scholarly journals Quaternary Geometry, Kinematics and Paleoearthquake History at the Intersection of the Strike-Slip North Island Fault System and Taupo Rift, New Zealand

2021 ◽  
Author(s):  
◽  
Vasiliki Mouslopoulou
Keyword(s):  
New Zealand ◽  
Late Quaternary ◽  
Strike Slip ◽  
Fault System ◽  
Alternative Mechanism ◽  
Normal Faulting ◽  
Fault Systems ◽  
The North ◽  
Australian Plate ◽  
C 30

<p>The North Island of New Zealand sits astride the Hikurangi margin along which the oceanic Pacific Plate is being obliquely subducted beneath the continental Australian Plate. The North Island Fault System1 (NIFS), in the North Island of New Zealand, is the principal active strike-slip fault system in the overriding Australian Plate accommodating up to 30% of the margin parallel plate motion. This study focuses on the northern termination of the NIFS, near its intersection with the active Taupo Rift, and comprises three complementary components of research: 1) the investigation of the late Quaternary (c. 30 kyr) geometries and kinematics of the northern NIFS as derived from displaced geomorphic landforms and outcrop geology, 2) examination of the spatial and temporal distribution of  paleoearthquakes in the NIFS over the last 18 kyr, as derived by fault-trenching and displaced landforms, and consideration of how these distributions may have produced the documented late Quaternary (c. 30 kyr) kinematics of the northern NIFS, and 3) Investigation of the temporal stability of the late Quaternary (c. 30 kyr) geometries and kinematics throughout the Quaternary (1-2 Ma), derived from gravity, seismic-reflection, drillhole, topographic and outcrop data. The late Quaternary (c. 30 kyr) kinematics of the northern NIFS transition northward along strike, from strike-slip to oblique-normal faulting, adjacent to the rift. With increasing proximity to the Taupo Rift the slip vector pitch on each of the faults in the NIFS steepens gradually by up to 60 degrees, while the mean fault-dip decreases from 90 degrees to 60 degrees W. Adjustments in the kinematics of the NIFS reflect the gradual accommodation of the NW-SE extension that is distributed outside the main physiographic boundary of the Taupo Rift. Sub-parallelism of slip vectors in the NIFS with the line of intersection between the two synchronous fault systems reduces potential space problems and facilitates the development of a kinematically coherent fault intersection, which allows the strike-slip component of slip to be transferred into the rift. Transfer of displacement from the NIFS into the rift accounts for a significant amount of the northeastward increase of extension along the rift. Steepening of the pitch of slip vectors towards the northern termination of the NIFS allows the kinematics and geometry of faulting to change efficiently, from strike-lip to normal faulting, providing an alternative mechanism to vertical axis rotations for terminating large strike-lip faults. Analyses of kinematic constraints from worldwide examples of synchronous strike-lip and normal faults that intersect to form two or three plate configurations, within either oceanic or continental crust, suggest that displacement is often transferred between the two fault systems in a similar manner to that documented at the NIFS - Taupo Rift fault intersection. The late Quaternary (c. 30 kyr) change in the kinematics of the NIFS along strike, from dominantly strike-slip to oblique-normal faulting, arises due to a combination of rupture arrest during individual earthquakes and variations in the orientation of the coseismic slip vectors. At least 80 % of all surface rupturing earthquakes appear to have terminated within the kinematic transition zone from strike-slip to oblique-normal slip. Fault segmentation reduces the magnitudes of large surface rupturing earthquakes in the northern NIFS from 7.4-7.6 to c. 7.0. Interdependence of throw rates between the NIFS and Taupo Rift suggests that the intersection of the two fault systems has functioned coherently for much of the last 0.6-1.5 Myr. Oblique-normal slip faults in the NIFS and the Edgecumbe Fault in the rift accommodated higher throw rates since 300 kyr than during the last 0.6-1.5 Myr. Acceleration of these throw rates may have occurred in response to eastward migration of rifting, increasing both the rates of faulting and the pitch of slip vectors. The late Quaternary (e.g. 30 kyr) kinematics, and perhaps also the stability, of the intersection zone has been geologically short lived and applied for the last c. 300 kyr.</p>

scholarly journals Quaternary Geometry, Kinematics and Paleoearthquake History at the Intersection of the Strike-Slip North Island Fault System and Taupo Rift, New Zealand

