Constraints on the shallow velocity structure of the Lucky Strike Volcano, Mid-Atlantic Ridge, from downward continued multichannel streamer data

Arnulf, A. F.; Harding, A. J.; Kent, G. M.; Singh, Shubpreet; Crawford, Wayne

doi:10.1002/2013jb010500

Cited by 27 publications

(40 citation statements)

References 83 publications

(202 reference statements)

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“…Arnulf et al () and Arnulf, Harding, Kent, Singh, et al () showed that the combination of a SOBE method and 3‐D traveltime tomography enables proper imaging of the high‐velocity gradient region at the base of layer 2A. The layer 2A thickness map of Figure a represents a smoothed surface corresponding to a velocity gradient of ~3/s and was created from picks on crossing vertical profiles extracted from the tomographic structure (solid blue lines in Figures c and d).…”

Section: Tomography Resultsmentioning

confidence: 99%

“…We then performed 3‐D linearized tomographic inversions of the combined 473,853 crustal OBS and SOBE Pg‐phases following the methodology of Arnulf, Harding, Kent, Singh, et al (), specific to SOBE MCS data, which was adapted from the Van Avendonk et al () approach for OBS data. The forward model was calculated using a shortest path method (Moser, ) with additional corrections to reduce traveltime errors associated with the discretization of the seafloor bathymetry.…”

Section: Tomography Data and Methodsmentioning

confidence: 99%

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Structure, Seismicity, and Accretionary Processes at the Hot Spot‐Influenced Axial Seamount on the Juan de Fuca Ridge

et al. 2018

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Axial Seamount is the most volcanically active site of the northeast Pacific, and it has been monitored with a growing set of observations and sensors during the last two decades. Accurate imaging of the internal structure of volcanic systems is critical to better understand magma storage processes and to quantify mass and energy transport mechanisms in the crust. To improve the three‐dimensional velocity structure of Axial Seamount, we combined 469,891 new traveltime arrivals, from 12 downward extrapolated seismic profiles, with 3,962 existing ocean‐bottom‐seismometers traveltime arrivals, into a joint tomographic inversion. Our approach reveals two elongated magma reservoirs, with melt fraction up to 65%, representing an unusually large volume of melt (26–60 km3), which is likely the result of enhanced magma supply from the juxtaposition of the Cobb hot spot plume (0.26–0.53 m3/s) and the Axial spreading segment (0.79–1.06 m3/s). The tomographic model also resolves a subsided caldera floor that provides an effective trap for ponding lava flows, via a “trapdoor” mechanism. Our model also shows that Axial's extrusive section is thinnest beneath the elevated volcano, where anomalously thick (11 km) oceanic crust is present. We therefore suggest that focused and enhanced melt supply predominantly thickens the crust beneath Axial Seamount through diking accretion and gabbro crystallization. Lastly, we demonstrate that our three‐dimensional velocity model provides a more realistic starting point for relocating the local seismicity, better resolving a network of conjugate outward and inward dipping faults beneath the caldera walls.©2018. The Authors.

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Section: Tomography Resultsmentioning

confidence: 99%

Section: Tomography Data and Methodsmentioning

confidence: 99%

Structure, Seismicity, and Accretionary Processes at the Hot Spot‐Influenced Axial Seamount on the Juan de Fuca Ridge

et al. 2018

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“…Resolution at the top of oceanic crust within the velocity models that make up the compilation is often low due to the lack of first‐arrival energy for rays that turn within the uppermost region (e.g., Ewing & Purdy, ). Higher resolution in the upper crust can be achieved by using long streamer data from seismic reflection studies, especially if data is downward continued to near the seafloor (Arnulf et al, ; Arnulf et al, ; Arnulf et al, ; Henig et al, ; Kardell et al, ; Nedimović et al, ); however, these studies do not provide full crustal‐scale velocity models and are not included in our compilation. High‐resolution upper crustal studies typically show low velocities within layer 2A near the seafloor with a high‐gradient region at the layers 2A and 2B boundary.…”

