Two-dimensional velocity macro model estimation from seismic reflection data by local differential semblance optimization: applications to synthetic and real data sets

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).

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Migration with reduced artifacts from internal multiple reflections

Geophysics ◽

10.1190/geo2019-0780.1 ◽

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.

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Labeling long‐period multiple reflections

Geophysics ◽

10.1190/1.1442569 ◽

1989 ◽

Vol 54 (1) ◽

pp. 122-126 ◽

Cited By ~ 5

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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Tomographic determination of velocity and depth in laterally varying media

Geophysics ◽

10.1190/1.1441970 ◽

1985 ◽

Vol 50 (6) ◽

pp. 903-923 ◽

Cited By ~ 346

Author(s):

T. N. Bishop ◽

K. P. Bube ◽

R. T. Cutler ◽

R. T. Langan ◽

P. L. Love ◽

...

Keyword(s):

Seismic Reflection ◽

Seismic Velocity ◽

Real Data ◽

Seismic Reflection Data ◽

Near Surface ◽

Reflection Data ◽

Tomographic Method ◽

Recorded Data ◽

The Difference

Estimation of reflector depth and seismic velocity from seismic reflection data can be formulated as a general inverse problem. The method used to solve this problem is similar to tomographic techniques in medical diagnosis and we refer to it as seismic reflection tomography. Seismic tomography is formulated as an iterative Gauss‐Newton algorithm that produces a velocity‐depth model which minimizes the difference between traveltimes generated by tracing rays through the model and traveltimes measured from the data. The input to the process consists of traveltimes measured from selected events on unstacked seismic data and a first‐guess velocity‐depth model. Usually this first‐guess model has velocities which are laterally constant and is usually based on nearby well information and/or an analysis of the stacked section. The final model generated by the tomographic method yields traveltimes from ray tracing which differ from the measured values in recorded data by approximately 5 ms root‐mean‐square. The indeterminancy of the inversion and the associated nonuniqueness of the output model are both analyzed theoretically and tested numerically. It is found that certain aspects of the velocity field are poorly determined or undetermined. This technique is applied to an example using real data where the presence of permafrost causes a near‐surface lateral change in velocity. The permafrost is successfully imaged in the model output from tomography. In addition, depth estimates at the intersection of two lines differ by a significantly smaller amount than the corresponding estimates derived from conventional processing.

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Processing and modelling of short-offset seismic refraction-coincident deep seismic reflection data sets in sedimentary basins: an approach for exploring the underlying deep crustal structures

Geophysical Journal International ◽

10.1111/j.1365-246x.2005.02792.x ◽

2005 ◽

Vol 163 (3) ◽

pp. 1112-1122 ◽

Cited By ~ 6

Author(s):

V. G. Krishna ◽

V. Vijaya Rao

Keyword(s):

Seismic Reflection ◽

Seismic Refraction ◽

Sedimentary Basins ◽

Data Sets ◽

Seismic Reflection Data ◽

Deep Seismic Reflection ◽

Reflection Data ◽

Crustal Structures

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Hectometer-scale, shallow buried honeycomb-like structures on the continental shelf of the Otway Basin, southeastern Australia

Interpretation ◽

10.1190/int-2020-0039.1 ◽

2020 ◽

Vol 8 (4) ◽

pp. SR65-SR81 ◽

Cited By ~ 1

Author(s):

Yakufu Niyazi ◽

Mark Warne ◽

Daniel Ierodiaconou

Keyword(s):

Seismic Reflection ◽

Geospatial Analysis ◽

Data Sets ◽

Soft Sediment ◽

3D Seismic ◽

Burial Diagenesis ◽

Seismic Reflection Data ◽

Reflection Data ◽

Southeastern Australia ◽

2D And 3D

The Plio-Pleistocene Whalers Bluff Formation (WBF) of the offshore Otway Basin is composed of mixed siliciclastic-carbonate sediments. In seismic cross sections, this formation includes an interval that consists of higher amplitude seismic reflections that display alternating depressional ponds and raised ridges. This interval is shallowly buried and lies between 40 and 150 ms two-way traveltime below the present-day seafloor. In this study, we have used 2D and 3D seismic data sets in combination with the available shallow subsurface well logs to characterize the geomorphology and investigate the origin of these enigmatic features. The ponds are expressed as densely packed, circular to polygonal, and in some cases, hexagonal-shaped features in time-slice maps, and they closely resemble previously documented honeycomb structures. In our study area, the honeycomb-like structures (HS) are comprised of large (200–800 m diameter range) depressed ponds that are separated by narrow (approximately 20 m at the top) reticulate ridges. In total, these HS cover an area of 760 km2. Geospatial analysis shows that the ponds of HS, especially those in the northeast of the study area, are aligned along the northwest–southeast trend lines. There are several possible origins for the HS. The most probable mechanism is that the HS resulted from the bulk contraction of soft sediment, associated with shallow-burial diagenesis processes such as subaqueous dewatering of the fine-grained successions within the WBF. Interestingly, irregular furrows of various lengths on the seafloor correspond to the ridges of the HS, and we hypothesize that these furrows may have formed due to differential compaction of the underlying alternating ponds and ridges. Our results demonstrate the benefits of using seismic reflection data sets in combination with geospatial analysis to investigate the buried paleogeomorphologic features and their impact on the present-day seafloor physiography. Geological feature: Honeycomb-like, soft sediment deformation associated with shallow-burial diagenesis, Otway Basin, southeastern Australia Cross-section appearance: Alternating depressional ponds and raised ridges Map view appearance: Densely packed, oval to polygonal-shaped features Features with a similar appearance: Acquisition footprints, carbonate mounds/dissolution features, polygonal faults, pockmarks, opal-A to opal-CT transition Formation: Whalers Bluff Formation, offshore Otway Basin Age: Pliocene to recent Location: Continental shelf of the Otway Basin, southeastern Australia Data sets: 2D and 3D seismic reflection data, borehole data, from Geological Survey of Victoria, Australia Analysis tools: Interpretation and visualization (Petrel 2019 and DUG Insight, v.4.7, 2020), Geospatial analysis (ESRI‘s ArcMap 10.5)

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Efficient tau‐p hyperbolic velocity filtering

Geophysics ◽

10.1190/1.1442873 ◽

1990 ◽

Vol 55 (5) ◽

pp. 619-625 ◽

Cited By ~ 11

Author(s):

Alan R. Mitchell ◽

Panos G. Kelamis

Keyword(s):

Physical Interpretation ◽

Seismic Reflection ◽

Real Data ◽

Data Input ◽

Computer Implementation ◽

Seismic Reflection Data ◽

Reflection Data ◽

Velocity Filtering

Time and offset varying velocity filtering can be achieved by limiting the data input to forward tau‐p transforms. This limiting procedure, called hyperbolic velocity filtering (HVF), suppresses transform‐related artifacts as well as coherent and noncoherent noise while retaining elliptical (reflection) events. We show that HVF can be viewed as a muting process in the slant‐stack domain. Based on this simple but physical interpretation of HVF, a more efficient computer implementation is proposed. We further examine possible applications of HVF for processing seismic reflection data and illustrate the results using both synthetic and real data examples.

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