On: “Variable‐depth magnetization mapping: Application to the Athabasca basin, northern Alberta and Saskatchewan, Canada” by M. Pilkington (GEOPHYSICS, 54, 1164–1173, September 1989)

Geophysics ◽  
1991 ◽  
Vol 56 (2) ◽  
pp. 308-308
Author(s):  
Nelson C. Steenland
Keyword(s):  
Seismic Source ◽  
Topographic Effect ◽  
Magnetic Intensity ◽  
Variable Depth ◽  
The West ◽  
Athabasca Basin ◽  
Contour Interval ◽  
Magnetic Basement ◽  
Intensity Map ◽  
Northern Alberta

Apparent magnetizations calculated from magnetic intensity depend on Z, and Pilkington attempts to remove this variableness by annihilating the topographic effect with the convolution of a topographic set from a seismic source (One would have to consult his references for a description of the topographic set.) having a crude contour interval of 300 m where maximal values are 1500 m. Then there are no data given to show that this surface is the surface of a magnetic basement. The largest element, an outcropping dome in the west with no corresponding anomaly on the intensity map, is not magnetic basement.

On: “Variable‐depth magnetization mapping: Application to the Athabasca basin, northern Alberta and Saskatchewan, Canada” by Mark Pilkington (GEOPHYSICS, 54, 1164–1179, September 1989)

Geophysics ◽  
1990 ◽  
Vol 55 (12) ◽  
pp. 1652-1652
Author(s):  
R. Jerry Brod
Keyword(s):  
Field Data ◽  
Resolving Power ◽  
Rock Properties ◽  
Magnetic Data ◽  
Geologic Mapping ◽  
Total Field ◽  
Variable Depth ◽  
Athabasca Basin ◽  
Frequency Domain Approach ◽  
Northern Alberta

The thrust of Pilkington’s paper is that a frequency‐domain approach to variable‐depth magnetization mapping is superior to a space‐domain approach and has been “shown to improve the geologic mapping capability over total‐field data.” He states that “apparent susceptivility or magnetization‐mapping methods have proven useful in improving the resolving power of total‐field magnetic data, leading to a more precise delineation of geologic boundaries and providing a map of susceptibility‐magnetization levels that can be related directly to rock properties.” He accepts the premise that northern Saskatchewan can be divided into domains on the basis of structure and lithology and that these “lithostructural domains can be distinguished on the basis of aeromagnetic character.”

scholarly journals Aeromagnetic Mapping of Iwo Region of Southwestern Nigeria for Lithostructural Delineation

2019 ◽  
Vol 3 (2) ◽  
pp. 20-30
Author(s):  
C.C. Okpoli ◽  
D. Oludeyi
Keyword(s):  
Automatic Gain Control ◽  
Gain Control ◽  
Analytical Signal ◽  
Magnetic Intensity ◽  
Southwestern Part ◽  
Basement Complex ◽  
Southwestern Nigeria ◽  
Pan African ◽  
Intensity Map ◽  
Insight Into

AbstractThe IGRF filtered Aeromagnetic data over Iwo, southwestern part of Nigeria within the basement complex was subjected to reduction to magnetic equator filtering, residual filtering, upward and downward continuation filtering, automatic gain control filtering, tilt angle derivative, second vertical derivative, analytical signal and Euler deconvolution. This reveals the geologic information such as structural trend. Based on the result of the total magnetic intensity map, reduction to equator map, analytical signal map and residual magnetic intensity map, it can be concluded that; The rocks in the study area have a trend of approximately northeast-southwest direction as seen on the upward continuation map. Most of the delineated lineaments found within the study area strike mostly in NNE-SSW, NE-SW and NW-SE with minor trend of E-W and ENE-WSW direction. Structural lineament orientation suggested that they were products of Pan-African orogeny (NE-SW, NW-SE and NNE-SSW trends) and pre-Pan-African orogeny (NNW-SSE and E-W trend). The interpretation of the aeromagnetic dataset gave an insight into the regional geology and structural trends of the area.

scholarly journals Multi-Dimensional Inversion of Airborne Total Magnetic Intensity Data at the West-of-Edfu Region, Upper Egypt

2017 ◽  
Vol 05 (01) ◽  
pp. 01-13
Author(s):  
Karam. S. I. Farag ◽  
Ahmad H. M. Habeeb ◽  
Ali M. S. Abdelaziz ◽  
Sami H. Abd El Nabi
Keyword(s):  
Intensity Data ◽  
Magnetic Intensity ◽  
The West ◽  
Upper Egypt

scholarly journals Magnetic Modeling and Potential Hydrocarbon Trap Over Yola and Environs Upper Benue Trough Northeastern Nigeria

