Conditions inside the Alpine Fault, which runs almost the entire length of New Zealand’s South Island, are much more extreme than previously thought. A new study describes the findings of a group of researchers who have drilled a borehole into the fault to examine its state. Their results showed extremely high temperatures and high fluid pressure. The conditions were most extreme in the “hanging wall” above the fault, where the average temperature gradient reached around 125°C per kilometre of depth. Normally such high values per kilometre tend to be associated with volcanic activity, but scientists say there’s no evidence of volcanism in the fault. However, these findings can still be used to understand fault movement. The fault is expected to rupture in an earthquake in the next few decades. The last earthquake on South Island occurred in 2009, reaching an estimated magnitude of 7.8.

Authors:

Rupert Sutherland, John Townend, Virginia Toy, Phaedra Upton, Jamie Coussens, Michael Allen, Laura-May Baratin, Nicolas Barth, Leeza Becroft, Carolin Boese, Austin Boles, Carolyn Boulton, Neil G. R. Broderick, Lucie Janku-Capova, Brett M. Carpenter, Bernard Célérier, Calum Chamberlain, Alan Cooper, Ashley Coutts, Simon Cox, Lisa Craw, Mai-Linh Doan, Jennifer Eccles, Dan Faulkner, Jason Grieve, Julia Grochowski, Anton Gulley, Arthur Hartog, Jamie Howarth, Katrina Jacobs, Tamara Jeppson, Naoki Kato, Steven Keys, Martina Kirilova, Yusuke Kometani, Rob Langridge, Weiren Lin, Timothy Little, Adrienn Lukacs, Deirdre Mallyon, Elisabetta Mariani, Cécile Massiot, Loren Mathewson, Ben Melosh, Catriona Menzies, Jo Moore, Luiz Morales, Chance Morgan, Hiroshi Mori, Andre Niemeijer, Osamu Nishikawa, David Prior, Katrina Sauer, Martha Savage, Anja Schleicher, Douglas R. Schmitt, Norio Shigematsu, Sam Taylor-Offord, Damon Teagle, Harold Tobin, Robert Valdez, Konrad Weaver, Thomas Wiersberg, Jack Williams, Nick Woodman & Martin Zimmer

Corresponding author:

Rupert Sutherland, Victoria University of Wellington, NZ, Email: Rupert.Sutherland@vuw.ac.nz

Canadian authors:

Douglas R. Schmitt & Deirdre Mallyon, Department of Physics, University of Alberta, Edmonton, AB; Ben Melosh, Department of Earth and Planetary Sciences, McGill University, Montreal, QC

Original paper published in Nature on May 17, 2017.