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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Shock Demagnetization of Pyrrhotite

Maps of the remanent magnetic field of Mars show demagnetized zones within and around giant impact basins. It is likely that vast regions of the Martian crust were demagnetized due to a shock-induced phase change or magnetic transition of magnetic minerals in the crust. This hypothesis is supported by the fact that around the Hellas and Argyre basins, the edges of the unmagnetized zones roughly correspond with peak shock pressure contour lines of a few GPa. Although pyrrhotite is not a major carrier of magnetization in the Earth s crust, it is a common phase in Martian meteorites and may be an important carrier in the Martian crust. Understanding the effects of shock waves on magnetic minerals is critical for determining the origin of the demagnetized zones in impact basins and possibly for identifying the major magnetic carrier phases. Here we present the results of the first controlled shock demagnetization measurements on pyrrhotite. Previous experiments: Shock demagnetization

Louzada, K. L.↗
NASA NTRS1991

The formation of terrains antipodal to major impacts

The SALE, or Simplified Arbitrary Lagrangian Eulerian code is presently used to calculate the antipodal pressures generated by large impacts on icy satellites and planets of various compositions and core sizes. While in a high density core/lower density mantle planet there is a refraction of the incident pressure wave away from the antipode by the core, resulting in a low antipodal pressure, a planet with a low velocity core with a higher-wave speed mantle will focus the waveform to maximize antipodal pressure. Specific impact basins on the moon, Mercury, and several icy satellites are modeled to ascertain whether the impacts were capable of producing the observed antipodal features.

Watts, Alison W.↗
NASA NTRS1991

A review of the regional geophysics of the Arizona Transition Zone

A review of existing geophysical information and new data presented in this special section indicate that major changes in crustal properties between the Basin and Range and Colorado Plateau occur in, or directly adjacent to, the region defined as the Arizona Transition Zone. Although this region was designated on a physiographic basis, studies indicate that it is also the geophysical transition between adjoining provinces. The Transition Zone displays anomalous crustal and upper mantle seismic properties, shallow Curie isotherms, high heat flow, and steep down-to-the-plateau Bouguer gravity gradients. Seismic and gravity studies suggest that the change in crustal thickness, from thin crust in the Basin and Range to thick crust in the Colorado Plateau, may occur as a series of steps rather than a planar surface. Anomalous P wave velocities, high heat flow, shallow Curie isotherms, and results of gravity modeling suggest that the upper mantle is heterogeneous in this region. A relatively shallow asthenosphere beneath the Basin and Range and Transition Zone contrasted with a thick lithosphere beneath the Colorado Plateau would be one explanation that would satisfy these geophysical observations.

Hendricks, J. D.↗
NASA NTRS1999

Variability in Sea Surface Height: A Qualitative Measure for the Meridional Overturning in the North Atlantic

Sea surface height (SSH) from altimeter observations from 1992 on and from modeling results is investigated to determine the modes of variability and the linkages to the state of oceanic circulation in the North Atlantic. First the altimeter and model simulated SSH are analyzed using the empirical orthogonal function (EOF) analysis. They are found to share a similar leading mode where the center of action is along the Gulf Stream and North Atlantic Current with opposite sign anomalies in the subpolar gyre and in the slope waters along the Eastern Seaboard. The time series of the leading EOF mode from the altimeter data shows that between winters of 1995 and 1996, SSH over the Gulf Stream decreased by about 12cm which change is reproduced by the model simulation. Based on the relationship from the model simulations between the time series of the SSH EOF1 and meridional heat transport, it is suggested that associated with this SSH change in 1995-96, the overturning has slowed down from its heights in the early 90's. Furthermore, it is shown that decadal variability in the leading SSH mode originates from the thermal forcing component. This adds confidence to the qualitative relationship between the state of overturning/meridional heat transport and SSH in the limited area described by the EOF1. SSH variability in the eastern side of the North Atlantic basin, outside the western boundary current region, is determined by local and remote (Rossby waves) wind stress curl forcing.

