Table of contents
      1. 1.1. Background
        1. 1.1.1. What is the Deep Fault Drilling Project?
        2. 1.1.2. What is “DFDP-2”?
        3. 1.1.3. Who is involved in this project?
        4. 1.1.4. How is the Deep Fault Drilling Project funded?
        5. 1.1.5. What is the Alpine Fault?
        6. 1.1.6. What is so special about the Alpine Fault? Why is the international scientific community interested?
        7. 1.1.7. Where can I actually see the Alpine Fault?
        8. 1.1.8. What do you hope to find that you don’t know already?
        9. 1.1.9. Where is drilling taking place?
        10. 1.1.10. Has this experiment been peer-reviewed?
        11. 1.1.11. What will the environmental impacts of this project be?
        12. 1.1.12. Has this sort of drilling into a big plate boundary fault been done before?
        13. 1.1.13. Will results of DFDP-2 be available to the public?
      2. 1.2. Drilling and measurements during DFDP-2
        1. 1.2.1. When is DFDP-2 drilling scheduled to start and how long will it take?
        2. 1.2.2. What equipment will be used in the drilling?
        3. 1.2.3. What samples will be collected and how will they be analysed?
        4. 1.2.4. What sort of measurements will be made in the DFDP-2 borehole?
        5. 1.2.5. What sorts of observatory equipment will be installed?
        6. 1.2.6. Can I visit the drill site?
        7. 1.2.7. What will be left on the drill site after the project is finished?
        8. 1.2.8. What steps have been taken to assess the hazard posed by drilling?
        9. 1.2.9. Is the borehole likely to encounter coal, oil, or gas?
        10. 1.2.10. Is the borehole likely to encounter high-pressure fluids?
      3. 1.3. Alpine Fault earthquakes
        1. 1.3.1. When did the Alpine Fault last rupture in a big earthquake?
        2. 1.3.2. How often do large Alpine Fault earthquakes occur?
        3. 1.3.3. Can we predict the next big Alpine Fault earthquake? What is the likelihood of a large Alpine Fault earthquake occurring?
        4. 1.3.4. How will the next Alpine Fault earthquake compare to the M7.1 Darfield earthquake of 4 September 2010?
        5. 1.3.5. Will there be any warning of an impending Alpine Fault earthquake?
        6. 1.3.6. Will drilling into the Alpine Fault cause a large earthquake?
        7. 1.3.7. What background seismicity occurs near the DFDP-2 borehole and how is it monitored?
        8. 1.3.8. What preparations are being made in case of an Alpine Fault rupture?
        9. 1.3.9. How long would the impacts of a big Alpine Fault earthquake last?
    1. 2. Resources
        1. 2.1.1. Where can I find more information about the Deep Fault Drilling Project?
        2. 2.1.2. Where can I learn more about the Alpine Fault?

    Background

    What is the Deep Fault Drilling Project?

    The Deep Fault Drilling Project (DFDP) is an international science experiment studying the Alpine Fault in western South Island. It fills a knowledge gap for the international science community trying to understand earthquake processes. It will sample rock types, physical properties, and ambient conditions of an earthquake-generating fault that is late in its earthquake cycle and due to fail in a large earthquake.

    The drilling project is important to New Zealand because it will provide scientific data to inform analysis of the largest seismic hazard in South Island. Better models of earthquake shaking may be derived and down-hole monitoring equipment may inform future warning systems or time-varying hazard estimates. Using rock and fluid samples, geophysical and hydraulic data, and by establishing a long-term observatory inside the fault zone, we will provide new insights into how the Alpine Fault and other large faults operate.

    What is “DFDP-2”?

    “DFDP-2” refers to the second phase of the Deep Fault Drilling Project and to the 1.3 km-deep borehole that is intended to be drilled during this phase of the project.

    Who is involved in this project?