2021 ◽  
Author(s):  
◽  
Vasiliki Mouslopoulou
Keyword(s):  
New Zealand ◽  
Late Quaternary ◽  
Strike Slip ◽  
Fault System ◽  
Alternative Mechanism ◽  
Normal Faulting ◽  
Fault Systems ◽  
The North ◽  
Australian Plate ◽  
C 30

<p>The North Island of New Zealand sits astride the Hikurangi margin along which the oceanic Pacific Plate is being obliquely subducted beneath the continental Australian Plate. The North Island Fault System1 (NIFS), in the North Island of New Zealand, is the principal active strike-slip fault system in the overriding Australian Plate accommodating up to 30% of the margin parallel plate motion. This study focuses on the northern termination of the NIFS, near its intersection with the active Taupo Rift, and comprises three complementary components of research: 1) the investigation of the late Quaternary (c. 30 kyr) geometries and kinematics of the northern NIFS as derived from displaced geomorphic landforms and outcrop geology, 2) examination of the spatial and temporal distribution of  paleoearthquakes in the NIFS over the last 18 kyr, as derived by fault-trenching and displaced landforms, and consideration of how these distributions may have produced the documented late Quaternary (c. 30 kyr) kinematics of the northern NIFS, and 3) Investigation of the temporal stability of the late Quaternary (c. 30 kyr) geometries and kinematics throughout the Quaternary (1-2 Ma), derived from gravity, seismic-reflection, drillhole, topographic and outcrop data. The late Quaternary (c. 30 kyr) kinematics of the northern NIFS transition northward along strike, from strike-slip to oblique-normal faulting, adjacent to the rift. With increasing proximity to the Taupo Rift the slip vector pitch on each of the faults in the NIFS steepens gradually by up to 60 degrees, while the mean fault-dip decreases from 90 degrees to 60 degrees W. Adjustments in the kinematics of the NIFS reflect the gradual accommodation of the NW-SE extension that is distributed outside the main physiographic boundary of the Taupo Rift. Sub-parallelism of slip vectors in the NIFS with the line of intersection between the two synchronous fault systems reduces potential space problems and facilitates the development of a kinematically coherent fault intersection, which allows the strike-slip component of slip to be transferred into the rift. Transfer of displacement from the NIFS into the rift accounts for a significant amount of the northeastward increase of extension along the rift. Steepening of the pitch of slip vectors towards the northern termination of the NIFS allows the kinematics and geometry of faulting to change efficiently, from strike-lip to normal faulting, providing an alternative mechanism to vertical axis rotations for terminating large strike-lip faults. Analyses of kinematic constraints from worldwide examples of synchronous strike-lip and normal faults that intersect to form two or three plate configurations, within either oceanic or continental crust, suggest that displacement is often transferred between the two fault systems in a similar manner to that documented at the NIFS - Taupo Rift fault intersection. The late Quaternary (c. 30 kyr) change in the kinematics of the NIFS along strike, from dominantly strike-slip to oblique-normal faulting, arises due to a combination of rupture arrest during individual earthquakes and variations in the orientation of the coseismic slip vectors. At least 80 % of all surface rupturing earthquakes appear to have terminated within the kinematic transition zone from strike-slip to oblique-normal slip. Fault segmentation reduces the magnitudes of large surface rupturing earthquakes in the northern NIFS from 7.4-7.6 to c. 7.0. Interdependence of throw rates between the NIFS and Taupo Rift suggests that the intersection of the two fault systems has functioned coherently for much of the last 0.6-1.5 Myr. Oblique-normal slip faults in the NIFS and the Edgecumbe Fault in the rift accommodated higher throw rates since 300 kyr than during the last 0.6-1.5 Myr. Acceleration of these throw rates may have occurred in response to eastward migration of rifting, increasing both the rates of faulting and the pitch of slip vectors. The late Quaternary (e.g. 30 kyr) kinematics, and perhaps also the stability, of the intersection zone has been geologically short lived and applied for the last c. 300 kyr.</p>