Hakkinen, Sirpa↗
NASA NTRS2019

Extratropical Large-Scale Traveling Weather Systems in the Southern Hemisphere on Mars

From late-autumn through early-spring, the middle- and high-latitudes of both hemispheres of Mars and its predominantly carbon-dioxide atmosphere support mean equator-to-pole thermal contrasts, and then, support a strong mean westerly polar vortex. Observations from orbiting spacecraft indicate that this intense mean baroclinicity-barotropicity supports large-scale eastward traveling weather systems (i.e., transient, traveling synoptic-period waves, on the order of the Rossby deformation scale). On Earth, extratropical weather disturbances arise from wind-shear instabilities, and these are critical components of the terrestrial global circulation. So it is the case for Mars. Large-scale traveling weather systems on Mars serve as agents in the transport of heat, momentum and scalar and tracer quantities (e.g., atmospheric dust, watervapor, ice clouds, chemical species, etc). Such weather systems interact with other large-scale atmospheric circulation components, namely, quasi-stationary (i.e., forced Rossby) modes; global thermal tidal modes; and then, upon large-/continental- geographical scales, upslope/ down-slope flows amongst high relief, low relief, impact basins, and volcanic rises, and more. The character of Mars' traveling extratropical weather disturbances in its southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (i.e., Mars GCM), and one from the Agency's Mars Climate Modeling Center (MCMC) based at the NASA Ames Research Center. The climate model includes several complex atmospheric physical packages. With such physics modules, our global climate simulations present comparatively well with observations of the planet's current water cycle (Haberle et al.,2019). The climate model is "forced" with an annual dust cycle (i.e., nudged based on MGS/TES observations). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Hollingsworth, Jeffery L.↗
NASA NTRS2022

Surface-to-Space Atmospheric Waves From Hunga Tonga–Hunga Ha’apai Eruption

The January 2022 Hunga Tonga–Hunga Ha’apai eruption was one of the most explosive volcanic events of the modern era, producing a vertical plume that peaked more than 50 km above the Earth. The initial explosion and subsequent plume triggered atmospheric waves that propagated around the world multiple times. A global-scale wave response of this magnitude from a single source has not previously been observed. Here we show the details of this response, using a comprehensive set of satellite and ground-based observations to quantify it from surface to ionosphere. A broad spectrum of waves was triggered by the initial explosion, including Lamb waves propagating at phase speeds of 318.2 ± 6 m s^(−1) at surface level and between 308 ± 5 to 319 ± 4 m s^(−1) in the stratosphere, and gravity waves propagating at 238 ± 3 to 269 ± 3 m s^(−1) in the stratosphere. Gravity waves at sub-ionospheric heights have not previously been observed propagating at this speed or over the whole Earth from a single source. Latent heat release from the plume remained the most significant individual gravity wave source worldwide for more than 12 h, producing circular wavefronts visible across the Pacific basin in satellite observations. A single source dominating such a large region is also unique in the observational record. The Hunga Tonga eruption represents a key natural experiment in how the atmosphere responds to a sudden point-source-driven state change, which will be of use for improving weather and climate models.

Corwin J. Wright↗
NASA NTRS2011

Teleconnection, Regime Shift, and Predictability of Climate Extremes: A Case Study for the Russian Heat Wave and Pakistan Flood in Summer 2010

In this talk, we present observational evidence showing that the two major extremes events of the summer of 2010, i.e., the Russian heat wave and the Pakistan flood were physically connected. We find that the Pakistan flood was contributed by a series of unusually heavy rain events over the upper Indus River Basin in July-August. The rainfall regimes shifted from an episodic heavy rain regime in mid-to-late July to a steady heavy rain regime in August. An atmospheric Rossby wave associated with the development of the Russian heat wave was instrumental in spurring the episodic rain events , drawing moisture from the Bay of Bengal and the northern Arabian Sea. The steady rain regime was maintained primarily by monsoon moisture surges from the deep tropics. From experiments with the GEOS-5 forecast system, we assess the predictability of the heavy rain events associated with the Pakistan flood. Preliminary results indicate that there are significantly higher skills in the rainfall forecasts during the episodic heavy rain events in July, compared to the steady rain period in early to mid-August. The change in rainfall predictability may be related to scale interactions between the extratropics and the tropics resulting in a modulation of rainfall predictability by the circulation regimes.