    DFDP is led by Rupert Sutherland (GNS Science), John Townend (Victoria University of Wellington) and Virginia Toy (University of Otago) and involves researchers and students from more than a dozen organisations in New Zealand, Canada, France, Germany, Japan, the United Kingdom, and the United States.

    How is the Deep Fault Drilling Project funded?

    DFDP’s two principal funding bodies are the Marsden Fund of the Royal Society of New Zealand and the International Continental Scientific Drilling Program. Additional funds for specific components of research have been provided by the Earthquake Commission, the National Science Foundation (United States), the National Environmental Research Council (United Kingdom), and the participating organisations via internal grants.

    What is the Alpine Fault?

    The Alpine Fault forms part of the boundary between the Australian and Pacific Plates in southern New Zealand. It lies near the base of the steep western range-front of the Southern Alps over a distance of approximately 500 km between Milford Sound and Marlborough. It is visible from space as a more-or-less straight line delineating the western side of the Southern Alps.  Southwest of Milford South, the Alpine Fault extends southwestwards offshore of Fiordland for about 200 km. North of Hanmer Springs it branches into several faults including the Hope Fault and the Wairau Valley Fault.

    Slip on the fault is responsible for lifting up the Southern Alps and for offsetting rocks laterally by hundreds of kilometres (e.g. the Red Hills in Nelson and Red Mountain in South Westland were once joined but have been offset from one another). During the last two million years, the central portion of the Alpine Fault has slipped at an average rate of approximately 27 mm/yr horizontally and 10 mm/yr vertically. This slip is understood by scientists to mostly occur during earthquakes of magnitude 7.5–8.0 every 200–400 years. In each earthquake, one side of the fault moves by approximately 7–9 m horizontally and 0–3 m vertically with respect to the other side of the fault.

    What is so special about the Alpine Fault? Why is the international scientific community interested?

    There are several reasons why the Alpine Fault is a globally important focus of research into earthquake and faulting processes. As the Alpine Fault slips, it displaces the rocks on either side horizontally and vertically: rocks on the eastern side of the fault move southwestwards and upwards each time the fault slips. The net result of this type of slip is that, over time, rocks that were deeply buried beneath the Southern Alps are exhumed to the earth’s surface. In fact, this exhumation takes place so rapidly (in geological terms) that the rocks do not have time to cool and many temperature-controlled processes that normally occur at great depth persist to much shallower depths. By studying these processes and the mineralogical and structural signatures they leave behind, scientists can learn about how the Alpine Fault behaves at the depths at which earthquakes nucleate (approximately 6–12 km). Using rock and fluid samples collected from boreholes, we can study pristine materials that have not been modified by weathering processes occurring at the earth’s surface; in other words, drilling enables us to see through the effects of near-surface weathering and erosion. Furthermore, the Alpine Fault dips downward into the earth at an angle of about 45°. This means that a vertical borehole can be drilled to penetrate the fault more cheaply and more easily than in the case of a vertical fault such as the San Andreas Fault, which has been a target of past scientific drilling operations (see: http://www.earthscope.org/science/observatories/safod).

    Most significantly of all, perhaps, is the fact that the Alpine Fault appears to produce large (M8) earthquakes approximately every 330 years and last ruptured in 1717 AD. This means that the fault is late in its average cycle of stress build-up between large earthquakes, and is expected to rupture at some point in coming decades. DFDP provides a rare opportunity to determine the state of the fault before it breaks — that is, to measure the pressures, temperatures, and stresses acting on the Alpine Fault in the build-up to a major earthquake. Other scientific drilling projects such as the Taiwan Chelungpu Drilling Porject (http://www.icdp-online.org/projects/...sia/chelungpu/) have mostly managed to drill into active faults after major earthquakes.

    Where can I actually see the Alpine Fault?

