Evolution of the physical, geochemical and mechanical properties of the Alpine Fault Zone: A journey through an active plate boundary

Lead Research Organisation: University of Liverpool
Department Name: Earth, Ocean and Ecological Sciences

Abstract

This proposal is the UK component of a major international campaign, the Deep Fault Drilling Project (DFDP) to drill a series of holes into the Alpine Fault, New Zealand. The overarching aim of the DFDP to understand better the processes that lead to major earthquakes by taking cores and observing a major continental fault during its build up to a large seismic event. The next stage of this project will be to drill and instrument a 1.5 km hole into the Alpine Fault.

Earthquakes are major geohazards. Although scientists can predict where on the Earth's surface earthquakes are most likely to occur, principally along plate boundaries, we have only imperfect knowledge. We also don't know when earthquakes will occur. This is well illustrated by recent events on the South Island of NZ. Two earthquakes in Christchurch in Sept 2010 and Feb 2011 caused 181 deaths and £7-10 billion of damage (~10% of NZ GDP). Yet Christchurch had previously been considered of relatively low seismic risk. In contrast, the western side of the South Island is defined by the Southern Alps, a major mountain chain (>3700 m) formed along the Australian-Pacific Plate boundary. Until a few million years ago this plate boundary was a strike-slip fault like the San Andreas Fault in California, but subtle changes in plate motion has led to the collision of the Pacific and Australian Plates. This caused uplift of the mountains and due to very high rates of rainfall and erosion, rapid exhumation of rocks that until recently had been deep within the Earth. Although these plates are moving past each other at ~30 mm/y and the uplift rate in the Southern Alps approaches 10 mm/y, there has not been a major earthquake along the Alpine Fault in NZ's, albeit short, written history. However, there is palaeo-seismic evidence that major earthquakes do occur along the Alpine Fault with magnitude ~8 earthquakes occurring every 200-400 years, with the latest event in 1717 AD.

Earthquake occur because stresses build-u within the relatively strong brittle upper crust. At greater depths (>15 km) rocks can flow plastically and plates can move past each other without building up dangerous stresses. On some faults, the brittle crust "creeps" in numerous small micro-earthquake events and this inhibits the build up of stress. Unfortunately there are few even micro-earthquake events along the Alpine Fault or surface evidence for deformation, suggesting that the stresses along this plate boundary have been building up since 1717 - if that stress was released in a single earthquake it would result in a horizontal offset across the fault of >8m!

A major hindrance to earthquake research is a lack of fault rock samples from the depths where stresses build up before an earthquake. Fault rocks exposed at the surface tend to be strongly altered. The strength of fault rocks will depend on a number of factors include pressure, temperature and the nature of the materials, but also whether there are geothermal fluids present. The geometry of the Alpine Fault is special in that the fault rocks that were recently deforming at depth within the crust are exposed close to the surface. Also because of rapid uplift and erosion the local geothermal gradients are high and relatively hot rocks are near the surface. This results in a relatively shallow depth (5-8 km) for the transition from brittle to plastic behaviour. This provides a unique opportunity to drill into the fault zone to recover cores of the fault, to undertake tests of the borehole strata, and to install within the borehole instruments to measure temperature, fluid pressures, and seismic activity. Once core samples are recovered we will perform geochemical and microstructural analyses on the fault rocks to understand the conditions at which they were deformed. We will subject them to geomechanical testing to see how changes in their environment affects the strength of the rocks and their ability to accommodate stresses before breaking.

Planned Impact

This project will make significant advancement towards understanding the behaviour of fault rocks within a major continental plate boundary, the Alpine Fault of New Zealand, and give broad insight into why earthquakes occur.

The following communities will principally benefit from this research:
-Local Government Agencies in New Zealand: The Alpine Fault is at a late stage of its inter-seismic cycle. Its rupture in a large earthquake will have major consequences on the population of the West Coast of the South Island, on all infrastructures as well as on tourism and the environment. Regional Councils, the NZ Transport Agency, the Department of Conservation (Te Papa Atawhai), and the Earthquake Commission of NZ (the government agency providing natural disaster insurance) are identified as primary users of knowledge relevant to earthquake hazards, which will inform existing and new/adapted regulations and policies. Parallel Agencies worldwide may also benefit from this research. Our engagement efforts will be undertaken in collaboration with NZ project partners (GNS Science; Univ. Otago, Auckland, Victoria), to best package our technical findings for local, regional and national geohazards professionals and the wider New Zealand community. Our aim is to develop published materials that are directly focused on geohazards issues. We will ensure our UK project website links effectively with existing and new NZ-based geohazard information.

-School children are inspired by earthquakes, their societal impacts, and the dynamics of our planet. Our gained knowledge, communicated at appropriate levels for different ages of children, will raise awareness of natural hazards and provide renewed interest in STEM subjects and technical careers related to Earth and its environment.

-The general public are interested in the devastating effects of natural disasters and become engaged when Earth processes and hazards are clearly explained through mass media.

