Slope failure and mass transport processes along the Queen Charlotte Fault Zone, western British Columbia

2018 ◽  
Vol 477 (1) ◽  
pp. 85-106 ◽  
Author(s):  
H. Gary Greene ◽  
J. Vaughn Barrie ◽  
Daniel S. Brothers ◽  
James E. Conrad ◽  
Kim Conway ◽  
...  
Keyword(s):  
Continental Slope ◽  
Fault Zone ◽  
Slope Failure ◽  
Transport Processes ◽  
North American Plate ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
The North ◽  
Transform Margin ◽  
Seismic Reflection Profiles

AbstractMultibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offshore of the Haida Gwaii is heavily gullied, few large-sized submarine landslides in this area are observed in the MBES images. However, smaller submarine seafloor slides exist locally in areas where fluid flow appears to be occurring and large seafloor slides have recently been detected at the base of the steep continental slope just above its contact with the abyssal plain on the Queen Charlotte Terrace. In addition, along the subtle slope re-entrant area offshore of the Dixon Entrance shelf bathymetric data suggest that extensive mass wasting has occurred in the vicinity of an active mud volcano venting gas. We surmise that the relative lack of submarine slides along the upper slope in close proximity to the Queen Charlotte Fault Zone may be the result of seismic strengthening (compaction and cohesion) of a sediment-starved shelf and slope through multiple seismic events.

Magma-rich transform margins: example from the Limpopo transform fault zone between Mozambique and Antarctica

2020 ◽  
Author(s):  
Sylvie Leroy ◽  
Vincent Roche ◽  
François Guillocheau ◽  
Pierre Dietrich ◽  
Sidonie Revillon ◽  
...  
Keyword(s):  
Fault Zone ◽  
Magnetic Data ◽  
Transform Fault ◽  
Passive Margins ◽  
The North ◽  
Oceanic Spreading ◽  
Transform Margin ◽  
Seismic Reflection Profiles ◽  
Uplift And Erosion ◽  
Transform Fault Zone

<p>Transform continental margins known across the Earth represent 31% of passive margins. Resulting from first-order plate tectonic processes, transform margins record a diachronous evolution mainly defined by three successive stages, including intra-continental transform faulting, active and passive transform margin. Due to their high complexity and a lack of large hydrocarbon discoveries (i.e. not a target for oil industry), they have only been sparsely studied, especially when compared with other margin types (i.e. divergent or convergent).</p><p>                  We present the structure and evolution of the NS-trending Limpopo Transform Fault Zone (LTFZ), corresponding to the main fracture zone from western part of the Africa-Antarctica Corridor (AAC). Here, we combine published and unpublished dataset (seismic reflection profiles, wells, multibeam bathymetry, gravity, magnetic data) in order to propose an interpretation of the LTFZ structure and adjoining segments and their evolution through time, from rifting to spreading.</p><p>The LTFZ is composed of two main segments: the East Limpopo segment and the Astrid conjugate one and the North and South Natal segment including the Dana-Galathea Plateau (Mozambique side) and the Maud rise/east of Grunehogna craton (Antarctica margin). The LTFZ offsets the segments of divergent conjugate margins (Southern Natal-off Grunehogna craton in the west and Beira High Angoche-Riiser Larsen Sea in the east) since 155 Ma (chron M25). We focus on the evolution of the transform fault zone from its initiation at chron M25 up to chron M0 (~126 Ma, Barremian). Oceanic spreading onset at chron M25 in the south of Beira High segment and Dana-Galathea Plateau triggered the uplift and erosion of the proximal parts of the margin and the formation of several seaward dipping reflectors wedges. Plate kinematic implies an NNW-SSE opening of the LTFZ. The oblique component of opening promotes the setting up of several volcanic wedges. These wedges rejuvenate southward trough time, which is consistent with the sliding of Antarctica with respect to Africa and thus confirm the diachronous evolution of the transform fault zone.</p>

scholarly journals Deep submarine landslide contribution to the 2010 Haiti earthquake tsunami

2020 ◽  
Vol 20 (7) ◽  
pp. 2055-2065
Author(s):  
Adrien Poupardin ◽  
Eric Calais ◽  
Philippe Heinrich ◽  
Hélène Hébert ◽  
Mathieu Rodriguez ◽  
...  
Keyword(s):  
Slope Failure ◽  
Tide Gauge ◽  
Strike Slip ◽  
Submarine Landslide ◽  
Secondary Source ◽  
Submarine Landslides ◽  
Haiti Earthquake ◽  
Southern Coast ◽  
Ground Acceleration ◽  
The North

