Cellular normal modes of alluvium response

  • W. R. Stephenson DSIR Physics and Engineering Laboratory, Lower Hutt, New Zealand


The concept of directed resonance is put forward, and its occurrence in New Zealand and overseas is documented. It is observed mainly on water-saturated recent alluvium. Analytical procedures for detecting directed resonance effects in earthquake records are outlined. The resonance parameters are shown to be independent of the particular earthquake, and highly dependent on local boundaries of the alluvium.

Cellular mode resonant response is suggested to be the mechanism generating directed resonance at individual sites, and is shown to occur for scale models of alluvial deposits.

Experimental apparatus which would be needed to unequivocally confirm the earthquake excitation of cellular resonant modes is described in an appendix.


Idriss, I. M. and Seed, H. B., "Seismic Response of Horizontal Soil Layers". J. Soil Mech. Fdns. Div. Am. Soc. Civ. Engrs. 94: SM4 p 1003 (1968) .

Idriss, I. M. "Finite Element Analysis for the Seismic Response of Earth Banks". J. Soil Mech. Fdns. Div. Am. Soc. Civ. Engrs. 94: SMS p 617 (1968).

Stephenson, W. R. "Microzoning for Design" in "Structural Design for Earthquakes", University of Auckland, New Zealand, August, 1972.

Skinner, R. I., Beck, J. L. and Bycroft, G. N. "A Practical System for Isolating Structures from Earthquake Attack". Intl. J. of Eq. Eng. and Struct. Dyn. 1975 (In print).

How to Cite
Stephenson, W. R. (1975). Cellular normal modes of alluvium response. Bulletin of the New Zealand Society for Earthquake Engineering, 8(4), 245-254. https://doi.org/10.5459/bnzsee.8.4.245-254