Christchurch seismic hazard pilot study
A pilot zoning study has been carried out for ground shaking hazard in the city of Christchurch, using the grade-3 procedures of the draft manual on seismic zonation for geotechnical hazards, being developed by Technical Committee TC-4 of the ISSMFE. Because of limited site data, we were not able to produce a complete zoning map for the city, but ground motions were estimated at six distinct sites for which borehole data was available, and this provided a good test for the procedures of the manual.
The city of Christchurch is situated on nearly 1 km of volcanic rock and alluvial sediments overlying greywacke basement, on the edge of the main seismic region of New Zealand. In addition to being an interesting site from the point of view of ground shaking, there are also liquefaction and slope stability hazards in the alluvial and beach sands found throughout the city, and in the recent loess deposits mantling the adjacent Port Hills.
In the pilot study of ground shaking hazard, a seismicity model for the central South Island region published recently by Elder et al. (1991) was combined with the attenuation model of Kawashima et al. (1984) recommended in the draft manual, to estimate rock motion at Christchurch, described by its acceleration response spectrum. Transfer functions were computed for the site response to estimate motions at the six selected sites using the Thomson-Haskell method. The results were highly sensitive to details of. the upper 30 m or so of the soil profile. In the local context, the large disparity between our estimates of ground shaking at Christchurch and those implicit in the draft revision of NZS 4203 are disturbing. According to our study the draft code underestimates shaking by about a factor of two or more.
Adams, J. (1980) "Paleoseismicity of the Alpine Fault Seismic Gap, New Zealand" Geology. Vol. 8, pp 72-76. DOI: https://doi.org/10.1130/0091-7613(1980)8<72:POTAFS>2.0.CO;2
Berrill, J.B. (1985a) "Seismic Hazard Analysis and Design Loads", Bull. N.Z. Nat. Soc. Earthq. Eng., Vol. 18, No 2, pp. 139-150.
Berrill, J.B. (1985b) "Distribution of Scatter in New Zealand Accelerograph Data", Bull. N.Z. Nat. Soc. Earthq. Eng., Vol. 18, No. 2, pp. 151-164.
Cowan, H.A. and McGlone, M. (1991) "Large Prehistoric Earthquakes and Rate of Slip on the Hope Fault at Glynn Wye, North Canterbury". J. Roy. Soc. N.Z., Vol. 21, pp 373-384. DOI: https://doi.org/10.1080/03036758.1991.10420834
Cornell, C.A. (1968) "Engineering Seismic Risk Analysis", Bull. Seism. Soc. Am., Vol. 58, pp 1583-1601.
Elder, D.McG., McCahon, I.F. and Yetton, M.D. (1991) "The Earthquake Hazard in Christchurch: a Detailed Evaluation", Research Report to EOC, Soils and Foundations Ltd, Christchurch, N.Z., 131 pp.
Fumal, T.E. and J.C. Tinsley (1985) "Mapping Shear-Wave Velocities of Near-Surface Geologic Materials", USGS Professional Paper No. 1360, pp. 127-149.
Haskell, N.A. (1960) "Crustal Reflection of Plane S-H Waves", Jour. Geophys. Res., Vol. 65, pp. 4147-4150. DOI: https://doi.org/10.1029/JZ065i012p04147
Joyner, W .B. and Boore, D.M. (1982) "Prediction of Earthquake Response Spectra", US Geol. Surv. Open-File Rept. 82-977, 16pp. DOI: https://doi.org/10.3133/ofr82977
Katayama, T., Iwasaki, T. and Seaki, M., (1978) "Statistical Analysis of Earthquake Acceleration Response Spectra", Trans. Japanese Society Civ. Eng., Vol. 10, pp. 311-313. DOI: https://doi.org/10.2208/jscej1969.1978.275_29
Kausel, E., Roesset, J.M., and Christian, J.T. (1976) "Non-linear Behavior in Soil-Structure Interaction", Jour. Geotech. Div. ASCE, Vol. 102, GT11, pp. 1159-1170.
Kawashima, K., Aizawa, K. and Takahashi, K. (1984) " Attenuation of Peak Ground Motion and Absolute Acceleration Response Spectra", Proc. 8th World Conf. Earthq. Eng., San Francisco, Vol. II pp 257-264.
McGuire, R.K. (1974) "Seismic Structural Response Risk Analysis Incorporating Peak Response Regressions on Earthquake Magnitude and Distance", PhD thesis, Mass. Inst. of Technology, 371 pp.
Matuschka, T., Berryman, K.R., O'Leary, A.J. McVerry, G.H. Mulholland, W.M. and Skinner, R.I. (1985) "New Zealand Seismic Analysis", Bull. N.Z. Soc. Earthq. Eng., Vol. 18, No. 4, pp. 313-322.
Nishenko, S.P. and Buland R. (1987). "A Generic Recurrence Interval Distribution for Earthquake Forecasting", Bull. Seism. Soc. Am., Vol. 77, pp. 1382-1399.
Peek, R.L. "Estimation of Seismic Risk for New Zealand: A Seismicity Model and Preliminary Design Spectra", Research Report No. 80:211, Dept. of Civil Engineering, University of Canterbury, 84 pp.
Rhodes, D.A., and Millar R.B. (1983) "Estimating the Hazard of Surface Faulting in a Single Fault Zone", in Seismotectonic Hazard Evaluation of the Clyde Dam Site, NZ Geological Survey Report EG 375.
Seed, H.B., Wong, R.T., Idriss, J.M., and Tokimatsu, K., (1984), Moduli and Damping Factors for Dynamic Analysis of Cohesionless Soils, Rep. UCB/EERC - 84/14, Earthq. Eng. Res. Center, Berkeley.
Smith, W.D. and Berryman, K. (1983) "Revised Estimates of Earthquake Hazard in New Zealand", Bulletin, N.Z. Nat. Soc. Earthq. Eng. Vol. 4, pp. 259-272.
Sun, J.I., Golesorkhi, R., and Seed, H.B., (1988), Dynamic Moduli and Damping Ratios for Cohesive Soils, Rep. UCB/EERC - 88/15, Earthq. Eng. Res. Center, Berkeley.
Copyright (c) 1993 J. B. Berril, R. O. Davis, I. F. McCahon
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