    There are several sites where you can get close to the Alpine Fault. In the township of Franz Josef, the fault crosses State Highway 6 diagonally and runs past the petrol station at the southern end of town. Where it crosses the road, it can be seen as a slight rise of about 30 cm. There is also a spectacular exposure of the fault at Gaunt Creek, southeast of Whataroa. The landowners run tours to this site (http://alpinefaulttours.co.nz/). For trampers, other world-class exposures of the fault can be seen a couple of hundred meters off the Hollyford Track at Hokuri Creek, and in the Martyr River at the south end of the Jackson River Road.

    The Geology Department of the University of Otago maintains a collection of Alpine Fault maps at http://www.otago.ac.nz/geology/research/structural_geology/alpinefault/index.html.

    What do you hope to find that you don’t know already?

    The Alpine Fault has not produced any large earthquakes in recorded history but there is geological record spanning thousands of years of repeated M8 earthquakes, the last being in approximately 1717 AD. What geologists and geophysicists worldwide want to better understand is how faults such as this one are loaded to the point of failure in an earthquake, and in particular what stresses, fluid pressures, and temperatures exist at the point of earthquake nucleation. By measuring these parameters in the DFDP-2 borehole almost 300 years after the Alpine Fault last ruptured, and at a depth below the zone of perturbed conditions associated with the mountainous topography, the science team will determine for the first time what conditions are deep in the heart of the earthquake machine.

    Where is drilling taking place?

    The first phase of the Deep Fault Drilling Project was completed in February 2011 with the completion of two shallow boreholes intersecting the shallow Alpine Fault at Gaunt Creek, near Whataroa.

    The second phase of the project, DFDP-2, will take place on farmland in the Whataroa River valley, upstream from the State Highway 6 bridge.

    Has this experiment been peer-reviewed?

    Yes, there has been extensive expert review of different aspects of the project since it first began in 2008. The science plans have been reviewed in the context of multiple funding applications, the technical and safety plans have been reviewed by expert panels, and the overall design and environmental impact of drilling have been reviewed at various times by the Department of Conservation and the West Coast Regional Council as part of required consenting processes. All scientific results arising from DFDP are also subject to separate peer review when being prepared for publication.

    What will the environmental impacts of this project be?

    This project will not have any significant environmental impact. The project will use techniques that are routinely used for groundwater drilling and in the geothermal energy industry. We will not be using oil-based drilling fluids or fracking techniques employed in the petroleum industry. The issue of whether earthquakes could be induced by DFDP-2 drilling has been independently reviewed by an expert panel.

    Has this sort of drilling into a big plate boundary fault been done before?

    Yes in several countries. Starting in 2004, scientists drilled a 3 km-deep hole into the San Andreas Fault in California in order to understand the stresses, pressures, and temperatures under which earthquakes occur (http://www.earthscope.org/science/observatories/safod). They collected rocks and fluids for laboratory analysis and inserted instruments to monitor the fault. In 2012, following the devastating Mw9 Tohoku-Oki earthquake in northeast Japan one year earlier, an international team (including project scientists Virginia Toy) drilled into the fault that had ruptured in order to measure the frictional heat produced during the earthquake and to study the fine-scale structure of the fault (http://www.jamstec.go.jp/chikyu/exp343/e/). Other ambitious fault drilling projects have been undertaken in Taiwan, China and Japan following large earthquakes, and in Greece and Turkey.

    Will results of DFDP-2 be available to the public?

    We anticipate strong media and public interest in DFDP-2 as the drilling and measurement programs proceed. In addition to media coverage, the science team will be providing regular updates via this project website, and the website hosted by the International Scientific Drilling Program (ICDP): http://www.icdp-online.org/projects/.../alpine-fault/

    We will also will give public talks in Whataroa and nearby communities during and after the drilling operations. The results stemming from this project will be published in peer-reviewed science journals.

    Drilling and measurements during DFDP-2

    When is DFDP-2 drilling scheduled to start and how long will it take?

    Site preparation will get underway in August or September 2014 and the main phase of DFDP-2 drilling is scheduled to commence in early October. The drilling and scientific measurement programs are expected to take approximately two months, although factors such as bad weather or technical hold-ups may prolong the experiment.

