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Articles 241 - 270 of 275

Full-Text Articles in Earth Sciences

Methods And Models For Estimating Advective Pore Water Exchange In Tidal Flats, Timothy J. Shaw Jan 2003

Methods And Models For Estimating Advective Pore Water Exchange In Tidal Flats, Timothy J. Shaw

Faculty Publications

No abstract provided.

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Volcanic Mound Fields On The East Pacific Rise, 16˚-19˚S: Low Effusion Rate Eruptions At Overlapping Spreading Centers For The Past 1 Myr, Scott M. White, Ken C. Macdonald, John Sinton Oct 2002

Volcanic Mound Fields On The East Pacific Rise, 16˚-19˚S: Low Effusion Rate Eruptions At Overlapping Spreading Centers For The Past 1 Myr, Scott M. White, Ken C. Macdonald, John Sinton

Faculty Publications

Volcanic mound fields identified on SeaMARC II and HMR1 12 kHz side-scan data from the southern East Pacific Rise (SEPR) occur near overlapping spreading centers (OSCs) and migration traces of OSCs. The volcanic mound fields appear as a distinctive hummocky seafloor fabric due to side-scan backscatter reflections from clusters of moundshaped reflectors. The lack of growth of the mound fields away from the ridge axis, and their occurrence in association with OSC traces, suggests that mound fields form along the ridge crest near OSCs. Volcanic mound fields are found where 120 kHz side-scan and visual observations find fields of pillow …

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Seismic Experiments Target Earthquake-Prone Region In Romania, F Hauser, C Prodehl, M Landes, A Bala, V Raileanu, J Bribach, James H. Knapp, Camelia C. Diaconescu, C Dinu, V Mocanu, W Fielitz, S Harder, G. Randy Keller, E Hegedues, R A. Stephenson Oct 2002

Seismic Experiments Target Earthquake-Prone Region In Romania, F Hauser, C Prodehl, M Landes, A Bala, V Raileanu, J Bribach, James H. Knapp, Camelia C. Diaconescu, C Dinu, V Mocanu, W Fielitz, S Harder, G. Randy Keller, E Hegedues, R A. Stephenson

Faculty Publications

No abstract provided.

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Correlation Between Volcanic And Tectonic Segmentation Of Fast-Spreading Ridges: Evidence From Volcanic Structures And Lava Flow Morphology On The East Pacific Rise At 9˚-10˚N, Scott M. White, Rachel M. Haymon, D J. Fornari, Michael R. Perfit, Ken C. Macdonald Aug 2002

Correlation Between Volcanic And Tectonic Segmentation Of Fast-Spreading Ridges: Evidence From Volcanic Structures And Lava Flow Morphology On The East Pacific Rise At 9˚-10˚N, Scott M. White, Rachel M. Haymon, D J. Fornari, Michael R. Perfit, Ken C. Macdonald

Faculty Publications

Combined analyses of volcanic features in DSL-120 sonar data and Argo I images along the ridge crest of the East Pacific Rise, 9_090–540N reveal a consistent decrease in inferred lava effusion rate toward the ends of third-order segments. The correlation of tectonic segmentation and volcanic style suggests that third-order segmentation corresponds to the volcanic segmentation of the ridge. Along-axis changes in volcanic structures (from collapse troughs to basaltic lava domes) and lava morphology (from sheet to pillow flows) coincide with the boundaries of morphologically defined third order tectonic segments of the ridge crest visible in shipboard multibeam bathymetry. Pillow lava …

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Volcanic Eruptions On Mid-Ocean Ridges: New Evidence From The Superfast Spreading East Pacific Rise, 17˚-19˚S, John Sinton, Eric Bergmanis, Ken Rubin, Rodey Batiza, Tracy K P Gregg, Karl Gronvold, Ken C. Macdonald, Scott M. White Jun 2002

Volcanic Eruptions On Mid-Ocean Ridges: New Evidence From The Superfast Spreading East Pacific Rise, 17˚-19˚S, John Sinton, Eric Bergmanis, Ken Rubin, Rodey Batiza, Tracy K P Gregg, Karl Gronvold, Ken C. Macdonald, Scott M. White

