Tectonic evolution of strike-slip zones on continental margins and their impact on the development of submarine landslides (Storegga Slide, northeast Atlantic)

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2397-2414 ◽  
Author(s):  
Jing Song ◽  
T.M. Alves ◽  
K.O. Omosanya ◽  
T.C. Hales ◽  
Tao Ze
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Slope Instability ◽  
Continental Margins ◽  
Submarine Landslides ◽  
The South ◽  
Borehole Data ◽  
Northeast Atlantic

Abstract Submarine landslides have affected the mid-Norwegian margin since the Last Glacial Maximum. However, the role of tectonic movements, and most especially fault reactivation, in generating landslides offshore Norway is largely unconstrained. This study uses high-quality three-dimensional seismic and borehole data to understand how landslide development is controlled by faults propagating within the uplifted south Modgunn arch. Variance and structural maps above the south Modgunn arch show that: (1) local scarps of recurrent landslides were formed close to the largest faults, and mainly above strike-slip faults; (2) distinct periods of fault generation were associated with tectonic events, such as the breakup of the northeast Atlantic Ocean, and those events forming the south Modgunn arch; and (3) important fluid-flow features coincide with faults and sill intrusions. In total, 177 faults were analyzed to demonstrate that fault throw values vary from 10 ms to 115 ms two-way traveltime (8 m to 92 m). We propose that the long-term activity of faults in the study area has contributed to fluid migration, weakened post-breakup strata, and controlled the development of submarine slope instability. In particular, strike-slip faults coincide with the locations of several Quaternary landslide scars near the modern seafloor. Similar processes to those documented in Norway may explain the onset of large-scale landslides on other continental margins.

scholarly journals Clustering of Quasars from the ROE/ESO Large-Scale AQD Survey for Quasars

1987 ◽  
Vol 124 ◽  
pp. 809-814
Author(s):  
Roger G. Clowes ◽  
Angela Iovino ◽  
Peter Shaver
Keyword(s):  
Clustering Analysis ◽  
High Probability ◽  
Large Scale ◽  
Three Dimensional ◽  
The South ◽  
First Results ◽  
Poster Paper ◽  
Connected Area

The new ROE/ESO large-scale AQD survey for quasars forms a connected area of ∼ 200 deg2 near the south galactic pole, and has resulted in the discovery of a total number of quasar candidates that is comparable to the number previously published from all other sources (see the poster paper by Iovino, Clowes & Shaver at this conference). In this paper we describe the first results of a three-dimensional self-clustering analysis of ∼ 1100 “high-probability” candidates occupying the assigned-redshift band of 1.8 to 2.4. Although the analysis is sensitive to very weak clustering we find no evidence that quasars are distributed in any way other than randomly. The implications of this result are discussed.

Neotectonics and large-scale geomorphology of Canada

1993 ◽  
Vol 17 (2) ◽  
pp. 248-264 ◽  
Author(s):  
John Adams ◽  
John J. Clague
Keyword(s):  
Large Scale ◽  
Late Quaternary ◽  
Strike Slip ◽  
Laurentide Ice Sheet ◽  
Continental Margins ◽  
Plate Boundaries ◽  
The West ◽  
Late Mesozoic ◽  
Tectonic Events ◽  
Mountain Systems

Canada includes active convergent and strike-slip plate boundaries, several major mountain systems, two passive continental margins, and a stable craton. Neotectonic activity, as indicated by earthquake occurrence, is highest along the west coast and lowest in the interior of the country. Correlations between tectonics and physiography are strongest in the west. Here, the landscape bears a strong imprint of convergent and strike-slip plate regimes. Late Mesozoic and early Cenozoic tectonic events established the setting in which the present physiography of western Canada developed, but the landscape acquired its present form much more recently, in Pliocene and Quaternary time. In contrast, the neotectonic imprint in eastern and northern Canada is enigmatic, and although major concentrations of earthquakes in many areas are associated with reactivated, early Phanerozoic structures, there has been only limited late Quaternary faulting. The vast Canadian craton, despite its very low seismicity, is deforming isostatically at a moderate rate due to melting of the Laurentide Ice Sheet thousands of years ago.

