Dating coseismic marine terrace formation during the Kaikoura 2016 earthquake

The recent earthquake in Kaikoura, New Zealand on 14th November 2016 resulted in the uplift of large stretches of coast. Previously intertidal rocky shore platforms cut into bedrock are now stranded high and dry above the tides. The opportunity to observe the marooning of raised marine terraces is rare, yet these are ubiquitous landforms flanking the coasts in tectonically active settings around the globe, from the edges of the Mediterranean Sea to the Pacific margin of the Andes and Rocky mountains. These marine terraces previously formed at sea level are important spatial and chronologic markers of the interactions between tectonic uplift and eustatic sea level change that allow reconstruction of a history of tectonic uplift rates. Terraces can be dated using cosmogenic isotopes (CIs), but the accuracy of ages is tied to inherent (and untested) assumptions about the nuclide inventory at the time of terrace abandonment. Moreover, their formation and abandonment are poorly understood because the processes involved are not typically observed in real time.

The goal of this project is to address both of these existing knowledge gaps and use a shore platform instantaneously uplifted and abandoned during the 14th November 2016 Kaikoura, New Zealand earthquake to directly observe the processes of formation and abandonment of marine platforms. The Kaikoura earthquake demonstrated that the formation of stranded marine terraces can be due to instantaneous, coseismic uplift of previously active rocky shore platforms. We will measure 10Be concentrations from the surface of a newly stranded shore platform in a transect of in-situ bedrock samples so as to determine the apparent platform age at the time of terrace formation. We will also use measured 10Be concentrations in concert with existing data on shore platform and coastal erosion to understand the prior history of shore-platform development leading up to the earthquake in order to understand the inheritance of 10Be accumulated during active coastal development. The proposed work is vital for the provision of a baseline for future studies both locally and globally. Sampling must take place as soon as possible, prior to any significant breakdown of the surface due to subaerial weathering, deposition or human modification. This rare event provides a unique opportunity to calibrate and validate existing models for platform abandonment and evolution, and in turn improve our assessment of vertical tectonic rates and associated hazards in tectonically active coastal regions around the globe.

Tectonic uplift and the interactions with relative sea level change and coastal erosion is of concern to a wide variety of organisations. Knowledge about earthquakes and uplift of coasts is required to quantify future earthquake and coastal erosion hazards and risks. This project will provide a stepping stone towards achieving these impact goals by pump-priming future research efforts with high quality baseline data, but will also deliver some shorter term impact goals to maximise the value of this short project whilst providing a springboard to achieve impact with future research.

Potential Beneficiaries

Primary beneficiaries of this work will be government organisations with responsibility to quantify the likelihood of earthquake hazards and associated risk, and those with responsibility for managing coastal erosion and storm surge risks in the face of rising sea levels and projections of heightened storm severity and frequency. Secondary beneficiaries of this project will be secondary school students and the general public.

Impact will maximised through three engagement activities:

1) Compile a report on the "State of science" of rock coast processes targeted at coastal practitioners and non-specialists, focused on the relationship between coastal erosion and geological processes. The document will be written with the support from PPs at Scottish Natural Heritage, Environment Canterbury and GNS Science and will be circulated widely to government agencies, local authorities, non-government organisations and consultants both in the UK and New Zealand.

2) Deliver new educational resources on rocky coast geomorphology to geography teachers, presented to the Scottish Geography Teachers Association. This will provide high school students with a better understanding of how rocky coasts are formed and develop through time, and how our coasts are likely to change in the future.

3) Engage the public with our research through face-to-face and online promotion. Members of the public will benefit through delivery of a public lecture and group workshop towards the end of the project. A web page will be established where regular project updates will be posted and promoted through social media.

We will establish and maintain close relationships with our project partners to embed them in these activities and our future research design. We will assess the extent to which these activities have improved our beneficiaries' knowledge and understanding using targeted surveys. Finally, we will promote activities widely using a strategic approach to social media that will maximise the exposure of our research to key organisations, the public and academic communities.