Deep Fault Drilling Project—Alpine Fault, New Zealand

Abstract

The Alpine Fault, South Island, New Zealand, constitutes a globally significant natural laboratory for research into how active plate-bounding continental faults work and, in particular, how rocks exposed at the surface today relate to deep-seated processes of tectonic deformation, seismogenesis, and mineralization. The along-strike homogeneity of the hanging wall, rapid rate of dextral-reverse slip on an inclined fault plane, and relatively shallow depths to mechanical and chemical transitions make the Alpine Fault and the broader South Island plate boundary an important international site for multi-disciplinary research and a realistic target for an ambitious long-term program of scientific drilling investigations.

Shear behavior of DFDP-1 borehole samples from the Alpine Fault, New Zealand, under a wide range of experimental conditions

“…Major earthquakes (M w > 7.0) are inferred to have occurred over the past 8,000 years with a recurrence of ~260-400 years (Bull 1996;Berryman et al 2012). No large earthquake has occurred in the past 300 years, suggesting that a hazardous, large-magnitude earthquake on the Alpine Fault may be imminent (Sutherland et al 2007(Sutherland et al , 2012Townend et al 2009Townend et al , 2013. Geodetic measurements along the central segment of the fault indicate that the Alpine Fault is fully locked at depths of 5-8 km and partially locked up to ~18 km, and is loaded from below by the lower crust at a rate representing 50-70 % of the plate convergence rate (Beavan et al 1999Norris and Cooper 2000;Wallace et al 2007).…”

“…The Alpine Fault was chosen for scientific drilling because it is nearing the end of its earthquake cycle, high exhumation rates that have resulted in well-exposed outcrops of representative lithologies from depth, well-constrained Quaternary slip rates, the presence of an extensive geophysical monitoring network, and a fault dip of ~45° which allows penetration by vertical boreholes (Townend et al 2009). Drilling on the central portion of the Alpine Fault commenced as part of the Deep Fault Drilling Project (DFDP) within the framework of the International Continental Scientific Drilling Project (ICDP).…”

“…Therefore, obtaining such samples has provided the impetus for large-scale scientific drilling projects (e.g., Ma et al 2006;Tobin and Kinoshita 2006;Zoback et al 2011). The Deep Fault Drilling Project (DFDP) was initiated in 2011 to investigate the Alpine Fault in New Zealand via coring, sampling, and wireline logging (Townend et al 2009). The Alpine Fault is a highly appropriate target for study due to its status as a major plate boundary fault capable of large (M w ~ 8) earthquakes, as well as the inference that it may be nearing the end of its earthquake cycle (Sutherland et al 2007;De Pascale and Langridge 2012).…”

Residual stress preserved in quartz from the San Andreas Fault Observatory at Depth

“…In an effort to better understand earthquake mechanisms, several deep drilling projects have been undertaken to retrieve material from seismically active zones of major faults, such as the San Andreas Fault Observatory at Depth (SAFOD) for the San Andreas fault in California (Zoback et al, 2011), the Nojima fault in Japan (Ohtani et al, 2000), the Taiwan Chelungpu-Fault Drilling Project (Ma et al, 2006), the Deep Fault Drilling Project for the Alpine fault in New Zealand (Townend et al, 2009), the Wenchuan earthquake Fault Scientific Drilling Project in China (Xue et al, 2013), and the Japan Trench Fast Drilling Project for the plate boundary thrust off the coast of Japan (Chester et al, 2013). Material retrieved from drill cores can be studied in the laboratory and thus provides direct information about physical and chemical processes that occur at depth within a seismically active zone.…”

Crustal seismic reflection profile across the alpine fault and coastal plain at Whataroa, South Island

“…Sircombe & Kamp 1998 This paper presents reflection and refraction models derived from the SIGHT Whataroa seismic reflection data and discusses the constraints that these data place on the dip and character of the Alpine Fault; the structure and relationship of the coastal plain sedimentary basin to the Alpine Fault and the South Westland Fault and other data in the region; and the depth of Moho and the constraints this provides on the deformation of the Australian plate by the overthrust Pacific Plate from the southeast. Furthermore, in view of the current interest in drilling the Alpine Fault at depth under the auspices of the International Continental Drilling Program (ICDP) (Townend et al 2009), these data provide some constraints on both the location of the fault at Whataroa and the acquisition parameters necessary to adequately image the fault subsurface seismically.…”