Impacts of surface fault rupture on residential structures during the 2016 Mw 7.8 Kaikōura earthquake, New Zealand

Abstract

Areas that experience permanent ground deformation in earthquakes (e.g., surface fault rupture, slope failure, and/or liquefaction) typically sustain greater damage and loss compared to areas that experience strong ground shaking alone. The 2016 Mw 7.8 Kaikōura earthquake generated ≥220 km of surface fault rupture. The amount and style of surface rupture deformation varied considerably, ranging from centimetre-scale distributed folding to metre-scale discrete rupture. About a dozen buildings – mainly residential (or residential-type) structures comprising single-storey timber-framed houses, barns and wool sheds with lightweight roofing material – were directly impacted by surface fault rupture with the severity of damage correlating with both local discrete fault displacement and local strain. However, none of these buildings collapsed. This included a house built directly atop a discrete rupture that experienced ~10 m of lateral offset. The foundation and flooring system of this structure allowed decoupling of much of the ground deformation from the superstructure thus preventing collapse. Nevertheless, buildings directly impacted by surface faulting suffered greater damage than comparable structures immediately outside the zone of surface rupture deformation. From a life-safety standpoint, all these buildings performed satisfactorily and provide insight into construction styles that could be employed to facilitate non-collapse performance resulting from surface fault rupture and, in certain instances, even post-event functionality.

Estimating Plate Tectonic Forces at the New Zealand Plate Boundary Using Strain Rates Derived From a Kinematic Model of Fault Slip

“…Our kinematic observations are smoothed strain rates derived from the HS22-CFM model of Hirschberg and Sutherland (2022), which is derived from Quaternary fault slip rates of the New Zealand Community Fault Model (Seebeck et al, 2022;Van Dissen et al, 2021). We smooth their velocity field using a Gaussian filter with σ = 50 km, which removes discontinuities in the velocity field at faults and simplifies the model to a continuum.…”

A Kinematic Model of Quaternary Fault Slip Rates and Distributed Deformation at the New Zealand Plate Boundary

“…We repeat our modeling using the recently released New Zealand Community Fault Model (NZ CFM) v1.0 (Seebeck et al, 2022;Van Dissen et al, 2021) in place of Litchfield et al's (2014) model. The NZ CFM-based model, which we call HS22-CFM, has a mean fit to fault observations of ∼0.8/observation.…”

Editorial

“…I hope by now you have managed to read the three papers in the previous issue [1][2][3]. These three papers exemplify the wide range of topics covered by the Bulletin in true sense.…”

“…These three papers exemplify the wide range of topics covered by the Bulletin in true sense. The first paper by Van Dissen et al [1] presented a case study of eight residential buildings directly impacted by the complex and unique surface fault rupture during the 2016 Kaikōura earthquake. The second paper by Khakurel et al [2] presented results of building cladding surveys conducted on residential buildings in Christchurch to quantify the proportion of different types of claddings used in residential buildings.…”