Extreme hydrothermal conditions at an active plate-bounding fault

TY - JOUR

T1 - Extreme hydrothermal conditions at an active plate-bounding fault

AU - Sutherland, Rupert

AU - Townend, John

AU - Toy, Virginia G.

AU - Upton, Phaedra

AU - Coussens, Jamie

AU - Allen, Michael

AU - Baratin, Laura-May

AU - Barth, Nicolas

AU - Becroft, Leeza

AU - Boese, Carolin

AU - Boles, Austin

AU - Boulton, Carolyn

AU - Broderick, Neil G. R.

AU - Janku-Capova, Lucie

AU - Carpenter, Brett M.

AU - Celerier, Bernard

AU - Chamberlain, Calum

AU - Cooper, Alan

AU - Coutts, Ashley

AU - Cox, Simon C.

AU - Craw, Lisa

AU - Doan, Mai-Linh

AU - Eccles, Jennifer

AU - Faulkner, Dan

AU - Grieve, Jason

AU - Grochowski, Julia

AU - Gulley, Anton

AU - Hartog, Arthur

AU - Howarth, Jamie

AU - Jacobs, Katrina

AU - Jeppson, Tamara

AU - Kato, Naoki

AU - Keys, Steven

AU - Kirilova, Martina

AU - Kometani, Yusuke

AU - Langridge, Rob

AU - Lin, Weiren

AU - Little, Timothy

AU - Lukacs, Adrienn

AU - Mallyon, Deirdre

AU - Mariani, Elisabetta

AU - Massiot, Cecile

AU - Mathewson, Loren

AU - Melosh, Ben

AU - Menzies, Catriona Dorothy

AU - Moore, Jo

AU - Morales, Luiz

AU - Morgan, Chance

AU - Mori, Hiroshi

AU - Niemeijer, Andre

AU - Nishikawa, Osamu

AU - Prior, Dave

AU - Sauer, Katrina

AU - Savage, Martha

AU - Schleicher, Anja M.

AU - Schmitt, Doug R.

AU - Shigematsu, Norio

AU - Taylor-Offord, Sam

AU - Teagle, Damon A. H.

AU - Tobin, Harold

AU - Valdez, Robert

AU - Weaver, Konrad

AU - Wiersberg, Thomas

AU - Williams, Jack

AU - Zimmer, Martin

N1 - We thank the Friend family for land access and the Westland community for support; Schlumberger for assistance with optical fibre technology; A. Benson, R. Conze, R. Marx, B. Pooley, A. Pyne and S. Yeo for engineering and site support; the CNRS University of Montpellier wireline logging group of P. Pezard, G. Henry, O. Nitsch and J. Paris; Arnold Contracting; Eco Drilling; and Webster Drilling. Funding was provided by the International Continental Scientific Drilling Program (ICDP), the NZ Marsden Fund, GNS Science, Victoria University of Wellington, University of Otago, the NZ Ministry for Business Innovation and Employment, NERC grants NE/J022128/1 and NE/J024449/1, the Netherlands Organization for Scientific Research VIDI grant 854.12.011 and the ERC starting grant SEISMIC 335915. ICDP provided expert review, staff training and technical guidance.

PY - 2017/6/1

Y1 - 2017/6/1

N2 - Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes1. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre2,3. At temperatures above 300–450 degrees Celsius, usually found at depths greater than 10–15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional–mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades4,5. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults.

AB - Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes1. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre2,3. At temperatures above 300–450 degrees Celsius, usually found at depths greater than 10–15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional–mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades4,5. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults.

UR - https://eprints.soton.ac.uk/410547/

U2 - 10.1038/nature22355

DO - 10.1038/nature22355

M3 - Article

VL - 546

SP - 137

EP - 140

JO - Nature

JF - Nature

SN - 0028-0836

ER -