Vertical-to-horizontal response spectral ratio for offshore ground motions: Analysis and simplified design equation

Abstract

In order to study the differences in vertical component between onshore and offshore motions, the vertical-to-horizontal peak ground acceleration ratio (V/H PGA ratio) and vertical-to-horizontal response spectral ratio (V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system (SEMS). The results indicate that the vertical component of offshore motions is lower than that of onshore motions. The V/H PGA ratio of acceleration time histories at offshore stations is about 50% of the ratio at onshore stations. The V/H for offshore ground motions is lower than that for onshore motions, especially for periods less than 0.8 s. Furthermore, based on the results in statistical analysis for offshore recordings in the K-NET, the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.

Keywords

offshore ground motion / vertical component / simplified design equation / vertical-to-horizontal response spectral ratio (V/H) / vertical-to-horizontal peak ground acceleration ratio (V/H PGA ratio) / K-NET network / seafloor earthquake measuring system (SEMS)

References

[1] RP2A-WSD A P I.Recommended practice for planning, designing and constructing fixed offshore platforms–working stress design [R], 2000

[2] ChenB-k, WangD-s, LiH-n, SunZ-g, ShiYan. Characteristics of earthquake ground motion on the seafloor [J]. Journal of Earthquake Engineering, 2015, 19(6): 874-904

[3] LuY-j, PengY-j, TangR-y, ShaH-j, ZhaoJ-tao. The discussion on some problems in seismic design code of offshore platform in China [J]. Progress in Geophysics, 2008, 23(2): 443-449

[4] BooreD M, SmithC E. Analysis of earthquake recordings obtained from the seafloor earthquake measurement system (SEMS) instruments deployed off the coast of southern California [J]. Bulletin of the Seismological Society of America, 1999, 89(1): 260-274

[5] DiaoH-q, HuJ-j, Xiel-li. Effect of seawater on incident plane P and SV waves at ocean bottom and engineering characteristics of offshore ground motion records off the coast of southern California, USA [J]. Earthquake Engineering and Engineering Vibration, 2014, 13(2): 181-194

[6] AmbraseysN N, DouglasJ. Near-field horizontal and vertical earthquake ground motions [J]. Soil Dynamics and Earthquake Engineering, 2003, 23(1): 1-18

[7] BozorgniaY, CampbellK W. The vertical-to-horizontal response spectral ratio and tentative procedures for developing simplified V/H and vertical design spectra [J]. Journal of Earthquake Engineering, 2004, 8(2): 175-207

[8] GulerceZ, AbrahamsonN A. Site-specific design spectra for vertical ground motion [J]. Earthquake Spectra, 2011, 27(4): 1023-1047

[9] TezcanJ, ChengQ. A nonparametric characterization of vertical ground motion effects [J]. Earthquake Engineering and Structural Dynamics, 2012, 41(3): 515-530

[10] BruneauM. Preliminary report of structural damage from the Loma Prieta (San Francisco) earthquake of 1989 and pertinence to Canadian structural engineering practice [J]. Canadian Journal of Civil Engineering, 1990, 17(2): 198-208

[11] ElgamalA, HeL. Vertical earthquake ground motion records: an overview [J]. Journal of Earthquake Engineering, 2004, 8(5): 663-697

[12] OuJ-p, LiH. The regional engineering damage and reconstruction strategy in Wenchuan earthquake of China [J]. Journal of Earthquake and Tsunami, 2011, 5(02): 189-216

[13] NortonJ A, KingA B, BullD K, ChapmanH E, McverryG H, LarkinT J, SpringK C. Northridge earthquake reconnaissance report [J]. Bulletin of the New Zealand National Society for Earthquake Engineering, 1994, 27(4): 235-344

[14] BozorgniaY, NiaziM, CampbellK W. Characteristics of free-field vertical ground motion during the Northridge earthquake [J]. Earthquake Spectra, 1995, 11(4): 515-525

[15] AoiS, KunugiT, FujiwaraH. Strong-motion seismograph network operated by NIED: K-NET AND KiK-NET [J]. Journal of Japan Association for Earthquake Engineering, 2004, 4(3): 65-74

[16] Earth, Planets and Space, 2004, 56(8

[17] NagashimaF, MatsushimaS, KawaseH, SanchezesmaF J, HayakawaT, SatohT, OshimaM. Application of horizontal-to-vertical spectral ratios of earthquake ground motions to identify subsurface structures at and around the K-NET site in Tohoku, Japan [J]. Bulletin of the Seismological Society of America, 2014, 1045): 2288-2302

[18] EguchiT, FujinawaY, FujitaE, IwasakiS I, WatabeI, FujiwaraH. A real-time observation network of ocean-bottomeismometers deployed at the Sagami trough subduction zone, central Japan [J]. Marine Geophysical Researches, 1998, 20: 73-94

[19] YazawaK, TsuchiyaH, IkedaF. Surficial sediment in Tokyo bay and Sagami bay [J]. Bulletin of the Kanagawa Prefectural Fisheries Experiment Station, 1986, 7: 5-16

[20] WuZ-j, WangL-m, WangP, ChenT, ShiH, YangX-peng. Influence of site conditions on ground motion at far field loess sites during strong earthquake [J]. Journal of Central South University, 2013, 20: 2333-2341

[21] PoggiV, EdwardsB, FahD. Characterizing the vertical-tohorizontal ratio of ground motion at soft-sediment sites [J]. Bulletin of the Seismological Society of America, 2012, 102(6): 2741-2756

[22] CrouseC B, QuilterJ. Seismic hazard analysis and development of design spectra for maul a platform [C]//. Proceedings of Pacific Conference on Earthquake Engineering, 1991137-148

[23] TakahashiK, OhnoS, TakemuraM, OhtaT, SugawaraY, HatoriT, OmoteS. Observation of earthquake strong motion with deep borehole: generation of vertical motion propagating in surface layers after S-wave arrival [C]//. Proceedings of the 10th World Conference on Earthquake Engineering, 19921245-1250

[24] YangJ, SatoT. Interpretation of seismic vertical amplification observed at an array site [J]. Bulletin of the Seismological Society of America, 2000, 90(2): 275-285