Faculty Publications

Side-scan sonar, submersible observations and sampling of lava flows from the East Pacific Rise, 17_–19_S constrain the character and variability of submarine volcanic eruptions along mid-ocean ridges. Nine separate lava sequences were mapped using relative age and lithological contrasts among recovered samples. Axial lengths activated during eruptive episodes range from _1 to >18 km; individual flow field areas vary from <1 to >19 km2. Estimated erupted volumes range from <1 to >200 _ 106 m3. The largest unit is the chemically uniform Animal Farm lava near 18_370S. The youngest lava is the Aldo-Kihi flow field, 17_240–340S, probably erupted in the early 1990s from a …

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Geochemistry Of Atmospheric Aerosols Generated From Lava-Seawater Interactions, Francis J. Sansone, Claudia R. Benitez-Nelson, Joseph A. Resing, Eric H. Decarlo, Sue M. Vink, Jacqueline A. Heath, Barry J. Huebert May 2002

Geochemistry Of Atmospheric Aerosols Generated From Lava-Seawater Interactions, Francis J. Sansone, Claudia R. Benitez-Nelson, Joseph A. Resing, Eric H. Decarlo, Sue M. Vink, Jacqueline A. Heath, Barry J. Huebert

Faculty Publications

[1] Trace elements were measured in the aerosol plume produced by lava‐seawater interactions along the shoreline of Kilauea volcano, Hawaii. Plume concentrations were normalized relative to Hawaiian basalt composition and showed a linear log‐log co‐variation with their emanation coefficient (an indicator of element volatility). Normalized aerosol concentrations also consistently covaried with corresponding normalized concentrations in dilute fumarolic gas from Kilauea volcano and fumarolic gas condensates from Kudryavy and Merapi volcanoes, despite different mechanisms of element volatilization. Conservatively estimated regional ocean deposition rates of Cu, Cd, Ni, Pb, Mn, Zn, Fe and P were >50 times background rates. Thus, upper ocean …

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Crustal Fissuring On The Crest Of The Southern East Pacific Rise At 17˚15'-40'S, Dawn J. Wright, Rachel M. Haymon, Scott M. White, Ken C. Macdonald Jan 2002

Crustal Fissuring On The Crest Of The Southern East Pacific Rise At 17˚15'-40'S, Dawn J. Wright, Rachel M. Haymon, Scott M. White, Ken C. Macdonald

Faculty Publications

Fissure densities and widths have been mapped along the axial zone of the superfast spreading southern East Pacific Rise (EPR) at 17_150–400S with the near-bottom DSL-120 and Argo II imaging systems. We observe that the youngest lava flows (on a relative age scale) are sparsely fissured and that there is a cumulative increase in fissure abundance with time that produces a strong positive correlation between fissure density and relative age of lava flows. Average fissure widths were used to estimate fissure depths. In the 17_150–400S area, calculated fissure depths are estimated to extend below the seismic layer 2A/2B boundary, and …

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Role Of A Phase: Change Moho In Stabilization And Preservation Of The Southern Uralide Orogen, Russia, Camelia C. Diaconescu, James H. Knapp Jan 2002

Role Of A Phase: Change Moho In Stabilization And Preservation Of The Southern Uralide Orogen, Russia, Camelia C. Diaconescu, James H. Knapp

Faculty Publications

Geophysical (URSEIS experiment) and geological data from the Southern Uralides of central Russia provide the basis for a geodynamic model involving eclogitization of the Uralian crustal root in Late Triassic to Early Jurassic time as a mechanism for stabilization and preservation of this Paleozoic orogen. The crustal structure of the orogen implies eastward subduction of the East European continental crust, and balanced restoration implies a significant volume of crust (comprised of ~70% European crust, and ~30% accreted terranes) was carried to sub-Moho depths of up to 70 km. The lack of a clearly defined near-vertical incidence reflection Moho corroborated by …