Lau, W. K.↗
NASA NTRS1975

South Louisiana remote-sensing environmental information system

Satellite gathered remote sensor data were used to update a basic environmental atlas of southern Louisiana to reflect recent dynamic geological changes, such as erosion by wave action along the coast and active delta building in the lower part of the Mississippi Basin. Standard pattern recognition programs were utilized to update LANDSAT pictures for three categories (generalized land use, ecological zones and vegetation) to obtain a simulated color photomap for LANDSAT frames for further rectification by a table lookup program.

Gordon, J. P.↗
NASA NTRS1981

The response of a linear baroclinic equatorial ocean to periodic forcing

An investigation is conducted regarding the periodic response of the linear inviscid shallow water equations in a meridionally unbounded basin to zonal forcings at a single low frequency omega. A general solution in the long wave approximation and on an equatorial beta-plane is obtained by summing the Kelvin mode and the finite sum of Rossby modes whose turning points lie equatorward of the turning latitude at frequency omega. The results of the investigation suggest that even if the low frequency forcing has a simple structure, considerable spatial inhomogeneity in the deep ocean response would have to be expected. On the basis of linear inviscid theory, some conclusions are drawn about the causes of the differences between equatorial thermocline response in the Atlantic and Pacific.

Cane, M. A.↗
NASA NTRS2001

Impacts of ENSO on the South American Summer Monsoon During 1997-1999

Using the National Center for Environmental Prediction (NCEP) Reanalysis, and CPC Merged Analysis Product (CMAP) rainfall, we have compared and contrasted the anomalies of the South American Summer Monsoon (SASM) during two extreme years of 1997/98 (EI Nino) and 1998/99 (La Nina). The results are assessed against a "canonical" ENSO response (CER) pattern for the SASM obtained from empirical mode decomposition based on a previous period (1980-1995). Overall, the SASM anomalies compare well with CER, but with some important differences. Anomalies occurring in the warm phase of the 1997-98 El Nino are very significant and robust, while those occurring in 1998/99 La Nina, appear to be reversed from 1997/98, but are relatively weak and less well-defined. The most pronounced signal in DJF 1997/98 is the development of drought conditions in northern Brazil, excessive rainfall over northern Peru and Ecuador, and over Uruguay and southern Brazil. The tropical rainfall anomalies are associated with the eastward shift of the Walker circulation, which is represented by pronounced low-level anomalous westerlies over the equatorial eastern Pacific and easterlies over northern Brazil. The easterlies are deflected sharply southeastward by the steep topography of the Andes, enhancing the low-level jet (LLJ) along the eastern foothills of the Andes near 15-20 S. The LLJ penetrates deep into the extratropics, yielding rainfall anomalies further poleward compared to CER. During DJF 1997/98, the eastward expansion of the warm tropospheric temperature over the Nino-3 region causes anomalous geopotential height to develop in the upper troposphere above the Altiplano, leading to a strengthened Bolivian High. An upper-tropospheric jet anomaly maximum is found over the subtropical continent near 30 S, due to increasing meridional gradient of tropospheric temperature, as well as teleconnection patterns linking the South Pacific and the South Atlantic. Consistent with the CER, the South Pacific High is weakened, and the South Atlantic High is strengthened in DJF 1997/98. However, rather than appearing as a coherent large scale signal over the entire Atlantic as in CER, the South Atlantic High anomalies in DJF 1997/98 split into two separate high pressure centers; one located south of the Amazon basin, and another over the southeastern South Atlantic. The former is induced as a Rossby-wave response by ENSO-Induced sinking motion over nor-them and eastern Brazil, and the latter may be associated with extratropical teleconnection signals. Anomalous convection observed over equatorial western Africa may also have contributed to the different circulation response over the Atlantic in DFJ 1997/99 compared to the CER. Comparison of the evolution of the SASM anomalies in 1997-99 with their corresponding annual cycles, suggest that the anomalies are phase-locked to and represent either enhancement or reduction of the annual variations. Results suggest that, from a system perspective the SASM was strengthened during the 1997/98 El Nino and weakened, albeit to a lesser extent, during the 1998/99 La Nina.