Engagement and Dissemination:
-The project will engage for 6 h/w a Knowledge Exchange Officer (KEO) to establish and keep updated the "Journey through a Plate Boundary - DFDP-2" Website. The KEO will liaise with our international partners and programs (e.g., ICDP), stake holders, NZ Local Government Agencies, industrial end-users, schools and the wider public. The KEO with PIs and researchers will develop digestible scientific explanations of the project aims and findings for schools and the wider public than can be accessed from the website. They will deliver outreach materials and presentations on the project and its outcomes to schools in the UK. The website will detail drilling operations of DFDP2 and report scientific outputs from the borehole observatory and from collaborating research groups. It will enable open-source access to abstracts, peer-reviewed publications, and reports. It will be linked with relevant existing websites at the GNS Science NZ (drill.gns.cri.nz) and GeoNet NZ that monitors geological hazards. The KEO will help organize the project end symposium with project partners and end-users.

-Public Lectures will be organised in local communities during the drilling operations, to inform and communicate with the general public and policy-makers on the scientific relevance of the drilling and its outcomes. DFDP Phase 1 sparked major media attention in NZ and we anticipate that Phase 2 will have even greater impact. The P.I.s, PDRAs and PhD student and the KEO will all engage UK Science Week, University Open Days, and other UK public engagement lectures.

-Communication with mass media will be organised through the Science Media Centre (SMC), London. Faulkner, Mariani and Teagle are part of the SMC existing database of scientists for breaking news. The P.I.s and DFDP Team have excellent track records of public and media engagement.

Training: PDRAs and PhD student will attend the "Communicating science to the public" training course organised by NERC.

Publications

10 25 50

publication icon
Faulkner D (2018) Pore Fluid Pressure Development in Compacting Fault Gouge in Theory, Experiments, and Nature in Journal of Geophysical Research: Solid Earth

 
Description We have been able to provide a full description of the suite of fault rocks surrounding a major plate boundary fault system.
We have discovered unusually high flux of hot fluid in the near surface close to the Alpine Fault Zone.
Exploitation Route This provides a framework for future studies on the Alpine Fault in New Zealand and other seismogenic plate boundary fault zones.
Sectors Construction,Environment

 
Description We have participated in outreach activities in the local community in New Zealand that would be most affected by seismic activity along the Alpine Fault Zone.
First Year Of Impact 2014
Sector Education
Impact Types Societal

 
Description Hydrothermal fault alteration 
Organisation Pontifical Catholic University of Chile
Country Chile 
Sector Academic/University 
PI Contribution Expertise provided on the structure of fault zones and the properties of damage zones, data processing and analysis and drafting of publications.
Collaborator Contribution Data collection, analysis and publication write up.
Impact Publications: Arancibia, G., Fujita, K., Hoshino, K., Mitchell, T.M., Cembrano, J., Gomila, R., Morata, D., Faulkner, D.R. and Rempe, M. 2014. Hydrothermal alteration in an exhumed crustal fault zone: geochemical mobility in the Caleta Coloso Fault, Atacama Fault System, Northern Chile. Tectonophysics 623, 147-168. doi: 10.1016/j.tecto.2014.03.024. Gomila, R., Arancibia G. Mitchell T., Cembrano J. and Faulkner D.R. palaeopermeability structure within fault-damage zones: A snap-shot from microfracture analyses in a strike-slip system. Journal of Structural Geology, 2015.
 
Description Marsden - Adam 
Organisation University of Auckland
Country New Zealand 
Sector Academic/University 
PI Contribution This is a recently funded Marsden application awarded to Dr Ludmila Adam on which I am a named collaborator.
Collaborator Contribution Dr Adam will visit my laboratory and we will pursue joint measurements on the elastic properties of rock using a range of techniques.
Impact None as yet.
Start Year 2014
 
Description Radio interview 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Interviewed on RadioCity Talk radio concerning earthquake research.
Year(s) Of Engagement Activity 2015
 
Description School engagement in New Zealand 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Dan Faulkner and Elisabetta Mariani helped develop an outreach activity for local school children on the West Coast of New Zealand during the drilling of DFDP2 (Deep Fault Drilling Program) in October/November 2014. We raised awareness of earthquake activity, the drilling project and what actions to take in the event of an earthquake to the school children and their teachers.

The childrens' awareness of seismic hazard and what precautions to take in the event of an earthquake was raised.
Year(s) Of Engagement Activity 2014
 
Description School visits - seismometers for schools project 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Numerous visits to schools have been made as part of the 'Seismometers for Schools' project.
Year(s) Of Engagement Activity 2014,2015,2016,2017
 
Description Scientific advisor for BBC iWonder website 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I was asked to be the scientific advisor for a BBC iWonder website on 'Predicting Earthquakes'.
Year(s) Of Engagement Activity 2015
URL http://www.bbc.co.uk/guides/zxyd2p3