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Validation Of Land Surface Models Using Satellite-Derived Surface Temperature, Joshua Rhoads, Ralph Dubayah, Dennis Lettenmaier, Greg O'Donnell, Venkataraman Lakshmi Sep 2001

Validation Of Land Surface Models Using Satellite-Derived Surface Temperature, Joshua Rhoads, Ralph Dubayah, Dennis Lettenmaier, Greg O'Donnell, Venkataraman Lakshmi

Faculty Publications

This research examines the feasibility of using remotely sensed surface temperature for validation and updating of land surface hydrologic models. Surface temperature simulated by the Variable Infiltration Capacity (VIC) hydrologie model is compared over the Arkansas-Red River basin with surface temperature retrievals from TOVS and GOES. The results show that modeled and satellite-derived surface temperatures agree well when aggregated in space or time. In particular, monthly mean temperatures agree on the pixel scale, and basin mean temperatures agree instantaneously. At the pixel scale, however, surface temperatures from both satellites were found to have higher spatial and temporal variabilities than the …

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Controls On Floc Size In A Continental Shelf Bottom Boundary Layer, Paul S. Hill, George Voulgaris, John H. Trowbridge May 2001

Controls On Floc Size In A Continental Shelf Bottom Boundary Layer, Paul S. Hill, George Voulgaris, John H. Trowbridge

Faculty Publications

Simultaneous in situ observations of floc size, waves, and currents in a continental shelf bottom boundary layer do not support generally accepted functional relationships between turbulence and floc size in the sea. In September and October 1996 and January 1997, two tripods were deployed in 70 m of water on the continental shelf south of Woods Hole, Massachusetts. On one a camera photographed particles in suspension 1.2 m above the bottom that had equivalent circular diameters larger than 250 um, and on the other, three horizontally displaced acoustic current meters measured flow velocity 0.35 m above the bottom. The …

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A Simple Surface Temperature Assimilation Scheme For Use In Land Surface Models, Venkataraman Lakshmi Dec 2000

A Simple Surface Temperature Assimilation Scheme For Use In Land Surface Models, Venkataraman Lakshmi

Faculty Publications

This paper examines the utilization of surface temperature as a variable which can be assimilated in off-line land surface hydrological models. The connection between the surface temperature and evapotranspiration is utilized in making adjustments to the model-computed surface soil moisture. This adjustment is a function of the difference between the model-computed and the observed surface temperature. Comparisons between the model-computed and satellite-observed surface temperatures have been carried out. The assimilation of surface temperature is carried out twice a day (corresponding to the A.M. and P.M. overpass of the NOAA 10) over the Red-Arkansas basin in the southwestern United States (31°50′N-36°N, …

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Basaltic Lava Domes, Lava Lakes, And Volcanic Segmentation On The Southern East Pacific Rise, Scott M. White, Ken C. Macdonald, Rachel M. Haymon Oct 2000

Basaltic Lava Domes, Lava Lakes, And Volcanic Segmentation On The Southern East Pacific Rise, Scott M. White, Ken C. Macdonald, Rachel M. Haymon

Faculty Publications

Meter-scale DSL-120 sonar mapping and coregistered Argo II photographic observations reveal changes in eruptive style that closely follow the third-order structural segmentation of the ridge axis on the southern East Pacific Rise, 17o11'-18o37'S. Near segment ends we observe abundant basaltic lava domes which average 20 rn in height and 200 rn in basal diameter and have pillow lava as the dominant lava morphology. The ubiquity of pillow lava suggests low effusion rate eruptions. The abundance of lava domes suggests that the fissure eruptions were of sufficient duration to focus and produce a line of volcanic edifices. …

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Comparison Of Tovs-Derived Land Surface Variables With Ground Observations, Venkataraman Lakshmi, Joel Susskind Jan 2000

Comparison Of Tovs-Derived Land Surface Variables With Ground Observations, Venkataraman Lakshmi, Joel Susskind

