Results of the CD-ROM project seismic refraction/wide-angle reflection experiment: The upper and middle crust

2005 ◽  
pp. 257-269 ◽  
Author(s):  
Hanna-Maria Rumpel ◽  
Claus Prodehl ◽  
Catherine M. Snelson ◽  
G. Randy Keller
Keyword(s):  
Seismic Refraction ◽  
Wide Angle ◽  
Cd Rom ◽  
Middle Crust

Lithospheric structure in northwestern Canada from Lithoprobe seismic refraction and related studies: a synthesis

2005 ◽  
Vol 42 (6) ◽  
pp. 1277-1293 ◽  
Author(s):  
Ron M Clowes ◽  
Philip TC Hammer ◽  
Gabriela Fernández-Viejo ◽  
J Kim Welford
Keyword(s):  
Seismic Data ◽  
Seismic Refraction ◽  
Velocity Model ◽  
Wide Angle ◽  
Slave Craton ◽  
Reflection Data ◽  
Western Cordillera ◽  
Thermal Constraints ◽  
Geological Information ◽  
Tectonic Boundaries

The SNORCLE refraction – wide-angle reflection (R/WAR) experiment, SNORE'97, included four individual lines along the three transect corridors. A combination of SNORE'97 results with those from earlier studies permits generation of a 2000 km long lithospheric velocity model that extends from the Archean Slave craton to the present Pacific basin. Using this model and coincident near-vertical incidence (NVI) reflection data and geological information, an interpreted cross section that exemplifies 4 Ga of lithospheric development is generated. The velocity structural models correlate well with the reflection sections and provide additional structural, compositional, and thermal constraints. Geological structures and some faults are defined in the upper crust. At a larger scale, the seismic data identify a variety of orogenic styles ranging from thin- to thick-skinned accretion in the Cordillera and crustal-scale tectonic wedging associated with both Paleoproterozoic and Mesozoic collisions. Models of Poisson's ratio support the NVI interpretation that a thick wedge of cratonic metasediments underlies the eastern accreted Cordilleran terranes. Despite the variety of ages, orogenic styles, and tectono-magmatic deformations that are spanned by the seismic corridors, the Moho remains remarkably flat and shallow (33–36 km) across the majority of the transect. Significant variations only occur at major tectonic boundaries. Laterally variable crustal velocities are consistently slower beneath the Cordillera than beneath the cratonic crust. This is consistent with the high temperatures (800–900 °C) required by the slow upper mantle velocities (7.8–7.9 km/s) observed beneath much of the Cordillera. Heterogeneity of the lithospheric mantle is indicated by wide-angle reflections below the Precambrian domains and the western Cordillera.

scholarly journals Extensional structure in Northern Honshu Arc as inferred from seismic refraction/wide-angle reflection profiling

2001 ◽  
Vol 28 (12) ◽  
pp. 2329-2332 ◽  
Author(s):  
Takaya Iwasaki ◽  
Wataru Kato ◽  
Takeo Moriya ◽  
Akiko Hasemi ◽  
Norihito Umino ◽  
...  
Keyword(s):  
Seismic Refraction ◽  
Wide Angle ◽  
Extensional Structure

scholarly journals Initial results from wide-angle seismic refraction lines in the southern Cape

2007 ◽  
Vol 110 (2-3) ◽  
pp. 407-418 ◽  
Author(s):  
J. Stankiewicz ◽  
T. Ryberg ◽  
A. Schulze ◽  
A. Lindeque ◽  
M.H. Weber ◽  
...  
Keyword(s):  
Seismic Refraction ◽  
Wide Angle ◽  
Initial Results

Wide-angle seismic imaging of pristine Archean crust in the Nain Province, Labrador

1998 ◽  
Vol 35 (6) ◽  
pp. 672-685 ◽  
Author(s):  
Thomas Funck ◽  
Keith E Louden
Keyword(s):  
Lower Crust ◽  
Velocity Structure ◽  
Basal Layer ◽  
Magnetic Data ◽  
Wide Angle ◽  
Quartz Content ◽  
Middle Crust ◽  
Archean Crust ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

