Facsimile Borehole Core: Dallington
One cylindrical facsimile core showing geological layers based on a borehole made in Dallington, Christchurch; created for the Canterbury Quakes exhibition, February-October 2012 and subsequent tour.
Borehole cores have been used to measure the difference in ground conditions in eastern and western parts of Christchurch and help to explain why the eastern suburbs had more liquefaction than western suburbs during large earthquakes. This simulated borehole core represents the ground conditions in Dallington, a suburb in the east of Christchurch. It has fine soil deposits so sediment is in the optimum size range for liquefaction to occur. In contrast, the western suburbs tend to have larger gravel like deposits, which are not prone to liquefaction. In Christchurch, liquefaction potential depends very much on the height of the groundwater table at the time of a large earthquake. The core shows that the groundwater table is only 1m below the surface, indicating that this ground has a higher potential to liquefy.