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

Abstract

The~40 km 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 ± 1.2 ka over the past~16 kyr, with the last event taking place at~3.3 ka. Earthquakes on the Vernon Fault are responsible for <25% of the Holocene subsidence rate of Big Lagoon over the last~13 ka. Most of the subsidence of this lagoon has been the result of surface deformation related with southern Hikurangi megathrust earthquakes.

Evidence for Past Subduction Earthquakes at a Plate Boundary with Widespread Upper Plate Faulting: Southern Hikurangi Margin, New Zealand

“…2), but despite its proximity, the Vernon fault has probably not played a role in recent tectonic subsidence of Big Lagoon (Bartholomew et al, 2014). At sites close to Big Lagoon, the Vernon fault has dip-slip rates of 0:04-0:14 mm=yr (Bartholomew et al, 2014).…”

“…2), but despite its proximity, the Vernon fault has probably not played a role in recent tectonic subsidence of Big Lagoon (Bartholomew et al, 2014). At sites close to Big Lagoon, the Vernon fault has dip-slip rates of 0:04-0:14 mm=yr (Bartholomew et al, 2014). The discrepancy between the Vernon fault vertical slip rate and the Big Lagoon subsidence rate (0:2-0:8 mm=yr) suggests the Vernon fault is not the primary driver of Big Lagoon subsidence.…”

The Timing and Style of Oblique Deformation Within New Zealand's Kaikōura Ranges and Marlborough Fault System Based on Low‐Temperature Thermochronology

“…The IKR may share a similar style, where the Clarence fault exhibits oblique motion at depth and primarily strike‐slip faulting at the free surface, resulting in dextral mapped offsets and broad hanging wall uplift (Nicol & Van Dissen, ). This type of “updip” strain partitioning has been proposed to apply to other faults in the Marlborough region as well (e.g., Bartholomew et al, ). Kaikōura Range topography may also relate to thrust faulting and range development during the early stages of plate collision (Baker & Seward, ; Brothers, ; Browne, ; King, ; Lamb, ; Lamb & Bibby, ; Lewis et al, ; Rait et al, ; Randall et al, ; Rattenbury et al, ; Walcott, ).…”

The Palos Verdes Fault offshore Southern California: Late Pleistocene to present tectonic geomorphology, seascape evolution, and slip rate estimate based on AUV and ROV surveys

“…A significant challenge for paleoseismology is obtaining primary, near‐field evidence for coseismic offset with accurate age constraints. For subaqueous studies, high‐resolution marine geophysical methods are capable of imaging vertically offset stratigraphy and evidence for punctuated fault growth [ Barnes and Pondard , ; Bartholomew et al , ; Brothers et al , , ; Pondard and Barnes , ], as well as offset seabed/lakefloor morphology that can be dated to constrain late Pleistocene and Holocene slip rates [ Dingler et al , ; Johnson et al , ; Kent et al , ; Ryan et al , ]. However, stratigraphic evidence for recent displacement along strike‐slip faults is difficult to resolve in deep‐water settings (>200 m) and two‐dimensional cross sections are most practical for imaging vertical displacement.…”