scholarly journals Technique for the imaging crystalline basement according to the DSS data

2021 ◽  
Vol 43 (5) ◽  
pp. 127-149
Author(s):  
O. O. Verpakhovska
Keyword(s):  
Finite Difference ◽  
Seismic Data ◽  
Deep Structure ◽  
Crystalline Basement ◽  
National Academy Of Sciences ◽  
Reflected Waves ◽  
Advantages And Disadvantages ◽  
Observation Systems ◽  
Layer Medium ◽  
Refracted Waves

The method of deep seismic sounding (DSS), the observation systems in which are characterized by an irregular arrangement of both sources and receivers along the profile, a significant step between receivers, as well as maximum source-receiver distances exceeding several hundred kilometers, makes it possible to obtain an image of the crystalline basement using seismic migration fields of reflected/refracted waves. The main part of the existing migration methods, the use of which makes it possible to form an image of the deep structure of the study area in the dynamic characteristics of the recorded wave field, is focused on processing seismic data obtained by the method of reflected waves with multiple overlap observation systems (MOV—CDP). And, as a rule, these migration methods are designed for a smooth change in speed with depth. At the same time, at the boundary of the crystalline basement, the speed changes very sharply, which must be taken into account when processing data using migration. The proposed method for constructing an image of the crystalline basement is based on the use of finite-difference migration of the field of reflected/refracted waves, which was developed at the Institute of Geophysics named after S. I. Subbotin National Academy of Sciences of Ukraine. This migration method is designed to isolate supercritically reflected and refracted waves recorded from the basement in the far zone of the source and takes into account the full trajectory of waves passing through a two-layer medium, at the boundary of which there is a significant jump in velocity. Thus, the migration of the field of reflected/refracted waves makes it possible to obtain a correct image of the structure of the refractive layer of the crystalline basement. The article describes in detail the algorithm of the technique for constructing an image of the crystalline basement using finite-difference migration of the field of reflected/refracted waves and its difference from similar methods of migration. The advantages and disadvantages of the proposed method are shown when solving problems of regional seismic research. Explained and illustrated the features of constructing the image of violations on the border of the foundation. The effectiveness of the technique is demonstrated on a model example and real seismic data observed by the DSS method on the territory of Ukraine.

Comparing Coding Viewing and Recording Methods to Quantify Embedded Instruction Learning Trials

2022 ◽  
pp. 105381512110695
Author(s):  
Mackenzie K. Martin ◽  
Patricia A. Snyder ◽  
Brian Reichow ◽  
Crystal D. Bishop
Keyword(s):  
Correlation Coefficients ◽  
Computer Assisted ◽  
Systematic Observation ◽  
Embedded Instruction ◽  
Advantages And Disadvantages ◽  
Observation Systems ◽  
Pencil And Paper ◽  
Dependent Samples ◽  
Learning Trials

The purpose of this study was to examine the comparability of counts of embedded instruction learning trials when different methods of viewing and recording direct behavioral observations were used. In 13 classrooms, while videotaping embedded instruction implementation for a larger randomized controlled efficacy trial was occurring, teachers’ implementation of trials was coded in situ using pencil-and-paper methods. Videos were later coded using computer-assisted methods. Dependent-samples t tests, Pearson product-moment correlation coefficients, and additional score agreement calculations were conducted. Statistically significant differences were found in the estimates of trial frequency. Correlational analyses showed positive and strong relationships between the coding methods. Coding agreement was higher across the entire observation versus during 10-min continuous event blocks. In situ coding took significantly less time than video coding. Results provide empirical evidence for the advantages and disadvantages of common viewing and recording methods for quantifying behavior as part of systematic observation systems.

