An application for removing cultural noise from aeromagnetic data

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 213-219 ◽  
Author(s):  
Stefan Muszala ◽  
Paul L. Stoffa ◽  
L. A. Lawver
Keyword(s):  
Noise Suppression ◽  
Aeromagnetic Data ◽  
Aeromagnetic Survey ◽  
University Of Texas ◽  
Cultural Objects ◽  
The North ◽  
Automated Method ◽  
North Slope Of Alaska ◽  
The Many ◽  
Cultural Noise

A high‐resolution aeromagnetic survey collected over the North Slope of Alaska by World Geoscience was acquired in response to a need for highly detailed data in an area where traditional geophysical techniques are expensive and prohibitive (McConnell, 1995) (Figure 1). These data were recently released to the University of Texas’ Institute for Geophysics and provide a unique opportunity to investigate the problem of cultural noise suppression in aeromagnetic data. The data contain isolated magnetic anomalies that are presumably from the many drill platforms and their accompanying cultural objects such as buildings and pipe repositories (Figure 2). We present a new, automated method to reduce the amplitude of these cultural anomalies without affecting the magnetic signal from the surrounding geology.

The effects of cathodically protected pipelines on aeromagnetic surveys

Geophysics ◽  
1986 ◽  
Vol 51 (8) ◽  
pp. 1671-1684 ◽  
Author(s):  
S. Parker Gay
Keyword(s):  
Oil And Gas ◽  
Electrical Current ◽  
Magnetic Anomalies ◽  
Gas Production ◽  
Aeromagnetic Data ◽  
Aeromagnetic Survey ◽  
Oil And Gas Production ◽  
Tie Lines ◽  
Cultural Noise ◽  
Line Standard

Many types of cultural noise are found in present‐day high‐resolution aeromagnetic data, and such noise must be removed if surveys flown in areas of existing cultural features are to be interpreted properly—particularly areas of oil and gas production. One of the worst causes of cultural noise in such areas is the dc electrical current passed through pipelines to prevent corrosion. This practice is called “cathodic protection,” and it is in common use worldwide; however, there is little or no discussion of the resulting magnetic anomalies in the geophysical literature. Cathodically protected pipeline (CPP) anomalies are particularly troublesome at the level of airborne surveys because they fall off slowly as the first power of the distance, rather than as the square or cube of the distance as in most sources of random cultural noise. However, the curve shapes of CPP anomalies are readily calculable: they depend upon the strike directions of the pipeline and the aeromagnetic profile, and on the inclination and declination of the Earth’s magnetic field. The amplitude of CPP anomalies depends upon the height of the magnetometer above the pipeline and the strength of the current in the line. Standard curves were plotted for several CPP anomalies due to long, straight, horizontal pipelines, worldwide, and were used to verify the existence of CPP anomalies in production survey lines and tie lines for an aeromagnetic survey at the magnetic latitude of Oklahoma, USA.

A direct noise attenuation approach in processing of land continuous records

2021 ◽  
Vol 40 (4) ◽  
pp. 288-296
Author(s):  
Chengbo Li ◽  
Charles C. Mosher ◽  
Yu Zhang
Keyword(s):  
Noise Suppression ◽  
Noise Attenuation ◽  
Multiple Sources ◽  
Permian Basin ◽  
Fixed Length ◽  
The North ◽  
Excitation Time ◽  
North Slope Of Alaska ◽  
Source Excitation ◽  
Incoherent Noise

Blended source acquisition has drawn great attention in industry due to its increased efficiency and reduced overall cost for acquiring seismic data. It eliminates the requirement of a minimum time (usually determined by record length) between adjacent shots and allows multiple sources to be activated simultaneously and independently. Conventional processing simply converts continuous records into fixed-length records using the source excitation time and then applies traditional denoising techniques to the fixed-length records. Source excitation time is used to extract fixed-length records that are the equivalent of traditional synchronous recording. Here, we elaborate on the usage of continuous records for land noise attenuation. Compared to conventional common shot/receiver/midpoint/offset domains, continuous records represent the data in the naturally recorded domain. This domain offers flexible and much longer record lengths to work with and, moreover, enables exploiting the characteristics of noise prior to correlation, shot slicing, or other preprocessing. We limit our discussions to the techniques and methods for attenuating coherent environmental and source-generated noise on vibroseis data. We have found that incoherent noise can be handled effectively by traditional noise suppression methods after deblending. We illustrate the effectiveness of noise attenuation in the continuously recorded domain for three different types of noise using field examples from the North Slope of Alaska and the Permian Basin.

