Stratal slicing, Part I: Realistic 3-D seismic model

Geophysics ◽  
1998 ◽  
Vol 63 (2) ◽  
pp. 502-513 ◽  
Author(s):  
Hongliu Zeng ◽  
Milo M. Backus ◽  
Kenneth T. Barrow ◽  
Noel Tyler
Keyword(s):  
Seismic Data ◽  
Seismic Event ◽  
Necessary Condition ◽  
Single Event ◽  
Seismic Model ◽  
Geological Time ◽  
Depositional Facies ◽  
Impedance Boundary ◽  
Depositional Units ◽  
Seismic Models

Two‐dimensional, fenced 2-D, and 3-D isosurface displays of some realistic 3-D seismic models built in the lower Miocene Powderhorn Field, Calhoun County, Texas, demonstrate that a seismic event does not necessarily follow an impedance boundary defined by a geological time surface. Instead, the position of a filtered impedance boundary relative to the geological time surface may vary with seismic frequency because of inadequate resolution of seismic data and to the en echelon or ramp arrangement of impedance anomalies of sandstone. Except for some relatively time‐parallel seismic events, the correlation error of event picking is large enough to distort or even miss the majority of the target zone on stratal slices. In some cases, reflections from sandstone bodies in different depositional units interfere to form a single event and, in one instance, an event tying as many as six depositional units (interbedded sandy and shaly layers) over 50 m was observed. Frequency independence is a necessary condition for selecting time‐parallel reference events. Instead of event picking, phantom mapping between such reference events is a better technique for picking stratal slices, making it possible to map detailed depositional facies within reservoir sequences routinely and reliably from 3-D seismic data.

Methods of spectral analysis of seismic data

1964 ◽  
Vol 54 (4) ◽  
pp. 1213-1232
Author(s):  
I. K. McIvor
Keyword(s):  
Spectral Analysis ◽  
Fourier Analysis ◽  
Seismic Data ◽  
Seismic Event ◽  
Time Varying

Abstract Three different methods of spectral analysis are compared on the basis of a common interpretation in terms of time-varying Fourier analysis. The spectra obtained by these methods for a particular seismic event are given and differences in the results are resolved.

Rupture Process of the 2019 Ridgecrest, California Mw 6.4 Foreshock and Mw 7.1 Earthquake Constrained by Seismic and Geodetic Data

2020 ◽  
Vol 110 (4) ◽  
pp. 1603-1626 ◽  
Author(s):  
Kang Wang ◽  
Douglas S. Dreger ◽  
Elisa Tinti ◽  
Roland Bürgmann ◽  
Taka’aki Taira
Keyword(s):  
Seismic Data ◽  
Seismic Event ◽  
Rupture Process ◽  
Earthquake Sequence ◽  
Depth Range ◽  
Coseismic Slip ◽  
Eastern California Shear Zone ◽  
Garlock Fault ◽  
The One ◽  
Good Coverage

ABSTRACT The 2019 Ridgecrest earthquake sequence culminated in the largest seismic event in California since the 1999 Mw 7.1 Hector Mine earthquake. Here, we combine geodetic and seismic data to study the rupture process of both the 4 July Mw 6.4 foreshock and the 6 July Mw 7.1 mainshock. The results show that the Mw 6.4 foreshock rupture started on a northwest-striking right-lateral fault, and then continued on a southwest-striking fault with mainly left-lateral slip. Although most moment release during the Mw 6.4 foreshock was along the southwest-striking fault, slip on the northwest-striking fault seems to have played a more important role in triggering the Mw 7.1 mainshock that happened ∼34  hr later. Rupture of the Mw 7.1 mainshock was characterized by dominantly right-lateral slip on a series of overall northwest-striking fault strands, including the one that had already been activated during the nucleation of the Mw 6.4 foreshock. The maximum slip of the 2019 Ridgecrest earthquake was ∼5  m, located at a depth range of 3–8 km near the Mw 7.1 epicenter, corresponding to a shallow slip deficit of ∼20%–30%. Both the foreshock and mainshock had a relatively low-rupture velocity of ∼2  km/s, which is possibly related to the geometric complexity and immaturity of the eastern California shear zone faults. The 2019 Ridgecrest earthquake produced significant stress perturbations on nearby fault networks, especially along the Garlock fault segment immediately southwest of the 2019 Ridgecrest rupture, in which the coulomb stress increase was up to ∼0.5  MPa. Despite the good coverage of both geodetic and seismic observations, published coseismic slip models of the 2019 Ridgecrest earthquake sequence show large variations, which highlight the uncertainty of routinely performed earthquake rupture inversions and their interpretation for underlying rupture processes.

