Reconciling an Early Nineteenth-Century Rupture of the Alpine Fault at a Section End, Toaroha River, Westland, New Zealand

2020 ◽  
Author(s):  
Robert M. Langridge ◽  
Pilar Villamor ◽  
Jamie D. Howarth ◽  
William F. Ries ◽  
Kate J. Clark ◽  
...  
Keyword(s):  
Nineteenth Century ◽  
New Zealand ◽  
Plate Boundary ◽  
Slip Rate ◽  
Fault System ◽  
Fault Rupture ◽  
Central Section ◽  
Surface Rupture ◽  
Early Nineteenth Century ◽  
Alpine Fault

ABSTRACT The Alpine fault is a high slip-rate plate boundary fault that poses a significant seismic hazard to southern and central New Zealand. To date, the strongest paleoseismic evidence for the onshore southern and central sections indicates that the fault typically ruptures during very large (Mw≥7.7) to great “full-section” earthquakes. Three paleoseismic trenches excavated at the northeastern end of its central section at the Toaroha River (Staples site) provide new insights into its surface-rupture behavior. Paleoseismic ruptures in each trench have been dated using the best-ranked radiocarbon dating fractions, and stratigraphically and temporally correlated between each trench. The preferred timings of the four most recent earthquakes are 1813–1848, 1673–1792, 1250–1580, and ≥1084–1276 C.E. (95% confidence intervals using OxCal 4.4). These surface-rupture dates correlate well with reinterpreted timings of paleoearthquakes from previous trenches excavated nearby and with the timing of shaking-triggered turbidites in lakes along the central section of the Alpine fault. Results from these trenches indicate the most recent rupture event (MRE) in this area postdates the great 1717 C.E. Alpine fault rupture (the most recent full-section rupture of the southern and central sections). This MRE probably occurred within the early nineteenth century and is reconciled as either: (a) a “partial-section” rupture of the central section; (b) a northern section rupture that continued to the southwest; or (c) triggered slip from a Hope-Kelly fault rupture at the southwestern end of the Marlborough fault system (MFS). Although, no single scenario is currently favored, our results indicate that the behavior of the Alpine fault is more complex in the north, as the plate boundary transitions into the MFS. An important outcome is that sites or towns near fault intersections and section ends may experience strong ground motions more frequently due to locally shorter rupture recurrence intervals.

scholarly journals A 2000 Yr Paleoearthquake Record along the Conway Segment of the Hope Fault: Implications for Patterns of Earthquake Occurrence in Northern South Island and Southern North Island, New Zealand

2019 ◽  
Vol 109 (6) ◽  
pp. 2216-2239 ◽  
Author(s):  
Alexandra E. Hatem ◽  
James F. Dolan ◽  
Robert W. Zinke ◽  
Russell J. Van Dissen ◽  
Christopher M. McGuire ◽  
...  
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Plate Boundary ◽  
Slip Rate ◽  
Fault System ◽  
Recent Event ◽  
Radiocarbon Age ◽  
Earthquake Record ◽  
Surface Ruptures ◽  
Age Constraints

Abstract Paleoseismic trenches excavated at two sites reveal ages of late Holocene earthquakes along the Conway segment of the Hope fault, the fastest-slipping fault within the Marlborough fault system in northern South Island, New Zealand. At the Green Burn East (GBE) site, a fault-perpendicular trench exposed gravel colluvial wedges, fissure fills, and upward fault terminations associated with five paleo-surface ruptures. Radiocarbon age constraints indicate that these five earthquakes occurred after 36 B.C.E., with the four most recent surface ruptures occurring during a relatively brief period (550 yr) between about 1290 C.E. and the beginning of the historical earthquake record about 1840 C.E. Additional trenches at the Green Burn West (GBW) site 1.4 km west of GBE reveal four likely coseismically generated landslides that occurred at approximately the same times as the four most recent GBE paleoearthquakes, independently overlapping with age ranges of events GB1, GB2, and GB3 from GBE. Combining age constraints from both trench sites indicates that the most recent event (GB1) occurred between 1731 and 1840 C.E., the penultimate event GB2 occurred between 1657 and 1797 C.E., GB3 occurred between 1495 and 1611 C.E., GB4 occurred between 1290 and 1420 C.E., and GB5 occurred between 36 B.C.E. and 1275 C.E. These new data facilitate comparisons with similar paleoearthquake records from other faults within the Alpine–Hope–Jordan–Kekerengu–Needles–Wairarapa (Al-Hp-JKN-Wr) fault system of throughgoing, fast-slip-rate (≥10  mm/yr) reverse-dextral faults that accommodate a majority of Pacific–Australia relative plate boundary motion. These comparisons indicate that combinations of the faults of the Al-Hp-JKN-Wr system may commonly rupture within relatively brief, ≤100-year-long sequences, but that full “wall-to-wall” rupture sequences involving all faults in the system are rare over the span of our paleoearthquake data. Rather, the data suggest that the Al-Hp-JKN-Wr system may commonly rupture in subsequences that do not involve the entire system, and potentially, at least sometimes, in isolated events.

