Considerations for a "design" earthquake

  • G. L. Evans University of Canterbury, Christchurch, New Zealand


Any structure is only as good as its foundation material. Under earthquake the properties of foundation materials can change drastically. Recent advances in soil dynamics indicate that the simplifying assumptions on which our seismic building code is based, are not adequate to cater for the variations in foundation conditions. The code provides
clear definition of seismic design forces, in terms of acceleration and period, but ignores any possible effects of displacement, velocity or wavelength. Currently available methods of design and analysis can provide for calculation of ground period, displacements, velocities, accelerations and stress values at any point in a soil mass. Although not perhaps suitable
for detailed code recommendations these methods can be used by designers where needed and the code could contain simplified but conservative data on the use of such methods, The design forces to be imposed on a structure and variations of these are defined exactly in the code, but these are not matched by the definition of base motions, which are influenced by magnitude of the earthquake, distance and soil properties. It should be possible to provide for a "design earthquake" which takes into account, type of structure, nature of
 risk, magnitude of earthquake, distance from active seismic areas and soil properties. Even relative factors, initially based on overseas research, relating these things would provide a more rational basis for seismic effects on structures than the simplified structure mass acceleration method used at present.


Jenschke, Clough and Penzien. “Characteristics of Strong Ground Motion". Proc. 3rd World Conf. Eq. Eng. Vol. 1. 1965.

Kanai. "On Earthquake Motions for Aseismic Designing". Proc. 4th World Conf. Eq. Eng. 1969.

Kobayashi. "Mechanism of Earthquake Damage to Embankments and Slopes", Proc. 4th World Conf. Eq. Eng. 1969.

Gutenburg & Richter. "Earthquake Magnitude Intensity Energy & Acceleration". Bull. Seism. Soc. Am. Vol. 46. 1956.

Gutenburg. "Effects of Ground on Earthquake Motion". Bull, Seism. Soc. Am. Vol. 47. 1957.

Seed and Idriss. "Influence of Soil Conditions on Ground Motions During Earthquake". Proc. A.S.C.E. Soil Mech. Div. SMI. 1969.

Dibaj and Penzien. "Response of Earth Dams to Travelling Seismic Waves." Proc. A.S.C.E. Soil Mech. Div. SM2. 1969.

Yershov, Lyamzine Shteinburg. "Methods of estimating the Effects of Superficial Deposits on the Intensity of Seismic Oscillations". Proc. 3rd World Conf. Eq. Eng.Vol.I. 1965.

Medvedev. "Engineering Seismology". Academy of Sciences U.S.S.R. Israel translation. 1965.

Dick."Extreme Value Theory and Earthquakes". Proc. 3rd World Conf. Eq.Eng.Vol.I. 1965.

Garden. "A General Introduction to the Seismic Design Problem". Bull. N.Z.Soc. Earthq. Engs. Vol. 2 No. 3. 1969.

How to Cite
Evans, G. L. (1972). Considerations for a "design" earthquake. Bulletin of the New Zealand Society for Earthquake Engineering, 5(2), 47-50.