Dispersive noise removal in t-x space: Application to Arctic data

Geophysics ◽  
1988 ◽  
Vol 53 (3) ◽  
pp. 346-358 ◽  
Author(s):  
Greg Beresford‐Smith ◽  
Rolf N. Rango
Keyword(s):  
Signal To Noise Ratio ◽  
Noise Analysis ◽  
Noise Removal ◽  
North Slope ◽  
Frequency Bandwidth ◽  
The North ◽  
North Slope Of Alaska ◽  
Seismic Records ◽  
Time Offset ◽  
Undersampled Data

Strongly dispersive noise from surface waves can be attenuated on seismic records by Flexfil, a new prestack process which uses wavelet spreading rather than velocity as the criterion for noise discrimination. The process comprises three steps: trace‐by‐trace compression to collapse the noise to a narrow fan in time‐offset (t-x) space; muting of the noise in this narrow fan; and inverse compression to recompress the reflection signals. The process will work on spatially undersampled data. The compression is accomplished by a frequency‐domain, linear operator which is independent of trace offset. This operator is the basis of a robust method of dispersion estimation. A flexural ice wave occurs on data recorded on floating ice in the near offshore of the North Slope of Alaska. It is both highly dispersed and of broad frequency bandwidth. Application of Flexfil to these data can increase the signal‐to‐noise ratio up to 20 dB. A noise analysis obtained from a microspread record is ideal to use for dispersion estimation. Production seismic records can also be used for dispersion estimation, with less accurate results. The method applied to field data examples from Alaska demonstrates significant improvement in data quality, especially in the shallow section.

Coherent noise in marine seismic data

Geophysics ◽  
1983 ◽  
Vol 48 (7) ◽  
pp. 854-886 ◽  
Author(s):  
Ken Larner ◽  
Ron Chambers ◽  
Mai Yang ◽  
Walt Lynn ◽  
Willon Wai
Keyword(s):  
Seismic Data ◽  
Noise Suppression ◽  
Seismic Source ◽  
Coherent Noise ◽  
Critical Data ◽  
Predictive Deconvolution ◽  
Scattered Energy ◽  
Marine Seismic ◽  
The Many ◽  
Water Bottom

Despite significant advances in marine streamer design, seismic data are often plagued by coherent noise having approximately linear moveout across stacked sections. With an understanding of the characteristics that distinguish such noise from signal, we can decide which noise‐suppression techniques to use and at what stages to apply them in acquisition and processing. Three general mechanisms that might produce such noise patterns on stacked sections are examined: direct and trapped waves that propagate outward from the seismic source, cable motion caused by the tugging action of the boat and tail buoy, and scattered energy from irregularities in the water bottom and sub‐bottom. Depending upon the mechanism, entirely different noise patterns can be observed on shot profiles and common‐midpoint (CMP) gathers; these patterns can be diagnostic of the dominant mechanism in a given set of data. Field data from Canada and Alaska suggest that the dominant noise is from waves scattered within the shallow sub‐buttom. This type of noise, while not obvious on the shot records, is actually enhanced by CMP stacking. Moreover, this noise is not confined to marine data; it can be as strong as surface wave noise on stacked land seismic data as well. Of the many processing tools available, moveout filtering is best for suppressing the noise while preserving signal. Since the scattered noise does not exhibit a linear moveout pattern on CMP‐sorted gathers, moveout filtering must be applied either to traces within shot records and common‐receiver gathers or to stacked traces. Our data example demonstrates that although it is more costly, moveout filtering of the unstacked data is particularly effective because it conditions the data for the critical data‐dependent processing steps of predictive deconvolution and velocity analysis.