    What equipment will be used in the drilling?

    The uppermost 100 m of DFDP-2 will be drilled using a pneumatic system that drives steel casing through the shallow gravel layers and which is commonly used for drilling water wells. The top 800 m or so of the borehole will be drilled using a method that produces chips of rock known as cuttings, rather than intact core: the mineralogy, structure, and other aspects of the cuttings will be analysed by geologists working on-site, and used to determine what kind of rock is being drilled through. Below 800 m, a diamond-bit coring system commonly used in the mining sector will be used to obtain continuous cylinders of rock. The upper section of the borehole will ultimately be cased with steel pipe surrounded by cement and the lower portion will be filled with a mixture of cement and impermeable grout once the scientific measurements have been completed and observatory equipment installed.

    What samples will be collected and how will they be analysed?

    Rock samples will be collected from the length of the DFDP-2 borehole and analysed on-site in near-real-time to determine their mineralogical composition (i.e. rock type) and physical properties (density, fluid content, electrical resistivity, etc.). The samples will then be packaged and shipped to the University of Otago in Dunedin where further analysis will be undertaken. Cores retrieved from below 800 m will be scanned using an instrument that provides a complete photographic image of the core and then analysed using a computerised tomography (CT) scanner at Dunedin Hospital to determine their internal structure. We will also make scans to measure the electrical resistivity, magnetic susceptibility, density, elastic, and thermal properties of the core.

    Water and gas samples will also be collected during drilling using equipment installed on the drill-rig. This information will be used to monitor conditions in the borehole as well as to determine the chemical composition and origin of fluids in the rocks surrounding the Alpine Fault.

    What sort of measurements will be made in the DFDP-2 borehole?

    A major component of the DFDP-2 science plan involves measuring the physical properties of the rocks that have been drilled through using sensitive equipment lowered into the borehole on a winch. We will be measuring the rocks’ electrical and elastic properties and the in situ temperatures, and acquiring 360° images of the borehole wall to study fractures and metamorphic structures. The borehole images also enable us to measure the directions of stresses acting on the Alpine Fault. We will be able to compare these results to measurements made on the recovered core as well.

    What sorts of observatory equipment will be installed?

    Subject to final decisions being made, the science team plans to install permanent pressure, temperature, and seismic monitoring sensors extending to the bottom of the DFDP-2 borehole at 1.3 km. Similar instrumentation was installed in the DFDP-1 boreholes drilled at Gaunt Creek in 2011 and is providing continuous measurements of conditions within the fault zone via GeoNet.

    Can I visit the drill site?

    To ensure the safety of the public, drillers, and scientists, access to the DFDP-2 drill site will be restricted. It is intended that once the experiment has been completed a road-side display highlighting key results of this research will be constructed. In future the tours of the Alpine Fault at Gaunt Creek may also visit this site (http://alpinefaulttours.co.nz/).

    What will be left on the drill site after the project is finished?

    Once the drilling and scientific activities have finished, a shipping container will be installed on the drill site above the borehole. This will house recording instrumentation and batteries etc. to enable permanent monitoring of temperatures, pressures, and seismic waves recorded on sensors installed in the borehole.

    What steps have been taken to assess the hazard posed by drilling?

    In March 2014, a technical review of the DFDP-2 borehole planning took place in Lower Hutt, involving scientific and engineering experts from New Zealand and the United States. This review provided advice to the project team on how to refine the technical plan. The following month, an earthquake safety review took place in Wellington. This review also involved scientific and engineering experts from New Zealand and overseas.

    Is the borehole likely to encounter coal, oil, or gas?

