Complex seismic trace analysis of thin beds

Geophysics ◽  
1984 ◽  
Vol 49 (4) ◽  
pp. 344-352 ◽  
Author(s):  
James D. Robertson ◽  
Henry H. Nogami
Keyword(s):  
Instantaneous Frequency ◽  
Trace Analysis ◽  
Frequency Tuning ◽  
Seismic Energy ◽  
High Amplitude ◽  
Opposite Polarity ◽  
Peak Period ◽  
Seismic Wavelet ◽  
Porous Sandstone ◽  
Seismic Sections

Displays of complex trace attributes can help to define thin beds in seismic sections. If the wavelet in a section is zero phase, low impedance strata whose thicknesses are of the order of half the peak‐to‐peak period of the dominant seismic energy show up as anomalously high‐amplitude zones on instantaneous amplitude sections. These anomalies result from the well‐known amplitude tuning effect which occurs when reflection coefficients of opposite polarity a half period apart are convolved with a seismic wavelet. As the layers thin to a quarter period of the dominant seismic energy, thinning is revealed by an anomalous increase in instantaneous frequency. This behavior results from the less well‐known but equally important phenomenon of frequency tuning by beds which thin laterally. Instantaneous frequency reaches an anomalously high value when bed thickness is about a quarter period and remains high as the bed continues to thin. In this paper, complex trace analysis is applied to a synthetic model of a wedge and to a set of broadband field data acquired to delineate thin lenses of porous sandstone. The two case studies illustrate that sets of attribute displays can be used to verify the presence and dimensions of thin beds when definition of the beds is not obvious on conventional seismic sections.

Complex seismic trace analysis

Geophysics ◽  
1979 ◽  
Vol 44 (6) ◽  
pp. 1041-1063 ◽  
Author(s):  
M. T. Taner ◽  
F. Koehler ◽  
R. E. Sheriff
Keyword(s):  
Instantaneous Frequency ◽  
Seismic Data ◽  
Trace Analysis ◽  
Color Patterns ◽  
Phase Information ◽  
Real Component ◽  
The Real ◽  
Geological Interpretation ◽  
Envelope Amplitude ◽  
Spatial Changes

The conventional seismic trace can be viewed as the real component of a complex trace which can be uniquely calculated under usual conditions. The complex trace permits the unique separation of envelope amplitude and phase information and the calculation of instantaneous frequency. These and other quantities can be displayed in a color‐encoded manner which helps an interpreter see their interrelationship and spatial changes. The significance of color patterns and their geological interpretation is illustrated by examples of seismic data from three areas.

Theory of 2-D complex seismic trace analysis

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 264-272 ◽  
Author(s):  
Arthur E. Barnes
Keyword(s):  
Phase Velocity ◽  
Group Velocity ◽  
Hilbert Transform ◽  
Instantaneous Frequency ◽  
Trace Analysis ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Instantaneous Amplitude ◽  
Dip Angle

The ideas of 1-D complex seismic trace analysis extend readily to two dimensions. Two‐dimensional instantaneous amplitude and phase are scalars, and 2-D instantaneous frequency and bandwidth are vectors perpendicular to local wavefronts, each defined by a magnitude and a dip angle. The two independent measures of instantaneous dip correspond to instantaneous apparent phase velocity and group velocity. Instantaneous phase dips are aliased for steep reflection dips following the same rule that governs the aliasing of 2-D sinusoids in f-k space. Two‐dimensional frequency and bandwidth are appropriate for migrated data, whereas 1-D frequency and bandwidth are appropriate for unmigrated data. The 2-D Hilbert transform and 2-D complex trace attributes can be efficiently computed with little more effort than their 1-D counterparts. In three dimensions, amplitude and phase remain scalars, but frequency and bandwidth are 3-D vectors with magnitude, dip angle, and azimuth.