Lau, K.-M.↗
NASA NTRS2015

Daily Global Mapping of Mars Ozone Column Abundances with MARCI UV Band Imaging

Since November of 2006, The Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO) has obtained multiple-filter daily global images of Mars centered upon a local time (LT) of 3 pm. Ultraviolet imaging bands placed within (260 nm) and longward (320 nm) of Hartley band (240-300 nm) ozone (O3) absorption support retrievals of atmospheric ozone columns, with detection limits (approximately 1 micrometer-atm) appropriate to mapping elevated O3 abundances at low latitudes around Mars aphelion, and over mid-to-high latitudes during fall/winter/spring seasons. MARCI O3 maps for these regions reveal the detailed spatial (approximately 1 deg lat/long, for 8 x 8 pixel binned resolution) and temporal (daily, with substantial LT coverage at pole) behaviors of water vapor saturation conditions that force large variations in water vapor photolysis products (HOx-OH, HO2, and H) responsible for the catalytic destruction of O3 in the Mars atmosphere. A detailed description of the MARCI O3 data set, including measurement and retrieval characteristics, is provided in conjunction with comparisons to Mars Express SPICAM ozone measurements (Perrier, S. et al. [2006]. J. Geophys. Res. (Planets) 111) and LMD GCM simulated O3 abundances (Lefevre, F. [2004]. J. Geophys. Res. (Planets) 109). Presented aspects of the MARCI ozone mapping data set include aphelion increases in low latitude O3, dynamically evolving high latitude O3 maxima associated with planetary waves and weather fronts during northern early spring, and distinctive winter/spring O3 and CO increases within the Hellas Basin associated with transport of condensation enhanced south polar air mass. Comparisons of coincident MARCI measurements and LMD simulations for ice cloud and O3 columns are considered in the context of potential heterogeneous photochemical processes (Lefevre, F. [2008]. Nature 454, 971-975), which are not strongly evidenced in the MARCI observations. Modest interannual variations are exhibited, most notably a 20% reduction in aphelion low latitude O3 columns following the 2007 perihelic global dust storm.

Clancy, R. Todd↗
NASA NTRS2005

Antipodal Magnetic Anomalies on the Moon, Contributions from Impact Induced Currents Due to Positive Holes and Flexoelectric Phenomina and Dynamo

Large impacts on the Moon generate large pressure pulses that penetrate the whole body. Several of these large impacts may have generated antipodal structure with anomalous magnetic intensity.These regions can be more than a thousand km across, with fields of the order of tens to hundreds of nT. This is the case of Orientale, Imbrium, Serenitatis, Crisium, and Nectaris impact basins. The production of large-scale magnetic fields and associated crustal magnetization due to lunar basin-forming impacts was hypothesized to have an origin in fields external to the impact plasma cloud that are produced by the magnetohydrodynamic interaction of the cloud with ambient magnetic fields and plasmas. During the period of compressed antipodal field amplification, seismic compressional waves from the impact converge at the antipode resulting in transient shock pressures that reach 2 GPa (20 kbar). This can produce conditions for shock magnetic acquisition of the crust antipodal to impact basins.

Kletetschka, G.↗
NASA NTRS2002

The 1998-2000 SHADOZ (Southern Hemisphere ADditional OZonesondes) Tropical Ozone Climatology: Stratospheric and Tropospheric Ozone Variability and the Zonal Wave-One - 2

This is the second 'reference' or 'archival' paper for the SHADOZ (Southern Hemisphere Additional Ozonesondes) network and is a follow-on to the recently accepted paper with similar first part of title. The latter paper compared SHADOZ total ozone with satellite and ground-based instruments and showed that the equatorial wave-one in total ozone is in the troposphere. The current paper presents details of the wave-one structure and the first overview of tropospheric ozone variability over the southern Atlantic, Pacific and Indian Ocean basins. The principal new result is that signals of climate effects, convection and offsets between biomass burning seasonality and tropospheric ozone maxima suggest that dynamical factors are perhaps more important than pollution in determining the tropical distribution of tropospheric ozone. The SHADOZ data at ( ) are setting records in website visits and are the first time that the zonal view of tropical ozone structure has been recorded - thanks to the distribution of the 10 sites that make up this validation network.