Strain partitioning around an indenter during oroclinal bending: kinematics of the Circum-Moesian fault system of the Carpatho-Balkanides

2021 ◽  
Author(s):  
Nemanja Krstekanic ◽  
Liviu Matenco ◽  
Uros Stojadinovic ◽  
Ernst Willingshofer ◽  
Marinko Toljić ◽  
...  
Keyword(s):  
Large Scale ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faults ◽  
Strain Partitioning ◽  
The South ◽  
The Carpathians ◽  
The North ◽  
Moesian Platform ◽  
Parallel Extension

<p>The Carpatho-Balkanides of south-eastern Europe is a double 180° curved orogenic system. It is comprised of a foreland-convex orocline, situated in the north and east and a backarc-convex orocline situated in the south and west. The southern orocline of the Carpatho-Balkanides orogen formed during the Cretaceous closure of the Alpine Tethys Ocean and collision of the Dacia mega-unit with the Moesian Platform. Following the main orogen-building processes, the Carpathians subduction and Miocene slab retreat in the West and East Carpathians have driven the formation of the backarc-convex oroclinal bending in the south and west. The orocline formed during clockwise rotation of the Dacia mega-unit and coeval docking against the Moesian indenter. This oroclinal bending was associated with a Paleocene-Eocene orogen-parallel extension that exhumed the Danubian nappes of the South Carpathians and with a large late Oligocene – middle Miocene Circum-Moesian fault system that affected the orogenic system surrounding the Moesian Platform along its southern, western and northern margins. This fault system is composed of various segments that have different and contrasting types of kinematics, which often formed coevally, indicating a large degree of strain partitioning during oroclinal bending. It includes the curved Cerna and Timok faults that cumulate up to 100 km of dextral offset, the lower offset Sokobanja-Zvonce and Rtanj-Pirot dextral strike-slip faults, associated with orogen parallel extension that controls numerous intra-montane basins and thrusting of the western Balkans units over the Moesian Platform. We have performed a field structural study in order to understand the mechanisms of deformation transfer and strain partitioning around the Moesian indenter during oroclinal bending by focusing on kinematics and geometry of large-scale faults within the Circum-Moesian fault system.</p><p>Our structural analysis shows that the major strike-slip faults are composed of multi-strand geometries associated with significant strain partitioning within tens to hundreds of metres wide deformation zones. Kinematics of the Circum-Moesian fault system changes from transtensional in the north, where the formation of numerous basins is controlled by the Cerna or Timok faults, to strike-slip and transpression in the south, where transcurrent offsets are gradually transferred to thrusting in the Balkanides. The characteristic feature of the whole system is splaying of major faults to facilitate movements around the Moesian indenter. Splaying towards the east connects the Circum-Moesian fault system with deformation observed in the Getic Depression in front of the South Carpathians, while in the south-west the Sokobanja-Zvonce and Rtanj-Pirot faults splay off the Timok Fault. These two faults are connected by coeval E-W oriented normal faults that control several intra-montane basins and accommodate orogen-parallel extension. We infer that all these deformations are driven by the roll-back of the Carpathians slab that exerts a northward pull on the upper Dacia plate in the Serbian Carpathians. However, the variability in deformation styles is controlled by geometry of the Moesian indenter and the distance to Moesia, as the rotation and northward displacements increase gradually to the north and west.</p>

scholarly journals Early extensional detachments in a contractional orogen: coherent, map-scale, submarine slides (mass transport complexes) on the outer slope of an Ediacaran collisional foredeep, eastern Kaoko belt, Namibia

2016 ◽  
Vol 53 (11) ◽  
pp. 1177-1189 ◽  
Author(s):  
Paul F. Hoffman ◽  
Eric J. Bellefroid ◽  
Benjamin W. Johnson ◽  
Malcolm S.W. Hodgskiss ◽  
Daniel P. Schrag ◽  
...  
Keyword(s):  
Large Scale ◽  
Sedimentary Facies ◽  
Passive Margin ◽  
Continental Margins ◽  
Submarine Landslides ◽  
Base Level ◽  
Basin Scale ◽  
Kaoko Belt ◽  
Map Scale ◽  
Orogenic Belts

