Synthesis of Oceanic Crustal Structure From Two‐Dimensional Seismic Profiles

Christeson, G. L.; Goff, John A.; Reece, R.

doi:10.1029/2019rg000641

Cited by 153 publications

(230 citation statements)

References 160 publications

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“…The crust under the EAB is ~20 km thick, which is much thicker than standard oceanic crust (Christeson et al, 2019; Grevemeyer et al, 2018; White et al, 1992) but thinner than standard continental crust (Christensen & Mooney, 1995). This crust is characterized by a strong variability in P wave velocity in the upper‐middle crust (Figures 4a and 5) and a high‐velocity lower crust ( Vp 7 ± 0.1 km/s) bounded by two wide‐angle reflections: an intracrustal reflection at its top ( PiP , Figures 2b–2d, 3, and 4a) and the Moho reflection at its bottom ( PmP , Figures 2c, 3, and 4a).…”

Section: Discussionmentioning

confidence: 99%

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

et al. 2020

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In continental settings, seismic failure is generally restricted to crustal depth. Crustal structure is therefore an important proxy to evaluate seismic hazard of continental fault systems. Here we present a seismic velocity model across the Gibraltar Arc System, from the Eurasian Betics Range (South Iberian margin), across offshore East Alboran and Pytheas (African margin) basins, and ending onshore in North Morocco. Our results reveal the nature and configuration of the crust supporting the coexistence of three different crustal domains: the continental crust of the Betics, the continental crust of the Pytheas Basin (south Alboran Basin) and onshore Morocco, and a distinct domain formed of magmatic arc crust under the East Alboran Basin. The magmatic arc under the East Alboran Basin is characterized by a velocity structure containing a relatively high-velocity lower crust (~7 km/s) bounded at the top and base by reflections. The lateral extension of this crust is mapped integrating a second perpendicular wide-angle seismic profile along the Eastern Alboran basin, together with basement samples, multibeam bathymetry, and a grid of deep-penetrating multichannel seismic profiles. The transition between crustal domains is currently unrelated to extensional and magmatic processes that formed the basin. The abrupt transition zones between the different crustal domains support that they are bounded by crustal-scale active fault systems that reactivate inherited structures. Seismicity in the area is constrained to upper-middle crust depths, and most earthquakes nucleate outside of the magmatic arc domain.

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Section: Discussionmentioning

confidence: 99%

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

et al. 2020

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“…A number of studies have documented the heterogeneity of very young crust, which can exhibit very strong lateral V p gradients on the scale of several kilometers (Arnulf et al, , ; Henig et al, ). While strong local horizontal gradients have been observed away from spreading centers (e.g., Stephen, ), Pacific crust older than 20 Ma is generally assumed to be largely uniform (Christeson et al, ; White et al, ). Around the Hawaiian islands, the oceanic crust increases from a typical thickness of approximately 6 km off the Swell to nearly 20 km beneath the island of Hawaii (e.g., Leahy et al, ; Watts et al, ; Watts & ten Brink, ; Zucca et al, ).…”

Section: Introductionmentioning

confidence: 99%

Seismic Structure of Marine Sediments and Upper Oceanic Crust Surrounding Hawaii

Doran

Laske

2019

JGR Solid Earth

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We present models of compressional and shear velocity structure of the oceanic sediments and upper crust surrounding the Hawaiian islands. The models were derived from analysis of seafloor compliance data and measurements of Ps converted phases originating at the sediment‐bedrock interface. These data were estimated from continuous broadband ocean bottom seismometer acceleration and pressure records collected during the Plume‐Lithosphere Undersea Mantle Experiment, an amphibious array of wideband and broadband instruments with an aperture of over 1,000 km. Our images result from a joint inversion of compliance and Ps delay data using a nonlinear inversion scheme whereby deviation from a priori constraints is minimized. In our final model, sediment thickness increases from 50 m at distal sites to over 1.5 km immediately adjacent to the islands. The sedimentary shear velocity profiles exhibit large regional variations. While sedimentary structure accounts for the majority of the compliance signal, we infer variations in shear velocity in the uppermost bedrock on the order of ±5%. We also require relatively high values of Poisson's ratio in the uppermost crust. Lower crustal velocities are generally seen to the north and west of the islands but do not appear well correlated with the Hawaiian Swell bathymetry. A region of strong low velocity anomalies to the northeast of Hawaii may be associated with the Molokai fracture zone.

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“…White et al, 1992;Grevemeyer et al, 2018;Christeson et al, 2019). The absolute seismic velocities are highly variable, however, for a gabbroic crust, velocities are typically between 6.7 km/s and 7.2 km/s (Grevemeyer et al, 2018;Christeson et al, 2019). The histogram in Figure 5e shows a gap for this range of velocities suggesting that no typical oceanic crust and no thick layer of gabbroic rocks are present along the profile.…”

Section: Nature Of the Lithospherementioning

confidence: 95%

“…Oceanic crust 220 typically consists of a high-velocity gradient in Layer 2 and a lower velocity gradient in Layer 3 (e.g. White et al, 1992;Grevemeyer et al, 2018;Christeson et al, 2019). The absolute seismic velocities are highly variable, however, for a gabbroic crust, velocities are typically between 6.7 km/s and 7.2 km/s (Grevemeyer et al, 2018;Christeson et al, 2019).…”

Section: Nature Of the Lithospherementioning

confidence: 99%

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Oligocene-Miocene extension led to mantle exhumation in the central Ligurian Basin, Western Alpine Domain

Dannowski

Kopp

Grevemeyer

et al. 2019

Preprint

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The Ligurian Basin is located in the Mediterranean Sea to the north-west of Corsica at the transition from the western Alpine orogen to the Apennine system and was generated by the south-eastward trench retreat of the Apennines-Calabrian subduction zone. Late Oligocene to Miocene rifting caused continental extension and subsidence, leading to the opening of 10 the basin. Yet, it still remains enigmatic if rifting caused continental break-up and seafloor spreading. To reveal its lithospheric architecture, we acquired a state of the art seismic refraction and wide-angle reflection profile in the Ligurian Basin. The seismic line was recorded in the framework of SPP2017 4D-MB, the German component of the European AlpArray initiative, and trends in a NE-SW direction at the centre of the Ligurian Basin, roughly parallel to the French coastline. The seismic data recorded on the newly developed GEOLOG recorder, designed at GEOMAR, are dominated by sedimentary 15 refractions and show mantle Pn arrivals at offsets of up to 70 km and a very prominent wide-angle Moho reflection. The main features share several characteristics (i.e. offset range, continuity) generally associated with continental settings rather than documenting oceanic crust emplaced by seafloor spreading. Seismic tomography results are augmented by gravity data and yield a 7.5-8 km thick sedimentary cover which is directly underlain by serpentinised mantle material at the south-western end of the profile. The acoustic basement at the north-eastern termination is interpreted to be continental crust, thickening towards 20 the NE.Our study reveals that the oceanic domain does not extend as far north as previously assumed and that extension led to extreme continental thinning and exhumation of sub-continental mantle which eventually became serpentinised.

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Synthesis of Oceanic Crustal Structure From Two‐Dimensional Seismic Profiles

Cited by 153 publications

References 160 publications

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

Seismic Structure of Marine Sediments and Upper Oceanic Crust Surrounding Hawaii

Oligocene-Miocene extension led to mantle exhumation in the central Ligurian Basin, Western Alpine Domain

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