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▲ ▲ Figure 1. Aerial image of the Canterbury Plains region. Black bordered areas are those that liquefied during the 4 September 2010M w 7.1 Darfield earthquake, while the white shaded areas are those that liquefied during the 22 February 2011 M w 6.2 Christchurchearthquake.(Environment Canterbury [ECan] 2004). This is especially thecase in the eastern portion of Christchurch where the groundwater table is only one to two meters below the ground surface.Unfortunately, the intense shaking of the Darfield andChristchurch earthquakes proved correct ECan’s (2004) findingsregarding the high liquefaction susceptibility of these soils.As shown in Figure 1, widespread liquefaction occurred inthe eastern part of Christchurch and in Kaiapoi during boththe Darfield and Christchurch earthquakes (also see Orense etal. 2011, page 905 of this issue). However, the Christchurchearthquake caused more widespread liquefaction in highlydeveloped areas than did the Darfield earthquake due to therelative close proximity of the fault rupture. For example,liquefaction occurred in large portions of the CBD duringthe Christchurch earthquake that did not liquefy during theDarfield earthquake (Cubrinovski et al. 2011, page 893 ofthis issue). The areas most severely affected by liquefactionwere the suburbs along the Avon River to the east of the CBD(Avonside, Dallington, Avondale, Burwood, and Bexley). Thesoils in these suburbs are predominantly loose fluvial depositsof clean fine sands and sands with non-plastic silts, with the top5–6 m in a very loose state (Gerstenberger et al. 2011). Also,the town of Kaiapoi was significantly impacted by liquefactionduring both events, especially portions of the town that werebuilt on abandoned river channels and fill (Wotherspoon et al.2011).Figure 3 illustrates the typical manifestation of liquefactionon the streets of Christchurch. The severity of the liquefactionled to large settlements of many houses including differentialsettlements that caused foundation and structuraldamage. The largest damage to land and built environmentwas caused by liquefaction-induced lateral spreading along theAvon River, streams, and wetlands in the eastern Christchurchsuburbs. As mentioned above, lateral spreading displacementsranged anywhere from a few tens of centimeters up to 2 m at theriver banks and extended inland as far as 200–300 m from thewaterway, severely damaging roads, pipe networks, and residentialproperties within the affected zone (Robinson et al. 2011).IN-SITU TESTSFollowing both the Darfield and Christchurch earthquakes,GEER team members from the United States and NewZealand performed in-situ tests using the DCP and SASW.Both tests are portable and provide information about thesubsurface properties, making them suitable for immediate928 Seismological Research Letters Volume 82, Number 6 November/December 2011