The existence of coherent, large-scale, submarine landslides on modern continental margins implies that their apparent rarity in ancient orogenic belts is due to non-recognition. Two map-scale, coherent, pre-orogenic, normal-sense detachment structures of Ediacaran age are present in the Kaoko belt, a well-exposed arc–continent collision zone in northwestern Namibia. The structures occur within the Otavi Group, a Neoproterozoic carbonate shelf succession. They are brittle structures, evident only through stratigraphic omissions of 400 m or more, that ramp down to the west with overall ramp angles of 1.1° and 1.3° with respect to stratigraphic horizons. The separations of matching footwall and hangingwall stratigraphic cut-offs require horizontal translations >20 km for each detachment. One of the detachments is remarkably narrow (5 km) in the up-dip direction, just one fourth of its translation. The other detachment is stratigraphically dated at the shelf–foredeep transition, when the passive margin was abortively subducted westward, in the direction of submarine sliding. Trenchward sliding on the foreslope occurred concurrently with deep karstification of the autochthonous carbonate succession to the east, presumably due to forebulge uplift and (or) conjectural basin-scale base-level fall. We expect that similar detachments exist in other orogenic belts, and failure to recognize them can lead to misinterpretations of stratigraphy, sedimentary facies, and paleogeography.

scholarly journals Bayesian Inference of Centroid Moment Tensors of the 2019 Ambon (Mw 6.5) Aftershock Earthquake Sequence, Indonesia: A Preliminary Result

2021 ◽  
Vol 873 (1) ◽  
pp. 012022
Author(s):  
A W Baskara ◽  
D P Sahara ◽  
A D Nugraha ◽  
A Muhari ◽  
A A Rusdin ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Model Parameters ◽  
The South ◽  
Centroid Moment Tensor ◽  
Waveform Data ◽  
Moment Tensors ◽  
The Impact ◽  
Dextral Strike Slip

Abstract The Ambon Mw 6.5 earthquake on September 26th, 2019, had contributed to give severe damages and significantly increased seismicity around Ambon Island and surrounding areas. Mainshock was followed by aftershocks with spatial distribution added to the impact of destructions in this region. We investigated aftershocks sequences to reveal the effect of mainshock toward the change in the in-situ stress field, including the possibility of the existing faults reactivation and the generation of aftershocks. We inferred centroid moment tensor (CMT) for significant aftershock events with Mw more than 4.0 using waveform data recorded from October 18th to December 15th, 2019. The aftershock focal mechanism was determined using the Bayesian full-waveform inversion code ISOLA-Obspy. This approach provides the uncertainty of the CMT model parameters. From ten CMT solution we had inferred in three seismic clusters, we found that majority of events have a strike-slip mechanism. Four events located on the south of the N-S trendings have a dextral strike-slip fault type, reflected the rupture of the mainshocks fault plane. Three events in the cluster of Ambon Island are dextral strike-slip, confirming the presence of the fault reactivation. Meanwhile, three CMT solutions in the north show the dextral strike-slip faulting and may belong to the mainshock main fault, connected with the cluster in the south.

scholarly journals Faults in the Asquempont area, southern Brabant Massif, Belgium

2004 ◽  
Vol 83 (2) ◽  
pp. 49-65
Author(s):  
T.N. Debacker ◽  
A. Herbosch ◽  
J. Verniers ◽  
M. Sintubin
Keyword(s):  
Large Scale ◽  
Strike Slip ◽  
Normal Faults ◽  
Reverse Fault ◽  
Borehole Data ◽  
Middle Cambrian ◽  
The Core ◽  
Geological Map ◽  
Surrounding Areas ◽  
Strike Slip Movement

AbstractThe literature suggests that the Asquempont fault, a supposedly important reverse fault forming the limit between the Lower to lower Middle Cambrian and the Ordovician in the Sennette valley, is poorly understood. Nevertheless, this fault is commonly equated with a pronounced NW-SE-trending aeromagnetic lineament, the Asquempont lineament, and both the geometry of the Asquempont lineament and the supposed reverse movement of the Asquempont fault are used to develop large-scale tectonic models of the Brabant Massif. New outcrop observations in the Asquempont area, the “type locality” of the Asquempont fault, in combination with outcrop and borehole data from surrounding areas, show that the Asquempont fault is not an important reverse fault, but instead represents a pre-cleavage, low-angle extensional detachment. This detachment formed between the Caradoc and the timing of folding and cleavage development and is not related to the aeromagnetic Asquempont lineament. The Asquempont area also contains several relatively important, steep, post-cleavage normal faults. Apparently, these occur in a WNW-ESE-trending zone between Asquempont and Fauquez, extending westward over Quenast towards Bierghes. This zone coincides with the eastern part of the WNW-ESE-trending Nieuwpoort-Asquempont fault zone, for which, on the basis of indirect observations, previously a strike-slip movement has been proposed. Our outcrop observations question this presumed strike-slip movement. The Asquempont fault may be related to the progressive unroofing of the core of the Brabant Massif from the Silurian onwards. Possibly, other low-angle extensional detachments similar to the Asquempont fault occur in other parts of the massif. Possible candidates are the paraconformity-like contacts depicted on the most recent geological map of the Brabant Massif.

