METHOD USING ELLIPSES TO INTERPRET SEISMIC REFLECTION DATA

Geophysics ◽  
1964 ◽  
Vol 29 (6) ◽  
pp. 926-934
Author(s):  
Gary S. Gassaway
Keyword(s):  
Seismic Reflection ◽  
Seismic Velocity ◽  
Vertical Section ◽  
Reflection Point ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
The One ◽  
Time Of Travel ◽  
Reflecting Surfaces ◽  
Reflecting Surface

The properties of an ellipse can be used to interpret seismic reflection data by using the positions in a vertical section of a shot and a geophone as the foci of an ellipse. With the shot and geophone as the foci, the total time of travel of a reflected seismic wave serves as the constant necessary to define the ellipse. The reflecting surface then is tangent to this ellipse. Therefore, if many ellipses are plotted, the reflecting surfaces may be found by drawing smooth curves that are tangent in common to closely intersecting families of arcs. This basic principle is extended to the interpretation of complex structures that are not perpendicular to the line of traverse and to areas where the seismic velocity changes with depth by the following steps: The shots and geophones are plotted on a graph where the units along both the ordinate and the abscissa are virtual seismic traveltimes. These positions of the shots and geophones are then used as the foci of the ellipses as above. The reflecting surfaces are then drawn tangent to the dark bands of closely intersecting elliptical arcs. From this graph the one‐way time from a shot to a point of reflection, and from the point of reflection to a geophone may be scaled off; this is done by drawing the elliptical radii from the shot and geophone to the point of tangency between the ellipse and reflecting surface. The lengths of these radii are the one‐way times at the time scale of the graph. With the attitude of the wavefront as it returned to the surface at a geophone determined by a spread of three parallel geophone lines, and the one‐way time from the reflection point, one has the necessary and sufficient data to find the point of reflection in space coordinates for the assumed velocity function. Using the ray paths from the shot and geophone to this reflection point, the dip and strike of the reflecting surface at this point are found. This process is then repeated for every shot‐geophone combination for each reflecting surface.

Tomographic determination of velocity and depth in laterally varying media

Geophysics ◽  
1985 ◽  
Vol 50 (6) ◽  
pp. 903-923 ◽  
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.

scholarly journals Predicting Missing Seismic Velocity Values Using Self-Organizing Maps to Aid the Interpretation of Seismic Reflection Data from the Kevitsa Ni-Cu-PGE Deposit in Northern Finland

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 529 ◽  
Author(s):  
Niina Junno ◽  
Emilia Koivisto ◽  
Ilmo Kukkonen ◽  
Alireza Malehmir ◽  
Markku Montonen
Keyword(s):  
Seismic Reflection ◽  
Seismic Velocity ◽  
Seismic Velocities ◽  
Self Organizing Map ◽  
Borehole Data ◽  
Self Organizing Maps ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Olivine Pyroxenite ◽  
Self Organizing

We use self-organizing map (SOM) analysis to predict missing seismic velocity values from other available borehole data. The site of this study is the Kevitsa Ni-Cu-PGE deposit within the mafic-ultramafic Kevitsa intrusion in northern Finland. The site has been the target of extensive seismic reflection surveys, which have revealed a series of reflections beneath the Kevitsa resource area. The interpretation of these reflections has been complicated by disparate borehole data, particularly because of the scarce amount of available sonic borehole logs and the varying practices in logging of borehole lithologies. SOM is an unsupervised data mining method based on vector quantization. In this study, SOM is used to predict missing seismic velocities from other geophysical, geochemical, geological, and geotechnical data. For test boreholes, for which measured seismic velocity logs are also available, the correlation between actual measured and predicted velocities is strong to moderate, depending on the parameters included in the SOM analysis. Predicted reflectivity logs, based on measured densities and predicted velocities, show that some contacts between olivine pyroxenite/olivine websterite-dominant host rocks of the Kevitsa disseminated sulfide mineralization—and metaperidotite—earlier extensively used “lithology” label that essentially describes various degrees of alteration of different olivine pyroxenite variants—are reflective, and thus, alteration can potentially cause reflectivity within the Kevitsa intrusion.