scholarly journals Holocene to latest Pleistocene incremental slip rates from the east-central Hope fault (Conway segment) at Hossack Station, Marlborough fault system, South Island, New Zealand: Towards a dated path of earthquake slip along a plate boundary fault

Geosphere ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 1558-1584
Author(s):  
Alexandra E. Hatem ◽  
James F. Dolan ◽  
Robert W. Zinke ◽  
Robert M. Langridge ◽  
Christopher P. McGuire ◽  
...  
Keyword(s):  
New Zealand ◽  
Plate Boundary ◽  
Slip Rate ◽  
Temporal Variations ◽  
Luminescence Dating ◽  
Fault System ◽  
Surface Deposition ◽  
Slip Rates ◽  
East Central ◽  
Fault Slip Rate

Abstract Geomorphic field and aerial lidar mapping, coupled with fault-parallel trenching, reveals four progressive offsets of a stream channel and an older offset of the channel headwaters and associated fill terrace–bedrock contact at Hossack Station along the Conway segment of the Hope fault, the fastest-slipping fault within the Marlborough fault system in northern South Island, New Zealand. Radiocarbon and luminescence dating of aggradational surface deposition and channel initiation and abandonment event horizons yields not only an average dextral rate of ∼15 mm/yr since ca. 14 ka, but also incremental slip rates for five different time periods (spanning hundreds to thousands of years) during Holocene to latest Pleistocene time. These incremental rates vary through time and are, from youngest to oldest: 8.2 +2.7/−1.5 mm/yr averaged since 1.1 ka; 32.7 +∼124.9/−10.1 mm/yr averaged over 1.61–1.0 ka; 19.1 ± 0.8 mm/yr between 5.4 and 1.6 ka; 12.0 ± 0.9 mm/yr between 9.4 and 5.4 ka, and 13.7 +4.0/−3.4 mm/yr from 13.8 to 9.4 ka, with generally faster rates in the mid- to late Holocene relative to slower rates prior to ca. 5.4 ka. The most pronounced variation in rates occurs between the two youngest intervals, which are averaged over shorter time spans (≤1700 yr) than the three older incremental rates (3700–4500 yr). This suggests that the factor of ∼1.5× variations in Hope fault slip rate observed in the three older, longer-duration incremental rates may mask even greater temporal variations in rate over shorter time scales.

scholarly journals The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand

2016 ◽  
Vol 445 ◽  
pp. 125-135 ◽  
Author(s):  
Catriona D. Menzies ◽  
Damon A.H. Teagle ◽  
Samuel Niedermann ◽  
Simon C. Cox ◽  
Dave Craw ◽  
...  
Keyword(s):  
New Zealand ◽  
Plate Boundary ◽  
Boundary Fault ◽  
Continental Plate ◽  
Alpine Fault

Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate

2021 ◽  
Author(s):  
Duna Roda-Boluda ◽  
Taylor Schildgen ◽  
Hella Wittmann-Oelze ◽  
Stefanie Tofelde ◽  
Aaron Bufe ◽  
...  
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Southern Alps ◽  
Fault System ◽  
Tectonic Deformation ◽  
Seismic Cycle ◽  
Erosion Rates ◽  
Alpine Fault ◽  
Oblique Convergence