scholarly journals Anatomy of strike-slip fault tsunami genesis

2021 ◽  
Vol 118 (19) ◽  
pp. e2025632118
Author(s):  
Ahmed Elbanna ◽  
Mohamed Abdelmeguid ◽  
Xiao Ma ◽  
Faisal Amlani ◽  
Harsha S. Bhat ◽  
...  
Keyword(s):  
Ground Motions ◽  
Three Dimensional ◽  
Coastal Areas ◽  
Strike Slip ◽  
Submarine Landslides ◽  
Tsunami Generation ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Earthquake Rupture Dynamics ◽  
Tsunami Model

Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated.

Three-dimensional geometry and growth of salt-detached strike-slip faults, Outer Kwanza Basin, offshore Angola

2021 ◽  
Author(s):  
Aurio Erdi ◽  
Christopher Jackson
Keyword(s):  
Three Dimensional ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Normal Faults ◽  
Plate Boundaries ◽  
Reverse Fault ◽  
Growth Strata ◽  
Flat Base ◽  
Isopach Maps ◽  
Base Salt

<p>Strike slip faults are a prominent tectonic feature in Earth to accommodate horizontal and/or oblique slip that trend parallel to fault strike. These faults are commonly formed on plate boundaries setting, where they are basement-involved and driven by elastic crustal loading at seismogenic depths. Still, we also observe the strike slip faults on salt-bearing slopes, where the faults are typically thin-skinned and accommodate spatial variability in the rate of seaward flow of salt and its overburden. In both cases, relatively little is still known of their three-dimensional geometry and growth in comparison to both normal and reverse fault, that have been extensively studied.</p><p>We use a high-quality, depth-migrated 3D seismic dataset to investigate salt-detached strike-slip faults in the mid-slope translational domain of the Outer Kwanza Basin, offshore Angola. We show that NE-SW-striking faults are presently located above elongate, margin-parallel, NE-trending ramps, more amorphous, dome-like structural highs, and areas of relatively subdued relief. The faults are broadly planar, display normal and/or reverse offsets, and may locally bound negative flower structures. These faults offset a range of salt and overburden structures, including salt walls and anticlines, and salt -detached thrusts and normal faults, defining six major structural compartments. Our displacement-distance (Tx) analysis of several faults reveal they are characterized by complex throw distributions that define 3-to-10, now hard-linked segments. In vertical profiles, these segments are characterized by symmetric-to-asymmetric throw distributions (Tz) that record throw maxima at the top of the Albian, Eocene and/or Early Miocene. Expansion indices (EI) and isopach maps demonstrate the presence of fault-related growth strata, with complex thickness patterns also reflecting the combined effect of vertical (i.e. diapirism) and horizontal (i.e. translation) salt tectonics.  Taken together, our observations suggest the salt detached strike-slip faults evolved during three key phases: (i) Albian – nucleation and local linkage of individual segments; (ii) Eocene-to-Oligocene – reactivation, propagation, and death of many now-linked segments; and (iii) Miocene – local fault reactivation due to salt diapirism.  </p><p>We show that salt detached strike-slip faults in the translational domain of the Outer Kwanza Basin grew above either rugose or relatively flat base-salt surface. More specifically, salt detached strike-slip faults, like normal and reverse faults documented elsewhere, grew in response to the propagation and eventual linkage of initially isolated segments. We also highlight that the coeval growth of salt walls can play a role in controlling the three-dimensional geometry and kinematics of salt detached strike-slip faults.</p>

scholarly journals Faults in the Asquempont area, southern Brabant Massif, Belgium

2004 ◽  
Vol 83 (1) ◽  
pp. 49-66 ◽  
Author(s):  
T.N. Debacker ◽  
A. Herbosch ◽  
J. Verbiers ◽  
M. Sintubin
Keyword(s):  
Large Scale ◽  
Strike Slip ◽  
Normal Faults ◽  
Reverse Fault ◽  
Borehole Data ◽  
Middle Cambrian ◽  
The Core ◽  
Geological Map ◽  
Surrounding Areas ◽  
Strike Slip Movement

