Dual-vergence structure from multiple migration of widely spaced OBSs

Yelisetti, Subbarao; Spence, G. D.; Scherwath, Martin; Riedel, Michael; Klaeschen, Dirk

doi:10.1016/j.tecto.2017.04.005

Cited by 7 publications

(2 citation statements)

References 21 publications

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“…Between 45° and 48°N, the outer prism is characterized by a dominantly landward‐vergent fold and thrust belt (e.g., Booth‐Rea et al., 2008; Fisher et al., 2005; Flueh et al., 1998). North of 48°N (off Vancouver Island) (e.g., Hyndman and Wang, 1995) and between ∼44 and 45°N (e.g., MacKay, 1995), seismic reflection data suggest a dominantly seaward‐vergent frontal thrust, although a recent study revealed dual‐vergence structure off central Vancouver Island (Yelisetti et al., 2017). South of 42°, mixed vergence has been noted (Gulick et al., 1998).…”

Section: Geologic Backgroundmentioning

confidence: 99%

The Hidden History of the South‐Central Cascadia Subduction Zone Recorded on the Juan de Fuca Plate Offshore Southwest Oregon

Tréhu

Tominaga

Lyle

et al. 2022

Geochem Geophys Geosyst

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New seismic reflection data collected and processed as part of early career scientist training at sea and in classroom projects fill gaps in seismic coverage of the Cascadia subduction zone and provide new insights into anomalous subduction behavior and mass wasting along the south‐central Cascadia Subduction Zone (CSZ) between 42°20’N and 44°15’N. The data reveal at least six distinct buried horizons of folded and faulted sediments similar to strata recently interpreted to result from in situ deformation induced by the load imposed by a large blocky mass transport deposit known as the 44°N slide. Although our results support prior studies indicating that the south‐central CSZ has experienced large slope instabilities, they indicate that the slides were more frequent but volumetrically smaller than previously thought. Similar strata have not been observed elsewhere beneath the abyssal plain adjacent to the Cascadia subduction zone. The structure of the deformation front along this segment is also indistinct, in contrast to the clear frontal faults outboard of folded trench strata observed immediately to the north and south (and generally throughout the rest of Cascadia). We attribute the anomalous nature of this segment of the margin to past subduction of shallow and rough seafloor, which resulted in greater uplift of the forearc than elsewhere along the margin. A consequence of this postulated history would be the shedding of older, more consolidated blocks onto the Juan de Fuca plate, resulting in the observed distinctive stratigraphy offshore southern Oregon.

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Section: Geologic Backgroundmentioning

confidence: 99%

The Hidden History of the South‐Central Cascadia Subduction Zone Recorded on the Juan de Fuca Plate Offshore Southwest Oregon

Tréhu

Tominaga

Lyle

et al. 2022

Geochem Geophys Geosyst

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“…Interpretation of seismic reflection profiles, traveltime inversion velocity models and biostratigraphic well data suggest that character of the basement has largely controlled deformation of the overlying Tofino basin sediments [5,[11][12][13][14][15]. On migrated seismic sections, some thrust faults appear to penetrate close to the top of the subducting oceanic crust [6,16]. The amount of displacement along the faults and style of deformation varies along the margin, which indicates localized variations of pore fluid pressure.…”

Section: Introductionmentioning

confidence: 99%

Seismic Velocity Structure Beneath the Tofino Forearc Basin Using Full Waveform Inversion

Yelisetti

Spence

2021

Energies

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Given the effects of steep dips and large lateral variations in seismic velocity beneath the Vancouver Island continental shelf, seismic processing and travel time inversion are inadequate to obtain a detailed velocity model of the subsurface. Therefore, seismic full waveform inversion is applied to multichannel seismic reflection data to obtain a high-resolution velocity model beneath the Tofino fore-arc basin under the continental shelf off Vancouver Island margin. Seismic velocities obtained in this study help in understanding the shallow shelf sediment structures, as well as the deeper structures associated with accreted terranes, such as Pacific Rim and Crescent terranes. Shallow high velocities, as large as ∼5 km/s, were modeled in the mid-shelf region at ∼1.5–2.0 km depth. These coincide with an anticlinal structure in the seismic data, and possibly indicate the shallowest occurrence of the volcanic Crescent terrane. In general, seismic velocities increase landward, indicating sediment over-consolidation related to the compressional regime associated with the ongoing subduction of the Juan de Fuca plate and the emplacement of Pacific Rim and Crescent accreted terranes. Seismic velocities show a sharp increase about 10 km west of Vancouver Island, possibly indicating an underlying transition to the Pacific Rim terrane. A prominent low velocity zone extending over 10 km is observed in the velocity model at 800–900 m below the seafloor. This possibly indicates the presence of a high porosity layer associated with lithology changes. Alternatively, this may indicate fluid over-pressure or over-pressured gas in this potential hydrocarbon environment.

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Tsunami earthquakes: Vertical pop-up expulsion at the forefront of subduction megathrust

Hananto

Leclerc

et al. 2020

Earth and Planetary Science Letters

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Dual-vergence structure from multiple migration of widely spaced OBSs

Cited by 7 publications

References 21 publications

The Hidden History of the South‐Central Cascadia Subduction Zone Recorded on the Juan de Fuca Plate Offshore Southwest Oregon

The Hidden History of the South‐Central Cascadia Subduction Zone Recorded on the Juan de Fuca Plate Offshore Southwest Oregon

Seismic Velocity Structure Beneath the Tofino Forearc Basin Using Full Waveform Inversion

Tsunami earthquakes: Vertical pop-up expulsion at the forefront of subduction megathrust

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