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Full-Text Articles in Physical Sciences and Mathematics
The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey Freymueller, James Kellogg
The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey Freymueller, James Kellogg
James N Kellogg
The CASA UNO Global Positioning System (GPS) experiment (January-February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400-1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day-to-day rms repeatabilities for the same …
Reply To Comment On "Subduction Of The Caribbean Plate And Basement Uplifts In The Overriding South American Plate", James Kellogg, William Bonini
Reply To Comment On "Subduction Of The Caribbean Plate And Basement Uplifts In The Overriding South American Plate", James Kellogg, William Bonini
James N Kellogg
No abstract provided.
Central And South America Gps Geodesy- Casa Uno, James Kellogg, Timothy Dixon
Central And South America Gps Geodesy- Casa Uno, James Kellogg, Timothy Dixon
James N Kellogg
In January 1988, scientists from over 25 organizations in 13 countries and territories cooperated in the largest Global Positioning System (GPS) campaign in the world to date (Table 1). 43 GPS receivers collected approximately 590 station-days of data in America, Samoa, Australia, Canada, Colombia, Costa Rica, Ecuador, New Zealand, Norway, Panama, Sweden, United States, West Germany, and Venezuela. The experiment was entitled CASA UNO, an acronym for Central and South America -- and uno is the Spanish word for one, designating first epoch measurements. The CASA UNO experiment was the first civilian effort implementing a global GPS satellite tracking network. …
A 3-D Gravity Tectonic Study Of Ita Mai Tai Guyot: An Uncompensated Seamount In The East Mariana Basin, Bruce Wedgeworth, James Kellogg
A 3-D Gravity Tectonic Study Of Ita Mai Tai Guyot: An Uncompensated Seamount In The East Mariana Basin, Bruce Wedgeworth, James Kellogg
James N Kellogg
Ita Mai Tai is a large, locally uncompensated seamount on the eastern edge of the East Mariana Basin. A large positive gravity anomaly of 254 mgal characterizes the summit and a low of -69 mgal, the surrounding moat. Using polygonal prisms to approximate the bathymetry, the observed gravity was inverted to calculate an average density of 2.59 g/ems for the seamount. Observed-calculated gravity residuals are reduced by including the flanking sedimentary basins and a dense volcanic conduit. The drill sites from DSDP Legs 20 and 89 describe a volcanic edifice formed in the Aptian!Albian on Jmassic/Cretaceous crust. The volcanism is …
Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James Kellogg
Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James Kellogg
James N Kellogg
Surface geology and seismic and well data from the northwestern flank of the Venezuelan Andes indicate overthrusting of Andean basement rocks toward the adjacent Maracaibo Basin along a blind thrust fault. The frontal monocline is interpreted as the forelimb of a northwestward verging fault-related fold deformed over a crustal-scarle map. The Andean block has been thrust 20 km to the northwest and uplifted 10 km on a ramp that dips about 20o-30o southeastward. The thrust fault ramps up through crystalline basement rocks to a decollement horizon within the shaly units of the Cretaceous Colon-Mito Juan formations. Backthrusts in the monocline …
First Gps Baseline Results From The North Andes, James Kellogg, Jeffrey Freymueller, Timothy Dixon, Ruth Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos
First Gps Baseline Results From The North Andes, James Kellogg, Jeffrey Freymueller, Timothy Dixon, Ruth Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos
James N Kellogg
The CASA UNO GPS (Global Positioning System) experiment (January-February 1988) has provided the first epoch baseline measurements for the study of plate motions and crustal deformation in and around the North Andes. Two dimensional horizontal baseline repeatabilities are as good as 5 parts in 108 for short baselines (100-1000km), and better than3 parts in 108 for long baselines (>1000km). Vertical repeatabilities are typically 4 -6 cm, with a weak dependence on baseline length. The expected rate of plate convergence across the Colombia Trench is 6-8 cm/yr, which should be detectable by the repeat experiment planned for 1991. …
Isostatic Compensation And Conduit Structures Of Western Pacific Seamounts: Results Of Three-Dimensional Gravity Modeling, James Kellogg, Bruce Wedgeworth, Jeffrey Freymueller
Isostatic Compensation And Conduit Structures Of Western Pacific Seamounts: Results Of Three-Dimensional Gravity Modeling, James Kellogg, Bruce Wedgeworth, Jeffrey Freymueller
James N Kellogg
Detailed three-dimensional polygonal prism models of two large western Pacific seamounts show that the 135 mgal difference in the observed sea surface gravity over the two can be best explained by similar mean densities (2.6 gjcm3) and crustal thickening under one seamount (Airy isostatic compensation). Observed calculated residuals are further reduced by including dense (2.9 gjcm3) vertical feeder pipes or volcanic conduits in the models. Dense conduits or fracture zones 5 to 17 km in diameter are located under many, if not all, craters on volcanic islands and seamounts. Results from the detailed seamount studies can be generalized using exact …
New Standards For Reducing Gravity Data: The North American Gravity Database, William Hinze, Carlos Aiken, John Brozena, Bernard Coakley, David Dater, Guy Flanagan, Rene Forsberg, Thomas Hildenbrand, G. Keller, James Kellogg, Robert Kucks, Xiong Li, Andre Mainville, Robert Morin, Mark Pilkington, Donald Plouff, Dhananjay Ravat, Daniel Roman, Jamie Urrutia-Fucugauchi, Marc Veronneau, Michael Webring, Daniel Winester
New Standards For Reducing Gravity Data: The North American Gravity Database, William Hinze, Carlos Aiken, John Brozena, Bernard Coakley, David Dater, Guy Flanagan, Rene Forsberg, Thomas Hildenbrand, G. Keller, James Kellogg, Robert Kucks, Xiong Li, Andre Mainville, Robert Morin, Mark Pilkington, Donald Plouff, Dhananjay Ravat, Daniel Roman, Jamie Urrutia-Fucugauchi, Marc Veronneau, Michael Webring, Daniel Winester
James N Kellogg
The North American gravity database as well as databases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revising procedures for calculating gravity anomalies, taking into account our enhanced computational power, improved terrain databases and datums, and increased interest in more accurately defining long-wavelength anomaly components. Users of the databases may note minor differences between previous and revised database values as a result of these procedures. Generally, the differences do not impact the interpretation of local anomalies but do improve regional anomaly studies. The most …