Harmonic distortion on a seismic reflection profile across the Quebec Appalachians: relation to Bouguer gravity and implications for crustal structure

1984 ◽  
Vol 21 (3) ◽  
pp. 346-353 ◽  
Author(s):  
Frederick A. Cook
Keyword(s):  
Seismic Reflection ◽  
Far East ◽  
Harmonic Distortion ◽  
High Amplitude ◽  
Seismic Reflection Profile ◽  
Bouguer Gravity ◽  
Seismic Reflection Data ◽  
Arrival Times ◽  
Amplitude Noise ◽  
Reflection Data

Seismic reflection data obtained across the Quebec Appalachians using the VIBROSEIS (trademark Conoco) technique were recorded with parameters that allowed harmonic distortion arrivals to interfere with layered reflections. The data exhibit reflections from layered miogeoclinal rocks dipping eastward beneath the allochthonous rocks of the orogen; the layering appears to terminate beneath the Notre Dame Anticlinorium. However, as the apparent termination of the layers also occurs at the arrival times of high-amplitude noise harmonics, it may have no geological significance. Precambrian Grenville crust, which probably underlies the layered sediments, extends at least as far east as the apparent termination, and may extend much farther. Examination of the Bouguer gravity field in relation to the seismic reflection data shows that a major gravity change is due to density differences that occur considerably west of the eastern limit of Precambrian Grenville crust. The gravity thus shows no correlation with surface structures proposed as suture zones. An actualistic model incorporates subduction of a passive (Atlantic-type) margin beneath an arc terrain during the Ordovician.

Shallow seismic reflection study of a glaciated valley

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1395-1407 ◽  
Author(s):  
Frank Büker ◽  
Alan G. Green ◽  
Heinrich Horstmeyer
Keyword(s):  
Seismic Reflection ◽  
High Amplitude ◽  
Data Sets ◽  
Seismic Section ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Northern Switzerland ◽  
Reflection Data ◽  
Shallow Seismic ◽  
Glaciated Valley

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).

Labeling long‐period multiple reflections

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 122-126 ◽  
Author(s):  
R. J. J. Hardy ◽  
M. R. Warner ◽  
R. W. Hobbs
Keyword(s):  
Seismic Reflection ◽  
High Amplitude ◽  
Data Sets ◽  
Multiple Reflections ◽  
Multiple Series ◽  
Seismic Reflection Data ◽  
Long Period ◽  
Reflection Data ◽  
Zero Offset ◽  
Marine Seismic

The many techniques that have been developed to remove multiple reflections from seismic data all leave remnant energy which can cause ambiguity in interpretation. The removal methods are mostly based on periodicity (e.g., Sinton et al., 1978) or the moveout difference between primary and multiple events (e.g., Schneider et al., 1965). They work on synthetic and selected field data sets but are rather unsatisfactory when applied to high‐amplitude, long‐period multiples in marine seismic reflection data acquired in moderately deep (700 m to 3 km) water. Differential moveout is often better than periodicity at discriminating between types of events because, while a multiple series may look periodic to the eye, it is only exactly so on zero‐offset reflections from horizontal layers. The technique of seismic event labeling described below works by returning offset information from CDP gathers to a stacked section by color coding, thereby discriminating between seismic reflection events by differential normal moveout. Events appear as a superposition of colors; the direction of color fringes indicates whether an event has been overcorrected or undercorrected for its hyperbolic normal moveout.

scholarly journals Intraplate depth-dependent lithospheric stretching imaged by seismic reflection data

2021 ◽  
Author(s):  
Shuwen Dong ◽  
Jianhua Li ◽  
Rui Gao ◽  
Peter Cawood ◽  
Hans Thybo ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Pure Shear ◽  
Mantle Flow ◽  
Seismic Reflection Profile ◽  
Zone Formation ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Lithospheric Extension ◽  
Lower Crustal Flow ◽  
Lower Crustal

Abstract Geological and geophysical data coupled with numerical simulations have shown that lithospheric extension at passive margins may be classified into three end-member scenarios of pure shear, simple shear, and depth-dependent deformation. However, how lithospheric extension evolves in an intraplate setting remains enigmatic due to lack of reliable constraints on the deep lithospheric architecture. Here we use a seismic reflection profile across the ~800-km-wide Cretaceous intraplate extensional system of South China to illustrate depth-dependent kinematic decoupling of extension in a mechanically stratified lithosphere. The extension was initially distributed in magma-poor conditions as expressed by normal faulting in the upper crust and lower-crustal flow toward the rift axis. Necking of the crust and Moho uplift led to mantle shear-zone formation, lower-crustal flow toward the rift flanks, and deep mantle flow. We demonstrate that the extensional modes vary with decreasing mantle strength from magma-poor to magma-rich domains, as reflected in decreasing crust-mantle decoupling with increased Moho temperatures (TM), and the replacement of a two-layer (brittle vs ductile) mantle by a fully ductile mantle. These findings reveal a first-order lithospheric configuration of intraplate depth-dependent extension driven by far-field stresses attributable to slab retreat.