Characterization of Active Faults Through the Gulf of Guayaquil, Ecuador: implication for the southern boundary of the North Andean Sliver

2020 ◽  
Author(s):  
Marc Regnier ◽  
Gabriela Ponce ◽  
Marianne Saillard ◽  
Laurence Audin ◽  
Sandro Vaca ◽  
...  
Keyword(s):  
Seismic Activity ◽  
B Value ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faulting ◽  
Seismic Belt ◽  
Large Magnitude ◽  
Volcanic Arc ◽  
The North ◽  
Gulf Of Guayaquil

&lt;p&gt;Along the Ecuadorian margin, the North Andean Sliver is moving in the northeastward direction due to the oblique subduction of the Nazca plate. The opening of the gulf of Guayaquil is a consequence of this motion. Two principal models compete to explain the opening. One proposes an opening achieved essentially with strike-slip motion along a single major fault through the gulf, the other with a combination of strike-slip and normal faulting on both sides of the gulf. The consequences in term of seismic hazard are very different. A single strike-slip fault model could imply a long fault segment capable of generating large magnitude events. In contrast, a multi-segments composite fault system will give conditions for producing small to medium size earthquakes. The southern Ecuador subduction zone is characterized by the absence of large historical earthquake. Data from the historical and instrumental seismicity for magnitude above 4 show the forearc has a high level of moderate seismic activity within and around the gulf that connects to the crustal seismic activity of the volcanic arc. In contrast, the forearc elsewhere shows very little or no seismic activity between the marine forearc zone and the volcanic arc. Regional and global CMTS data show a large number of mechanisms within the gulf that do not line up on a simple straight fault system. We present new earthquake data from the recently upgraded national seismic network of Ecuador. They provide the first image of SW-NE trending crustal faults stretching in the central part of the gulf and running eastward south of the Puna island. The main seismic belt appears to be discontinuous, made of short length segments with variable trends. The variety of focal solutions also indicates complex faulting. As the shape of this seismic belt is in good agreement with the orientation of the GPS velocity vectors, this new fault zone is readily interpreted as the southernmost segment of the actual NAS boundary. Others seismic clusters are observed parallel to the northern coast of the gulf, indicating active structures eventually accommodating the North-South opening of the gulf through normal faulting. b-value analysis of the main seismic belt seismicity shows high b value (&gt;1) indicating either highly fractured or heterogeneous medium, or/and low stress level within the gulf of Guayaquil. This is again in agreement with a multi-segmented faulting system and also with the lack of large magnitude event in the historical seismic data. A cross-section for the entire seismic belt shows a depth extend of the crustal seismic activity down to 30 km which confirms the seismic belt to be a sliver boundary.&lt;/p&gt;

Recent coastal deformation near the Strait of Hormuz

1982 ◽  
Vol 382 (1783) ◽  
pp. 441-457 ◽  
Keyword(s):  
Saudi Arabia ◽  
Maximum Rate ◽  
Radiocarbon Dating ◽  
Late Quaternary ◽  
Strike Slip ◽  
Normal Faulting ◽  
Slip Vector ◽  
The North ◽  
Strait Of Hormuz ◽  
Uplift Rates