Review article: Reclaiming the rebellion: 1798 in 1998

1999 ◽  
Vol 31 (123) ◽  
pp. 395-410
Author(s):  
Ian McBride
Keyword(s):  
New York ◽  
Rural Communities ◽  
Review Article ◽  
Physical Force ◽  
Celtic Tiger ◽  
Men And Women ◽  
International Dimension ◽  
Good Friday ◽  
The North ◽  
The Many

Few Irish men and women can have escaped the mighty wave of anniversary fever which broke over the island in the spring of 1998. As if atoning for the failed rebellion itself, the bicentenary of 1798 was neither ill-coordinated nor localised, but a genuinely national phenomenon produced by years of planning and organisation. Emissaries were dispatched from Dublin and Belfast to remote rural communities, and the resonant names of Bartlett, Whelan, Keogh and Graham were heard throughout the land; indeed, the commemoration possessed an international dimension which stretched to Boston, New York, Toronto, Liverpool, London and Glasgow. In bicentenary Wexford — complete with ’98 Heritage Trail and ’98 Village — the values of democracy and pluralism were triumphantly proclaimed. When the time came, the north did not hesitate, but participated enthusiastically. Even the French arrived on cue, this time on bicycle. Just as the 1898 centenary, which contributed to the revitalisation of physical-force nationalism, has now become an established subject in its own right, future historians will surely scrutinise this mother of all anniversaries for evidence concerning the national pulse in the era of the Celtic Tiger and the Good Friday Agreement. In the meantime a survey of some of the many essay collections and monographs published during the bicentenary will permit us to hazard a few generalisations about the current direction of what might now be termed ‘Ninety-Eight Studies’.

scholarly journals Diocesan Licensing and Medical Practitioners in South-West England, 1660–1780

2004 ◽  
Vol 48 (1) ◽  
pp. 49-68 ◽  
Author(s):  
Ian Mortimer
Keyword(s):  
Early Modern ◽  
Specific Context ◽  
Medical Practitioners ◽  
Medical Expertise ◽  
North West ◽  
The North ◽  
Decentralized Trade ◽  
South West ◽  
The Many ◽  
South West England

The licensing of provincial surgeons and physicians in the post-Restoration period has proved an awkward subject for medical historians. It has divided writers between those who regard the possession of a local licence as a mark of professionalism or proficiency, those who see the existence of diocesan licences as a mark of an essentially unregulated and decentralized trade, and those who discount the distinction of licensing in assessing medical expertise availability in a given region. Such a diversity of interpretations has meant that the very descriptors by which practitioners were known to their contemporaries (and are referred to by historians) have become fragmented and difficult to use without a specific context. As David Harley has pointed out in his study of licensed physicians in the north-west of England, “historians often define eighteenth-century physicians as men with medical degrees, thus ignoring … the many licensed physicians throughout the country”. One could similarly draw attention to the inadequacy of the word “surgeon” to cover licensed and unlicensed practitioners, barber-surgeons, Company members in towns, self-taught practitioners using surgical manuals, and procedural specialists whose work came under the umbrella of surgery, such as bonesetters, midwives and phlebotomists. Although such fragmentation of meaning reflects a diversity of practices carried on under the same occupational descriptors in early modern England, the result is an imprecise historical literature in which the importance of licensing, and especially local licensing, is either ignored as a delimiter or viewed as an inaccurate gauge of medical proficiency.

Cloud Properties over the North Slope of Alaska: Identifying the Prevailing Meteorological Regimes

2012 ◽  
Vol 25 (23) ◽  
pp. 8238-8258 ◽  
Author(s):  
Johannes Mülmenstädt ◽  
Dan Lubin ◽  
Lynn M. Russell ◽  
Andrew M. Vogelmann
Keyword(s):  
Time Series ◽  
Climate Model ◽  
North Slope ◽  
Test Cases ◽  
Synoptic Scale ◽  
Long Time Series ◽  
The North ◽  
Cloud Properties ◽  
North Slope Of Alaska ◽  
Long Time