Faculty Publications

The Tiros Operational Vertical Sounder (TOVS) Pathfinder Path A retrieved surface skin temperature, surface air temperatures, and surface specific humidity are compared with data obtained from three large-scale field campaigns: the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE), the Hydrologic Atmospheric Pilot Experiment (HAPEX) in the Sahel, and the Boreal Ecosystem-Atmosphere Study (BOREAS). The long-term estimates of surface skin temperatures, surface air temperatures, and surface vapor pressure were unbiased, and the standard deviations of the errors were about 4°C, 3.5°C, and 3.5 mbar, respectively. The monthly mean variables obtained from the TOVS data at four times …

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Distribution Of Isolated Volcanoes On The Flanks Of The East Pacific Rise, 15.3°-20°S, Scott M. White, Ken C. Macdonald, Daniel S. Scheirer, Marie-Helene Cormier Dec 1998

Distribution Of Isolated Volcanoes On The Flanks Of The East Pacific Rise, 15.3°-20°S, Scott M. White, Ken C. Macdonald, Daniel S. Scheirer, Marie-Helene Cormier

Faculty Publications

Volcanic constructions, not associated with seamount (or volcano) chains, are abundant on the flanks of the East Pacific Rise (EPR) but are rare along the axial high. The distribution of isolated volcanoes, based on multibeam bathymetric maps, is approximately symmetric about the EPR axis. This symmetry contrasts with the asymmetries in the distribution of volcano chains (more abundant on the west flank), the seafloor subsidence rates (slower on the west flank), and the distribution of plate-motion-parallel gravity lineaments (more prominento nthe west flank). Most of the isolated volcanoes complete their growth within -14 km of the axis on crust younger …

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Chemical Signals From Submarine Fluid Advection Onto The Continental Shelf, W. S. Moore, Timothy J. Shaw Sep 1998

Chemical Signals From Submarine Fluid Advection Onto The Continental Shelf, W. S. Moore, Timothy J. Shaw

Faculty Publications

No abstract provided.

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Precambrian Moho Offset And Tectonic Stability Of The East European Platform From The Urseis Deep Seismic Profile, Camelia C. Diaconescu, James H. Knapp, Larry D. Brown, David N. Steer, Manfred Stiller Mar 1998

Precambrian Moho Offset And Tectonic Stability Of The East European Platform From The Urseis Deep Seismic Profile, Camelia C. Diaconescu, James H. Knapp, Larry D. Brown, David N. Steer, Manfred Stiller

Faculty Publications

Deep seismic reflection data from the 1995 Urals Seismic Experiment and Integrated Studies (URSEIS) transect of the Southern Urals document a distinct ∼5 km vertical offset of the Moho beneath the Uralian foreland, here named the Makarovo fault zone. This offset does not disrupt the overlying Riphean sedimentary section, nor does it correlate with any major surface lineaments or known Phanerozoic subduction features. It is thus interpreted to be an Archean or Early Proterozoic fault zone (possibly a terrane boundary) that disrupts an even older Moho. Most important is the implication that this structure and the Moho it offsets were …

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Evaluation Of The Acoustic Doppler Velocimeter (Adv) For Turbulence Measurements, George Voulgaris, John H. Trowbridge Jan 1998

Evaluation Of The Acoustic Doppler Velocimeter (Adv) For Turbulence Measurements, George Voulgaris, John H. Trowbridge

Faculty Publications

Accuracy of the acoustic Doppler velocimeter (ADV) is evaluated in this paper. Simultaneous measurements of open-channel flow were undertaken in a 17-m flume using an ADV and a laser Doppler velocimeter. Flow velocity records obtained by both instruments are used for estimating the true (‘‘ground truth’’) flow characteristics and the noise variances encountered during the experimental runs. The measured values are compared with estimates of the true flow characteristics and values of variance (^u92&, ^w92&) and covariance (^u9w9&) predicted by semiempirical models for open-channel flow. The analysis showed that the ADV sensor can measure mean velocity and Reynolds stress within …

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Evaluation Of Special Sensor Microwave/Imager Satellite Data For Regional Soil Moisture Estimation Over The Red River Basin, Venkataraman Lakshmi, Eric F. Wood, Bhaskar J. Choudhury Oct 1997

