Liquefaction at Kaiapoi in the 1901 Cheviot, New Zealand, earthquake

Abstract

Seismic liquefaction occurred in northeast Kaiapoi during the 1901 Cheviot earthquake. A contemporary newspaper report describes the ejection of sand and lateral spreading in Waites' market garden at the east end of Sewell Street, Kaiapoi and also south of the Waimakariri River near Belfast. Piezocone probing and rotary drilling on the Waites property in Sewell Street and at three other sites in northeast Kaiapoi found loose, fine sands and silty sands with cone resistance 4: as low as 2 to 3 MPa; it is not surprising that liquefaction was observed in 1901. Lack of precise seismological parameters for the 1901 earthquake precludes any definite conclusions about the performance of liquefaction potential models. However, the occurrence of liquefaction strongly suggests that the M6.5 magnitude estimated by Dibble et al. [1980] is too small, and that local magnitude in 1901 was larger than the surface-wave value of about 6.9 of Dowrick and Smith [1990]. A value in the range of 7.1 to 7.5 seems more likely. Comparison of Dutch cone penetrometer resistances and standard penetration test N-values supports the old qc (bars)/N = 4 rule. Because of the large amount of scatter, use of the more refined rule of Robertson of Campanella, where qc /N is a function of D50, does not seem justified. The penetration testing results confirm that there is a significant risk of liquefaction at Kaiapoi. Furthermore, we now have four reference sites, each with slightly different soil conditions, whose performance can be monitored following future earthquakes in the region.