3D constraints and finite-difference modeling of massive sulfide deposits: The Kristineberg seismic lines revisited, northern Sweden

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC69-WC79 ◽  
Author(s):  
Mahdieh Dehghannejad ◽  
Alireza Malehmir ◽  
Christopher Juhlin ◽  
Pietari Skyttä
Keyword(s):  
Finite Difference ◽  
Seismic Data ◽  
Massive Sulfide ◽  
Northern Sweden ◽  
Seismic Reflection Data ◽  
Sulfide Deposits ◽  
Time Migration ◽  
Massive Sulfide Deposits ◽  
Prestack Time Migration ◽  
Seismic Lines

The Kristineberg mining area in the western part of the Skellefte ore district is the largest base metal producer in northern Sweden and currently the subject of extensive geophysical and geologic studies aimed at constructing 3D geologic models. Seismic reflection data form the backbone of the geologic modeling in the study area. A geologic cross section close to the Kristineberg mine was used to generate synthetic seismic data using acoustic and elastic finite-difference algorithms to provide further insight about the nature of reflections and processing challenges when attempting to image the steeply dipping structures within the study area. Synthetic data suggest processing artifacts manifested themselves in the final 2D images as steeply dipping events that could be confused with reflections. Fewer artifacts are observed when the data are processed using prestack time migration. Prestack time migration also was performed on high-resolution seismic data recently collected near the Kristineberg mine and helped to image a high-amplitude, gently dipping reflection occurring stratigraphically above the extension of the deepest Kristineberg deposit. Swath 3D processing was applied to two crossing seismic lines, west of the Kristineberg mine, to provide information on the 3D geometry of an apparently flat-lying reflection observed in both of the profiles. The processing indicated that the reflection dips about 30° to the southwest and is generated at the contact between metasedimentary and metavolcanic rocks, the upper part of the latter unit being the most typical stratigraphic level for the massive sulfide deposits in the Skellefte district.

scholarly journals Comparison study between the elevation and datum statics in NC 210, western Libya

2021 ◽  
Author(s):  
Riyadh Alhajni
Keyword(s):  
Conventional Method ◽  
Seismic Data ◽  
Seismic Velocity ◽  
Sand Dunes ◽  
Angle Of Repose ◽  
Amplitude Analysis ◽  
Reflected Waves ◽  
Geometric Spreading ◽  
Amplitude Compensation ◽  
Seismic Lines

Abstract This research compares the results of each method to solve problems caused by sand dunes, In the southwestern region of Libya, the Murzuq basin is covered with sand dunes, which are a significant source of noise in land seismic data, which caused issues in seismic processing, also sand dunes cause increases of travel time of reflected events in seismic data, procuring false structures this problem caused by residual static errors. The presence of extensive sand dunes causes logistic and technical difficulties for seismic reflection prospecting, Due to the steep angle of repose of the sand dunes faces and the low seismic velocity within them, which causes significant time delay to the reflected waves. In this research, three seismic lines (202, 207, 209), of total length 12 km, have been completely reprocessed at Western Geco processing center (Tripoli) using omega software. the methods of gain corrections: time function gain and geometric spreading. Spreading amplitude compensation, has been proceed the results will be compared to another method of gain corrections called residual amplitude analysis compensation (RAAC) which is has better results for static problems the conventional method of computing field statics has been implemented and the result is compared with elevation static. It is obtained by using uphole method (conventional method) yielded a significant improvement over the elevation method.

Deep structure of the Atlantic margins and neighboring oceanic crust from wide-angle seismic data and plate kinematic reconstructions.

2021 ◽  
Author(s):  
Frauke Klingelhoefer ◽  
Youssef Biari ◽  
Dieter Franke ◽  
Thomas Funck ◽  
Lies Loncke ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Seismic Data ◽  
Deep Structure ◽  
Volcanic Eruptions ◽  
Wide Angle ◽  
Seismic Profiles ◽  
Initial Rupture ◽  
Mechanisms Of Formation ◽  
Break Up ◽  
Transform Margin

