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Late Quaternary faulting in the Kaikoura region, southeastern Marlborough, New Zealand
Active faults in the Kaikoura region include the Hope,
Kekerengu, and Fidget Faults, and the newly discovered
Jordan Thrust, Fyffe, and Kowhai Faults. Ages of faulted
alluvial terraces along the Hope Fault and the Jordan
Thrust were estimated using radiocarbon-calibrated
weathering-rind measurements on graywacke clasts. Within
the study area, the Hope Fault is divided, from west to
east, into the Kahutara, Mt. Fyffe, and Seaward segments.
The Kahutara segment has a relatively constant Holocene
right-lateral slip rate of 20-32 mm/yr, and an earthquake
recurrence interval of 86 to 600 yrs: based on single-event
displacements of 3 to 12 m. The western portion of the Mt.
Fyffe segment has a minimum Holocene lateral slip rate of
16 ± 5 mm/yr .(southeast side up); the eastern portion has
horizontal and vertical slip rates of 4.8 ± 2.7 mm/yr and
1.7 ± 0.2 mm/yr, respectively (northwest side up). There
is no dated evidence for late Quaternary movement on the
Seaward segment, and its topographic expression is much
more subdued than that of the two western segments.
The Jordan Thrust extends northeast from the Hope
Fault, west of the Seaward segment. The thrust has
horizontal and vertical slip rates of 2.2 ± 1.3 mm/yr and
2.1 ± 0.5 mm/yr, respectively (northwest side up), and a
maximum recurrence interval of 1200 yrs: based on 3 events
within the last 3.5 ka. Drainage-divide elevation and
mountain-front morphology of the Seaward Kaikoura Range,
abundant evidence for recent activity on the Jordan Thrust,
and lack of activity on the Seaward segment indicate that
the late Quaternary displacement on the Hope Fault is
transferred northward, west of the Seaward segment. The
low slip rates for the thrust, compared to the higher
lateral slip rates along the Kahutara and Mt. Fyffe
segments, suggest that displacement on the Jordan Thrust
does not accommodate all the displacement transferred from
the Hope Fault. The remaining displacement is accommodated
by distributed shear within the Torlesse rocks behind the
thrust, and folds in front of and behind the thrust,
although the latter was not documented for the Holocene
The Lake Edgar Fault: an active fault in Southwestern Tasmania, Australia, with repeated displacement in the Quaternary
The Lake Edgar Fault in Western Tasmania, Australia is marked by a prominent fault scarp and is a recently reactivated
fault initially of Cambrian age. The scarp has a northerly trend and passes through the western abutment
of the Edgar Dam, a saddle dam on Lake Pedder. The active fault segment displaces geologically young river
and glacial deposits. It is 29 ± 4 km long, and dips to the west. Movement on the fault has ruptured the ground
surface at least twice within the Quaternary and possibly the last ca. 25 000 years; the most recent rupture has
occurred since the last glaciation (within the last ca. 10000 years). This is the only known case of surface faulting
in Australia with evidence for repeated ruptures in the Late Pleistocene. Along its central portion the two
most recent surface-faulting earthquakes have resulted in about 2.5 m of vertical displacement each (western side
up). The Lake Edgar Fault is considered capable of generating earthquakes in the order of magnitude 61/2-71/4.
