Applications of digital methodology to the NATMAP Shield Margin Project

1999 ◽  
Vol 36 (2) ◽  
pp. 161-173 ◽  
Author(s):  
H John Broome ◽  
David Viljoen
Keyword(s):  
Three Dimensional ◽  
Geological Mapping ◽  
Digital Data ◽  
Data Sets ◽  
Digital Products ◽  
Seismic Reflection Data ◽  
Cd Rom ◽  
Reflection Data ◽  
Mapping Process ◽  
Rectangular Area

The NATMAP Shield Margin Project, which began in 1991, straddles the Manitoba-Saskatchewan border and studied a rectangular area with east-west and north-south extents of approximately 250 and 150 km, respectively. Among the principal objectives of the NATMAP program were a compilation of a digital geoscience database for the study area and development of digital methodology to build this database and its utilization to aid in reaching the geological goals of the project. It was anticipated that these initiatives would encourage integrated interpretation of data, improve the effectiveness of the geological mapping process, and accelerate publication of results. One of the keys to effectively applying digital methods to a geological mapping project is maintaining data in digital form throughout the project, from the field through to publication. Transcription errors are eliminated and the production of both preliminary and final maps and digital products is accelerated. Access to digital data also facilitates application of digital tools for analysis and visualization. Integrated image products generated from geophysical and geological data sets were used throughout the project and assisted in development of geological models and their visualization. Three-dimensional visualization methods were used to combine NATMAP surface and subsurface mapping with Lithoprobe interpretations of seismic reflection data. The digital database was used to prepare a digital archive of the project which will be published in CD-ROM after completion of the project.

Migration‐based traveltime waveform inversion of 2-D simple structures: A synthetic example

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 845-860 ◽  
Author(s):  
François Clément ◽  
Guy Chavent ◽  
Susana Gómez
Keyword(s):  
Least Squares ◽  
Waveform Inversion ◽  
Domain Of Attraction ◽  
Optimization Methods ◽  
Data Sets ◽  
Seismic Reflection Data ◽  
Prestack Migration ◽  
Reflection Data ◽  
Full Wave ◽  
The Time Domain

Migration‐based traveltime (MBTT) formulation provides algorithms for automatically determining background velocities from full‐waveform surface seismic reflection data using local optimization methods. In particular, it addresses the difficulty of the nonconvexity of the least‐squares data misfit function. The method consists of parameterizing the reflectivity in the time domain through a migration step and providing a multiscale representation for the smooth background velocity. We present an implementation of the MBTT approach for a 2-D finite‐difference (FD) full‐wave acoustic model. Numerical analysis on a 2-D synthetic example shows the ability of the method to find much more reliable estimates of both long and short wavelengths of the velocity than the classical least‐squares approach, even when starting from very poor initial guesses. This enlargement of the domain of attraction for the global minima of the least‐squares misfit has a price: each evaluation of the new objective function requires, besides the usual FD full‐wave forward modeling, an additional full‐wave prestack migration. Hence, the FD implementation of the MBTT approach presented in this paper is expected to provide a useful tool for the inversion of data sets of moderate size.

Plumbing and architecture of a crustal mineralizing system in the Archean Superior Province, Canada

2021 ◽  
Author(s):  
Eric Roots ◽  
Graham Hill ◽  
Ben M. Frieman ◽  
James A. Craven ◽  
Richard S. Smith ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Spatial Association ◽  
Three Dimensional ◽  
3D Models ◽  
Superior Province ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Abitibi Subprovince ◽  
Lower Crustal

<p>The role of melts and magmatic/metamorphic fluids in mineralization processes is well established. However, the role of crustal architecture in defining source and sink zones in the middle to lower crust remains enigmatic. Integration of three dimensional magnetotelluric (MT) modelling and seismic reflection data across the Archean Abitibi greenstone belt of the Superior Province, Canada, reveals a ‘whole-of-crust’ mineralizing system and highlights the controls by crustal architecture on metallogenetic processes. Electrically conductive conduits in an otherwise resistive upper crust are coincident with truncations and offsets of seismic reflections that are mostly interpreted as major brittle-ductile fault zones. The spatial association between these features and low resistivity zones imaged in the 3D models suggest that these zones acted as pathways through which fluids and melts ascended toward the surface. At mid-crustal levels, these ‘conduit’ zones connect to ~50 km long, north-south striking conductors, and are inferred to represent graphite and/or sulphide deposited from cooling fluids. At upper mantle to lower crustal depths, east-west trending conductive zones dominate and display shallow dips. The upper mantle features are broadly coincident with the surface traces of the major deformation zones with which a large proportion of the gold endowment is associated. We suggest that these deep conductors represent interconnected graphitic zones perhaps augmented by sulphides that are relicts from metamorphic fluid and melt emplacement associated primarily with the later stages of regional deformation.  Thus, from the combined MT and seismic data, we develop a crustal-scale architectural model that is consistent with existing geological and deformational models, providing constraints on the sources for and signatures of fluid and magma emplacement that resulted in widespread metallogenesis in the Abitibi Subprovince.</p>

scholarly journals Improved Interpretation of Deep Seismic Reflection Data in Areas of Complex Geology Through Integration With Passive Seismic Data Sets

