Kinematics and paleoseismology of the Vernon Fault, Marlborough Fault System, new zealand: Implications for contractional fault bend deformation, earthquake triggering, and the record of hikurangi subduction earthquakes
Bartholomew T.D.,Victoria University of Wellington |
Little T.A.,Victoria University of Wellington |
Clark K.J.,Nuclear science Ltd |
Van Dissen R.,Nuclear science Ltd |
Barnes P.M.,NIWA - National Institute of Water and Atmospheric Research
Tectonics | Year: 2014
The ∼40km long Vernon Fault, in the Marlborough Fault System of New Zealand, is characterized by dextral slip with subordinate reverse slip and exhibits abrupt variations in strike of up to 90°. Onshore fieldwork, paleoseismic trenching, and offshore high-frequency seismic reflection data are integrated together to identify the kinematics and paleoseismic history of three sections of the fault: (1) the NNE striking Vernon Hills section which branches off from the Awatere Fault; (2) the NE striking Big Lagoon section which borders Big Lagoon to the south and extends ~9‰km offshore to the east; and (3) the E-W striking Wairau Basin section, which is entirely submarine. The Vernon Fault can be shown to have a dextral slip rate of 0.8-4.9‰mm/yr with a preferred estimate of 0.9 mm/yr (on the Big Lagoon section). We infer that a further unrecognized 3-4‰mm/yr of dextral slip has been accommodated off fault as a result of accumulated slip on small and/or blind reverse faults adjacent to a 6‰km wide restraining bend in the main fault. The onshore and offshore paleoseismic records are in good agreement. These indicate three to five events at eight sites and a mean recurrence interval of 3.9±1.2ka over the past ∼16kyr, with the last event taking place at ∼3.3ka. Earthquakes on the Vernon Fault are responsible for <25% of the Holocene subsidence rate of Big Lagoon over the last ∼13ka. Most of the subsidence of this lagoon has been the result of surface deformation related with southern Hikurangi megathrust earthquakes. Key Points Dominance of strike-slip faulting in a sharp restraining bend Paleoearthquake ages overlapped on several connected faults Onshore and offshore data were used to resolve fault kinematics and paleoseismicity ©2014. American Geophysical Union. All Rights Reserved.
Helson J.,Ministry of Fisheries |
Leslie S.,Canadian Department of Fisheries and Oceans |
Clement G.,Clement and Associates Ltd |
Wells R.,Deepwater Group Ltd |
Wood R.,Nuclear science Ltd
Marine Policy | Year: 2010
New Zealand has a large exclusive economic zone (EEZ) that contains a variety of marine habitats and commercially-important species. The commercial fishing industry operating within New Zealand's EEZ is of significant value to the economy and fisheries resources are managed through the extensive use of Individual Transferable Quotas (ITQs). One of the benefits of ITQs has been to better align some of the private incentives of quota owners with the public interest. These incentives contributed to an initiative proposed by the fishing industry to close large areas of New Zealand's EEZ to protect the seabed from trawling. These closed areas are termed benthic protection areas (BPAs) and protect the benthic biodiversity of about 1.1 million square kilometres of seabed-approximately 30% of New Zealand's EEZ. A significant proportion of New Zealand's known seamounts and active hydrothermal vents are protected by these closed areas. We describe and discuss the criteria used to select BPAs and some of the criticism of this marine protection initiative. We argue that the assignment of strong property rights in fishing resources was an important precondition to an industry initiative that has a significant public benefit. Where private and public interests are well aligned, government can adopt an enabling and facilitation role, ceding direct control of processes in order to get the results the align with the public interest. © 2009 Elsevier Ltd. All rights reserved.
Amos C.B.,University of California at Santa Barbara |
Amos C.B.,University of California at Berkeley |
Burbank D.W.,University of California at Santa Barbara |
Read S.A.L.,Nuclear science Ltd.
Tectonics | Year: 2010
Rarely are geologic records available to constrain the spatial and temporal evolution of thrust-fault growth as slip accumulates during repeated earthquake events. Here, we utilize multiple generations of dated and deformed fluvial terraces to explore two key aspects of the along-strike kinematic development of the Ostler fault zone in southern New Zealand over the past ∼100 k.y.: accumulation of fault slip through space and time and fixed-length thrust growth that results in patterns of drainage diversion suggestive of laterally propagating faults. Along the Ostler fault, surface deformation patterns revealed by topographic surveying of terrace profiles in nine transverse drainages define systematic variations in fault geometry and suggest deformation over both listric and planar thrust ramps. Kinematic modeling of folded terrace profiles and >100 fault-scarp surveys along major fault sections reveals remarkably similar slip distributions for multiple successions of geomorphic surfaces spanning ∼100 k.y. Spatially abrupt and temporally sustained displacement gradients across zones of fault section overlap suggest that either persistent barriers to fault propagation or interference between overlapping faults dominate the interactions of fault tips from the scale of individual scarps to the entire fault zone. Deformed terrace surfaces dated using optically stimulated luminescence and cosmogenic radionuclides indicate steady, maximum rates of fault slip of ∼1.9 mm/yr during the Late Quaternary. Slip data synthesized along the central Ostler fault zone imply that displacement accumulated at approximately constant fault lengths over the past ∼100 k.y. A northward temporal progression of abandoned wind gaps along this section thus reflects lateral tilting in response to amplification of displacement, rather than simple fault lengthening or lateral propagation. Oscillations of climate at ∼104-yr time scales modulate the formation and incision of geomorphic surfaces during successive glacial stages. Superimposed on apparently steadier rates of fault slip, such climate-dependent surfaces contribute to a pattern of progressive drainage deflection along the central Ostler fault zone that is largely independent of fault propagation. © 2010 by the American Geophysical Union.