Paleoseismicity of the Alpine Fault and Hikurangi

 

This project uses the analysis of ocean floor sediments to help discover a 20,000 year history of major earthquakes in the Alpine Fault and Hikurangi region.

The problem

Understanding past earthquakes is one of the keys to predicting how a fault with behave in the future. The mechanisms and timing of the earthquakes associated with plate boundary rupture in the Alpine Fault and Hikurangi subduction zone regions are poorly known. There are only four recognised paleoearthquakes associated with ruptures of the Alpine Fault and a few that are attributed, though ambiguously, to the Hikurangi Subduction zone.

The analysis of ocean floor sediments (built up over thousands of years) for evidence of major earthquakes in the past has been successful in other countries, but this technique has never been used in New Zealand before.

We aim to build this record by analysing high-resolution sedimentation records from marine cores collected in these areas. The research will significantly advance our understanding of fundamental seismotectonic processes; earthquake behaviour of major plate boundary structures; background tectonic framework and hazard landscape of New Zealand; and rates of tectonic processes that drive landscape instability and deformation.

The research will significantly advance our understanding of fundamental seismotectonic processes; earthquake behaviour of major plate boundary structures; background tectonic framework and hazard landscape of New Zealand; and rates of tectonic processes that drive landscape instability and deformation.

The solution

The research is based on the high-resolution analysis of marine sediment cores collected along the Westland, Fiordland and north-eastern North Island continental shelves and slopes. These include long cores from RV Marion Dufresne acquired during the NIWA co-led international Matacore project. These cores contain a large number of marine sediment deposits from catastrophic events (turbidites), which have been used by others as proxies for ancient earthquakes.

We hypothesise that earthquakes generated along the Alpine Fault and the Hikurangi subduction margin produced distinctive turbidites that can be used as co-seismic proxies. This will provide good spatial and temporal constraints on these earthquakes sources. Ages and origins of the turbidites will be derived from sedimentological, physical and magnetic analyses of a comprehensive suite of core samples.. The co-seismic origin of turbidites will be established by demonstrating their synchronicity over multiple catchments, a key criterion to differentiate earthquake from climatic triggering. Identified paleoearthquakes younger than 1000 years will be correlated to events identified through other studies.

We have developed national and international collaborations for this research. The team has extensive technical and scientific expertise in submarine landslides, seismic processes, stable isotopes, paleotsunamis and sedimentology and a well established record of scientific and public dissemination. Otago University will bring expertise and state-of-the-art technologies to study the paleomagnetic signal in marine sediments.

Collaborations are in place with institutions in France (CNRS Rennes and UMR Géosciences Azur) and the USA (VIMS and SKIO, and NSF-MARGINS participants), who have built expertise on the use of turbidites as co-seismic proxies on the Cascadian, Oregon, Ligurian and Ecuadorian margins.

The result

This program has only started in July 2008, and to date, good progress has been made in building an inventory of all sedimentary cores collected within the region of interest that are available for this project. Complementary work is also being undertaken on-land by GNS Science and synergies are being created with other research groups who could contribute expertise to the offshore studies (sedimentology, paleomagnetism, geochemical analyses) from Victoria and Auckland Universities. Dr Jean-Noël Proust (CNRS-Géosciences Rennes), a key collaborator in the project, visited NIWA to initiate the selection of cores and discuss the strategic sampling strategy to implement.

Media library

The aim of this research program, which commenced in July 2008, is to extend the record of ancient earthquake from the Hikurangi and Alpine Fault area, using evidence of major ground shaking in marine sedimentation records. This is being performed using sedimentary cores already collected from the area. Good progress has been made in building an inventory of all sedimentary cores collected within the region of interest that are available for this project. Complementary work is also being undertaken on-land by GNS Science and synergies are being created with other research groups who could contribute expertise to the offshore studies from Victoria and Auckland Universities.

Dr Jean-Noël Proust (CNRS-Géosciences Rennes), a key collaborator in the project, visited NIWA to initiate the selection of cores and discuss the strategic sampling strategy to implement. The University of Rennes has obtained funding for a PhD research project on paleo-seismicity and paleo-flood in the East Cape region. This will be co-supervised by a NIWA scientist and aid our research effort.

A two-day science planning workshop was held in Wellington with most scientists involved in the project being present, including a French collaborator from CNRS-Géosciences Rennes, France. The workshop enabled participants to discuss and agree on a core sampling and analysis strategy and a timeline. Targeted areas and cores where the research should focus initially were identified, as well as methods for dating individual seismic events.

NIWA Contacts

Principal Scientist - Marine Geology
Page last updated: 
22 February 2014
Sediment Core - Geoffroy Lamarche
Research subject: Oceans