SEISMIC MODEL EXPERIMENTS WITH SHEAR WAVES

Geophysics ◽  
1959 ◽  
Vol 24 (1) ◽  
pp. 40-48 ◽  
Author(s):  
J. F. Evans
Keyword(s):  
Field Experiments ◽  
Shear Waves ◽  
High Amplitude ◽  
Homogeneous Layer ◽  
Small Scale ◽  
Seismic Model ◽  
Low Velocity ◽  
Model Experiments ◽  
Velocity Surface ◽  
Seismic Models

The experimental study of shear waves in the earth has been limited by the difficulty of producing them in sufficient strength. However, sensitive piezoelectric shear plates can now be made which enable experimentation with shear waves using small‐scale seismic models. Seismic model experiments serve to demonstrate the simplicity of SH‐shear wave reflections in a single homogeneous layer, the production of SH waves by an impulsive horizontal thrust, and the development of relatively high amplitude Love waves in a low‐velocity surface layer. The results of these model experiments with shear waves are in general agreement with and confirm theory. They also agree with the results of field experiments in the scattered cases for which comparison is available.

3-D coherency filtering

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1310-1314 ◽  
Author(s):  
Qing Li ◽  
Kris Vasudevan ◽  
Frederick A. Cook
Keyword(s):  
Seismic Data ◽  
Seismic Event ◽  
Signal To Noise Ratio ◽  
Random Noise ◽  
Three Dimensions ◽  
Coherent Noise ◽  
Coherent Signal ◽  
Frequency Space ◽  
Time Space ◽  
Incoherent Noise

Coherency filtering is a tool used commonly in 2-D seismic processing to isolate desired events from noisy data. It assumes that phase‐coherent signal can be separated from background incoherent noise on the basis of coherency estimates, and coherent noise from coherent signal on the basis of different dips. It is achieved by searching for the maximum coherence direction for each data point of a seismic event and enhancing the event along this direction through stacking; it suppresses the incoherent events along other directions. Foundations for a 2-D coherency filtering algorithm were laid out by several researchers (Neidell and Taner, 1971; McMechan, 1983; Leven and Roy‐Chowdhury, 1984; Kong et al., 1985; Milkereit and Spencer, 1989). Milkereit and Spencer (1989) have applied 2-D coherency filtering successfully to 2-D deep crustal seismic data for the improvement of visualization and interpretation. Work on random noise attenuation using frequency‐space or time‐space prediction filters both in two or three dimensions to increase the signal‐to‐noise ratio of the data can be found in geophysical literature (Canales, 1984; Hornbostel, 1991; Abma and Claerbout, 1995).

Time-lapse seismic analysis of overburden water injection at the Ekofisk field, southern North Sea

Geophysics ◽  
2020 ◽  
Vol 85 (1) ◽  
pp. B9-B21
Author(s):  
Filipe Borges ◽  
Martin Landrø ◽  
Kenneth Duffaut
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Seismic Event ◽  
Seismic Analysis ◽  
Water Injection ◽  
Time Lapse ◽  
Reservoir Compaction ◽  
Southern North Sea ◽  
Stress Changes ◽  
Before And After

On 7 May 2001, a seismic event occurred in the southern North Sea in the vicinity of the Ekofisk platform area. Analysis of seismological recordings of this event indicated that the epicenter is likely within the northern part of the field and its hypocenter lies in the shallow sedimentary layer. Further investigation in this same area revealed a small seabed uplift and identified an unintentional water injection in the overburden. The injection presumably caused the seabed uplift in addition to stress changes in the overburden. To better understand the consequences of this water injection, we analyze marine seismic data acquired before and after the seismological event. The 4D analysis reveals a clear traveltime shift close to the injection well, as well as a weak amplitude difference. We find that these measured time shifts correspond reasonably well with modeled time shifts based on a simple geomechanical model. The modeling also correlates well with the observed bathymetry changes at the seabed and with global positioning system measurements at the platforms. Although no explicit amplitude sign of the seismic event could be detected in the seismic data, the modeled stress changes, combined with the effect of decades of production-induced reservoir compaction, suggest a source mechanism for the far-field seismological recordings of the May 7th event.

