The collision zone between the North d'Entrecasteaux Ridge and the New Hebrides Island Arc: 2. Structure from multichannel seismic data

1991 ◽  
Vol 96 (B3) ◽  
pp. 4479-4495 ◽  
Author(s):  
Michael A. Fisher ◽  
Jean-Yves Collot ◽  
Eric L. Geist
Keyword(s):  
Seismic Data ◽  
Island Arc ◽  
The North ◽  
Collision Zone ◽  
New Hebrides ◽  
Multichannel Seismic Data

Nonstretch moveout correction of long-offset multichannel seismic data for subbasalt imaging: Example from the North Atlantic

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. R83-R91 ◽  
Author(s):  
Hassan Masoomzadeh ◽  
Penny J. Barton ◽  
Satish C. Singh
Keyword(s):  
North Atlantic ◽  
Seismic Data ◽  
Cost Effective ◽  
Data Set ◽  
Velocity Function ◽  
The North ◽  
Long Offset ◽  
The North Atlantic ◽  
New Processing ◽  
Multichannel Seismic Data

We have developed a pragmatic new processing strategy to enhance seismic information obtained from long-offset multichannel seismic data. The conventional processing approach, which treats data on a sample-by-sample basis, is applied at a coarser scale on groups of samples. Using this approach, a reflected event and its vicinity remain unstretched during the normal moveout correction. Isomoveout curves (lines of equal moveout) in the time-velocity panel are employed to apply a constant moveout correction to selected individual events, leading to a nonstretch stack. A zigzag stacking-velocity function is introduced as a combination of segments of appropriate isomoveout curves. By employing a zigzag velocity function, stretching of key events is avoided and thus information at far offset is preserved in the stack. The method is also computationally cost-effective. However, the zigzag stacking-velocity field must be consistent with target horizons. This method of horizon-consistent nonstretch moveout has been applied to a wide-angle data set from the North Atlantic margin, providing improved images of the basement interface, which was previously poorly imaged.

A seismic refraction and reflexion study of the continent-ocean transition beneath the north Biscay margin

1982 ◽  
Vol 305 (1489) ◽  
pp. 5-25 ◽  
Keyword(s):  
Seismic Data ◽  
Seismic Refraction ◽  
Passive Margin ◽  
Ocean Crust ◽  
Northern Margin ◽  
The North ◽  
Seismic Refraction Data ◽  
Processing Techniques ◽  
Multichannel Seismic Data ◽  
Refraction Data

The structure of the northern margin of the Bay of Biscay consists of a series of tilted and rotated blocks bounded by prominent listric faults whose polarity is consistently down toward the continent-ocean boundary. These blocks formed by rifting in late Jurassic - early Cretaceous time and are now thinly covered by post-rift sediments of Aptian to Recent age. Seismic refraction profiles were occupied on the shelf, on either side of and across the continent-ocean transition to the shelf, using P ubs and O bs with explosives and a 4 x 1000 in 3 (4 x 16400 cm 3 ) airgun array. Two-ship expanding spread multichannel (48-trace) seismic reflexion profiles and 30 km fixed offset reflexion profiles were located along the seismic refraction profiles on either side of the transition. A two-ship 30 km fixed offset multichannel profile was located across the transition as well as a 5 km fixed offset multichannel profile extending from the ocean crust to the shelf. Conventional 48-trace single ship multichannel profiles were located along all the refraction and two-ship reflexion lines. Interpretation of the refraction profiles has been made by using ray tracing as well as synthetic seismograms. Conventional seismic processing techniques have been used to prepare the two-ship multichannel seismic data for interpretation. The survey is believed to be the first attempt to apply two-ship multichannel seismic data to the study of the change in crustal structure of a rifted passive margin from the shelf to the ocean crust. The results from the experiment led to the identification of a zone of transition between continental and oceanic crust about 8 km wide. The seismic refraction data show progressive thinning of the continental crust from 33 km to about 5 km close to the transition zone. However, extension values calculated in the upper crust from the rotation of fault blocks are much less (1.1—1.4) and suggest that the majority of the thinning is achieved by extensive attenuation of the lower crust.

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