scholarly journals Reprocessed multi-channel seismic-reflection data set from the Arctic Ocean, collected using icebreakers between 2007-2011 and 2014-2016 for the Canadian Extended Continental Shelf program

2021 ◽  
Author(s):  
J Shimeld ◽  
K Boggild ◽  
D C Mosher ◽  
H R Jackson
Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1395-1407 ◽  
Author(s):  
Frank Büker ◽  
Alan G. Green ◽  
Heinrich Horstmeyer

Shallow seismic reflection data were recorded along two long (>1.6 km) intersecting profiles in the glaciated Suhre Valley of northern Switzerland. Appropriate choice of source and receiver parameters resulted in a high‐fold (36–48) data set with common midpoints every 1.25 m. As for many shallow seismic reflection data sets, upper portions of the shot gathers were contaminated with high‐amplitude, source‐generated noise (e.g., direct, refracted, guided, surface, and airwaves). Spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source‐generated noise, and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections. Resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi‐continuous reflection zones. The uppermost reflection zone at 20 to 50 ms (∼15 to ∼40 m depth) originated from a boundary between glaciolacustrine clays/silts and underlying glacial sands/gravels (till) deposits. Of particular importance was the discovery that the deepest part of the valley floor appeared on the seismic section at traveltimes >180 ms (∼200 m), approximately twice as deep as expected. Constrained by information from boreholes adjacent to the profiles, the various seismic units were interpreted in terms of unconsolidated glacial, glaciofluvial, and glaciolacustrine sediments deposited during two principal phases of glaciation (Riss at >100 000 and Würm at ∼18 000 years before present).


Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. A25-A29
Author(s):  
Lele Zhang

Migration of seismic reflection data leads to artifacts due to the presence of internal multiple reflections. Recent developments have shown that these artifacts can be avoided using Marchenko redatuming or Marchenko multiple elimination. These are powerful concepts, but their implementation comes at a considerable computational cost. We have derived a scheme to image the subsurface of the medium with significantly reduced computational cost and artifacts. This scheme is based on the projected Marchenko equations. The measured reflection response is required as input, and a data set with primary reflections and nonphysical primary reflections is created. Original and retrieved data sets are migrated, and the migration images are multiplied with each other, after which the square root is taken to give the artifact-reduced image. We showed the underlying theory and introduced the effectiveness of this scheme with a 2D numerical example.


Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. B149-B160 ◽  
Author(s):  
Cedric Schmelzbach ◽  
Heinrich Horstmeyer ◽  
Christopher Juhlin

A limited 3D seismic-reflection data set was used to map fracture zones in crystalline rock for a nuclear waste disposal site study. Seismic-reflection data simultaneously recorded along two roughly perpendicular profiles (1850 and [Formula: see text] long) and with a [Formula: see text] receiver array centered at the intersection of the lines sampled a [Formula: see text] area in three dimensions. High levels of source-generated noise required a processing sequence involving surface-consistent deconvolution, which effectively increased the strength of reflected signals, and a linear [Formula: see text] filtering scheme to suppress any remaining direct [Formula: see text]-wave energy. A flexible-binning scheme significantly balanced and increased the CMP fold, but the offset and azimuth distributions remain irregular; a wide azimuth range and offsets [Formula: see text] are concentrated in the center of the survey area although long offsets [Formula: see text] are only found at the edges of the site. Three-dimensional dip moveout and 3D poststack migration were necessary to image events with conflicting dips up to about 40°. Despite the irregular acquisition geometry and the high level of source-generated noise, we obtained images rich in structural detail. Seven continuous to semicontinuous reflection events were traced through the final data volume to a maximum depth of around [Formula: see text]. Previous 2D seismic-reflection studies and borehole data indicate that fracture zones are the most likely cause of the reflections.


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