Thompson, Anne M.↗
NASA NTRS1999

Wind Induced Sediment Resuspension in a Microtidal Estuary

Bottom sediment resuspension frequency, duration and extent (% of bottom sediments affected) were characterized for the fifteen month period from September 1995 to January 1997 for the Barataria Basin, LA. An empirical model of sediment resuspension as a function of wind speed, direction, fetch and water depth was derived from wave theory. Water column turbidity was examined by processing remotely sensed radiance information from visible and near-IR AVHRR imagery. Based on model predictions, wind induced resuspension occurred during all seasons of this study. Seasonal characteristics for resuspension reveal that late fall, winter and early spring are the periods of most frequent and intense resuspension. Model predictions of the critical wind speed required to induce resuspension indicate that winds of 4 m/s (averaged over all wind directions resuspend approximately 50% of bottom sediments in the water bodies examined. Winds of this magnitude (4 m/s) occurred for 80% of the time during the late fall, winter and early spring and for approximately 30% of the time during the summer. More than 50% of the bottom sedimets are resuspended throughout the year, indicating the importance of resuspension as a process affecting sediment and biogeochemical fluxes in the Barataria Basin.

Booth, J. G.↗
NASA NTRS2020

An Introduction to the NASA GMAO Coupled Atmosphere-Ocean System - GEOS-S2S Version 3

Recently NASA's Global Modeling and Assimilation Office (GMAO) has developed a new Subseasonal to Seasonal Prediction system Version 3 (GEOS-S2S-3). This upgrade replaces the GEOS-S2S-2 which is NASA's current contribution to the North American Multi-Model Experiment seasonal prediction project (Kirtman et al., 2014). The main improvements for our S2S-3 system include 1) a higher resolution MOM5 (Griffies et al., 2005) ocean model (now 0.25o x 0.25o x 50 layers), 2) an improved atmospheric/ocean interface layer (Akella and Suarez, 2018), and 3) assimilation of a long-track satellite salinity into the ocean model (Hackert et al, 2019). Atmospheric forcing is provided by the NASA MERRA-2 reanalysis (Gelaro et al., 2017). Initialization for the ocean relies on the GMAO ocean reanalysis system which assimilates all available in situ temperature and salinity, satellite sea surface salinity, and sea level using the Local Ensemble Transform Kalman Filter (LETKF) implementation of (Penny et al., 2013) on a 5 day assimilation cycle with 20 fixed ensemble members.In this presentation, we will authenticate our new S2S-3 ocean reanalysis using standard GODAE validation metrics. For example, we will compare gridded fields of mean and standard deviation of the ocean reanalysis versus observed fields. We will show correlation/RMS of model versus observations and temperature and salinity mean profiles for the various basins and latitude bands. Basin-scale volume transports, such as the Atlantic Meridional Overturning Circulation and the Indonesian Throughflow will be validated. Equatorial ocean waves will be compared by decomposing sea level into Kelvin and Rossby components. For each of these metrics, we plan to validate the results and then compare our new S2S-3 against the current production version, S2S-2. Finally, we will compare 9-month seasonal forecasts initialized from these two systems for the tropical Pacific NINO3.4 region over the period 1981-present.

Molod, Andrea↗
NASA NTRS2011

Introduction to: Atlantic Meridional Overturning Circulation(AMOC)