A detailed refraction - wide-angle reflection seismic experiment was carried out in northern Labrador to determine the velocity structure of relatively unaltered Archean crust in the Nain Province. Six 3-component land seismometers were used to record an airgun source along a profile parallel to the coast. Forward modeling of traveltimes and amplitudes yields a P- and S-wave velocity model that shows two crustal blocks separated by a fault. Magnetic data suggest, but do not prove, that the fault is the offshore continuation of the Handy fault. A southwards thickening of the lower crust across the fault indicates that a transcurrent component might have been associated with the faulting. The total crustal thickness is 33 km to the north and 38 km to the south of the fault. The presence of PmS reflections imply a sharp transition at the Moho. Upper crustal velocities of 5.8-6.3 km/s and Poisson's ratios of 0.20 and 0.24, north and south of the fault respectively, are consistent with a gneissic composition, but suggest a higher quartz content in the northern block. Velocities in the middle crust increase to 6.5 km/s, where a discontinuity at a depth between 16 and 18 km marks the transition to the lower crust with velocities between 6.6 and 6.9 km/s. Poisson's ratios of 0.24 and 0.26 indicate, respectively, a felsic middle crust and an intermediate composition for the lower crust. The absence of a high-velocity basal layer is in accordance with other examples of Archean crust.

Interpretation of three-dimensional seismic refraction data from western Hecate Strait, British Columbia: structure of the crust

1993 ◽  
Vol 30 (7) ◽  
pp. 1440-1452 ◽  
Author(s):  
J. A. Hole ◽  
R. M. Clowes ◽  
R. M. Ellis
Keyword(s):  
Velocity Structure ◽  
Seismic Refraction ◽  
Three Dimensional ◽  
Surface Expression ◽  
Wide Angle ◽  
Lateral Velocity ◽  
Near Surface ◽  
Velocity Anomaly ◽  
Air Gun ◽  
Refraction Data

As part of a multidisciplinary investigation of the structure and tectonics of the Queen Charlotte Basin and underlying crust, deep multichannel seismic reflection and coincident crustal refraction data were collected in 1988. Energy from the reflection air-gun array source was recorded at land sites at offsets appropriate to record crustal refraction and wide-angle reflection data. Refraction data recorded in a broadside geometry provide good three-dimensional coverage of western Hecate Strait. These data are modelled using tomographic inversion techniques to determine the three-dimensional velocity structure of the crust in this region. The one-dimensional average velocity increases rapidly with depth to 6.5 km/s at 7 km depth. Velocities from 7 to at least 12 km depth remain approximately constant and are associated with rocks of the Wrangellia terrane. Significant lateral velocity variations, including large differences in near-surface velocities attributable to surface features, relatively low velocities representing interbedded Tertiary sediments and volcanics, and a deep high-velocity anomaly that may represent the root of an igneous intrusion, are mapped. Wide-angle reflections from the Moho are used to determine the thickness of the crust. The Moho is at 29 km depth beneath the east coast of the Queen Charlotte Islands. This is deeper than the Moho observed below Queen Charlotte Sound and as deep as, or deeper than, that below Hecate Strait. Crustal thinning during Tertiary extension was thus greatest beneath the surface expression of the Queen Charlotte Basin, leaving the crust under the islands considerably thicker than under the basin. In an alternate or additional explanation, compression at the continental margin during the last 4 Ma may have been taken up by thickening or underplating of the continental crust beneath the islands. If the Pacific plate is subducting beneath the islands, the Moho observations constrain the slab to dip greater than 20–26°.

Crustal structure across the Three Gorges area of the Yangtze platform, central China, from seismic refraction/wide-angle reflection data

2009 ◽  
Vol 475 (3-4) ◽  
pp. 423-437 ◽  
Author(s):  
Zhongjie Zhang ◽  
Zhiming Bai ◽  
Walter Mooney ◽  
Chunyong Wang ◽  
Xuebo Chen ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Seismic Refraction ◽  
Central China ◽  
Wide Angle ◽  
Three Gorges ◽  
Yangtze Platform ◽  
Three Gorges Area ◽  
Reflection Data ◽  
The Three Gorges
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