Sensitivity of the dispersion correction to Q error

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 288-290 ◽  
Author(s):  
Richard E. Duren ◽  
E. Clark Trantham
Keyword(s):  
Amplitude Spectrum ◽  
Careful Attention ◽  
Dispersion Correction ◽  
Event Time ◽  
Seismic Wavelet ◽  
Reflection Time ◽  
Seismic Image ◽  
Time Zones ◽  
Seismic Sections ◽  
Zero Phase

A controlled‐phase acquisition and processing methodology for our company has been described by Trantham (1994). He pointed out that it is careful attention to wavelet phase that leads to improved well ties and a more geologically accurate seismic image. In addition, we prefer zero‐phase wavelets on our seismic sections. For a given amplitude spectrum they have the simplest shape and the highest peak; further, the peak occurs at the reflection time of the event. This alignment is important since the seismic wavelet generally broadens with increasing depth with a zero‐phase wavelet remaining symmetrical about the event time. Our experience has been that a true zero‐phase section can be tied over the entire length of a synthetic trace without having to slide the synthetic trace to tie different time zones.

THE ATTENUATION OF HIGH-AMPLITUDE WAVES IN ROCKS

1964 ◽  
Vol 42 (3) ◽  
pp. 526-534
Author(s):  
R. F. Mereu
Keyword(s):  
Absorption Coefficient ◽  
Seismic Energy ◽  
High Amplitude ◽  
Absorption Coefficients ◽  
The Absolute ◽  
Coefficients Of Absorption

The pin-contactor method was modified so that it could be used to measure coefficients of absorption of high-amplitude waves in cylinders of rocks and metals. Experiments performed with granite, marble, and aluminum showed that the coefficients of absorption for marble and aluminum for pressures below 100 kb are more than three times that for granite. Also, for pressures greater than 22 kb the absorption coefficient for marble is more than twice that for pressures below this level. It should be emphasized that the absolute values of the absorption coefficients found in these experiments depend on the geometry; however, the relative values indicate the extent of the differences in the properties of the rocks. The compressibilities of both marble and granite were found to be constant for pressures in the 2 to 100 kb range. The results of these experiments and similar ones could lead to a better understanding of how the energy of explosions can be coupled into seismic energy more efficiently.

scholarly journals Spatially and temporally systematic hydrologic changes within large geoengineered landslides, Cromwell Gorge, New Zealand, induced by multiple regional earthquakes

2021 ◽  
Author(s):  
GA O'Brien ◽  
SC Cox ◽  
John Townend
Keyword(s):  
Groundwater Level ◽  
Spectral Characteristics ◽  
Seismic Energy ◽  
High Amplitude ◽  
Ground Acceleration ◽  
Earthquake Parameters ◽  
Groundwater Levels ◽  
Time To Peak ◽  
Long Duration ◽  
Groundwater Level Changes

©2016. American Geophysical Union. All Rights Reserved. Geoengineered groundwater systems within seven large (23 × 104–9 × 106 m2), deep-seated (40–300 m), previously slow-creep (2–5 mm/yr.) schist landslides in the Cromwell Gorge responded systematically to 11 large (Mw > 6.2) earthquakes at epicentral distances of 130–630 km between 1990 and 2013. Landslide groundwater is strongly compartmentalized and often overpressured, with permeability of 10−17 to 10−13 m2 and flow occurring primarily through fracture and crush zones, hindered by shears containing clayey gouge. Hydrological monitoring recorded earthquake-induced meter- or centimeter-scale changes in groundwater levels (at 22 piezometers) and elevated drainage discharge (at 11 V notch weirs). Groundwater level changes exhibited consistent characteristics at all monitoring sites, with time to peak-pressure changes taking ~1 month and recovery lasting 0.7–1.2 years. Changes in weir flow rate near instantaneous (peaking 0–6 h after earthquakes) and followed by recession lasting ~1 month. Responses at each site were systematic from one earthquake to another in terms of duration, polarity, and amplitude. Consistent patterns in amplitude and duration have been compared between sites and with earthquake parameters (peak ground acceleration (PGA), seismic energy density (e), shaking duration, frequency bandwidth, and site amplitude). Shaking at PGA ~0.27% g and e ~ 0.21 J m−3 induced discernable gorge-wide hydrological responses at thresholds comparable to other international examples. Groundwater level changes modeled using a damped harmonic oscillator characterize the ability of the system to resist and recover from extrinsic perturbations. The observed character of response reflects spectral characteristics as well as energy. Landslide hydrological systems appear most susceptible to damage and hydraulic changes when earthquakes emit broad-frequency, long-duration, high-amplitude ground motion.