    Based on what it known about the geology of the West Coast and the Alpine Fault specifically, it is considered extremely unlikely that coal, oil, or gas will be encountered in DFDP-2. The borehole is expected to pass through a shallow layer of alluvial gravels (which currently form the base of the Whataroa and other West Coast river valleys), possibly underlain by glacier-deposited sediments, highly deformed schist and fault rocks (which form the hills on either side of the drill-site, and finally deformed granitic rocks that are exposed nearby to the northwest of the drill site. The nearest known coal measures are found approximately 90 km away at Paringa in Tertiary sedimentary rocks not previously found near Whataroa. However, continuous gas monitoring will be conducted on the drill-rig to ensure that in the unlikely event that hydrocarbons are present they can be detected swiftly and the drilling processes modified accordingly.

    Is the borehole likely to encounter high-pressure fluids?

    During drilling of the DFDP-1 boreholes in 2011, we discovered that the shallow Alpine Fault serves as a very effective hydraulic barrier to fluid flow from one side of the fault to the other. Fluid pressures on either side of the fault were found to be controlled by topographic elevation and the water table. In other words, fluid pressures encountered in DFDP-1 were low but the fault sustained a fluid pressure difference related to the difference in topographic elevation between the eastern (mountainous) and western (low-land) sides of the fault.

    We expect to encounter a similar hydraulic situation in DFDP-2, exacerbated however by the greater depth of the borehole. However, materials will be kept on the drill site to respond to higher than anticipated fluid pressures if necessary.

    Alpine Fault earthquakes

    When did the Alpine Fault last rupture in a big earthquake?

    The Alpine Fault has not produced a large earthquake in historic times and scientific inferences about when earthquakes have occurred previously are based on careful interpretation of geological features. The fault last ruptured about 297 years ago — mostly likely in 1717 AD — and produced an earthquake of about magnitude 8 (M8). This earthquake ruptured the southern two thirds of the fault between Milford Sound and east of Greymouth, a distance of about 400 km. The second, third and fourth most recent Alpine Fault earthquakes are understood to have occurred in approximately 1620 AD, 1450 AD, and 1100 AD and to have ruptured different sections of the fault.

    How often do large Alpine Fault earthquakes occur?

    Research published by scientists from GNS Science in 2012 documented an 8000 year-long record of 24 Alpine Fault earthquakes based on data collected near Lake McKerrow, northeast of Milford Sound. Based on the dates of each earthquake measured using radiocarbon analysis, the researchers calculated an average time between successive large earthquakes of approximately 330 years. This sequence of earthquakes is remarkably regular by the standards of other large faults that have been studied in this way, but does not mean that the Alpine Fault ruptures like clockwork every 330 years: in fact, the intervals between successive earthquake measured at lake McKerrow varied between approximately 140 years and 510 years.

    Can we predict the next big Alpine Fault earthquake? What is the likelihood of a large Alpine Fault earthquake occurring?

    It is not possible to predict the time, location, or size of individual earthquakes reliably. However, using measurements of past earthquakes and knowledge of the frequencies of earthquakes of different sizes, it is possible to calculate the likelihood of an earthquake of a particular size occurring in a specific interval of time.

    Using the record of pre-historic Alpine Fault earthquakes from Lake McKerrow, the probability of a large (M8) earthquake in the next 50 years has been calculated to be approximately 30%.

    How will the next Alpine Fault earthquake compare to the M7.1 Darfield earthquake of 4 September 2010?

    For every one unit increase in magnitude (e.g. from M4 to M5) there is an approximately 30-fold increase in energy release. This means, for instance, that an Alpine Fault earthquake of M8.1 would release about 30 times more energy that the Darfield earthquake of M7.1. An Alpine Fault earthquake will likely rupture a larger fault length (several hundreds of kilometres rather than several tens of kilometres) over a longer period of time (100s of seconds rather than tens of seconds) and affect a much larger area than the Darfield earthquake. Moreover, it is likely that the aftershock sequence following an Alpine Fault earthquake will involve earthquakes of as much as M7.

