COMPOSITE REFLECTIONS

Geophysics ◽  
1950 ◽  
Vol 15 (1) ◽  
pp. 30-49 ◽  
Author(s):  
Norman Ricker ◽  
R. D. Lynn
Keyword(s):  
Free Surface ◽  
Shear Wave ◽  
Horizontal Component ◽  
Seismic Prospecting ◽  
Reflection Seismic ◽  
Quiet Region ◽  
Dilatational Wave ◽  
Cotton Valley ◽  
Ground Roll

This paper discusses the development of a method of reflection seismic prospecting based on the use of the seismic PS phase—a disturbance which has traveled from the shot to the reflecting bed as a dilatational wave and from the reflecting bed to the earth’s free surface as a shear wave, where it is picked up by horizontal component geophones. The reflection occurs on the seismogram in the otherwise quiet region between the dilatational waves and the ground roll and thus is never obscured by the ground roll. The reflection is quite clear and capable of spot correlation from spread to spread. The use of the method in delineating the Homer and Cotton Valley structures, near Minden, Louisiana, is described in detail. The method appears to be applicable to regions where an unconsolidated subsurface extends downwards from the earth’s surface to a single hard bed serving as a reflector. Criteria for identifying the disturbance as a composite reflection are given and the advantages and limitations of the method are discussed.

Single-station SVD-based polarization filtering of ground roll: Perfection and investigation of limitations and pitfalls

Geophysics ◽  
2012 ◽  
Vol 77 (2) ◽  
pp. V41-V59 ◽  
Author(s):  
Olena Tiapkina ◽  
Martin Landrø ◽  
Yuriy Tyapkin ◽  
Brian Link
Keyword(s):  
Time Window ◽  
Synthetic Data ◽  
Vertical Component ◽  
Horizontal Component ◽  
Frequency Bandwidth ◽  
Polarization Filter ◽  
Data Set ◽  
Single Station ◽  
Ground Roll ◽  
Polarization Filtering

The advent of single receiver point, multi-component geophones has necessitated that ground roll be removed in the processing flow rather than through acquisition design. A wide class of processing methods for ground-roll elimination is polarization filtering. A number of these methods use singular value decomposition (SVD) or some related transformations. We focus on a single-station SVD-based polarization filter that we consider to be one of the best in the industry. The method is comprised of two stages: (1) ground-roll detection and (2) ground-roll estimation and filtering. To detect the ground roll, a special attribute dependent on the singular values of a three-column matrix formed by a sliding time window is used. The ground roll is approximated and subtracted using the first two eigenimages of this matrix. To limit the possible damage to the signal, the filter operates within the record intervals where the ground roll is detected and within the ground-roll frequency bandwidth only. We improve the ground-roll detector to make it theoretically insensitive to ambient noise and more sensitive to the presence of ground roll. The advantage of the new detector is demonstrated on synthetic and field data sets. We estimate theoretically and with synthetic data the attenuation of the underlying reflections that can be caused by the polarization filter. We show that the underlying signal always loses almost all the energy on the vertical component and on the horizontal component in the ground-roll propagation plane and within the ground-roll frequency bandwidth. The only signal component, if it exists, that can retain a significant part of its energy is the horizontal component orthogonal to the above plane. When 2D 3C field operations are conducted, the signal particle motion can deviate from the ground-roll propagation plane and can therefore retain some of its energy due to a set of offline reflections. In the case of 3D 3C seismic surveys, the reflected signal always deviates from the ground-roll propagation plane on the receiver lines that do not contain the source. This is confirmed with a 2.5D 3C synthetic data set. We discuss when the ability of the filter to effectively subtract the ground roll may, or may not, allow us to ignore the inevitable harm that is done to the underlying reflected waves.

scholarly journals Finite-difference modelling to evaluate seismic P-wave and shear-wave field data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 33-47 ◽  
Author(s):  
T. Burschil ◽  
T. Beilecke ◽  
C. M. Krawczyk
Keyword(s):  
Wave Field ◽  
Shear Wave ◽  
Field Data ◽  
P Wave ◽  
Sh Wave ◽  
Surface Shear ◽  
Near Surface ◽  
Reflection Seismic ◽  
Surface Shear Wave ◽  
Seismic Measurements

