Geologic interpretation of magnetic and gravity data in the Copper River Basin, Alaska

1964 ◽  
Author(s):  
G.E. Andreasoen ◽  
Arthur Grantz ◽  
Isidore Zietz ◽  
D.F. Barnes
Keyword(s):  
River Basin ◽  
Gravity Data ◽  
Geologic Interpretation

scholarly journals Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

2021 ◽  
Vol 11 (14) ◽  
pp. 6363
Author(s):  
Muhammad Noor Amin Zakariah ◽  
Norsyafina Roslan ◽  
Norasiah Sulaiman ◽  
Sean Cheong Heng Lee ◽  
Umar Hamzah ◽  
...  
Keyword(s):  
River Basin ◽  
Rock Type ◽  
Gravity Data ◽  
Power Spectral Analysis ◽  
Depth Estimation ◽  
Structural Features ◽  
Peninsular Malaysia ◽  
Gravity Survey ◽  
Basement Rock ◽  
Geophysical Techniques

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

scholarly journals Monitoring mass changes in the Volta River basin using GRACE satellite gravity and TRMM precipitation

2012 ◽  
Vol 18 (4) ◽  
pp. 549-563 ◽  
Author(s):  
Vagner G. Ferreira ◽  
Zheng Gong ◽  
Samuel A. Andam-Akorful
Keyword(s):  
River Basin ◽  
Gravity Data ◽  
West African ◽  
Rainfall Time Series ◽  
Tropical Rainfall Measurement Mission ◽  
Satellite Gravity ◽  
Rainfall Events ◽  
The North ◽  
Trmm Precipitation ◽  
Grace Satellite

GRACE satellite gravity data was used to estimate mass changes within the Volta River basin in West African for the period of January, 2005 to December, 2010. We also used the precipitation data from the Tropical Rainfall Measurement Mission (TRMM) to determine relative contributions source to the seasonal hydrological balance within the Volta River basin. We found out that the seasonal mass change tends to be detected by GRACE for periods from 1 month in the south to 4 months in the north of the basin after the rainfall events. The results suggested a significant gain in water storage in the basin at reference epoch 2007.5 and a dominant annual cycle for the period under consideration for both in the mass changes and rainfall time series. However, there was a low correlation between mass changes and rainfall implying that there must be other processes which cause mass changes without rainfall in the upstream of the Volta River basin.

On: “Diapiric Salt Volume Offshore Louisiana,” by T. R. LaFehr and Alan T. Herring (GEOPHYSICS, December 1971, p. 1205–1251)

Geophysics ◽  
1972 ◽  
Vol 37 (5) ◽  
pp. 907-907
Author(s):  
Lewis R. Tucker
Keyword(s):  
Gulf Of Mexico ◽  
Gravity Data ◽  
Large Family ◽  
Actual Knowledge ◽  
Geologic Interpretation ◽  
Calculated Quantity

In the interest of brevity, I will summarize the points I raised and the conclusions I drew in my somewhat extended correspondence with LaFehr and Herring concerning my objections to their paper. 1) Any geologic interpretation of gravity data includes a number of assumptions. 2) Of all these assumptions, the most tenuous one is that concerning a “regional.” 3) Once assumptions have been made, the answer is only the end result of an arithmetical exercise; the conclusion has been established already. 4) In the specific case of the calculated quantity of salt in the study area in the Gulf of Mexico, many of the “facts” that had to be included in the reduction of the data are actually assumptions that, through constant repetition, are now thought of as actual knowledge. 5) The conclusion in their paper as to the quantity of salt is only one of a large family of results, though it may be in the correct magnitude.

Geologic interpretation of magnetic data in the Copper River basin, Alaska

1960 ◽  
Author(s):  
Gordon E. Andreasen ◽  
Arthur Grantz ◽  
Isidore Zietz
Keyword(s):  
River Basin ◽  
Magnetic Data ◽  
Geologic Interpretation

Basin architecture and density structure beneath the Strait of Georgia, British Columbia

2003 ◽  
Vol 40 (7) ◽  
pp. 965-981 ◽  
Author(s):  
C Lowe ◽  
S A Dehler ◽  
B C Zelt
Keyword(s):  
Seismic Velocity ◽  
Gravity Data ◽  
Velocity Model ◽  
Seismic Structure ◽  
Strait Of Georgia ◽  
3 Dimensional ◽  
The North ◽  
Georgia Basin ◽  
Geologic Interpretation ◽  
Velocity Information