scholarly journals The 102–103° E geodivider in the modern lithosphere structure of Сentral Asia

2018 ◽  
Vol 9 (3) ◽  
pp. 989-1006 ◽  
Author(s):  
Yu. G. Gatinsky ◽  
T. V. Prokhorova ◽  
D. V. Rundquist
Keyword(s):  
Seismic Energy ◽  
The North ◽  
Large Structures ◽  
Central Asian ◽  
The Pacific ◽  
Three Rivers Region ◽  
Seismic Sections ◽  
Three Rivers ◽  
Crust Thickness ◽  
Metallogenic Characteristics

A quasi-linear zone of noticeable geological and geophysical changes, which coincides approximately with 102–103° E meridians, is termed by the authors as “geodivider”. Active submeridional faults are observed predominantly along the zone and coincide with its strike. Seismicity is most intensive in the central part of this zone, from the Lake Baikal to the Three Rivers Region at the Sino-Myanmar frontier. Transects with deep seismic sections and energy dissipation graphs show most sharply increasing seismic energy amounts and hypocenter depths in the western part of the geodivider which delimits (in the first approximation) the Central Asian and East Asian transitional zones between the North Eurasian, Indian and Pacific lithosphere plates. The transpression tectonic regime dominates west of the geodivider under the influence of the Hindustan Indentor pressure, and the transtension regime prevails east of it due to the Pacific subduction slab submergence and continuation. The regime change coincides with an abrupt increase in the crust thickness – from 35–40 km to 45–70 km – west of the geodivider, as reflected in the geophysical fields and metallogenic characteristics of the crust. The direction ofP- andS-waves anisotropy together with the GPS data show decoupling layers of the crust and mantle in the southern part of the geodivider. According to our investigations, the 102–103° E geodivider is a regional geological-geophysical border that may be compared with the Tornquist Line, and, by its scale, with the Uralian and Appalachian fronts and some others large structures.

Case history of the exploration of the Grand Isle 95 Field in the Gulf of Mexico

Geophysics ◽  
1983 ◽  
Vol 48 (7) ◽  
pp. 900-909
Author(s):  
Poh‐Hsi Pan
Keyword(s):  
High Amplitude ◽  
Seismic Exploration ◽  
Careful Examination ◽  
Gas Oil ◽  
Seismic Modeling ◽  
Exploration And Exploitation ◽  
History Of ◽  
Oil Water ◽  
Seismic Sections ◽  
Seismic Lines

Grand Isle 95 Field is located 40 miles offshore Louisiana in 200 ft of water. First stage seismic exploration work was completed by Mobil in 1972. High‐amplitude events were observed on the seismic sections which were believed to be related to the existence of hydrocarbons. Reprocessed seismic lines showed some amplitude change near two questionable flat spots which were thought to be the gas‐oil and oil‐water sand contacts. Careful examination of the original seismic record proved that one of the flat events was caused by noise or distortions under the fault. Subsequent seismic modeling studies led to the success of exploration and exploitation of the field.

Nonstationary phase estimation using regularized local kurtosis maximization

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. A75-A80 ◽  
Author(s):  
Mirko van der Baan ◽  
Sergey Fomel
Keyword(s):  
Statistical Estimation ◽  
Phase Estimation ◽  
Time Varying ◽  
Seismic Wavelet ◽  
Optimization Framework ◽  
Phase Rotation ◽  
Seismic Sections ◽  
The Stability ◽  
Kurtosis Maximization ◽  
Zero Phase

Phase mismatches sometimes occur between final processed seismic sections and zero-phase synthetics based on well logs — despite best efforts for controlled-phase acquisition and processing. Statistical estimation of the phase of a seismic wavelet is feasible using kurtosis maximization by constant-phase rotation, even if the phase is nonstationary. We cast the phase-estimation problem into an optimization framework to improve the stability of an earlier method based on a piecewise-stationarity assumption. After estimation, we achieve space-and-time-varying zero-phasing by phase rotation.