<p>In order to study opening mechanisms and their variation in the Atlantic ocean basins, we compiled existing wide-angle and deep seismic data along conjugate margins and performed plate tectonic reconstructions of the original opening geometries to define conjugate margin pairs. A total of 23 published wide-angle seismic profiles from the different margins of the Atlantic basin were digitized, and reconstructions at break-up and during early stages of opening were performed. Main objectives were to understand how magma-rich and magma-poor margins develop and to define more precisely the role of geologic inheritance (i.e., preexisting structures) in the break-up phase. At magma-poor margins, a phase of tectonic opening without accretion of a typical oceanic crust often follows initial rupture, leading to exhumation of serpentinized upper mantle material. Along volcanic margins the first oceanic crust can be overthickened, and both over- and underlain by volcanic products. The first proto-oceanic crust is often accreted at slow to very slow rates, and is thus of varied thickness, mantle content and volcanic overprint. Accretion of oceanic crust at slow to very slow spreading rates can also be highly asymmetric, so the proto oceanic crust at each side of conjugate margin pairs can differ. Another major aim of this study was to understand the mechanisms of formation and origins of transform marginal plateaus. These are bathymetric highs located at the border of two ocean basins of different ages and are mostly characterized by one or several volcanic phase during their formation. They often form conjugate pairs along a transform margin as it evolves and might have been the last land bridges during breakup, thereby influencing mammal migration and proto-oceanic currents in very young basins. At these plateaus, volcanic eruptions can lead to deposits of (at least in part subaerial) lava flows several km thick, better known by their geophysical signature as seaward dipping reflectors. Continental crust, if present, is heavily modified by volcanic intrusions. These marginal plateaus might form when rifting stops at barriers introduced by the transform margin, leading to the accumulation of heat in the mantle and increased volcanism directly before or after the cessation of rifting.</p>

Inversion of seismic refraction and reflection data for building long-wavelength velocity models

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. R81-R93 ◽  
Author(s):  
Haiyang Wang ◽  
Satish C. Singh ◽  
Francois Audebert ◽  
Henri Calandra
Keyword(s):  
Wave Equation ◽  
Short Wavelength ◽  
Velocity Model ◽  
Density Model ◽  
Data Set ◽  
Reflected Waves ◽  
Long Wavelength ◽  
Velocity Models ◽  
Computation Efficiency ◽  
Refracted Waves

Long-wavelength velocity model building is a nonlinear process. It has traditionally been achieved without appealing to wave-equation-based approaches for combined refracted and reflected waves. We developed a cascaded wave-equation tomography method in the data domain, taking advantage of the information contained in the reflected and refracted waves. The objective function was the traveltime residual that maximized the crosscorrelation function between real and synthetic data. To alleviate the nonlinearity of the inversion problem, refracted waves were initially used to provide vertical constraints on the velocity model, and reflected waves were then included to provide lateral constraints. The use of reflected waves required scale separation. We separated the long- and short-wavelength subsurface structures into velocity and density models, respectively. The velocity model update was restricted to long wavelengths during the wave-equation tomography, whereas the density model was used to absorb all the short-wavelength impedance contrasts. To improve the computation efficiency, the density model was converted into the zero-offset traveltime domain, where it was invariant to changes of the long-wavelength velocity model. After the wave-equation tomography has derived an optimized long-wavelength velocity model, full-waveform inversion was used to invert all the data to retrieve the short-wavelength velocity structures. We developed our method in two synthetic tests and then applied it to a marine field data set. We evaluated the results of the use of refracted and reflected waves, which was critical for accurately building the long-wavelength velocity model. We showed that our wave-equation tomography strategy was robust for the real data application.

The deep structure of the earth’s crust beneath the White Sea based on seismic data

2011 ◽  
Vol 66 (3) ◽  
pp. 213-219
Author(s):  
V. B. Piip ◽  
L. P. Tsydypova ◽  
N. V. Shalaeva ◽  
E. A. Teplyakova
Keyword(s):  
Seismic Data ◽  
White Sea ◽  
Deep Structure ◽  
Earth’S Crust ◽  
The White Sea ◽  
Earth's Crust
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