Evaluation Of Special Sensor Microwave/Imager Satellite Data For Regional Soil Moisture Estimation Over The Red River Basin, Venkataraman Lakshmi, Eric F. Wood, Bhaskar J. Choudhury

Faculty Publications

Regional-scale estimation of soil moisture using in situ field observations is not possible due to problemswith the representativeness of the sampling and costs. Remotely sensed satellite data are helpful in this regard.Here, the simulations of 19- and 37-GHz vertical and horizontal polarization brightness temperatures and estimationof soil moistures using data from the Special Sensor Microwave/Imager (SSM/I) for 798 0.258 3 0.258boxes in the southwestern plains region of the United States for the time period between 1 August 1987 and31 July 1988 are presented. A coupled land-canopy–atmosphere model is used for simulating the brightnesstemperatures. The land-surface hydrology is modeled using a …

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A Soil-Canopy-Atmosphere Model For Use In Satellite Microwave Remote Sensing, Venkataraman Lakshmi, Eric F. Wood, Bhaskar J. Choudhury Mar 1997

A Soil-Canopy-Atmosphere Model For Use In Satellite Microwave Remote Sensing, Venkataraman Lakshmi, Eric F. Wood, Bhaskar J. Choudhury

Faculty Publications

Regional and global scale studies of land-surface-atmosphere interactions require the use of observations for calibration and validation. In situ field observations are not representative of the distributed nature of land surface characteristics, and large-scale field experiments are expensive undertakings. In light of these requirements and shortcomings, satellite observations serve our purposes adequately. The use of satellite data in land surface modeling requires developing a hydrological model with a thin upper layer to be compatible with the nature of the satellite observations and that would evaluate the soil moisture and soil temperature of a thin layer close to the surface. This …

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The Implications Of Turbidite-Driven Redox Changes In Sediments Of The Iberia Abyssal Plain, Timothy J. Shaw, P. A. Meyers Jan 1996

The Implications Of Turbidite-Driven Redox Changes In Sediments Of The Iberia Abyssal Plain, Timothy J. Shaw, P. A. Meyers

Faculty Publications

No abstract provided.

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Organic Matter Accumulation, Sulfate Reduction, And Methanogenesis In Pliocene–Pleistocene Turbidites On The Iberia Abyssal Plain, P. A. Meyers, Timothy J. Shaw Jan 1996

Organic Matter Accumulation, Sulfate Reduction, And Methanogenesis In Pliocene–Pleistocene Turbidites On The Iberia Abyssal Plain, P. A. Meyers, Timothy J. Shaw

Faculty Publications

No abstract provided.

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Seismogeological Features Of The Crust In Romania, V Mocanu, C Dinu, F Radulescu, M Diaconescu, Camelia C. Diaconescu, A Pompilian Jan 1996

Seismogeological Features Of The Crust In Romania, V Mocanu, C Dinu, F Radulescu, M Diaconescu, Camelia C. Diaconescu, A Pompilian

Faculty Publications

The Romanian area consists of old consolidated units of pre-Alpine age (the Moesian, Moldavian and Scythian platforms) and Alpine orogenic units (the Carpathian arc and North-Dobrudjan orogen). General seismogeological peculiarities of the pre-Alpine tectonic units are presented, as well as some structural characteristics of the Transylvanian Basin and the Pannonian Depression. Both shallow and deep seismic reflection/refraction data as well as log information and some potential field data were used for the investigation of the crustal structure. The varibility in the seismogeological pattern and crustal thickness shown by the different tectonic units is due to the differences in structure and …

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Tectonic Development Of Panama, Costa Rica, And The Colombian Andes: Constraints From Global Positioning System Geodetic Studies And Gravity, James N. Kellogg, Victor Vega Jan 1995

Tectonic Development Of Panama, Costa Rica, And The Colombian Andes: Constraints From Global Positioning System Geodetic Studies And Gravity, James N. Kellogg, Victor Vega

