Seismic activity during the 2010/2011 Canterbury Earthquake Sequence (CES) caused widespread damage to sloping ground in residential areas on the Port Hills in Christchurch. Much of the damage manifested as cracking and displacement of the ground surface. While actions were taken to repair some damage, it was largely untreated in the short term, resulting in concerns about the effect that this may have on the stability of the affected slopes in future rainfall events.
This paper presents the preliminary findings of an assessment of the occurrence and nature of small scale (<100 m2) land instability that occurs on residential properties in Port Hills suburbs, as a result of rainfall events, using insurance data obtained before and after the CES. Using insurance claims as a proxy for small scale landslips on Port Hills suburbs shows there is no distinct change in the frequency of small scale landslip activity since the beginning of the CES.