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▲ ▲ Figure 2. Aerial image of Christchurch and its environs. Bullets are the location of the strong motion instrument stations, with thegeometric mean of the peak horizontal accelerations listed for the M w 7.1 Darfield earthquake (first number) and the M w 6.2 Christchurchearthquake (second number).post-earthquake reconnaissance investigations. Of particularinterest to the team were the properties of the soils thatliquefied in either, or both, the Darfield and Christchurchearthquakes. In the following, the DCP and SASW equipment,tests performed, and data reduction are described inmore detail.Dynamic Cone Penetrometer (DCP)The dynamic cone penetrometer (DCP) used for this studywas designed by Professor George Sowers (Sowers and Hedges1966) and is shown in Figure 4. This system utilizes a 6.8-kgmass (15-lb drop weight) on an E-rod slide drive to penetratean oversized 45° apex angle cone. The cone is oversized toreduce rod friction behind the tip. At sites that liquefied, theDCP tests were performed in hand-augered holes that werebored to the top of the layer that liquefied, as determined bycomparing the liquefaction ejecta to the auger tailings. At thesites tested that did not liquefy, the augered holes were boredto the top of the potentially liquefiable layer (i.e., sand layerbelow the ground water table), if such a layer was found. Theaugered holes minimized rod friction and allowed collectionof samples of the liquefiable soil. Experience has shown thatthe DCP can be used effectively in augered holes to depths upto 4.6 to 6.1 m.The DCP tests consist of counting the number of drops ofthe 6.8-kg mass that is required to advance the cone ~4.5 cm(1.75 inches), with the number of drops, or blow count, referredto as the DCP N-value or N DCPT . N DCPT is approximatelyequal to the standard penetration test (SPT) blow count upto an N-value of about 10 (Sowers and Hedges 1966; Green etal. forthcoming). However, beyond an N-value of 10, the relationshipbecomes non-linear. Figure 5A shows the relationshipbetween SPT and DCP N-values that was used in this study,which is a slightly modified version of the one proposed bySowers and Hedges (1966). The modifications to the Sowersand Hedges (1966) relationship are specific to the soils in theCanterbury region and are based on comparing the N DCPTvalues to SPT N-values, cone penetration test (CPT) tip resistance,and shear wave velocity measurements made near theDCP test sites.Following the procedure outlined in Olson et al. (forthcoming),the SPT equivalent N-values (N SPTequiv ) values werenormalized for effective overburden stress and hammer energyusing the following relationship:Seismological Research Letters Volume 82, Number 6 November/December 2011 929