Kaikoura Quake Information Brought Together

Kaikoura Quake Information Brought Together in One Science Volume

GNS Science staff are major contributors to a landmark collection of research papers on the geoscience nitty-gritty of the 14 November 2016 magnitude 7.8 Kaikōura earthquake, which has been published this week.

The special Kaikōura Earthquake issue of the Bulletin of the Seismological Society of America contains 21 detailed articles that have been written by expert teams over the past 18 months.
The 21 papers join at least 60 others already published on the earthquake and its impacts.

A number of the papers in the bulletin are large collaborative efforts, with one having 47 co-authors. It involved analysis of all of the surface faulting and was led by earthquake geologist Nicola Litchfield of GNS Science.

It showed about two-thirds of the earthquake’s energy was released on the 24 surface-rupturing faults, with the remaining third occurring on the underlying Hikurangi subduction interface. This is the boundary where the Pacific and Australian tectonic plates meet.

The paper also noted that the rupture intervals of the two dozen faults involved in the earthquake range from 300 to 10,000 years. But scientists estimate the occasion when the all the intervals coincide, as happened in November 2016, is between 5000 and 10,000 years. This underlines that the Kaikōura earthquake was a rare event.

The Bulletin of the Seismological Society of America has its origins in the 1906 San Francisco earthquake and is regarded as one of the top earthquake science journals in the world.

Every so often, the Society publishes a ‘special issue’ in addition to its regular two-monthly edition. There have been eight special issues on different themes in the past 10 years.

The earthquake caused extensive surface deformation as it ruptured 24-plus faults with the largest horizontal displacement of 12m on the Kēkerengū Fault and vertical displacement (uplift) of 9m on the Papatea Fault. Along 110km of coastline, vertical movement ranged from subsidence of 2.5m to uplift of 6.5m.

There was also a small tsunami and tens of thousands of landslides over an area of about 10,000 square kilometres.

The rupture began near Waiau in North Canterbury and travelled northeast at about 2km-a-second and ended up off Cape Campbell in Marlborough. It covered 174km in about 74 seconds. The direction of rupture – southwest to northeast – strongly focused seismic energy toward the north.

An unusual feature were fault step-overs of up to 22km, where the rupture jumped between faults. This length of step-over had not previously been seen anywhere in the world.

For scientists, the quake provided a rare opportunity to study the surface expression and impacts of a major fault rupture.

Among the research themes explored in this publication are the complex distribution of surface ruptures and displacements, the subsequent slow-slip episode in the Hikurangi subduction zone, and how stress is transferred among tectonic regimes.

Topics covered in detail include satellite detection of land movement, geotechnical engineering, seismic energy radiation patterns, liquefaction, tsunami modelling and inundation, social science, and ground movement and shaking intensities in Wellington.

Earthquake-induced landslides also feature strongly in the publication. A paper led by engineering geologist Chris Massey of GNS Science with a large international team of colleagues characterises the large number of landslides associated with the earthquake.

It identifies distance from fault rupture as a better predictor of landslide density than maps of peak ground acceleration or peak ground velocity. The scientists also found that coastal slopes are more vulnerable to landslides than inland slopes in similar materials, likely because of many decades of being exposed to energetic coastal processes.

Staff at GNS Science are lead authors on three of the 21 papers and co-authors on a further seven. In total, 32 GNS Science staff contributed as either authors or co-authors.

The volume was coordinated by an editorial team comprising scientists Kelvin Berryman, Anna Kaiser and Ian Hamling from GNS Science and Tim Stahl from Canterbury University. The publication is the culmination of about eight months of work by this team.

Dr Berryman said the publication represented a milestone in the documentation of the processes and impacts of the Kaikōura earthquake and would be an important reference for the scientific community worldwide on this event. He added that the expertise and knowledge contained in the publication would feed into planning and mitigation of large earthquake impacts globally.

The Bulletin can be accessed here: https://pubs.geoscienceworld.org/bssa/issue/108/3B

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