2020 ◽  
pp. 10-23
Author(s):  
Musa Hayatudeen ◽  
Nsikak Edet Bassey ◽  
Bello Rasaq
Keyword(s):  
Band Pass Filter ◽  
Magnetic Intensity ◽  
Aeromagnetic Data ◽  
Pass Filter ◽  
Benue Trough ◽  
Hydrocarbon Trap ◽  
Magnetic Modeling ◽  
Band Pass ◽  
Intensity Map ◽  
Oil Company

With a renewed interest to search for hydrocarbons in the hinter land of Nigeria’s inland basin climaxed after the discovery of a rewarding oil prospects around the Kolmani river II as recently announced by the National Oil Company, the Nigeria National Petroleum Corporation (NNPC). This research was based on analyzing the high-resolution aeromagnetic data over the study area using the Oasis Montaj TM software, in order to get the total magnetic intensity map as well as the residual map, band pass filter map was used to generate magnetic aureoles. GM-SYS module of the Oasis montaj was used for the modeling exercise, the models reveal the horst and graben architecture of the basement with the grabens serving as depocentres, hydrocarbon potentials of the area were highlighted using magnetic aureoles mapping.

scholarly journals Earthquake july 17, 2017, Mw = 7.8 near the Komandorsky islands and strong seismic manifestations in the western segment of Aleut island arc

2019 ◽  
pp. 52-66
Author(s):  
A. I. Lutikov ◽  
E. A. Rogozhin ◽  
G. Yu. Donzova ◽  
V. N. Zhukovez
Keyword(s):  
Seismic Moment ◽  
Main Shock ◽  
Seismic Source ◽  
Focal Mechanisms ◽  
Commander Islands ◽  
The West ◽  
Slow Increase ◽  
Commander Island ◽  
Western Segment ◽  
Tectonic Position

The tectonic position, seismological characteristics and features of the aftershock process of the source of the strongest Near-Aleutian earthquake on July 17, 2017 on the Commander Islands with Мw = 7.8 are considered. The analysis showed that the seismic source according to the distribution of aftershock epicenters in the form of a linearly elongated narrow zone with a length of about 400 km almost completely occupied the northern slope of the Commander island elevation and was located in the Bering fault zone. It covered the whole of this seismic-generating zone up to the transverse structure to the west of the Near Islands (Attu is.). In accordance with the focal mechanisms solution and the nature of the displacements in the foci of the main shock, the strongest foreshocks and aftershocks, the shift in the source was an almost pure right-sided shift. The aftershock process of the July 17 earthquake developed quite enough inertly for an earthquake of such strength. In addition, it has two features in comparison with the aftershock processes of most of the Kuril-Kamchatka earthquakes: 1) low release of the cumulative scalar seismic moment (M0cum aft), which according to various estimates was from 0.75% to 1.0% of the seismic moment of the main shock (M0me); 2) a very slow increase in the deficit in the release of the seismic moment (M0). At the same time, the duration of the quasi-stationary phase of M0cum release in aftershocks, estimated at about ½ year and covering a significant part of the duration of the entire aftershock process of this earthquake, seems unusually long. These features of the aftershock process of the Middle Aleutian earthquake on July 17, 2017 distinguish it from the aftershock processes characteristic of most strong Kuril-Kamchatka earthquakes. In general, its source can be considered as a transform between the two Benioff zones – Aleutian and Kuril-Kamchatka, and not subduction, that is characterise the last two.

Notes on the Horizontal Circulation of Ocean Currents

1956 ◽  
Vol 37 (3) ◽  
pp. 96-100 ◽  
Author(s):  
Gerhard Neumann
Keyword(s):  
Steady State ◽  
Simple Model ◽  
Atlantic Ocean ◽  
Oceanic Circulation ◽  
Variable Depth ◽  
The West ◽  
Steady State Current ◽  
Geographical Latitude ◽  
Horizontal Circulation ◽  
Current Systems

The effect of a variable depth of the wind driven oceanic circulation on the steady state current systems is discussed with the aid of a simple model. There is much evidence that in the Atlantic Ocean the depth of the layer of no motion increases poleward proportionally to the sine of the geographical latitude in both hemispheres. It seems not unlikely that the oceans react to the planetary vorticity effect in such a way that they rather tend to adjust the level of no motion than to displace the whole gyre of the wind driven circulation to the west.

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