Abstract. The devastating Mw 7.1 Haiti earthquake in 2010 was accompanied by local tsunamis that caused fatalities and damage to coastal infrastructure. Some were triggered by slope failures of river deltas in the close vicinity of the epicenter, while others, 30 to 50 km to the north across the Bay of Gonâve, are well explained by the reverse component of coseismic ground motion that accompanied this mostly strike-slip event. However, observations of run-up heights up to 2 m along the southern coast of the island at distances up to 100 km from the epicenter, as well as tide gauge and DART buoy records at distances up to 600 km from the epicenter, have not yet received an explanation. Here we demonstrate that these observations require a secondary source, most likely a submarine landslide. We identify a landslide scar 30 km from the epicenter off the southern coast of Haiti at a depth of 3500 m, where ground acceleration would have been sufficient to trigger slope failure in soft sediments. This candidate source, 2 km3 in volume, matches observations remarkably well assuming that the sediment collapse obeys a viscous flow with an initial apparent viscosity of 2×105 Pa s. Although that particular source cannot be proven to have been activated in 2010, our results add to a line of evidence that earthquake-triggered submarine landslides can cause significant tsunamis in areas of strike-slip tectonic regime.

Tertiary extension and tilting in the Queen Charlotte Islands, evidence from dyke swarms and their paleomagnetism

1992 ◽  
Vol 29 (9) ◽  
pp. 1878-1898 ◽  
Author(s):  
E. Irving ◽  
J. G. Souther ◽  
J. Baker
Keyword(s):  
North American ◽  
Late Eocene ◽  
North American Plate ◽  
Western Margin ◽  
Queen Charlotte Islands ◽  
The North ◽  
Early Oligocene ◽  
Magnetic Stability ◽  
Transform Margin ◽  
Dyke Swarms

The Queen Charlotte Islands form the western margin of the Tertiary Queen Charlotte Basin, which is situated on the western margin of the North American Plate. They contain seven major dyke swarms of Late Eocene to Miocene age, a period when the relative motions of the Pacific and the North American plates in this region were dominantly dextral strike slip (transform margin), with intervals of highly oblique divergence and convergence. Within each swarm, dykes have a systematic trend. However, trends vary from swarm to swarm, indicating that the stress field varied. A total of 678 cores (1352 specimens) were collected from 129 dykes in six swarms over a distance of about 200 km. Magnetic stability is variable. One hundred and one dykes yielded records of the paleofield. Data are also reported from an Oligocene pluton (5 sites, 27 cores, 52 specimens) and Miocene lavas (8 sites, 52 cores, 101 specimens). Both normal and reversed magnetizations occur, but irrespective of sign, the mean directions of remanent magnetization of each swarm and of the pluton and the lavas have systematically steeper inclinations than the value calculated from coeval rocks in North America. To explain this it is proposed that, after dyke emplacement, the sampling areas were tilted to the north or northwest by amounts that vary between 9 and 16°. Apparently, crustal tilting, similar in magnitude and direction, extended over distances of approximately 200 km. This cannot reflect tilting of a single block. Instead, it is argued that at least the southern Queen Charlotte Islands underwent considerable northerly or north-northwesterly directed extension and normal block faulting, which followed and in part was concurrent with the formation of widespread mid-Tertiary dyke swarms, plutons and lava flows. Making use of the fact that dykes propagate perpendicular to the direction of extension, and combining previously measured dyke orientations with paleomagnetic data, three stages of extension are proposed: east–west extension sometime during the Late Eocene to Early Oligocene; north–south extension sometime in the interval Late Oligocene to Early Miocene; and northwest–southeast extension sometime during Late Miocene or later time.

The nature of small to medium earthquakes along the Eastern Mediterranean passive continental margins, and their possible relationships to landslides and submarine salt-tectonic-related shallow faults

2018 ◽  
Vol 477 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Oded Katz ◽  
Yariv Hamiel
Keyword(s):  
Continental Slope ◽  
Slope Failure ◽  
Eastern Mediterranean ◽  
Hazard Analysis ◽  
Focal Depth ◽  
Seismic Source ◽  
Continental Margins ◽  
Submarine Landslides ◽  
Seismic Origin ◽  
First Time

AbstractWe analysed here, for the first time, 278 small to medium earthquakes that have occurred since 1985 along a 200 km section of the Levant passive continental margins, offshore Israel. The earthquakes are spatially overlapping with numerous submarine landslides and thin-skinned salt-tectonic-related faults scarps, bisecting the continental slope. Thus, we focus on the genetic relationship between the earthquakes, the faults and the landslides.We found that a subgroup of 55 earthquakes is spatially overlapping with the marine extension of the Carmel Fault and thus might be of tectonic origin. A second subgroup, hosting approximately 130 earthquakes, is spatially overlapping with the longshore salt-tectonic-related submarine faults. However, due to the non-shallow focal depth of most of these earthquakes, salt tectonics was ruled out as their possible seismic origin. Thus, the seismic source for theanalysed earthquakes is yet to be revealed.We further found that the observed medium earthquakes (M > 4) have a calculated reoccurrence time of more than 10 years and they are capable of inducing submarine slope failure within the studied area. Hence, they might play a role in submarine mass-wasting processes along the studied continental slope, and must now be considered in future hazard analysis.

