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http://hdl.handle.net/2122/6470
Authors: | Langridge, R. M.* Villamor, P.* Basili, R.* Almond, P.* Martinez-Diaz, J. J.* Canora, C.* |
Title: | Revised slip rates for the Alpine fault at Inchbonnie: Implications for plate boundary kinematics of South Island, New Zealand | Other Titles: | Revised slip rates for the Alpine fault at Inchbonnie | Journal: | Lithosphere | Series/Report no.: | 3/2(2010) | Publisher: | Geological Society of America | Issue Date: | 25-May-2010 | DOI: | 10.1130/L88.1 | URL: | lithosphere.gsapubs.org | Keywords: | Alpine fault plate boundary slip rate New Zealand |
Subject Classification: | 04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology 04. Solid Earth::04.04. Geology::04.04.02. Geochronology 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology 04. Solid Earth::04.04. Geology::04.04.09. Structural geology 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics |
Abstract: | The northeast-striking, dextral-reverse Alpine fault transitions into the Marlborough Fault System near Inchbonnie in the central South Island, New Zealand. New slip-rate estimates for the Alpine fault are presented following a reassessment of the geomorphology and age of displaced late Holocene alluvial surfaces of the Taramakau River at Inchbonnie. Progressive avulsion and abandonment of the Taramakau floodplain, aided by fault movements during the late Holocene, have preserved a left-stepping fault scarp that grows in height to the northeast. Surveyed dextral (22.5 ± 2 m) and vertical (4.8 ± 0.5 m) displacements across a left stepover in the fault across an alluvial surface are combined with a precise maximum age from a remnant tree stump (≥1590–1730 yr) to yield dextral, vertical, and reverse-slip rates of 13.6 ± 1.8, 2.9 ± 0.4, and 3.4 ± 0.6 mm/yr, respectively. These values are larger (dextral) and smaller (dip slip) than previous estimates for this site, but they refl ect advances in the local chronology of surfaces and represent improved time-averaged results over 1.7 k.y. A geological kinematic circuit constructed for the central South Island demonstrates that (1) 69%–89% of the Australian-Pacific plate motion is accommodated by the major faults (Alpine-Hope-Kakapo) in this transitional area, (2) the 50% drop in slip rate on the Alpine fault between Hokitika and Inchbonnie is taken up by the Hope and Kakapo faults at the southwestern edge of the Marlborough Fault System, and (3) the new slip rates are more compatible with contemporary models of strain partitioning presented from geodesy. |
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