Georgia Basin is located within one of the most seismically active and populated areas on Canada's west coast. Over the last decade, geological investigations have resolved important details concerning the basin's shallow structure and composition. Yet, until recently, relatively little was known about deeper portions of the basin. In this study, new seismic velocity information is employed to develop a 3-dimensional density model of the basin. Comparison of the calculated gravity response of this model with the observed gravity field validates the velocity model at large scales. At smaller scales, several differences between model and observed gravity fields are recognized. Analysis of these differences and correlation with independent geoscience data provide new insights into the structure and composition of the basin-fill and underlying basement. Specifically, four regions with thick accumulations of unconsolidated Pleistocene and younger sediments, which were not resolved in the velocity model, are identified. Their delineation is particularly important for studies of seismic ground-motion amplification and offshore aggregate assessment. An inconsistency between the published geology and the seismic structure beneath Texada and Lasqueti Islands in the central Strait of Georgia is investigated; however, the available gravity data cannot preferentially validate either the geologic interpretation or the seismic model in this region. We interpret a northwest-trending and relatively linear gradient extending from Savory Island in the north to Boundary Bay in the south as the eastern margin of Wrangellia beneath the basin. Finally, we compare Georgia Basin with the Everett and Seattle basins in the southern Cascadia fore arc. This comparison indicates that while a single mechanism may be controlling present-day basin tectonics and deformation within the fore arc this was not the case for most of the Mesozoic and Tertiary time periods.

Edge enhancement of potential-field data using normalized statistics

Geophysics ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. H1-H4 ◽  
Author(s):  
Gordon R. J. Cooper ◽  
Duncan R. Cowan
Keyword(s):  
Standard Deviation ◽  
Potential Field ◽  
Field Data ◽  
Gravity Data ◽  
Edge Enhancement ◽  
Potential Field Data ◽  
Geologic Interpretation ◽  
Derivatives Of ◽  
High Pass ◽  
Detection Filter

Edge enhancement in potential-field data helps geologic interpretation. There are many methods for enhancing edges, most of which are high-pass filters based on the horizontal or vertical derivatives of the field. Normalized standard deviation (NSTD), a new edge-detection filter, is based on ratios of the windowed standard deviation of derivatives of the field. NSTD is demonstrated using aeromagnetic data from Australia and gravity data from South Africa. Compared with other filters, the NSTD filter produces more detailed results.

An integrated geophysical approach for imaging subbasalt sedimentary basins: Case study of Jam River Basin, India

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. B141-B147 ◽  
Author(s):  
V. Chakravarthi ◽  
G. B. K. Shankar ◽  
D. Muralidharan ◽  
T. Harinarayana ◽  
N. Sundararajan
Keyword(s):  
Gravity Field ◽  
River Basin ◽  
Gravity Data ◽  
Sedimentary Basins ◽  
Gravity Inversion ◽  
Data Points ◽  
3D Gravity ◽  
Regional Gravity ◽  
Godavari Basin

An integrated geophysical strategy comprising deep electrical resistivity and gravity data was devised to image subbasalt sedimentary basins. A 3D gravity inversion was used to determine the basement structure of the Permian sediments underlying the Cretaceous formation of the Jam River Basin in India. The thickness of the Cretaceous formation above the Permian sediments estimated from modeling 60 deep-electric-sounding data points agrees well with drilling information. The gravity effect of mass deficit between the Cretaceous and Permian formations was found using 3D forward modeling and subsequently removed from the Bouguer gravity anomaly along with the regional gravity field. The modified residual gravity field was then subjected to3D inversion to map the variations in depth of the basement beneath the Permian sediments. Inversion of gravity data resulted in two basement ridges, running almost east to west, dividing the basin into three independent depressions. It was found that the Katol and Kondhali faults were active even during post-Cretaceous time and were responsible for the development of the subsurface basement ridges in the basin. The inferred 3D basement configuration of the basin clearly brought out the listric nature of these two faults. Further, the extension of the Godavari Basin into the Deccan syneclise and the fact that the source-rock studies show the presence of hydrocarbons in the Sironcha block in the northern part of the Godavari Basin also shed some light on the hydrocarbon potential of the Jam River Basin.

scholarly journals Water Storage, Net Precipitation, and Evapotranspiration in the Mackenzie River Basin from October 2002 to September 2009 Inferred from GRACE Satellite Gravity Data

2011 ◽  
Vol 12 (3) ◽  
pp. 467-473 ◽  
Author(s):  
E. Morrow ◽  
J. X. Mitrovica ◽  
G. Fotopoulos
Keyword(s):  
River Basin ◽  
River Discharge ◽  
Linear Trend ◽  
Gravity Data ◽  
Water Storage ◽  
Model Errors ◽  
Satellite Gravity ◽  
Mackenzie River Basin ◽  
Grace Satellite ◽  
Mackenzie River

Abstract Gravity Recovery and Climate Experiment (GRACE) satellite gravity data are used to determine the variability of terrestrial water storage within the Mackenzie River basin from October 2002 to September 2009. During that period, it is estimated that there is no significant (7 yr) linear trend in the water storage after having accounted for postglacial rebound using the ICE-5G (VM2) ice sheet and Earth viscosity model. Errors in this model may alter this conclusion. The GRACE gravity data are also combined with precipitation and river discharge datasets to estimate trends in net precipitation and evapotranspiration in the basin. Net precipitation is seen to have a significant trend with a corresponding increase in river discharge. Evapotranspiration was found to be constant over the study period.

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