Radiocarbon dating of marine shorelines on the flanks of anticlines on the southeastern Zagros coast indicates Holocene uplift rates of 1.8-6.6 mm/year. The corresponding values for shortening assuming décollement yield a resultant slip vector for the last 7000 years of 29 mm/year bearing N 33° E. During the same period the Musandam Peninsula, on the Arabian side of the Strait of Hormuz, subsided towards the north and east at a maximum rate of 8.5 mm/year. Reports of rapid Holocene uplift in the mountains of Oman are not substantiated by the shoreline evidence on the Arabian and Gulf coasts south of Musandam. The lower Mesopotamian plains and the coast of eastern Saudi Arabia also indicate tectonic stability during the late Quaternary. In contrast the western Makran was affected by extensive normal faulting and some strike-slip faulting in the course of the last 35 000 years. The pattern of deformation is consistent with the geophysical evidence but also shows that current seismicity on the Strait of Hormuz is not typical of Holocene conditions in the area.

Is the North Altyn fault part of a strike-slip duplex along the Altyn Tagh fault system?

Geology ◽  
2000 ◽  
Vol 28 (3) ◽  
pp. 255 ◽  
Author(s):  
Eric Cowgill ◽  
An Yin ◽  
Wang Xiao Feng ◽  
Zhang Qing
Keyword(s):  
Strike Slip ◽  
Fault System ◽  
Altyn Tagh Fault ◽  
The North ◽  
Altyn Tagh

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

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new &lt;sup&gt;10&lt;/sup&gt;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 &gt;10 mm/yr, but we find that erosion rates of &gt;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 &lt;sup&gt;10&lt;/sup&gt;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&lt;sup&gt;3&lt;/sup&gt; 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 &lt;sup&gt;10&lt;/sup&gt;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.&lt;/p&gt;&lt;p&gt;Our results highlight the potential for &lt;sup&gt;10&lt;/sup&gt;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.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Inversion of regional surface-wave spectra for source parameters of aftershocks from the 1992 Petrolia earthquake sequence

1995 ◽  
Vol 85 (3) ◽  
pp. 705-715
Author(s):  
Mark Andrew Tinker ◽  
Susan L. Beck
Keyword(s):  
Surface Wave ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Strike Slip ◽  
Earthquake Sequence ◽  
Fault System ◽  
Accretionary Wedge ◽  
Wave Spectra ◽  
The North ◽  
Gorda Plate

Abstract Regional distance surface waves are used to study the source parameters for moderate-size aftershocks of the 25 April 1992 Petrolia earthquake sequence. The Cascadia subduction zone had been relatively seismically inactive until the onset of the mainshock (Ms = 7.1). This underthrusting event establishes that the southern end of the North America-Gorda plate boundary is seismogenic. It was followed by two separate and distinct large aftershocks (Ms = 6.6 for both) occurring at 07:41 and 11:41 on 26 April, as well as thousands of other small aftershocks. Many of the aftershocks following the second large aftershock had magnitudes in the range of 4.0 to 5.5. Using intermediate-period surface-wave spectra, we estimate focal mechanisms and depths for one foreshock and six of the larger aftershocks (Md = 4.0 to 5.5). These seven events can be separated into two groups based on temporal, spatial, and principal stress orientation characteristics. Within two days of the mainshock, four aftershocks (Md = 4 to 5) occurred within 4 hr of each other that were located offshore and along the Mendocino fault. These four aftershocks comprise one group. They are shallow, thrust events with northeast-trending P axes. We interpret these aftershocks to represent internal compression within the North American accretionary prism as a result of Gorda plate subduction. The other three events compose the second group. The shallow, strike-slip mechanism determined for the 8 March foreshock (Md = 5.3) may reflect the right-lateral strike-slip motion associated with the interaction between the northern terminus of the San Andreas fault system and the eastern terminus of the Mendocino fault. The 10 May aftershock (Md = 4.1), located on the coast and north of the Mendocino triple junction, has a thrust fault focal mechanism. This event is shallow and probably occurred within the accretionary wedge on an imbricate thrust. A normal fault focal mechanism is obtained for the 5 June aftershock (Md = 4.8), located offshore and just north of the Mendocino fault. This event exhibits a large component of normal motion, representing internal failure within a rebounding accretionary wedge. These two aftershocks and the foreshock have dissimilar locations in space and time, but they do share a north-northwest oriented P axis.

