Reliability of lateral stretch estimates in 2010-2011 Canterbury earthquakes

Several methods are available in the literature to estimate the extent of liquefaction induced lateral spreading at a given site, the most commonly used being that of Zhang et al (2004). During the 2010-2011 sequence of earthquakes in Canterbury, lateral spreading occurred extensively across the region.

Following recent site specific investigations, site inspections, land owner evidence and the significant quantity of data available on Project Orbit, the authors compare estimates of lateral movement computed using the Zhang et al method with estimates of actual movement that occurred across several sites within Canterbury.

The concept of lateral stretch, being the differential lateral spread over a 20 metre distance perpendicular to a free face, is introduced. It is found that predictions of lateral stretch using the Zhang et al method give moderately good agreement with the measured values. Suggested 5th and 95th percentile design limits are presented.