Abstract Long time series of Arctic atmospheric measurements are assembled into meteorological categories that can serve as test cases for climate model evaluation. The meteorological categories are established by applying an objective k-means clustering algorithm to 11 years of standard surface-meteorological observations collected from 1 January 2000 to 31 December 2010 at the North Slope of Alaska (NSA) site of the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM). Four meteorological categories emerge. These meteorological categories constitute the first classification by meteorological regime of a long time series of Arctic meteorological conditions. The synoptic-scale patterns associated with each category, which include well-known synoptic features such as the Aleutian low and Beaufort Sea high, are used to explain the conditions at the NSA site. Cloud properties, which are not used as inputs to the k-means clustering, are found to differ significantly between the regimes and are also well explained by the synoptic-scale influences in each regime. Since the data available at the ARM NSA site include a wealth of cloud observations, this classification is well suited for model–observation comparison studies. Each category comprises an ensemble of test cases covering a representative range in variables describing atmospheric structure, moisture content, and cloud properties. This classification is offered as a complement to standard case-study evaluation of climate model parameterizations, in which models are compared against limited realizations of the Earth–atmosphere system (e.g., from detailed aircraft measurements).

scholarly journals Ice processes and growth history on Arctic and sub-Arctic lakes using ERS-1 SAR data

Polar Record ◽  
1995 ◽  
Vol 31 (177) ◽  
pp. 115-128 ◽  
Author(s):  
K. Morris ◽  
M. O. Jeffries ◽  
W. F. Weeks
Keyword(s):  
Arctic Lakes ◽  
Polar Regions ◽  
Lake Ice ◽  
Sar Images ◽  
The North ◽  
Growth History ◽  
North Slope Of Alaska ◽  
Term Monitoring ◽  
Selection Of

AbstractA survey of ice growth and decay processes on a selection of shallow and deep sub-Arctic and Arctic lakes was conducted using radiometrically calibrated ERS-1 SAR images. Time series of radar backscatter data were compiled for selected sites on the lakes during the period of ice cover (September to June) for the years 1991–92 and 1992–93. A variety of lake-ice processes could be observed, and significant changes in backscatter occurred from the time of initial ice formation in autumn until the onset of the spring thaw. Backscatter also varied according to the location and depth of the lakes. The spatial and temporal changes in backscatter were most constant and predictable at the shallow lakes on the North Slope of Alaska. As a consequence, they represent the most promising sites for long-term monitoring and the detection of changes related to global warming and its effects on the polar regions.

Overburden geochemical signature of the Lac des Iles platinum group element deposit, northwestern Ontario, Canada

2007 ◽  
Vol 44 (8) ◽  
pp. 1151-1168 ◽  
Author(s):  
Peter J Barnett
Keyword(s):  
Mineral Exploration ◽  
Shallow Groundwater ◽  
Soil System ◽  
Near Surface ◽  
Rock Fragments ◽  
The North ◽  
Northwestern Ontario ◽  
Airborne Contamination ◽  
The Many ◽  
Lac Des Iles

Many previously published studies of the behaviour of Pt and Pd in till and soils have been done in areas of complex stratigraphy or very thin overburden cover, making the interpretation of soil results difficult because of the many variables associated with these settings. At the Lac des Iles mine site in northwestern Ontario, there are excellent exposures of the overburden in a series of exploration trenches. Glacial dispersal trains can be observed in till (C horizon) geochemistry (e.g., Ni, Cr, Cu, and Co). Regional geochemical dispersal trains of elements, such as Ni, Cr, Mg, and Co associated with the North Lac des Iles intrusion, can be detected for about 4 km beyond the western margin of the Mine Block intrusion. Entire dispersal trains range from 5 to 7 km in length and about 1 to 2 km in width. The dispersal of North Lac des Iles intrusion rock fragments tends to mask the response of the Mine Block intrusion. Dispersal trains of Pt and Pd are not well defined and tend to be very short, <1 km in length, due to the initial low concentrations of these elements in C-horizon till samples from the Lac Des Iles area. An exception to this is the Pd dispersal train originating from the high-grade zone that is up to 3 km long. Pd, Pt, Ni, and Cu appear to be moving both within and out of the soil system downslope into surface and shallow groundwater. It is suggested that these elements, to varying degrees, are moving in solution. Airborne contamination from mine operations of the humus has adversely affected the ability to determine the effectiveness of humus sampling for mineral exploration at Lac des Iles. The airborne contamination likely influences the geochemical results from surface water, shallow groundwater, and near-surface organic bog samples, particularly for the elements Pd and Pt.

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