The Gell River Fault is another fault nearby that was apparently also active in the Late Pleistocene. It has yet to
be studied in detail but the scarp appears to be more degraded and therefore older than the most recent movement
on the Lake Edgar Fault
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
Paleoseismic trenches excavated at two sites reveal ages of late Holocene earthquakes along the Conway segment of the Hope fault, the fastestâslipping fault within the Marlborough fault system in northern South Island, New Zealand. At the Green Burn East (GBE) site, a faultâperpendicular trench exposed gravel colluvial wedges, fissure fills, and upward fault terminations associated with five paleoâsurface 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 AlpineâHopeâJordanâKekerenguâNeedlesâWairarapa (AlâHpâJKNâWr) fault system of throughgoing, fastâslipârate (â â„10ââmm/yrâ ) reverseâdextral faults that accommodate a majority of PacificâAustralia relative plate boundary motion. These comparisons indicate that combinations of the faults of the AlâHpâJKNâWr system may commonly rupture within relatively brief, â€100âyearâlong sequences, but that full âwallâtoâwallâ rupture sequences involving all faults in the system are rare over the span of our paleoearthquake data. Rather, the data suggest that the AlâHpâJKNâWr system may commonly rupture in subsequences that do not involve the entire system, and potentially, at least sometimes, in isolated events
Evolution and progressive geomorphic manifestation of surface faulting: A comparison of the Wairau and Awatere faults, South Island, New Zealand
Field mapping and lidar analysis of surface faulting patterns expressed in flights of geologically similar fluvial terraces at the well-known Branch River and Saxton River sites along the Wairau (Alpine) and Awatere strike-slip faults, South Island, New Zealand, reveal that fault-related deformation patterns expressed in the topography at these sites are markedly less structurally complex along the higher-displacement (hundreds of kilometers), structurally mature Wairau fault than along the Awatere fault (âŒ13â20 km total slip). These differences, which are generally representative of the surface traces of these faults, provide direct evidence that surface faulting becomes structurally simpler with increasing cumulative fault offset. We also examine the degree to which off-fault deformation (OFD) is expressed in the landscape at the Saxton River site along the less structurally mature Awatere fault. Significantly greater amounts of OFD are discernible as a wide damage zone (âŒ460 m fault-perpendicular width) in older (ca. 15 ka), more-displaced (64â74 m) fluvial terraces than in younger (ca. 1â7 ka), less-displaced (<55 m) terraces; no OFD is discernible in the lidar data on the least-displaced (<35 m) terraces. From this, we infer that OFD becomes progressively more geomorphically apparent with accumulating displacement. These observations imply that (1) the processes that accommodate OFD are active during each earthquake, but may not be evident in deposits that have experienced relatively small displacements; (2) structures accommodating OFD will become progressively geomorphically clearer with increasing displacement; (3) geomorphic measurements of overall fault zone width taken in deposits that have experienced small displacements will be underestimates; and (4) fault slip rates based on geomorphic surface offsets will be underestimates for immature faults if based solely on measurements along the high-strain fault core
Highly variable latest Pleistocene-Holocene incremental slip rates on the Awatere fault at Saxton River, South Island, New Zealand, revealed by lidar mapping and luminescence dating
Geomorphic mapping using high-resolution lidar imagery and luminescence dating reveal highly variable incremental Holocene-latest Pleistocene slip rates at the well-known Saxton River site along the Awatere fault, a dextral strike-slip fault in the Marlborough Fault System, South Island, New Zealand. Using lidar and field observations, we measured seven fault offsets recorded by fluvial terraces and bedrock markers. Improved dating of the offsets is provided by post-IR-IRSL225 luminescence ages. Incremental slip rates varied from 15 mm/yr over intervals of thousands of years and tens of meters of slip, demonstrating order-of-magnitude temporal variations in rate at a single site. These observations have basic implications for earthquake fault behavior, lithospheric mechanics, discrepancies between geodetic and geologic slip rates, and probabilistic seismic hazard assessment
A method to evaluate the degree of bleaching of IRSL signals in feldspar: The 3ET method
In addition to dating, IRSL luminescence signals can preserve information about erosional, transport, and depositional histories of a population of grains. Knowledge of the degree of bleaching can be useful in understanding the processes that occurred during previous depositional events, as certain transport conditions result in a well bleached signal, while others result in grains retaining an inherited signal from prior events. This information can be accessed by making single-grain IRSL measurements across successively increasing temperatures, thereby isolating signals from traps of different bleachabilities.
A new approach offers a way to evaluate the completeness of bleaching of a grain by testing patterns of equivalent dose (DE) values measured at three elevated temperatures (3ET), 50, 125, and 225 °C. Consistent DE estimates across two or more temperatures suggest a single bleaching event of sufficient duration to fully depopulate the traps involved. Incompletely bleached grains with inconsistent DE values across temperatures will lack a 3ET âplateau.â Modes in the distribution of DE values for fully bleached grains can suggest depositional ages, subject to assessment of fading. We developed a Python code in a Jupyter Notebook environment for data analysis and visualization to expedite processing the large data sets produced by the 3ET protocol.