scholarly journals Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre

2019 ◽  
Vol 219 (1) ◽  
pp. 159-184 ◽  
Author(s):  
C Peirce ◽  
A H Robinson ◽  
A M Campbell ◽  
M J Funnell ◽  
I Grevemeyer ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Fault Zone ◽  
Lower Crust ◽  
P Wave ◽  
Fault System ◽  
Transform Fault ◽  
Apparent Lack ◽  
The North ◽  
Transform Margin

SUMMARY The Swan Islands Transform Fault (SITF) marks the southern boundary of the Cayman Trough and the ocean–continent transition of the North American–Caribbean Plate boundary offshore Honduras. The CAYSEIS experiment acquired a 180-km-long seismic refraction and gravity profile across this transform margin, ∼70 km to the west of the Mid-Cayman Spreading Centre (MCSC). This profile shows the crustal structure across a transform fault system that juxtaposes Mesozoic-age continental crust to the south against the ∼10-Myr-old ultraslow spread oceanic crust to the north. Ocean-bottom seismographs were deployed along-profile, and inverse and forward traveltime modelling, supported by gravity analysis, reveals ∼23-km-thick continental crust that has been thinned over a distance of ∼70 km to ∼10 km-thick at the SITF, juxtaposed against ∼4-km-thick oceanic crust. This thinning is primarily accommodated within the lower crust. Since Moho reflections are not widely observed, the 7.0 km s−1 velocity contour is used to define the Moho along-profile. The apparent lack of reflections to the north of the SITF suggests that the Moho is more likely a transition zone between crust and mantle. Where the profile traverses bathymetric highs in the off-axis oceanic crust, higher P-wave velocity is observed at shallow crustal depths. S-wave arrival modelling also reveals elevated velocities at shallow depths, except for crust adjacent to the SITF that would have occupied the inside corner high of the ridge-transform intersection when on axis. We use a Vp/Vs ratio of 1.9 to mark where lithologies of the lower crust and uppermost mantle may be exhumed, and also to locate the upper-to-lower crustal transition, identify relict oceanic core complexes and regions of magmatically formed crust. An elevated Vp/Vs ratio suggests not only that serpentinized peridotite may be exposed at the seafloor in places, but also that seawater has been able to flow deep into the crust and upper mantle over 20–30-km-wide regions which may explain the lack of a distinct Moho. The SITF has higher velocities at shallower depths than observed in the oceanic crust to the north and, at the seabed, it is a relatively wide feature. However, the velocity–depth model subseabed suggests a fault zone no wider than ∼5–10 km, that is mirrored by a narrow seabed depression ∼7500 m deep. Gravity modelling shows that the SITF is also underlain, at >2 km subseabed, by a ∼20-km-wide region of density >3000 kg m−3 that may reflect a broad region of metamorphism. The residual mantle Bouguer anomaly across the survey region, when compared with the bathymetry, suggests that the transform may also have a component of left-lateral trans-tensional displacement that accounts for its apparently broad seabed appearance, and that the focus of magma supply may currently be displaced to the north of the MCSC segment centre. Our results suggest that Swan Islands margin development caused thinning of the adjacent continental crust, and that the adjacent oceanic crust formed in a cool ridge setting, either as a result of reduced mantle upwelling and/or due to fracture enhanced fluid flow.

Submarine landslides on the north continental slope of the South China Sea

2018 ◽  
Vol 17 (1) ◽  
pp. 83-100 ◽  
Author(s):  
Weiwei Wang ◽  
Dawei Wang ◽  
Shiguo Wu ◽  
David Völker ◽  
Hongliu Zeng ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Slope ◽  
South China ◽  
The South China Sea ◽  
Submarine Landslides ◽  
The South ◽  
China Sea ◽  
The North

scholarly journals Deep Submarine Landslide Contribution to the 2010 Haiti Earthquake Tsunami

2020 ◽  
Author(s):  
Adrien Poupardin ◽  
Eric Calais ◽  
Philippe Heinrich ◽  
Hélène Hébert ◽  
Mathieu Rodriguez ◽  
...  
Keyword(s):  
Slope Failure ◽  
Tide Gauge ◽  
Strike Slip ◽  
Submarine Landslide ◽  
Secondary Source ◽  
Submarine Landslides ◽  
Haiti Earthquake ◽  
Southern Coast ◽  
Ground Acceleration ◽  
The North