Section: Discussionmentioning

confidence: 99%

Synthesis of Oceanic Crustal Structure From Two‐Dimensional Seismic Profiles

Christeson

Goff

Reece

2019

Reviews of Geophysics

165

209

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We present a new synthesis of oceanic crustal structure from two‐dimensional seismic profiles to explore differences related to spreading rate and age. Primary results are as follows: (1) Layer 2 has an average thickness of 1.84 km but is thicker for young slow‐spreading crust and thinner for young superfast‐spreading crust. At faster‐spreading rates the layer 2/3 boundary likely corresponds to the lithologic boundary between dikes and gabbros. At slow‐spreading centers, the layer 2/3 boundary is interpreted to mark a change in porosity with depth within the dikes. (2) Total crustal thickness averages 6.15 km and is similar across all spreading rates. (3) Velocities at the top of layer 2 increase rapidly from 3.0 km/s at 0 Ma to 4.6 km/s at 10.5 Ma, with a slower increase to 5.0 km/s at 170 Ma. The rapid increase in velocity at young ages is attributed to crack closure by precipitation of hydrothermal alteration products; the increase at older ages suggests that this process persists as the oceanic crust evolves. (4) There is a correlation between velocities at the top of layer 2 and sediment thickness, with velocities of 5.8–5.9 km/s associated with a sediment thickness of 4.0–4.3 km. The thick sediment may collapse large‐scale features such as lava tubes and fractures. (5) Average velocities at the top of layer 3 are lower for young slow‐spreading and intermediate‐spreading oceanic crust (6.1–6.2 km/s) than for older or faster‐spreading oceanic crust (6.5–6.7 km/s). These low velocities are likely associated with faults penetrating into the sheeted dikes.

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“…This limit corresponds to the northernmost corrugation ridge in the bathymetry, Figure b, and to the limit inferred from gravity modeling [ Blackman et al ., ]. The small hill at 3 km distance is the southern limit of the surficial volcanics as inferred from side scan sonar imaging [ Blackman et al ., ], and the velocity model shows the development of a thin, 0.1 km thick, surface layer with a basement velocity of 2.5 km/s (Figure b), a value typical of seismic layer 2A and volcanics in young crust [e.g., Arnulf et al ., ]. Below the surface layer, velocities and gradients are similar to those of the Southern Ridge, but ∼0.5–1 km/s faster than those measured in the adjacent hanging wall block and in the conjugate volcanic crust, east of the MAR axis [ Henig et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Velocity structure near IODP Hole U1309D, Atlantis Massif, from waveform inversion of streamer data and borehole measurements

Harding

Arnulf

Blackman

2016

Geochem Geophys Geosyst

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Seismic full waveform inversion (FWI) is a promising method for determining the detailed velocity structure of the igneous oceanic crust, especially for locations such as the Mid‐Atlantic Ridge with significant lateral heterogeneity and seafloor topography. We examine the accuracy of FWI by inverting, after downward continuation to datum just above the seafloor, a multichannel seismic (MCS) profile from Atlantis Massif oceanic core complex at 30°N that passes close to Integrated Ocean Drilling Program (IODP) Hole U1309D and comparing the results against borehole measurements and existing on‐bottom refraction data. The comparisons include the results of IODP Expedition 340T, which extended the sonic logging and vertical seismic profiling to the bottom of the borehole at 1400 m below seafloor. Compared to travel time tomography, the refinement in velocity and velocity gradient produced by FWI significantly improves the overall match to the borehole measurements, and allows the multilevel pattern of deformation and alteration of the detachment footwall seen in Hole U1309D to be extrapolated across the Central Dome. Prestack depth migration of the profile using the FWI velocities reveals the top and edges of the high‐velocity, gabbroic core of the massif. It also indicates that the comparatively uniform gabbroic rocks drilled at Hole U1309D extend to ∼2.5 km below seafloor but overlie an extended, ∼2 km thick, mantle transition zone.

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Constraints on the shallow velocity structure of the Lucky Strike Volcano, Mid-Atlantic Ridge, from downward continued multichannel streamer data

Cited by 27 publications

References 83 publications

Structure, Seismicity, and Accretionary Processes at the Hot Spot‐Influenced Axial Seamount on the Juan de Fuca Ridge

Structure, Seismicity, and Accretionary Processes at the Hot Spot‐Influenced Axial Seamount on the Juan de Fuca Ridge

Synthesis of Oceanic Crustal Structure From Two‐Dimensional Seismic Profiles

Velocity structure near IODP Hole U1309D, Atlantis Massif, from waveform inversion of streamer data and borehole measurements

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