    It is important to remember that the size of an earthquake is not the only factor determining its severity, as has been starkly illustrated by the 2010–2012 Canterbury earthquake sequence and the much greater effect of the M6.2 Christchurch earthquake than the M7.1 Darfield earthquake five months earlier.

    Will there be any warning of an impending Alpine Fault earthquake?

    The next big earthquake will almost certainly occur with no discernible warning signs or premonitory signals. However, DFDP is intended to provide new insight into how faults operate and interact, and by monitoring pressures, temperatures and stresses near the Alpine Fault on an on-going basis we will learn much about how the fault is being loaded towards the point of eventual rupture.

    Will drilling into the Alpine Fault cause a large earthquake?

    No, for several reasons. The volume of rock affected by drilling is extremely small (with dimensions of the order of a few metres) compared to the scale of the Alpine Fault itself (with dimensions on the orders of tens to hundreds of kilometres), and the depth of penetration (1.3 km) is very shallow compared to the depths at which most earthquakes nucleate (several kilometres). Drilling operations will be conducted using techniques that minimize the degree of pressurization in the borehole and no large-volume fluid injection experiment will be undertaken.  Finally, the low levels of earthquakes occurring naturally within several kilometres of the DFDP-2 drill-site, and their low magnitudes, indicate that the rock mass is generally not close to failing.

    An earthquake safety review was conducted in April 2014 to review plans for DFDP-2 and the effects, if any, that drilling might have on the likelihood of an Alpine Fault earthquake. The panel consisted of experts in seismology, geology, science management, and drilling engineering from New Zealand, the United States, and Italy.

    What background seismicity occurs near the DFDP-2 borehole and how is it monitored?

    Earthquakes occur sporadically throughout the Southern Alps, and since 2008 these have been monitored with several dense seismic networks operated by Victoria University of Wellington and collaborating organisations, in addition to the nationwide GeoNet system. The most recent additions to the combined network were four new seismic monitoring stations installed within 1.5 km of the DFDP-2 drill site in 2013 to monitor earthquake activity in the immediate vicinity.

    During a seven month period in 2013, fewer than 40 earthquakes were recorded within 10 km of DFDP-2 and of these all but two were deeper than 2 km and all but five were deeper than 5 km. Given this background level of naturally occurring seismicity, it is possible that earthquakes unrelated to drilling operations may occur during the DFDP-2 experiment. Indeed, it is possible but unlikely that the anticipated M8 Alpine Fault earthquake will occur.

    What preparations are being made in case of an Alpine Fault rupture?

    Regional councils and civil defence authorities throughout the South Island, and especially on the West Coast, have been making preparations for some time. These address large-scale infrastructure (transport, power, communications) and steps required of individuals and community groups.

    How long would the impacts of a big Alpine Fault earthquake last?

    Research conducted at the University of Otago and GNS Science in the last few years has revealed that the environmental effects of a large Alpine Fault earthquake will last for several decades. These effects include the mobilization of large volumes of rock from areas of steep topography in landslides, and the transportation of this material down the West Coast river system. It is likely that these processes will affect transportation, communication, and power infrastructure for many years. Additionally, aftershocks triggered by the main earthquake could be expected to be as large as M7 and to continue for many years also. Thus, the effects of the next big Alpine Fault earthquake will extend well belong the immediate period of damage and disruption.

    Resources

    Where can I find more information about the Deep Fault Drilling Project?

    GNS Science Youtube channel: https://www.youtube.com/user/GNSscience

    Previous media releases and press coverage: https://wiki.gns.cri.nz/DFDP/DFDP_Publicity

    Where can I learn more about the Alpine Fault?

    TV3 news item about the GNS Science study of Alpine Fault earthquakes: http://www.3news.co.nz/Alpine-Fault-considered-ticking-time-bomb/tabid/817/articleID/259452/Default.aspx

    Web page info about Alpine Fault:

    http://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Major-Faults-in-New-Zealand/Alpine-Fault

     

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