FISH: Laura-May Baratin: The Deep Fault Drilling Project, Alpine Fault: Getting inside the earthquake machine

Dec 2, 2016 - 12:00 PM to 1:00 PM EST

Speaker: 

Laura-May Baratin, Victoria University of Wellington

Laura-May Baratin, PhD Candidate at Victoria U. of Wellington, presents "The Deep Fault Drilling Project, Alpine Fault: Getting inside the earthquake machine."

"The Deep Fault Drilling Project (DFDP) is an multinational scientific drilling effort to study the structure, evolution and seismogenesis of the New Zealand Alpine Fault via in-situ measurements of fault rock properties. The Alpine Fault, New Zealand’s major on-land plate boundary structure, has not ruptured in historic times, but paleoseismic records indicate possible MW 7-8 earthquakes with a ∼330 yr recurrence, the last one being in ∼1717 AD.  DFDP is the first detailed study of an active fault that is due to rupture in a large earthquake. Previous fault zone drilling experiments have targeted faults that had recently ruptured in an earthquake. Our aim was to measure ambient conditions at depth, to collect rock, gas and fluid samples and to install sensors for long-term earthquake monitoring. The first phase of the project was completed in early 2011 at Gaunt Creek (DFDP-1). Two shallow boreholes were drilled through the hanging wall of the Alpine Fault and into the footwall at depths of 128m and 98m. The second phase of drilling (DFDP-2) was undertaken in late 2014 in the Whataroa Valley, 7km northeast of DFDP-1. This phase of drilling was intended to characterize the temperature, pressure, stress and structure of the hanging- and footwalls of the Alpine Fault, and to intersect the principle slip zone at a depth of ∼1km. Unfortunately several technical problems occured during that phase of drilling that culminated in a casing failure at 436m, leading to a premature end of drilling at 893m. In conjunction with the drilling and on-site science activities, a real-time seismic monitoring scheme and “traffic-light” response protocol were established to detect, locate and if necessary respond to seismicity within 30 km of the drill-site. This network was operated around the clock between late August 2014 and early January 2015 and detected and located 493 earthquakes of ML0.6–4.2. None of these earthquakes occurred within 3km of the drill-site, nor did any of the seismicity detected require changes to drilling operations. This talk will focus on highlighting the main results from DFDP and detailing the procedures used for monitoring real-time seismicity."