Development of a Pipeline Post Seismic Response Screening Process

2018 ◽  
Author(s):  
David J. Warman ◽  
David Z. Kendrick ◽  
John D. Mackenzie
Keyword(s):  
Seismic Event ◽  
General Procedure ◽  
Buried Pipelines ◽  
Screening Process ◽  
Design Basis ◽  
Threat Categories ◽  
Von Mises ◽  
Seismic Models ◽  
Seismic Magnitude ◽  
High Threat

US pipeline operators may receive USGS automated earthquake notifications. In most of these cases, the seismic event poses little threat to pipeline assets. However, until an analysis is performed there can be uncertainty as to when and what actions should be taken. The paper describes the development and implementation of a simplified screening process to assess the effects of seismic events on buried pipelines. A design basis was established based on a literature review of seismic models, seismic-pipeline interactions, von Mises equivalent pipeline stress limits, standards, regulations, and practices that are currently used to assess seismic effects on buried pipelines. This design basis was used to develop a screening tool that provides a simple “pass/no pass” determination and is based on the readily obtained attributes (seismic magnitude and pipeline distance from the earthquake epicenter). “No Pass” scenarios are sub-divided into medium or high threat categories, with the latter likely needing to be evaluated on a more detailed basis. General guidelines and charts have been developed and incorporated into a general procedure to assess when and what actions should be taken.

STATISTICALLY OPTIMAL STACKING OF SEISMIC DATA

Geophysics ◽  
1970 ◽  
Vol 35 (3) ◽  
pp. 436-446 ◽  
Author(s):  
John C. Robinson
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Mean Value ◽  
Seismic Model ◽  
Seismic Record ◽  
Signal To Noise ◽  
Statistical Procedures ◽  
Common Depth Point ◽  
Noise Energy ◽  
Seismic Records

A theory for weighting seismic records in the stacking process has been developed from a statistical seismic model. The model applies to common‐depth‐point seismic records which have been statically and dynamically corrected; the same model applies to an ordinary stacking procedure. The model stipulates for the signal and noise components, respectively, of a seismic record that (1) the signal is coincident with and similarly shaped to the signal on other records, and (2) the noise is statistically independent of that on any other record and of the signal and has zero mean value. In accord with the model, a seismic record is completely described for the purpose of weighting by its signal scale and its signal‐to‐noise energy ratio. Several statistical procedures for evaluating these parameters for seismic field data are presented. The most favorable procedure is demonstrated with both synthetic and field seismic records.

Interpretive advantages of 90°-phase wavelets: Part 1 — Modeling

Geophysics ◽  
2005 ◽  
Vol 70 (3) ◽  
pp. C7-C15 ◽  
Author(s):  
Hongliu Zeng ◽  
Milo M. Backus
Keyword(s):  
Seismic Data ◽  
High Frequency ◽  
Thick Layer ◽  
Amplitude Data ◽  
Frequency Components ◽  
Wireline Logs ◽  
Phase Data ◽  
Dual Polarity ◽  
Seismic Models ◽  
Zero Phase

We discuss, in a two-part article, the benefits of 90°-phase wavelets in stratigraphic and lithologic interpretation of seismically thin beds. In Part 1, seismic models of Ricker wavelets with selected phases are constructed to assess interpretability of composite waveforms in increasingly complex geologic settings. Although superior for single surface and thick-layer interpretation, zero-phase seismic data are not optimal for interpreting beds thinner than a wavelength because their antisymmetric thin-bed responses tie to the reflectivity series rather than to impedance logs. Nonsymmetrical wavelets (e.g., minimum-phase wavelets) are generally not recommended for interpretation because their asymmetric composite waveforms have large side lobes. Integrated zero-phase traces are also less desirable because they lose high-frequency components in the integration process. However, the application of 90°-phase data consistently improves seismic interpretability. The unique symmetry of 90°-phase thin-bed response eliminates the dual polarity of thin-bed responses, resulting in better imagery of thin-bed geometry, impedance profiles, lithology, and stratigraphy. Less amplitude distortion and less stratigraphy-independent, thin-bed interference lead to more accurate acoustic impedance estimation from amplitude data and a better tie of seismic traces to lithology-indicative wireline logs. Field data applications are presented in part 2 of this article.

Sign in / Sign up

Export Citation Format

Share Document