<p>The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.</p><p>To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new <sup>10</sup>Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These <sup>10</sup>Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~10<sup>3</sup> yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our <sup>10</sup>Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.</p><p>Our results highlight the potential for <sup>10</sup>Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.</p><p> </p><p> </p>

Highly localized upper mantle deformation during plate boundary initiation near the Alpine fault, New Zealand

Geology ◽  
2021 ◽  
Author(s):  
Steven Kidder ◽  
David J. Prior ◽  
James M. Scott ◽  
Hamid Soleymani ◽  
Yilun Shao
Keyword(s):  
New Zealand ◽  
Upper Mantle ◽  
Plate Boundary ◽  
New Approach ◽  
Fine Grained ◽  
Alpine Fault ◽  
Narrow Width ◽  
Plate Boundary Deformation ◽  
Boundary Deformation ◽  
Total Shear

Peridotite xenoliths entrained in magmas near the Alpine fault (New Zealand) provide the first direct evidence of deformation associated with the propagation of the Australian-Pacific plate boundary through the region at ca. 25–20 Ma. Two of 11 sampled xenolith localities contain fine-grained (40–150 mm) rocks, indicating that deformation in the upper mantle was focused in highly sheared zones. To constrain the nature and conditions of deformation, we combine a flow law with a model linking recrystallized fraction to strain. Temperatures calculated from this new approach (625–970 °C) indicate that the observed deformation occurred at depths of 25–50 km. Calculated shear strains were between 1 and 100, which, given known plate offset rates (10–20 mm/yr) and an estimated interval during which deformation likely occurred (<1.8 m.y.), translate to a total shear zone width in the range 0.2–32 km. This narrow width and the position of mylonite-bearing localities amid mylonite-free sites suggest that early plate boundary deformation was distributed across at least ~60 km but localized in multiple fault strands. Such upper mantle deformation is best described by relatively rigid, plate-like domains separated by rapidly formed, narrow mylonite zones.

The discovery of a new sedimentary basin: offshore Raukumara, East Coast, North Island, New Zealand

2008 ◽  
Vol 48 (1) ◽  
pp. 53 ◽  
Author(s):  
Chris Uruski ◽  
Callum Kennedy ◽  
Rupert Sutherland ◽  
Vaughan Stagpoole ◽  
Stuart Henrys
Keyword(s):  
New Zealand ◽  
Oil And Gas ◽  
East Coast ◽  
Plate Boundary ◽  
Source Rocks ◽  
Fault System ◽  
Northern Coast ◽  
The South ◽  
Petroleum Potential ◽  
The North

The East Coast of North Island, New Zealand, is the site of subduction of the Pacific below the Australian plate, and, consequently, much of the basin is highly deformed. An exception is the Raukumara Sub-basin, which forms the northern end of the East Coast Basin and is relatively undeformed. It occupies a marine plain that extends to the north-northeast from the northern coast of the Raukumara Peninsula, reaching water depths of about 3,000 m, although much of the sub-basin lies within the 2,000 m isobath. The sub-basin is about 100 km across and has a roughly triangular plan, bounded by an east-west fault system in the south. It extends about 300 km to the northeast and is bounded to the east by the East Cape subduction ridge and to the west by the volcanic Kermadec Ridge. The northern seismic lines reveal a thickness of around 8 km increasing to 12–13 km in the south. Its stratigraphy consists of a fairly uniformly bedded basal section and an upper, more variable unit separated by a wedge of chaotically bedded material. In the absence of direct evidence from wells and samples, analogies are drawn with onshore geology, where older marine Cretaceous and Paleogene units are separated from a Neogene succession by an allochthonous series of thrust slices emplaced around the time of initiation of the modern plate boundary. The Raukumara Sub-basin is not easily classified. Its location is apparently that of a fore-arc basin along an ocean-to-ocean collision zone, although its sedimentary fill must have been derived chiefly from erosion of the New Zealand land mass. Its relative lack of deformation introduces questions about basin formation and petroleum potential. Although no commercial discoveries have been made in the East Coast Basin, known source rocks are of marine origin and are commonly oil prone, so there is good potential for oil as well as gas in the basin. New seismic data confirm the extent of the sub-basin and its considerable sedimentary thickness. The presence of potential trapping structures and direct hydrocarbon indicators suggest that the Raukumara Sub-basin may contain large volumes of oil and gas.

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