Brøgger Seminar Series
The Deep Fault Drilling Project, Alpine Fault, New Zealand — Getting Inside the Earthquake Machine 

Catriona Menzies by Catriona Menzies 
National Oceanography Centre, Southampton, UK

When? Thursday 29th October, 15h00
Where? Ahlmannsalen, Geovetenskapens hus

The central section of the Alpine Fault (Source: wiki.gns.cri.nz) 
Abstract
The Deep Fault Drilling Project (DFDP) is an international, multi-phase project to drill into the Alpine Fault Zone in South Island New Zealand. The project aims to investigate a plate boundary fault zone before rupture to identify what controls the timing of earthquakes and how such faults evolve throughout the seismic cycle. The fault has historically produced large earthquakes (M ~8) (Sutherland et al., 2007) and late in its 329±68 year seismic cycle, having last ruptured in 1717 (Berryman et al., 2012). The project will sample fault zone materials, make downhole measurements and install long-term observatories in a series of progressively deeper boreholes through the Alpine Fault. To date two phases of the project have been completed. DFDP-1 involved drilling of two shallow boreholes ~100 and 150 m deep in January and February 2011 both of which cored the Alpine Fault damage zone and intercepted the principal slip zone of the Alpine Fault. This phase identified a 0.53 MPa fluid pressure differential between the hangingwall and footwall indicating that the Alpine Fault principal slip zone is a fluid flow barrier (Sutherland et al., 2012). The second phase (DFDP-2) aimed to intercept the Alpine Fault at ~1.3 km depth to measure, sample and observe the fault zone below the influence of topographic stresses. Due to technical problems drilling stopped short of the Alpine Fault at ~900 m depth. Despite these difficulties results from DFDP-2 illustrate the importance of “drilling deep” as very high geothermal gradients (~140 °C/km) and fluid pressures (80 m head at 800 m) were measured, both of which have implications for the nature of earthquake rupture on the Alpine Fault and will be the focus of future research resulting from this drilling effort. 

 

 

 

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