Landslides and liquefaction generated by the cook strait and lake grassmere earthquakes: A reconnaissance report

Abstract

Following both the Cook Strait earthquake (Mw 6.6; 21 July, 2013) and the Lake Grassmere earthquake (Mw 6.6; 16 August, 2013) reconnaissance visits were made of the epicentral regions to document the general distribution and extend of landslides, liquefaction, and other ground damage effects generated by these earthquakes. The extent of landsliding generated in central New Zealand by these two earthquakes was at the lower end of the expected range for shallow earthquakes of these magnitudes. Liquefaction effects generated by the Cook Strait and Lake Grassmere earthquakes in central New Zealand were substantially less than those generated by the 2010-2011 Canterbury earthquakes in the Christchurch area, despite the fact that the Cook Strait and Lake Grassmere earthquakes were of comparable size and proximity, and impacted grossly similar geological settings. There is no evidence of primary ground-surface fault rupture during the Lake Grassmere earthquake.