Geodetic strain and the deformational history of the North Island of New Zealand during the late Cainozoic

1987 ◽  
Vol 321 (1557) ◽  
pp. 163-181 ◽  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Late Quaternary ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Metamorphic Belt ◽  
Volcanic Region ◽  
The North ◽  
Plate Boundary Zone

The subduction zone under the east coast of the North Island of New Zealand comprises, from east to west, a frontal wedge, a fore-arc basin, uplifted basement forming the arc and the Central Volcanic Region. Reconstructions of the plate boundary zone for the Cainozoic from seafloor spreading data require the fore-arc basin to have rotated through 60° in the last 20 Ma which is confirmed by palaeomagnetic declination studies. Estimates of shear strain from geodetic data show that the fore-arc basin is rotating today and that it is under extension in the direction normal to the trend of the plate boundary zone. The extension is apparently achieved by normal faulting. Estimates of the amount of sediments accreted to the subduction zone exceed the volume of the frontal wedge: underplating by the excess sediments is suggested to be the cause of late Quaternary uplift of the fore-arc basin. Low-temperature—high-pressure metamorphism may therefore be occurring at depth on the east coast and high-temperature—low-pressure metamorphism is probable in the Central Volcanic Region. The North Island of New Zealand is therefore a likely setting for a paired metamorphic belt in the making.

scholarly journals Triple junction kinematics accounts for the 2016 Mw7.8 Kaikoura earthquake rupture complexity

2019 ◽  
Vol 116 (52) ◽  
pp. 26367-26375 ◽  
Author(s):  
Xuhua Shi ◽  
Paul Tapponnier ◽  
Teng Wang ◽  
Shengji Wei ◽  
Yu Wang ◽  
...  
Keyword(s):  
New Zealand ◽  
Triple Junction ◽  
Large Scale ◽  
Strike Slip ◽  
Plate Motion ◽  
Fault System ◽  
Coseismic Deformation ◽  
Coseismic Slip ◽  
Slab Geometry ◽  
Kaikoura Earthquake

The 2016, moment magnitude (Mw) 7.8, Kaikoura earthquake generated the most complex surface ruptures ever observed. Although likely linked with kinematic changes in central New Zealand, the driving mechanisms of such complexity remain unclear. Here, we propose an interpretation accounting for the most puzzling aspects of the 2016 rupture. We examine the partitioning of plate motion and coseismic slip during the 2016 event in and around Kaikoura and the large-scale fault kinematics, volcanism, seismicity, and slab geometry in the broader Tonga–Kermadec region. We find that the plate motion partitioning near Kaikoura is comparable to the coseismic partitioning between strike-slip motion on the Kekerengu fault and subperpendicular thrusting along the offshore West–Hikurangi megathrust. Together with measured slip rates and paleoseismological results along the Hope, Kekerengu, and Wairarapa faults, this observation suggests that the West–Hikurangi thrust and Kekerengu faults bound the southernmost tip of the Tonga–Kermadec sliver plate. The narrow region, around Kaikoura, where the 3 fastest-slipping faults of New Zealand meet, thus hosts a fault–fault–trench (FFT) triple junction, which accounts for the particularly convoluted 2016 coseismic deformation. That triple junction appears to have migrated southward since the birth of the sliver plate (around 5 to 7 million years ago). This likely drove southward stepping of strike-slip shear within the Marlborough fault system and propagation of volcanism in the North Island. Hence, on a multimillennial time scale, the apparently distributed faulting across southern New Zealand may reflect classic plate-tectonic triple-junction migration rather than diffuse deformation of the continental lithosphere.

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