Delineating ophiolite-derived host rocks of massive sulfide Cu-Co-Zn deposits with 2D high-resolution seismic reflection data in Outokumpu, Finland

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC213-WC222 ◽  
Author(s):  
I. T. Kukkonen ◽  
S. Heinonen ◽  
P. Heikkinen ◽  
P. Sorjonen-Ward
Keyword(s):  
Seismic Data ◽  
Host Rock ◽  
Seismic Reflection ◽  
Massive Sulfide ◽  
High Amplitude ◽  
Ore Deposits ◽  
Acoustic Properties ◽  
Rock Properties ◽  
Seismic Reflection Data ◽  
Reflection Data

Seismic reflection data was applied to a study of the upper crustal structures in the Outokumpu mining and exploration area in eastern Finland. The Cu-Co-Zn sulfide ore deposits of the Outokumpu area are hosted by Palaeoproterozoic ophiolite-derived altered ultrabasic rocks (serpentinite, skarn rock, and quartz rock) and black schist within turbiditic mica schist. Mining in the Outokumpu area has produced a total of 36 Mt of ore from three historical and one active mine. Seismic data comprises 2D vibroseis data surveyed along a network of local roads. The seismic sections provide a comprehensive 3D view of the reflective structures. Acoustic rock properties from downhole logging and synthetic seismograms indicate that the strongly reflective packages shown in the seismic data can be identified as the host-rock environments of the deposits. Reflectors show excellent continuity along the structural grain of the ore belt, which allows correlating reflectors with surface geology, magnetic map, and drilling sections into a broad 3D model of the ore belt. Massive ores have acoustic properties that make them directly detectable with seismic reflection methods assuming the deposit size is sufficient for applied seismic wavelengths. The seismic data revealed numerous interesting high-amplitude reflectors within the interpreted host-rock suites potentially coinciding with sulfides.

An interpretation of the gravity anomaly at Warlingham, Surrey

1996 ◽  
Vol 133 (5) ◽  
pp. 619-624
Author(s):  
P. Kearey ◽  
A. M. Rabae
Keyword(s):  
Gravity Anomaly ◽  
Seismic Reflection ◽  
The Body ◽  
Seismic Reflection Profile ◽  
Seismic Reflection Data ◽  
Shaped Body ◽  
The North ◽  
Reflection Data ◽  
Platform Comparison ◽  
Upper Boundary

AbstractAn interpretation of the negative gravity anomaly at Warlingham, Surrey, controlled by a seismic reflection profile and several boreholes, suggest that it may be caused by a wedge-shaped body of lowdensity Upper Palaeozoic rocks. The seismic reflection data suggest that the upper boundary of the body may be thrust-controlled and originated during Variscan compression. The location of the thrusting appears to be controlled by the southern margin of the stable London Platform. Comparison with similar structures of this type elsewhere suggests that the Variscan Front in this area lies just to the north of Warlingham.

Seismic-Reflection Identification of Susquehanna River Paleochannels on the Mid-Atlantic Coastal Plain

1994 ◽  
Vol 42 (2) ◽  
pp. 166-175 ◽  
Author(s):  
Robert B. Genau ◽  
John A. Madsen ◽  
Susan McGeary ◽  
John F. Wehmiller
Keyword(s):  
High Resolution ◽  
Coastal Plain ◽  
Seismic Reflection ◽  
River System ◽  
High Amplitude ◽  
Seismic Profile ◽  
Atlantic Coastal Plain ◽  
Seismic Reflection Data ◽  
Susquehanna River ◽  
Reflection Data

AbstractLand-based, high-resolution seismic-reflection methods were used to image Quaternary paleochannels of the Susquehanna River system. Using a portable, 12-channel signal-enhancing seismograph, 12 accelerometers as receivers, and a 4.54-kg sledge hammer struck against an aluminum plate as a source, a sixfold, multichannel seismic profile 2.5 km long was acquired at Taylors Island, Maryland. On the processed seismic profile, pronounced high-amplitude seismic reflections delineate the unconformity between Quaternary and underlying Tertiary sediments and the disconformable contact separating Miocene and Eocene deposits. Subsurface-seismic stratigraphic relationships that clearly indicate the presence of two paleochannels were observed, one believed to be the Exmore paleochannel, projected to underlie northern Taylors Island based on marine seismic data. An overlapping sequence of fill sediments was observed on the eastern margin of the Exmore paleochannel. The second paleochannel may be a tributary of the Exmore or possibly the western edge of the younger Eastville paleochannel. Results from this study indicate that land-based, shallow, high-resolution seismic-reflection data can be used to delineate subsurface geomorphology successfully in coastal plain environments. This technique of defining erosional surfaces and depositional units beneath present land areas, when integrated with chronostratigraphic data, is a powerful tool for developing a better understanding of the Quaternary record.

The style of transverse faulting in the Dead Sea basin from seismic reflection data: The Amazyahu fault

2006 ◽  
Vol 55 (3) ◽  
pp. 129-139 ◽  
Author(s):  
Avihu Ginzburg ◽  
Moshe Reshef ◽  
Zvi Ben-Avraham ◽  
Uri Schattner
Keyword(s):  
Seismic Reflection ◽  
Dead Sea ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dead Sea Basin ◽  
The Dead
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