A 2-D, ray-based, depth migration method for deep seismic reflections

Raynaud, B.

doi:10.1111/j.1365-246x.1988.tb01395.x

Cited by 26 publications

(10 citation statements)

References 16 publications

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“…Geometrical optics can thus be used to predict the arrival-times, but not the amplitudes, of observed reflections. This justifies the use of a depth migration method based on ray-tracing (Raynaud 1988).…”

Section: Discussionmentioning

confidence: 99%

Diffraction modelling of 3-D lower-crustal reflectors

Raynaud¹

1988

Geophysical Journal International

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The length of the acoustic path and the limited band-width of the lower crustal reflections in near-normal-incidence profiles give a Fresnel Zone radius of the order of 2-3 km for the lower crust. In this situation, interpretations of the lower crust cannot be based solely on geometrical optics, which is a high-frequency approximation, but must take into account the effects of diffraction. A mathematical model based on the Kirchhoff Integral estimates diffraction effects in the acoustic field and allows the reflections observed from a laterally varying, first-order discontinuity to be calculated for arbitrary source and receiver locations.A simplified form of the Kirchhoff Integral provides a clear physical model for the form of the reflected field including diffraction effects. This model is used to study synthetic sections and several useful interpretational rules for deep reflection data are inferred. The simplified formula indicates the limitations of interpretations based on geometrical optics. It shows that although geometrical optics cannot explain the amplitudes of the reflected image, it does correctly predict the arrival-times of the major observed reflections. This justifies a depth migration method based on ray-tracing.

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Section: Discussionmentioning

confidence: 99%

Diffraction modelling of 3-D lower-crustal reflectors

Raynaud¹

1988

Geophysical Journal International

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“…13) and depth migrated the section using sediment velocities from the wide‐angle model (Bullock 2004) to produce an accurate model of depth to top basement to constrain the magnetic model. Full model depth migrations have been attempted by Raynaud (1988) and Louden & Chian (1999), but prior to this study velocities have not been well constrained west of the continental slope.…”

Section: Additional Datamentioning

confidence: 99%

From continental extension to seafloor spreading: crustal structure of the Goban Spur rifted margin, southwest of the UK

Bullock

Minshull

2005

Geophysical Journal International

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S U M M A R YWe present a 169-km wide-angle velocity model across the Goban Spur rifted margin, southwest of the UK. A 120-km-wide intermediate region is identified between the first clear seafloor spreading magnetic anomaly (anomaly 34r) and thinned continental crust, where velocities increase from 4.5 km s −1 to 6.8 km s −1 in the top 4 km beneath acoustic basement. At depth it can be divided into a region where a 1.5-km-thick high-velocity layer (7.2-7.6 km s −1 ) exists and a region where this layer is absent but velocities of ∼7 km s −1 are present. Wide-angle PmP arrivals are observed across the whole of the intermediate region but a normal incidence reflection Moho is not present.Based on these velocities and combined with seismic reflection, gravity and magnetic modelling along this transect we interpret the intermediate region to consist of a 70 km wide zone of exhumed mantle with high Poisson's ratio at top basement (>0.34), an extremely low topographic expression and a high-velocity deep layer. Empirical relationships between velocity and degree of serpentinization suggest that serpentinite content decreases with depth from 100 per cent at top basement to <25 per cent from 5-7 km into basement. The observed magnetic anomaly is best fit by a thin magnetized layer (1 km) of magnetization 2-3 A m −1 . The intense magnetization may be due to magnetite formation during a prolonged interaction of serpentinite with sea water. Between this exhumed mantle and anomaly 34r is a 50-km-wide region raised 400 m above the adjacent exhumed mantle, consisting of a series of basement ridges. Poisson's ratio is not well defined in this region, which may be composed of anomalous oceanic crust or exhumed mantle.

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“…The data were migrated in line drawing form using ray theory (Raynaud, 1988;Holliger and Kissling, 1991;Fig. 8) in order to avoid typical problems associated with the migration of deep crustal data such as low signal/noise ratios, complicated velocity structures, and apparent discontinuities in deep reflectors due to near-surface effects (Warner, 1987).…”

Section: Line Drawing and Migrationmentioning

confidence: 99%

Seismic profiling constraints on the evolution of the central Brooks Range, Arctic Alaska

Wissinger

Levander

Oldow

et al. 1998

Architecture of the Central Brooks Range Fold and Thrust Belt, Arctic Alaska

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A seismic reflection profile from the 1990 Brooks Range seismic experiment indicates a strongly reflective upper and lower crust (0 to 50 km) throughout the northern and central parts of the range in units comprising the Brooks Range orogen. The northern range is characterized by two zones of subhorizontal reflections at 2 to 3 s and 4 to 6 s, which mark the base of the Endicott Mountains allochthon and the basal decollement of the contractional belt, respectively. The central range is characterized by a series of stacked, ~80-km-long, moderately south-dipping reflections interpreted as imbricates of the Doonerak duplex. The duplex is overlain by complex reflectivity patterns in the region of the Skajit allochthon. South of the Doonerak duplex in the metamorphic rocks of the Schist belt, the upper crust appears nonreflective. In the southern range, gently to moderately north-dipping reflectors are imaged beneath the Yukon-Koyukuk basin at 5 to 6 s and are interpreted to mark an older decollement level separating lower Paleozoic rocks of the Schist belt from Pre-Cambrian units. The boundaries of the Yukon-Koyukuk basin and the subsurface extent of the Kobuk dextral fault are not imaged.The seismic reflection data support the existence of crustal-scale duplexing, breach thrusting, and large-scale north-directed thrusting of allochthonous crustal assemblages. Crustal thickness in the Brooks Range ranges from ~35 km in the hinterland to 50 km beneath the range front where an asymmetric crustal root is imaged. We have used the seismic reflection data and surface geologic constraints to identify the boundaries of major structural assemblages in the Brooks Range and restore three interpretations of the range to their pre-Jurassic configurations. Minimum shortening estimates along the seismic line range from 500 to 600 km of Mesozoic-Recent shortening with end-member estimates of Cenozoic shortening in the Doonerak duplex approximating 85 and 380 km.

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A 2-D, ray-based, depth migration method for deep seismic reflections

Cited by 26 publications

References 16 publications

Diffraction modelling of 3-D lower-crustal reflectors

Diffraction modelling of 3-D lower-crustal reflectors

From continental extension to seafloor spreading: crustal structure of the Goban Spur rifted margin, southwest of the UK

Seismic profiling constraints on the evolution of the central Brooks Range, Arctic Alaska

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