Automatic NMO correction in anisotropic media and non-hyperbolic NMO velocity field estimation

2016 ◽  
Vol 56 (2) ◽  
pp. 592
Author(s):  
Mohamed Sedek ◽  
Lutz Gross
Keyword(s):  
Velocity Field ◽  
Seismic Reflection ◽  
Fast Method ◽  
Gas Field ◽  
Seismic Reflection Data ◽  
Anisotropic Effect ◽  
Reflection Data ◽  
Nmo Correction ◽  
Zero Offset ◽  
The One

The authors propose a new method to automatically normal move-out correct pre-stack seismic reflection data that is sorted by CDP gathers, and to estimate the normal move-out (NMO) velocity (Vnmo) as a full common depth point (CDP) velocity field that instantaneously varies with offsets/azimuths. The method is based on doing a pre-defined number of NMO velocity iterations using linear vertical interpolation of different NMO velocities at each seismic trace individually. At each iteration the seismic trace is shifted and multiplied by the zero offset trace followed by the summation of the product. Then, after all the iterations are done, the one with the maximum summation value is chosen, which is assumed to be the most suitable NMO velocity trace that accurately flattens seismic reflection events. The other traces follow the same process, and a final velocity field is then extracted. Another new, simple and fast method is also introduced to estimate the anisotropic effect from the extracted NMO velocity field. The method runs by calculating the spatial variation of the estimated NMO velocities at each arrival time and offset/azimuth, therefore instantaneously estimating the anisotropic effect. Isotropic and anisotropic synthetic geological models were built based on a ray-tracing algorithm to test the method. A range of synthetic background noise was applied, starting from 10–30%. The method has also been tested on Hess’s model and coal seam gas field data CDP examples. An Alaskan pre-stack seismic CDP field example has also been used.

Lithoprobe onshore seismic reflection transects across the Newfoundland Appalachians

1992 ◽  
Vol 29 (9) ◽  
pp. 1865-1877 ◽  
Author(s):  
Garry M. Quinlan ◽  
Jeremy Hall ◽  
Harold Williams ◽  
James A. Wright ◽  
Stephen P. Colman-Sadd ◽  
...  
Keyword(s):  
Lower Crust ◽  
Seismic Reflection ◽  
Vertical Section ◽  
Upper Crust ◽  
Seismic Reflection Data ◽  
Spatially Correlated ◽  
Reflection Data ◽  
Iapetus Ocean

Vibroseis seismic reflection data have been recorded to 18 s two-way traveltime along three transects across the island of Newfoundland. The upper crust has both steep and subhorizontal reflectors consistent with a ramp–flat style of deformation, whereas the middle and lower crust are largely free of regional flats. Reflectors descend through ca. 20 km of vertical section in the middle and lower crust to flatten into the Moho or perhaps cut through it in places. The Moho is interpreted to be no younger than the dipping reflectors. Reflection fabrics, interpreted to be indicators of dominantly Mid-Ordovician to Mid-Silurian strain, show consistent orientations among the transects and divide the crust into two blocks. A northwestern block is characterized by upper and middle crustal reflectors dipping mostly southeast at variable angles. This block is underlain to the southeast by supposedly younger and dominantly northwesterly dipping reflectors that define a northwest-tapering, wedge-shaped block floored by the Moho. This latter block is cut by isolated southeast-dipping, upper crustal reflectors near the southeast ends of the seismic transects. One of these reflectors is spatially correlated with the Bay d'Est Fault, on which the last ductile motion was south over north thrusting of Mid-Silurian age. The two crustal blocks are proposed to represent the Laurentian and Gondwanan plates juxtaposed during closure of the Iapetus Ocean. The Gondwanan plate appears to be underthrust westward beneath the Laurentian plate, perhaps by as much as 200 km.

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

Archive of digital boomer seismic reflection data collected offshore east-central Florida during USGS cruise 00FGS01, July 14-22, 2000

Data Series ◽  
10.3133/ds496 ◽  
2009 ◽  
Author(s):  
Janice A. Subino ◽  
Shawn V. Dadisman ◽  
Dana S. Wiese ◽  
Karynna Calderon ◽  
Daniel C. Phelps
Keyword(s):  
Seismic Reflection ◽  
Seismic Reflection Data ◽  
East Central ◽  
Central Florida ◽  
Reflection Data

Archive of digital CHIRP seismic reflection data collected during USGS cruise 06SCC01 offshore of Isles Dernieres, Louisiana, June 2006

Data Series ◽  
10.3133/ds259 ◽  
2007 ◽  
Author(s):  
Arnell S. Harrison ◽  
Shawn V. Dadisman ◽  
Nick F. Ferina ◽  
Dana S. Wiese ◽  
James G. Flocks
Keyword(s):  
Seismic Reflection ◽  
Seismic Reflection Data ◽  
Reflection Data
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