Faculty Publications

Global Positioning System (GPS) measurements suggest the existence of a rigid Panama- Costa Rica microplate that is moving northward relative to the stable Caribbean Plate. Northward motion of South America relative to the Caribbean plate is independently suggested by the April 1991 Costa Rica earthquake, active folding in the North Panama deformed belt, and a south-dipping Wadati-Benioff zone beneath Panama. Panama may also be continuing to collide eastward with the northern Andes. Rapid subduction is occurring at the Middle America (72mm/yr), Ecuador (70mm/yr), and Colombia (50mm/yr) trenches. The northern Andes are moving northeastward relative to stable South America. Preliminary GPS …

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Plate Motions In The North Andean Region, Jeffrey T. Freymueller, James N. Kellogg, Victor Vega Dec 1993

Plate Motions In The North Andean Region, Jeffrey T. Freymueller, James N. Kellogg, Victor Vega

Faculty Publications

Repeated geodetic measurements with the Global Positioning System (GPS) provide direct measurements of displacements due to plate motions and active crustal deformation in Central America and northern South America, an area of complex interaction of the Nazca, Cocos, Caribbean and South American plates. The displacement rates for the period 1988-1991, obtained from the results of the first three Central And South America (CASA) GPS campaigns, are in general agreement with the predictions of the NUVEL-1 plate motion model, but there are differences in detail between the observations and the model. The Nazca-North Andes convergence rate vector measured by GPS is …

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Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James N. Kellogg Dec 1993

Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James N. Kellogg

Faculty Publications

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 …

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Scaling Water And Energy Fluxes In Climate Systems: Three Land-Atmospheric Modeling Experiments, Eric F. Wood, Venkataraman Lakshmi May 1993

Scaling Water And Energy Fluxes In Climate Systems: Three Land-Atmospheric Modeling Experiments, Eric F. Wood, Venkataraman Lakshmi

Faculty Publications

The effects of small-scale heterogeneity in land-surface characteristics on the large-scale fluxes of water and energy in the land-atmosphere system have become a central focus of many of the climatology research experiments. The acquisition of high-resolution land-surface data through remote sensing and intensive land-climatology field experiments(like HAPEX and EIFE) has provided data to investigate the interactions between microscale land-atmosphere interactions and macroscale models. One essential research question is how to account for the small-scale heterogeneities and whether `effective' parameters can be used in the macroscale models. To address this question ofscaling, three modeling experiments were performed and are reviewed in …

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A Monte Carlo Study Of Rainfall Sampling Effect On A Distributed Catchment Model, Witold F. Krajewski, Venkataraman Lakshmi, Konstantine P. Georgakakos, Subhash C. Jain Jan 1991

A Monte Carlo Study Of Rainfall Sampling Effect On A Distributed Catchment Model, Witold F. Krajewski, Venkataraman Lakshmi, Konstantine P. Georgakakos, Subhash C. Jain

Faculty Publications

A Monte Carlo study of a physically based distributed-parameter hydrologic model is described. The catchment model simulates overland flow and streamflow, and it is based on the kinematic wave concept. Soil Conservation Service curves are used to model rainfall excess within the basin. The model was applied to the Ralston Creek watershed, a small (7.5 km2) rural catchment in eastern Iowa. Sensitivity of the model response with respect to rainfall-input spatial and temporal sampling density was investigated. The input data were generated by a space-time stochastic model of rainfall. The generated rainfall fields were sampled by the varied-density …

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Central And South America Gps Geodesy- Casa Uno, James N. Kellogg, Timothy H. Dixon Mar 1990

Central And South America Gps Geodesy- Casa Uno, James N. Kellogg, Timothy H. Dixon

Faculty Publications

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. …

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The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey T. Freymueller, James N. Kellogg Mar 1990

The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey T. Freymueller, James N. Kellogg

Faculty Publications

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 …

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First Gps Baseline Results From The North Andes, James N. Kellogg, Jeffrey T. Freymueller, Timothy H. Dixon, Ruth E. Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James L. Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos Mar 1990

First Gps Baseline Results From The North Andes, James N. Kellogg, Jeffrey T. Freymueller, Timothy H. Dixon, Ruth E. Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James L. Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos

Faculty Publications

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. …

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