2018 ◽  
Vol 123 (12) ◽  
pp. 10,810-10,830
Author(s):  
Michael Dentith ◽  
Huaiyu Yuan ◽  
Ruth Elaine Murdie ◽  
Perla Pina-Varas ◽  
Simon P. Johnson ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Data Sets ◽  
Seismic Reflection Data ◽  
Deep Seismic Reflection ◽  
Reflection Data ◽  
Passive Seismic ◽  
Complex Geology

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).

Three-dimensional geometry and growth of a basement-involved fault network developed during multiphase extension, Enderby Terrace, North West Shelf of Australia

2021 ◽  
Author(s):  
Hongdan Deng ◽  
Ken McClay
Keyword(s):  
Three Dimensional ◽  
Sedimentary Basins ◽  
Fault Reactivation ◽  
Late Triassic ◽  
Seismic Reflection Data ◽  
North West ◽  
Reflection Data ◽  
Data Volume ◽  
Vertical Linkages ◽  
Fault Network

<div>Basement fault reactivation, and the growth, interaction, and linkage with new fault segments are fundamentally three-dimensional and critical for understanding the evolution of fault network development in sedimentary basins. This paper analyses the evolution of a complex, basement-involved extensional fault network on the Enderby Terrace on the eastern margin of the Dampier sub-basin, NW Shelf of Australia. A high-resolution, depth-converted, 3D seismic reflection data volume is used to show that multiphase, oblique extensional reactivation of basement-involved faults controlled the development of the fault network in the overlying strata. Oblique reactivation of the pre-existing faults initially led to the formation of overlying, en échelon Late Triassic – Middle Jurassic fault segments that, as WNW–directed rifting progressed on the margin, linked by breaching of relay ramp to form two intersecting fault systems (F1 and F2-F4). Further reactivation in the Latest Jurassic – Early Cretaceous (NNW–SSE extension) produced an additional set of en échelon fault arrays in the cover strata. The final fault network consists of main or principal faults and subordinate or splay faults, together with branch lines that link the various components. Our study shows that breaching of relay ramps and/or vertical linkages produces vertical and horizontal branch lines giving complex final fault geometries. We find that repeated activity of the basement-involved faults tends to form continuous and planar fault architectures that favor displacement transfer between the main constituent segments along strike and with depth.</div>

Migration with reduced artifacts from internal multiple reflections

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. A25-A29
Author(s):  
Lele Zhang
Keyword(s):  
Seismic Reflection ◽  
Computational Cost ◽  
Data Sets ◽  
Square Root ◽  
Multiple Reflections ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Recent Developments ◽  
Multiple Elimination

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.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

scholarly journals Entrainment and abrasion of megaclasts during submarine landsliding and their impact on flow behaviour

2018 ◽  
Vol 477 (1) ◽  
pp. 223-240 ◽  
Author(s):  
D. M. Hodgson ◽  
H. L. Brooks ◽  
A. Ortiz-Karpf ◽  
Y. Spychala ◽  
D. R. Lee ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Submarine Landslides ◽  
Seismic Reflection Data ◽  
Karoo Basin ◽  
Reflection Data ◽  
Seabed Topography ◽  
Flow Evolution ◽  
Basal Shear ◽  
Process Product

AbstractMany mass transport complexes (MTCs) contain up to kilometre-scale (mega)clasts encased in a debritic matrix. Although many megaclasts are sourced from the headwall areas, the irregular basal shear surfaces of many MTCs indicate that megaclast entrainment during the passage of flows into the deeper basin is also common. However, the mechanisms responsible for the entrainment of large blocks of substrate, and their influence on the longitudinal behaviour of the associated flows, have not been widely considered. We present examples of megaclasts from exhumed MTCs (the Neuquén Basin, Argentina and the Karoo Basin, South Africa) and MTCs imaged in three-dimensional seismic reflection data (Magdalena Fan, offshore Colombia and Santos Basin, offshore Brazil) to investigate these process–product interactions. We show that highly sheared basal surfaces are well developed in distal locations, sometimes extending beyond their associated deposit. This points to deformation and weakening of the substrate ahead of the flow, suggesting that preconditioning of the substrate by distributed shear ahead of, and to the side of, a mass flow could result in the entrainment of large fragments. An improved understanding of the interactions between flow evolution, seabed topography, and the entrainment and abrasion of megaclasts will help to refine estimates of run-out distances, and therefore the geohazard potential of submarine landslides.

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.

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