A striking conclusion of the Intergovernmental Panel on Climate Change 2007 report is the crucial role that the Atlantic Meridional Overturning Circulation (AMOC) may play in anthropogenic climate change. However, these IPCC coupled climate simulations show a broad range of uncertainty in the magnitude and timing of AMOC transport change ranging from none to nearly complete collapse within the 21st century. The potential consequences of large changes in the characteristics of AMOC have motivated the creation in the United States of an interagency program and implementation plan to develop monitoring and prediction capabilities for the AMOC This program parallels the development of substantial monitoring efforts by European, South American and African countries -- notably the UK Rapid and Rapid-Watch programs. The papers contained in this volume are derived from presentations at the First U.S. Atlantic Meridional Overturning Circulation (AMOC) Meeting held 4 - 6 May, 2009 to review the US implementation plan and its coordination with other monitoring activities. The Atlantic Meridional Overturning Circulation consists of multiple components illustrated in an attached figure. Water enters the South Atlantic at upper and intermediate depths through both western and eastern routes (where eddy transport is especially important) and is transported northward across the equator, where it recirculates within the northern subtropical and subpolar gyres. The northern end is defined by the sinking regions of the Nordic Seas and the Labrador Sea where the waters that eventually form the upper and lower branches of North Atlantic Deep Water are conditioned. High surface salinities, the result of high net evaporation in the tropics and subtropics (including the Mediterranean Sea), and presence of regions of the Arctic Ocean that remain ice-free even in winter allow for the rapid cooling and thus densification of surface water. This dense surface water becomes the source of deep water formation in the sinking regions. In addition to transporting mass, the AMOC transports roughly half of the total amount of heat carried northward through the northern subtropics (down the temperature-gradient) by the ocean. In contrast in the Southern Hemisphere AMOC transports heat up-gradient from the cool Circumpolar Current to the warm tropics. Paleoevidence suggests that AMOC heat transport in the two hemispheres has varied over time in ways intimately tied to millennial changes in the Earth's climate. In one example, the abrupt Younger Dryas spell of cold weather over the North Atlantic, which began 13,000 years ago, has generally been linked to a millennial shutdown of the AMOC as a result of massive freshwater discharge from the North American continent. The current AMOC monitoring array consists of a series of instrumented transects located across key passages (see Cunningham et al., 2010 for a recent review). In the Arctic and sub-Arctic, transects cross Fram Strait, Denmark Strait and the Faroe Channel (connecting Greenland, Iceland, and the United Kingdom), as well as the entrance to the Labrador Sea. Further south and extending outwards from the east coast of North America there are a series of monitoring arrays including arrays of the Canadian Atlantic Zone Monitoring Program, deployments of the Rapid Western Atlantic Variability Experiment (WAVE), Line W at 39 N, as well as the Rapid-MOC moored array. The latter spans the entire Atlantic basin along 26.5 N. At tropical latitudes we have the Meridional Overturning Variability Experiment (MOVE) array at 16 N, while in the Southern Hemisphere a corresponding basin-spanning transect is being established at the latitude of Cape of Good Hope, complemented by arrays at Drake Passage.

Hakkinen, Sirpa↗
NASA NTRS1973

Optical data processing and projected applications of the ERTS-1 imagery covering the 1973 Mississippi River Valley floods

Flooding along the Mississippi River and some of its tributaries was imaged by the multispectral scanner (MSS) on the Earth Resources Technology Satellite (ERTS-1) on at least three orbits during the spring of 1973. The ERTS data provided the first opportunity for mapping the regional extent of flooding at the time the imagery was acquired. Special optical data processing techniques were used to produce a variety of multispectral color composites which enhanced floodplain details. One of these, a two-color composite of near infrared bands 6 and 7, was enlarged and registered to 1:250,0OO-scale topographic maps and used as the basis for preparation of flood image maps. Two specially filtered three-color composites of MSS bands 5, 6, and 7 and 4, 5, and 7 were prepared to aid in the interpretation of the data. The extent of the flooding was vividly depicted on a single image by two-color temporal composites produced on the additive-color viewer using band 7 flood data superimposed on pre-flood band 7 images. On May 24, when the floodwaters at St. Louis receded to bankfull stage, imagery was again obtained by ERTS. Analysis of temporal data composites of the pre-flood and post-flood band 7 images indicate that changes in surface reflectance characteristics caused by the flooding can be delineated, thus making it possible to map the overall area flooded without the necessity of a real-time system to track and image the peak flood waves. Regional planning and disaster relief agencies such as the Corps of Engineers, Office of Emergency Preparedness, Soil Conservation Service, interstate river basin commissions and state agencies, as well as private lending and insurance institutions, have indicated strong potential applications for ERTS image-maps of flood-prone areas.

Morris Deutsch↗
NASA NTRS1981

Characterization of the structure and tectonic of South America

Geologic studies of the South American plate were undertaken. The Guayana shield is reasonably well studied, and although data are sparce, the central Brazilian shield appears similar. Both the Amazon and Parnaiba basins seem to be related to an aulocogen structure. The collection of crustal structure information and the generation of measurement of surface wave dispersion in the shield areascontinues. Long period seismograms are digitized and analyzed. Exisiting crusted and upper mantle studies were indexed. Both MAGSAT scaler and vector magnetic anomaly data were used with regional gravity anomaly data to investigate the regional tectonic features of the South American plate.

Keller, G. R.↗