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Deep Fault Drilling Project (DFDP)

 

Description

Alpine FaultThe mid-crust is the locus of several fundamental geological and geophysical phenomena: these include the transitions from brittle to ductile behaviour and from unstable to stable frictional sliding; earthquake nucleation and predominant moment release; the peak in the crustal stress envelope; the transition from predominantly cataclastic to mylonitic fault rocks; and mineralisation associated with fracture permeability. Our current understanding of faulting and seismogenesis in this tectonically important zone is largely based on remote geophysical observations of active faults and direct geological observations of fossil faults.

The Alpine Fault, New Zealand, is a globally significant dextral-reverse fault that is thought to fail in large earthquakes (c. Mw 7.9) every 200-400 years and last ruptured in 1717 AD. Ongoing uplift has rapidly exhumed a crustal section from c. 20 km, providing a young (<1 Myr), well-preserved sample of mid-crustal structures currently active at depth.

Here we outline a novel experiment in which we drill, sample, and monitor the Alpine Fault to address fault zone evolution via brittle and ductile processes operating in the upper and mid-crust. The remarkable along-strike homogeneity of the Alpine Fault's hanging wall, the rapid rate of slip, and the dextral-reverse kinematics that progressively exhume the fault's own faulting products together enable us to examine the progressive evolution of fault zone materials by effectively targeting a single rock mass at two points on its exhumation trajectory. We will do this by placing a borehole at a measurable distance tectonically upstream (i.e. back along the exhumation trajectory) from a well-exposed and thoroughly documented surface outcrop of the fully evolved suite of fault rocks. By comparing fault rocks exposed at the surface with their correlatives at depth along a single exhumation trajectory, we can take advantage of a rare window into the physical character of the seismologically expressed brittle-ductile transition zone in a fault that is active today and which can be geophysically monitored in the coming decades.

We propose to hold a five-day international workshop in early 2009 at which we bring together scientists with expertise in a broad range of fields to discuss and plan a program of site characterisation and deep fault drilling into the central Alpine Fault.

(© NASA: Jacques Descloitres, MODIS Rapid Response Team at NASA GSFC)


 

Location

Oceania, New Zealand, South Island, Alpine Fault

 

Coordinates

43° 17' 5'' S, 170° 24' 22'' E (Please scroll down to end of page for more information.)

 

Project Start and End
  •  not decided yet

 

Programs and Funding

 

Principal Investigators
  • Rupert Sutherland, Victoria University of Wellington, School of Geography, Environment and Earth Sciences
  • John Townend, Victoria University of Wellington, School of Geography, Environment and Earth Sciences
  • Virginia Gail Toy, University of Otago, Department of Geological Sciences

 

Cooperating Principal Investigators

No Co-PIs found for this project

 

Partners and Contractors

 

Keywords

Active Faults, Alpine Fault, Brittle, DFDP, Ductile, ICDP-2011/01, New Zealand, Seismogenic Zone

 

Current State

Completed

 

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