Abstract. The devastating Mw 7, 2010, Haiti earthquake was accompanied by local tsunamis that caused fatalities and damage to coastal infrastructure. Some were triggered by slope failures of river deltas in close vicinity of the epicenter, while others, 30 to 50 km to the north across the Bay of Gonâve, are well explained by the reverse component of coseismic ground motion that accompanied this mostly strike-slip event. However, observations of run-up heights up to 2 m along the southern coast of the island at distances up to 100 km from the epicenter, as well as tide gauge and DART buoy records at distances up to 600 km from the epicenter have not yet received an explanation. Here we demonstrate that these observations require a secondary source, most likely a submarine landslide. We identify a landslide scar 30 km from the epicenter off the southern coast of Haiti at a depth of 3500 m, where ground acceleration would have been sufficient to trigger slope failure in soft sediments. This candidate source, 2 km3 in volume, matches observation remarkably well assuming that the sediment collapse obeys a viscous flow with an initial apparent viscosity of 2 × 105 Pa s. Although that particular source cannot be proven to have been activated in 2010, our results add to a line of evidence that earthquake-triggered submarine landslides can cause significant tsunamis in areas of strike-slip tectonic regime.

Submarine canyons, slope failures and mass transport processes in southern Cascadia

2020 ◽  
Vol 500 (1) ◽  
pp. 453-475 ◽  
Author(s):  
Jenna C. Hill ◽  
Janet T. Watt ◽  
Daniel S. Brothers ◽  
Jared W. Kluesner
Keyword(s):  
Deep Water ◽  
Slope Failure ◽  
Water Channel ◽  
Transport Processes ◽  
Cascadia Subduction Zone ◽  
Submarine Landslides ◽  
Slope Failures ◽  
Submarine Canyons ◽  
Ground Shaking ◽  
Lower Slope

AbstractMarine turbidite records have been used to infer palaeoseismicity and estimate recurrence intervals for large (>Mw7) earthquakes along the Cascadia Subduction Zone. Conventional models propose that upper slope failures are funneled into submarine canyons and develop into turbidity flows that are routed down-canyon to deep-water channel and fan systems. However, the sources and pathways of these turbidity flows are poorly constrained, leading to uncertainties in the connections between ground shaking, slope failure and deep-water turbidites. We examine the spatial distribution of submarine landslides along the southern Cascadia margin to identify source regions for slope failures that may have developed into turbidity flows. Using multibeam bathymetry, sparker multichannel seismic and chirp sub-bottom data, we observe relatively few canyon head slope failures and limited evidence of large landslides on the upper and middle slope. Most of the submarine canyons are draped with sediment infill in the upper reaches and do not appear to be active sediment conduits during the recent sea-level highstand. In contrast, there is evidence of extensive mass wasting of the lower slope and non-channelized downslope flows. Contrary to previous studies, we propose that failures along the lower slope are the primary sources for deep-sea seismoturbidites in southern Cascadia.

Tectonic and geomorphic controls on the distribution of submarine landslides across active and passive margins, eastern New Zealand

2019 ◽  
Vol 500 (1) ◽  
pp. 477-494 ◽  
Author(s):  
S. J. Watson ◽  
J. J. Mountjoy ◽  
G. J. Crutchley
Keyword(s):  
New Zealand ◽  
Slope Failure ◽  
Submarine Landslide ◽  
Passive Margin ◽  
Continental Margins ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Active Margin ◽  
Passive Margins ◽  
Marine Habitats

AbstractSubmarine landslides occur on continental margins globally and can have devastating consequences for marine habitats, offshore infrastructure and coastal communities due to potential tsunamigenesis. Therefore, understanding landslide magnitude and distribution is central to marine and coastal hazard planning.We present the first submarine landslide database for the eastern margin of New Zealand comprising >2200 landslides occurring in water depths from c. 300–4000 m. Landslides are more prevalent and, on average, larger on the active margin compared with the passive margin. We attribute higher concentrations of landslides on the active margin to tectonic processes including uplift and oversteepening, faulting and seamount subduction. Submarine landslide scars are concentrated around canyon systems and close to canyon thalwegs. This suggests that not only does mass wasting play a major role in canyon evolution, but also that canyon-forming processes may provide preconditioning factors for slope failure.Results of this study offer unique insights into the spatial distribution, magnitude and morphology of submarine landslides across different geological settings, providing a better understanding of the causative factors for mass wasting in New Zealand and around the world.

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