AbstractThe literature suggests that the Asquempont fault, a supposedly important reverse fault forming the limit between the Lower to lower Middle Cambrian and the Ordovician in the Sennette valley, is poorly understood. Nevertheless, this fault is commonly equated with a pronounced NW-SE-trending aeromagnetic lineament, the Asquempont lineament, and both the geometry of the Asquempont lineament and the supposed reverse movement of the Asquempont fault are used to develop large-scale tectonic models of the Brabant Massif. New outcrop observations in the Asquempont area, the “type locality” of the Asquempont fault, in combination with outcrop and borehole data from surrounding areas, show that the Asquempont fault is not an important reverse fault, but instead represents a pre-cleavage, low-angle extensional detachment. This detachment formed between the Caradoc and the timing of folding and cleavage development and is not related to the aeromagnetic Asquempont lineament. The Asquempont area also contains several relatively important, steep, post-cleavage normal faults. Apparently, these occur in a WNW-ESE-trending zone between Asquempont and Fauquez, extending westward over Quenast towards Bierghes. This zone coincides with the eastern part of the WNW-ESE-trending Nieuwpoort-Asquempont fault zone, for which, on the basis of indirect observations, previously a strike-slip movement has been proposed. Our outcrop observations question this presumed strike-slip movement. The Asquempont fault may be related to the progressive unroofing of the core of the Brabant Massif from the Silurian onwards. Possibly, other low-angle extensional detachments similar to the Asquempont fault occur in other parts of the massif. Possible candidates are the paraconformity-like contacts depicted on the most recent geological map of the Brabant Massif.

Characterisation of seismogenic zones and gas hydrates accumulation regions in the South Caribbean margin using 3D lithospheric-scale thermal and rheological models

2020 ◽  
Author(s):  
Ángela María Gómez-García ◽  
Álvaro González ◽  
Magdalena Scheck-Wenderoth ◽  
Denis Anikiev ◽  
Gaspar Monsalve ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Continental Margins ◽  
South American ◽  
Submarine Landslides ◽  
The South ◽  
Rheological Models ◽  
South American Plate ◽  
Northern Margin ◽  
The Caribbean

<p>Active continental margins are potentially exposed to geohazards of different nature, including earthquakes and gas hydrate destabilisation, which may result in submarine landslides and devastating tsunamis. The northern margin of the South American plate is characterised by two flat-slab subductions: the Nazca plate from the west, and the Caribbean plate from the north. This defines a complex and poorly understood tectonic setting which poses a risk for the inhabitants of the region.</p><p>Gaining insight into the physical conditions (such as rock strength and temperature) at which earthquakes nucleate in this region requires building an improved lithospheric model, and determining the thermal and rheological states of the tectonic plates involved in this subduction system.</p><p>Combining 3D lithospheric-scale thermal and rheological modelling is a novel approach to establish the spatial variation of seismogenic zones, both at shallow and intermediate depths, thus providing crucial information about the range of conditions at which earthquakes may occur. This method is especially useful in regions like the South Caribbean where more classical approaches are limited because seismic records do not extend far back in time and the frequency of megathrust earthquakes is low.</p><p>Furthermore, in river-dominated continental margins, such as the South Caribbean, the destabilisation of gas hydrates deposits has been recently recognised as one of the most important triggering factors of submarine landslides. Gas hydrates are stable in low-temperature and high-pressure environments, normally found in marine sediments within continental slopes, with dominant temperatures ranging from 5°C to 10°C, at depths greater than 400 m. However, the gas hydrate stability zone is mainly controlled by the local geothermal gradient and the bottom water temperature, being both parameters influenced by the particular setting of each region.</p><p>Our research aims to evaluate the physical state of the seismogenic zones in the northern margin of the South American plate and Panama microplate, and to identify the locations of potential gas hydrates accumulation in the South Caribbean margin.</p><p>Here we present the complete workflow of this analysis, starting from the definition of an up-to-date 3D lithospheric-scale model which has been validated with the forward modelling of gravity anomalies. This model is the main input for calculating the 3D steady-state thermal field and the 3D pressure field, using the software LYNX. Based on our modelled results, we evaluate the rheological behaviour of the present-day lithospheric configuration, considering the locations of the earthquakes from the Bulletin of the International Seismological Centre. Finally, by modelling the temperature and pressure within the marine sediments, we constrain the spatial distribution of the potential gas hydrate stability zone.</p><p>With this work we exemplify how 3D lithospheric-scale thermal and rheological models may contribute to the assessment of geohazards in a region such as the Caribbean Sea, where hundreds of thousands of coastal inhabitants, tourists and infrastructures are potentially at risk.</p>

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