction zone events causing tsunamis in and around the Philippines,” Bulletin of the Int. Institute of Seismology and Earthquake Engineering, Vol.45, pp. 49-54, 2011.
  36. [36] G. P. Hayes, G. L. Moore, D. E. Portner, M. Hearne, H. Flamme, M. Furtney, and G. M. Smoczyk, “Slab2, a comprehensive subduction zone geometry model,” Science, Vol.362, No.6410, pp. 58-61, 2018. https://doi.org/10.1126/science.aat4723
  37. [37] B. Gutenberg and C. F. Richter, “Frequency of earthquakes in California,” Bulletin of the Seismological society of America, Vol.34, No.4, pp. 185-188, 1944. https://doi.org/10.1785/BSSA0340040185
  38. [38] H. C. Peñarubia, K. L. Johnson, R. H. Styron, T. C. Bacolcol, W. I. G. Sevilla, J. S. Perez, J. D. Bonita, I. C. Narag, R. U. Solidum, Jr., M. M. Pagani, and T. I. Allen, “Probabilistic seismic hazard analysis model for the Philippines,” Earthquake Spectra. Vol.36, Issue 1_suppl, pp. 44-68, 2020. https://doi.org/10.1177/8755293019900521
  39. [39] D. M. Boore, J. P. Stewart, E. Seyhan, and G. M. Atkinson, “NGA-West2 equations for predicting PGA, PGV, and 5% damped PSA for shallow crustal earthquakes,” Earthquake Spectra, Vol.30, No.3, pp. 1057-1085, 2014. https://doi.org/10.1193/070113EQS184M
  40. [40] B. S. Chiou and R. R. Youngs, “Update of the Chiou and Youngs NGA model for the average horizontal component of peak ground motion and response spectra,” Earthquake Spectra, Vol.30, No.3, pp. 1117-1153, 2014. https://doi.org/10.1193/072813EQS219M
  41. [41] J. X. Zhao, J. Zhang, A. Asano, Y. Ohno, T. Oouchi, T. Takahashi, H. Ogawa, K. Irikura, H. K. Thio, P. G. Somerville, Y. Fukushima, and Y. Fukushima, “Attenuation relations of strong ground motion in North America,” Bulletin of the Seismological Society of America, Vol.96, No.3, pp. 898-913, 2006. https://doi.org/10.1785/0120050122
  42. [42] G. A. Parker, J. P. Stewart, D. Boore, G. M. Atkinson, and B. Hassani, “NGA-subduction global ground motion models with regional adjustment factors,” Earthquake Spectra, Vol.38, No.1, pp. 456-493, 2022. https://doi.org/10.1177/87552930211034889
  43. [43] N. A. Abrahamson, W. J. Silva, and R. Kamai, “Summary of the ASK14 ground motion relation for active crustal regions,” Earthquake Spectra, Vol.30, No.3, pp. 1025-1055, 2014. https://doi.org/10.1193/070913EQS198M
  44. [44] K. Lamichhane, S. Bhattarai, K. C. Rajan, K. Sharma, and R. Pokhrel, “State-of-the-art review of probabilistic seismic hazard analysis in Nepal: Status, challenges, and recommendations,” Geoenvironmental Disasters, Vol.12, No.1, Article No.15, 2025. https://doi.org/10.1186/s40677-025-00320-0
  45. [45] P. Bazzurro and C. A. Cornell, “Disaggregation of seismic hazard,” Bulletin of the Seismological Society of America, Vol.89, No.2, pp. 501-520, 1999. https://doi.org/10.1785/BSSA0890020501
  46. [46] J. N. Brune, “Tectonic stress and the spectra of seismic shear waves from earthquakes,” J. of geophysical research, Vol.75, No.26, pp. 4997-5009, 1970. https://doi.org/10.1029/JB075i026p04997
  47. [47] L. Ramon L, T. Huff, and D. R. VandenBerge, “Long-Period Transition for Subduction Earthquake Spectra,” Practice Periodical on Structural Design and Construction, Vol.29, Issue 2, Article No.04024007, 2024. https://doi.org/10.1061/PPSCFX.SCENG-1400

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Last updated on Feb. 04, 2026