Abstract. High-resolution reflection seismic methods are an established non-destructive tool for engineering tasks. In the near surface, shear-wave reflection seismic measurements usually offer a higher spatial resolution in the same effective signal frequency spectrum than P-wave data, but data quality varies more strongly. To discuss the causes of these differences, we investigated a P-wave and a SH-wave seismic reflection profile measured at the same location on the island of Föhr, Germany and applied seismic reflection processing to the field data as well as finite-difference modelling of the seismic wave field. The simulations calculated were adapted to the acquisition field geometry, comprising 2 m receiver distance (1 m for SH wave) and 4 m shot distance along the 1.5 km long P-wave and 800 m long SH-wave profiles. A Ricker wavelet and the use of absorbing frames were first-order model parameters. The petrophysical parameters to populate the structural models down to 400 m depth were taken from borehole data, VSP (vertical seismic profile) measurements and cross-plot relations. The simulation of the P-wave wave-field was based on interpretation of the P-wave depth section that included a priori information from boreholes and airborne electromagnetics. Velocities for 14 layers in the model were derived from the analysis of five nearby VSPs (vP =1600–2300 m s-1). Synthetic shot data were compared with the field data and seismic sections were created. Major features like direct wave and reflections are imaged. We reproduce the mayor reflectors in the depth section of the field data, e.g. a prominent till layer and several deep reflectors. The SH-wave model was adapted accordingly but only led to minor correlation with the field data and produced a higher signal-to-noise ratio. Therefore, we suggest to consider for future simulations additional features like intrinsic damping, thin layering, or a near-surface weathering layer. These may lead to a better understanding of key parameters determining the data quality of near-surface shear-wave seismic measurements.

Reflection of coupled dilatational and shear waves in the generalized micropolar thermoelastic materials

2020 ◽  
Vol 26 (21-22) ◽  
pp. 1948-1955 ◽  
Author(s):  
Rengsi Lianngenga ◽  
Sanasam S Singh
Keyword(s):  
Wave Propagation ◽  
Free Surface ◽  
Boundary Conditions ◽  
Shear Wave ◽  
Shear Waves ◽  
Energy Ratios ◽  
Micropolar Thermoelasticity ◽  
Incident Waves

The problem of wave propagation in the generalized theory of micropolar thermoelasticity under the Green–Lindsay model has been investigated. We have investigated the reflected dilatational and shear waves due to incident waves at a plane-free surface of generalized micropolar thermoelastic materials. The amplitude and energy ratios corresponding to the reflected coupled dilatational and coupled shear waves are derived using boundary conditions at the free surface. These ratios are also computed numerically for a particular model. Note that there are critical angles for the incident shear wave.

On the prediction of settlement from high-resolution shear-wave reflection seismic data: The Trondheim harbour case study, mid Norway

2013 ◽  
Vol 167 ◽  
pp. 72-83 ◽  
Author(s):  
J.S. L'Heureux ◽  
M. Long ◽  
M. Vanneste ◽  
G. Sauvin ◽  
L. Hansen ◽  
...  
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Seismic Data ◽  
Wave Reflection ◽  
Reflection Seismic

A NOTE ON MULTIPLE REFLECTIONS

Geophysics ◽  
1949 ◽  
Vol 14 (3) ◽  
pp. 357-360
Author(s):  
G. E. Higgins
Keyword(s):  
Multiple Reflections ◽  
Geophysical Investigation ◽  
Seismic Prospecting ◽  
Reflection Seismic ◽  
Near Shore ◽  
Seismic Investigation

It was most interesting to read the January 1948 issue of Geophysics which was devoted to articles on multiple reflections and I would endorse the plea of Mr. Robert H. Mansfield for an issue of Geophysics to be devoted to the troublesome problems of offside energy in seismic prospecting. Trinidad has recently been the scene of intensive geophysical investigation, both gravimeter and reflection on seismic, and while neither method gives unambiguous answers to the local geologic problems, it is about the reflection seismic results which I should like to discuss. The first period of intensive seismic investigation in Trinidad was during 1938–1939 and certain anomalies observed then received further investigation during 1946–1947. During both periods of investigation, two particular phenomena were observed which may be called: 1. Near‐shore effect. 2. Coning.

Sign in / Sign up

Export Citation Format

Share Document