The Tjellefonna fault system of Western Norway: Linking late-Caledonian extension, post-Caledonian normal faulting, and Tertiary rock column uplift with the landslide-generated tsunami event of 1756

2009 ◽  
Vol 474 (1-2) ◽  
pp. 106-123 ◽  
Author(s):  
T.F. Redfield ◽  
P.T. Osmundsen
Keyword(s):  
Fault System ◽  
Normal Faulting ◽  
Western Norway ◽  
Rock Column ◽  
Tsunami Event

Quaternary and active faulting observed on the 1985 Academia Sinica - Royal Society Geotraverse of Tibet

1988 ◽  
Vol 327 (1594) ◽  
pp. 337-363 ◽  
Keyword(s):  
Average Rate ◽  
Strike Slip ◽  
Fault System ◽  
Ground Moraine ◽  
Normal Faulting ◽  
Stream Channels ◽  
Quaternary Period ◽  
Terminal Moraine ◽  
Northern Half ◽  
Southern Half

Active and recent faulting along the main north—south road in Tibet is dominated by normal faulting occurring on northerly-trending planes and by strike-slip faulting, both of which reflect an east-west extension of the plateau. Normal faulting is prevalent in the southern half of the plateau, but we saw no evidence for any major graben in the northern half. Strike-slip faulting on roughly easterly-trending structures is m ore prevalent in the northern half, but conjugate faulting, with right-lateral slip on northwesterly-trending planes and left-lateral slip on northeasterly-trending planes, is common in the southern half. In two areas, we also observed components of thrust faulting, apparently in association with young strikeslip faulting. Our most important results are bounds on the rates of slip on the two main strands of the Kunlun strike-slip fault system, which trends east-w est through the Kunlun range. Ground moraine containing boulders of pyroxenite is separated by 30 km from the nearest outcrop of such rock, implying that amount of displacement in the last 1.5 to 3 M a. Therefore the average rate of slip during the Quaternary period has been between 10 and 20 mm/a , with a likely value of 13 mm/a . Abundant fresh tension cracks and mole tracks imply continued slip on the main strand, the Xidatan -Tuosuohu-Maqu fault, and the likely occurrence of a major earthquake in the last few hundred years. Consistent offsets of gullies and dry stream channels of about 10 m may reflect slip of that amount during such an earthquake, and possible multiple offsets at one site suggest that slip may occur by large displacements of 10 m during infrequent great earthquakes. Along the other strand, the Kunlun Pass fault, offsets of roughly 50 to 150 m of, apparently, post-glacial valleys and of one glacier and its terminal moraine suggest a Holocene rate of slip between 5 and 20 mm/a , and most likely about 10 mm/a , on this fault. These rapid rates of displacement imply that Tibet is being extruded rapidly eastward, at a rate com parable to the rate at which India is penetrating into Eurasia, and therefore that, at present, a substantial fraction of this penetration is being absorbed by the eastward extrusion of Tibet.

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;

scholarly journals Two-Phase Exhumation of the Santa Rosa Mountains: Low- and High-Angle Normal Faulting During Initiation and Evolution of the Southern San Andreas Fault System

Tectonics ◽  
2017 ◽  
Vol 36 (12) ◽  
pp. 2863-2881 ◽  
Author(s):  
Cody C. Mason ◽  
James A. Spotila ◽  
Gary Axen ◽  
Rebecca J. Dorsey ◽  
Amy Luther ◽  
...  
Keyword(s):  
San Andreas Fault ◽  
Fault System ◽  
High Angle ◽  
Normal Faulting ◽  
Two Phase ◽  
San Andreas ◽  
San Andreas Fault System

Faulting, doming and basin formation during orogenic arcuation – the case of the Shkoder-Peja Normal Fault System (northern Albania and Kosovo)