The 3ET protocol was tested on a radiocarbon dated sequence of playa samples from California, USA and on a set of fluvial terraces in the Marlborough region of New Zealand as part of a larger project to reconstruct regional seismic history. Where standard pIRIR apparent ages can be inconsistent or ambiguous, 3ET age estimates produce generally consistent apparent ages. Modes of 3ET plateaus can be used to infer the most recent and prior events that resulted in a sub-population of grains being fully bleached. These initial results suggest that the 3ET method can be useful to characterize both the age and degree of bleaching of depositional events
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
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 associÂated fill terraceâbedrock 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 aggraÂdational 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/â1.5 mm/yr averaged since 1.1 ka; 32.7 +~124.9/â10.1 mm/yr averaged over 1.61â1.0 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/â3.4 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 (â€1700 yr) than the three older incremental rates (3700â4500 yr). This suggests that the factor of ~1.5Ă 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
Multimillennial incremental slip rate variability of the Clarence fault at the Tophouse Road site, Marlborough Fault System, New Zealand
Incremental slip rates of the Clarence fault, a dextral fault in the Marlborough fault system of South Island, New Zealand, varied by a factor of 4â5 during Holoceneâlatest Pleistocene time, as revealed by geomorphic mapping and luminescence dating of faulted fluvial landforms at the Tophouse Road site. We used high-resolution lidar microtopographic data and field surveys to map the fine-scale geomorphology and precisely restore the offset features. We dated the offsets using a stratigraphically informed protocol for infrared stimulated luminescence dating. These data show that incremental slip rates varied from ~2.0 to 9.6Â mm/year, averaged over multiple earthquakes and millennial timescales. Comparison to incremental slip rates of the nearby Awatere fault suggests that these faults may behave in coordinated (and anticorrelated) fashion. This study adds to a growing body of evidence suggesting that incremental slip rate variation spanning multiple earthquake cycles may be more common than previously recognized
Paired opposing leukocyte receptors recognizing rapidly evolving ligands are subject to homogenization of their ligand binding domains
Some leukocyte receptors come in groups of two or more where the partners share ligand(s) but transmit opposite signals. Some of the ligands, such as MHC class I, are fast evolving, raising the problem of how paired opposing receptors manage to change in step with respect to ligand binding properties and at the same time conserve opposite signaling functions. An example is the KLRC (NKG2) family, where opposing variants have been conserved in both rodents and primates. Phylogenetic analyses of the KLRC receptors within and between the two orders show that the opposing partners have been subject to post-speciation gene homogenization restricted mainly to the parts of the genes that encode the ligand binding domains. Concerted evolution similarly restricted is demonstrated also for the KLRI, KLRB (NKR-P1), KLRA (Ly49), and PIR receptor families. We propose the term merohomogenization for this phenomenon and discuss its significance for the evolution of immune receptors
Development and Function of CD94-Deficient Natural Killer Cells
The CD94 transmembrane-anchored glycoprotein forms disulfide-bonded heterodimers with the NKG2A subunit to form an inhibitory receptor or with the NKG2C or NKG2E subunits to assemble a receptor complex with activating DAP12 signaling proteins. CD94 receptors expressed on human and mouse NK cells and T cells have been proposed to be important in NK cell tolerance to self, play an important role in NK cell development, and contribute to NK cell-mediated immunity to certain infections including human cytomegalovirus. We generated a gene-targeted CD94-deficient mouse to understand the role of CD94 receptors in NK cell biology. CD94-deficient NK cells develop normally and efficiently kill NK cell-susceptible targets. Lack of these CD94 receptors does not alter control of mouse cytomegalovirus, lymphocytic choriomeningitis virus, vaccinia virus, or Listeria monocytogenes. Thus, the expression of CD94 and its associated NKG2A, NKG2C, and NKG2E subunits is dispensable for NK cell development, education, and many NK cell functions
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