Ghosting and marine signature deconvolution: A prerequisite for detailed seismic interpretation

Geophysics ◽  
1983 ◽  
Vol 48 (11) ◽  
pp. 1468-1485 ◽  
Author(s):  
Dushan B. Jovanovich ◽  
Roger D. Sumner ◽  
Sharon L. Akins‐Easterlin
Keyword(s):  
Gulf Coast ◽  
Seismic Line ◽  
Near Surface ◽  
Seismic Wavelet ◽  
Phase Errors ◽  
Air Gun ◽  
Statistical Hypotheses ◽  
Seismic Sections ◽  
Sonic Logs ◽  
Zero Phase

Detailed lithologic interpretation of seismic sections and/or pseudo‐sonic logs generated from seismic data requires that the seismic trace can be modeled as a reflection series convolved with a zero‐phase broadband wavelet. Ghosting and marine signature deconvolution processing is a prerequisite for assuring that the seismic wavelet on a marine CDP section will be zero phase. A deterministic approach to deconvolution is centered around the concept of abandoning the purely statistical method of wavelet estimation and actually measuring the seismic wavelet. A proper signature recording for marine data is, therefore, a crucial component of deterministic deconvolution. Another important element in the deterministic deconvolution sequence is the application of a deghosting filter to remove near‐surface reflections. Proper application of a deghosting filter significantly improves the correlation between log synthetics and the seismic trace. It has been found that statistical deconvolution schemes, because of the number of statistical hypotheses required to produce a deconvolution filter, produce residual wavelets that are highly variable in character and whose average phases cover the entire phase spectrum, modulo 2π. Examples of a Gulf Coast marine line which was shot with Aquapulse™, air gun, and Maxipulse™ sources by the RV Hollis Hedberg are presented to demonstrate the differences between statistical and deterministic deconvolution processing sequences. It will be shown, using sonic logs from wells adjacent to the seismic line, that the deterministic deconvolution sections for all three sources are close to zero phase while the statistical deconvolution sections have residual average phase errors between 180 and 270 degrees. The deterministic deconvolution sections have a high degree of correlation among themselves and to the wells adjacent to the line, while the statistical deconvolution sections correlate poorly to each other and to the wells. Synthetic seismograms and their impedance logs, and the seismic sections and their corresponding pseudo‐sonic logs, are used to demonstrate how deconvolution influences lithologic interpretation. ™Western Geophysics Co.

Synthetic seismic sections for acoustic, elastic, anisotropic, and vertically inhomogeneous layered media

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 710-735 ◽  
Author(s):  
F. Hron ◽  
B. T. May ◽  
J. D. Covey ◽  
P. F. Daley
Keyword(s):  
Three Dimensional ◽  
High Amplitude ◽  
Density Functions ◽  
Degree Of Anisotropy ◽  
First Arrival ◽  
Media Types ◽  
Time Distance ◽  
Converted Waves ◽  
Seismic Sections ◽  
Velocity Spectra

Synthetic seismic sections computed during forward modeling differ depending upon the type of media used to define the model. Four media types considered here are acoustic, elastic, elliptically anisotropic, and vertically inhomogeneous; significant differences are found among the seismic sections for these cases. Automatic ray generation, using kinematic and dynamic analog groups, permits retention and explicit identification of all significant arrivals, including primaries, multiples, converted waves, etc., for three‐dimensional, horizontally layered structures. Comparisons between arrivals common to the various models are shown by synthetic trace sections, amplitude‐distance plots, and velocity spectra. Results show significant energy in converted waves in the elastic models and marked differences between amplitude‐distance curves for elastic and acoustic cases. Anisotropic media produce noticeable differences in both amplitude‐ and time‐distance curves as a function of the degree of anisotropy. Modeling with vertically inhomogeneous media is practical and appealing because of how velocity and density functions are defined. Interestingly, a diving wave of high amplitude shown in our seismograms closely resembles the strong first arrival often present on field‐recorded seismograms.

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