2021 ◽  
Author(s):  
Marc U. Grund ◽  
Mark R. Handy ◽  
Jörg Giese ◽  
Jan Pleuger ◽  
Lorenzo Gemignani ◽  
...  
Keyword(s):  
Hanging Wall ◽  
Normal Fault ◽  
Sedimentary Basins ◽  
Vertical Displacement ◽  
Ductile Deformation ◽  
Fault System ◽  
Normal Faulting ◽  
Two Phase ◽  
Brittle Faulting ◽  
Topographic Constraints

&lt;p&gt;The junction between the Dinarides and the Hellenides coincides with an orogenic bend characterized by a complex system of faults, domes and sedimentary basins. The major structure at this junction is the Shkoder-Peja Normal Fault (SPNF) system, which trends oblique to the orogen and is segmented along strike, with ductile-to-brittle branches in its southwestern and central parts that border two domes in its footwall: (1) the Cukali Dome (RSCM peak-T 190-280&amp;#176;C), a doubly-plunging upright antiform deforming Dinaric nappes, including the Krasta-Cukali nappe with its Middle Triassic to Early Eocene sediments; (2) the newly discovered Decani Dome (RSCM peak-T 320-460&amp;#176;C) delimited to the E by the ~1500 m wide Decani Shear Zone (DSZ) that exposes Paleozoic to Mesozoic strata of the East Bosnian Durmitor nappe (EBD). In the northeasternmost segment, the strike of the SPNF system changes from roughly orogen-perpendicular to orogen-parallel. There, the SPNF system has brittle branches- most notably the Dukagjini Fault (DF) that forms the northwestern limit of the Western Kosovo Basin (WKB).&lt;/p&gt;&lt;p&gt;The westernmost ductile-brittle SPNF segment strikes along the southern limb of the Cukali Dome with an increasing vertical offset from 0 m near Shkoder eastwards to &gt;1000 m at the eastern extent of the dome (near Fierza) where normal faulting cuts the nappe contact between the High Karst and Krasta-Cukali unit. The central segment north of the Tropoja Basin, with several smaller branches changing in strike, has a vertical throw of at least 1500 meters based on topographic constraints. Even further to the northeast, the SPNF system includes the moderately E-dipping DSZ juxtaposing the EBD in its footwall against m&amp;#232;lange of the West Vardar unit in its hanging wall, where offset is difficult to determine. 3 km eastwards, in the hanging wall to the DSZ, the brittle DF accommodates another 1000 m of vertical displacement as constrained by maximum depth of sediments of the WKB.&lt;/p&gt;&lt;p&gt;Ductile deformation along the Cukali and Decani Domes occurred sometime between the end of Dinaric thrusting and the formation of the WKB. Brittle faulting partly reactivates ductile segments, but also creates new branches (DF) within the hanging wall of the ductile DSZ. These were active during mid-Miocene to Pliocene times as constrained by syn-tectonic sediments in the WKB. We interpret the SPNF system as a two-phase composite extensional structure with normal faulting that migrated from its older trace along the ductile DSZ to the brittle DF as indicated by cross-cutting relations. The Decani Dome, with higher metamorphic temperature conditions than the Cukali Dome, may reflect the south-westernmost extent of late Paleogene extension in the Dinarides. It may be related to other core complexes and possibly to limited subduction rollback beneath the Dinarides (Matenco and Radivojevi, 2012). Extension from mid-Miocene time onwards was probably related to Hellenic CW rotation during Neogene orogenic arcuation, possibly triggered by enhanced rollback beneath the Hellenides (Handy et al., 2019).&lt;/p&gt;&lt;p&gt;Handy, M.R.,et al. 2019: Tectonics, v. 38, p. 2803&amp;#8211;2828, doi:10.1029/2019TC005524.&lt;/p&gt;&lt;p&gt;Matenco, L.,&amp; Radivojevi, D. 2012: Tectonics, v. 31, p. 1&amp;#8211;31, doi:10.1029/2012TC003206.&lt;/p&gt;

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