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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A model of convergent plate margins based on the recent tectonics of Shikoku, Japan

A viscoelastic finite element plate tectonic model is applied to displacement data for the island of Shikoku, Japan. The flow properties and geometry of the upper portions of the earth are assumed known from geophysical evidence, and the loading characteristics are determined from the model. The nature of the forces acting on the Philippine Sea plate, particularly in the vicinity of the Nankai trough, is determined. Seismic displacement data related to the 1946 Nankaido earthquake are modeled in terms of a thick elastic plate overlying a fluidlike substratum. The sequence of preseismic and seismic displacements can be explained in terms of two independent processes operating on elastic lithospheric plates: a strain accumulation process caused by vertical downward forces acting on or within the lithosphere in the vicinity of the trench, and a strain release process caused by plate failure along a preexisting zone on weakness. This is a restatement of Reid's elastic rebound theory in terms of elastic lithospheric plates.

Bischke, R. E.↗
NASA NTRS1974

Benefits to the study of oceanic tectonics expected from Seasat-A

A more detailed gravity field such as provided by the SEASAT-A altimeter would help resolve several problems of marine geology, such as the relationship of spreading rises to convective upstreams and the tectonics of subduction zones and the associated marginal basins. In addition, the gravity field should be measured in more detail over continental shelves accessible to mineral exploration. A secondary contribution of SEASAT-A would be to sedimentation processes, through its influence on models of ocean currents.

Kaula, W. M.↗
NASA NTRS1975

Regional tectonic evaluation of the Tuscan Apenine, vulcanism, thermal anomalies and the relation to structural units

The author has identified the following significant results. The geological interpretation on data exhibiting the Italian peninsula led to the recognition of tectonic features which are explained by a clockwise rotation of various blocks along left-handed transform faults. These faults can be interpreted as resulting from shear due to main stress directed north-eastwards. A land use map of the mountainous regions of Italy was produced on a scale of 1:250,000. For the digital treatment of MSS-CCTs an image processing software was written in FORTRAN 4. The software package includes descriptive statistics and also classification algorithms.

Bodechtel, J.↗
NASA NTRS1976

Mare ridges and related highland scarps - Result of vertical tectonism

Two fresh-looking scarps on the rim of the Serenitatis Basin were structurally analyzed in detail on high-resolution stereoscopic photographs. The scarps are topped by wrinkle ridges on the mare and transgress into adjacent highlands. They are faults that offset mare and highland surfaces. The faults appear to have high-angle fault planes and both normal and reverse separation which suggests tensional as well as compressional stresses. These observations, though contradictory in regional stress systems, are compatible with local adjustments resulting from vertical tectonic movement. A model is developed that fits the observations and proposes that ridges and scarps formed through vertical structural adjustment caused by gravitational settling, and following older structural trends.

Lucchitta, B. K.↗
NASA NTRS1977

Lunar farside tectonics and volcanism

The reported study is primarily concerned with the identification and mapping of structural and volcanic features on the lunar farside. The study represents a continuation and extension of a similar investigation made of the nearside of the moon by Scott et al. (1975). Mapping reveals that tectonic structures on the moon's farside are comparatively scarce and such less prominently developed than those on the nearside. Rilles and mare-type ridges that form major linear and basin concentric systems on the nearside are nearly absent on the farside as are large normal faults like Rupes Recta and Rupes Cauchy. The azimuth orientations of five types of geologic structures were measured, including lineaments, crater chains, terra ridges, faults and linear rilles, and straight segments of crater rims. Mare basalts are concentrated in low regions, especially in a large southern basin which is also the site of relatively numerous volcanic constructs as well as geochemical and magnetic anomalies.

Scott, D. H.↗
NASA NTRS1978

Application of LANDSAT images in the Minas Gerais tectonic division

The interpretation of LANDSAT data for a regional geological investigation of Brazil is provided. Radar imagery, aerial photographs and aeromagnetic maps were also used. Automatic interpretation, using LANDSAT OCT's was carried out by the 1-100 equipment. As a primary result a tectonic map was obtained, at 1:1,000,000 scale, of an area of about 143,000 square kilometers, in the central portion of Minas Gerais and Eastern Goias States, known as regions potentially rich in mineral resources.

Dacunha, R. P.↗
NASA NTRS1979

Studies of oceanic tectonics based on GEOS-3 satellite altimetry

Using statistical analysis, geoidal admittance (the relationship between the ocean geoid and seafloor topography) obtained from GEOS-3 altimetry was compared to various model admittances. Analysis of several altimetry tracks in the Pacific Ocean demonstrated a low coherence between altimetry and seafloor topography except where the track crosses active or recent tectonic features. However, global statistical studies using the much larger data base of all available gravimetry showed a positive correlation of oceanic gravity with topography. The oceanic lithosphere was modeled by simultaneously inverting surface wave dispersion, topography, and gravity data. Efforts to incorporate geoid data into the inversion showed that the base of the subchannel can be better resolved with geoid rather than gravity data. Thermomechanical models of seafloor spreading taking into account differing plate velocities, heat source distributions, and rock rheologies were discussed.

Poehls, K. A.↗
NASA NTRS1978

The tectonic and volcanic history of Mercury as inferred from studies of scarps, ridges, troughs, and other lineaments

Tectonic and volcanic modification of the Mercurian surface is discussed, and nine landform classes are defined. An evolutionary chronology, based on reported interpretations of scarp, ridge, trough, and other lineament features, is presented, and the roles (in chronological order) of accretion and differentiation, tidal spindown, plains volcanism, heavy bombardment, cooling/contraction, Caloris impact, intense surface modification, basin subsidence, local plains volcanism, isostatic basin uplift, and light cratering are considered. The observational data were obtained by Mariner 10.

Dzurisin, D.↗
NASA NTRS1979

Crustal structure, geophysical models and contemporary tectonism of the Colorado Plateau

A regional analysis of the crust and upper mantle of the Colorado Plateau is presented, using existing geophysical and geological data combined with new surface wave dispersion and groundwater geothermometry data; the tectonic implications of these models are also investigated. Surface wave and seismic refraction data indicate that the crust of the interior of the Colorado Plateau is 44 + or - 3 km thick, and its crustal structure is typical of stable continental areas. Pn velocities, however, appear to be lower (7.8 km/s) than would be expected in a stable region, while silica geothermometry indicates that the average heat flow for the plateau is 55 mW per sq m (1.3 HFU).

Keller, G. R.↗
NASA NTRS1979

Elastic lithosphere thickness on the moon from mare tectonic features - A formal inversion

The thickness (T) of the lunar elastic lithosphere at the time (3.6 to 3.8 billion years ago) of the earliest preserved basalt flows in circular mare basins can be estimated by inverting the observed locations of extensional tectonic features in and surrounding the maria. In performing the inversion, the lithosphere is modeled as an elastic shell with a liquid interior, and the basalt load for each mare is approximated by a set of concentric cylinders. To permit solving the forward problem of placing radial limits on the positions of the rilles around a given mare, an additional parameter F, the ratio of the radial stress at the radial limits to the maximum radial stress, is introduced. T and F are chosen to give the best weighted-squares fit of the radial limits to the observations, and are used as the initial values in a linearized matrix inversion to check the resolution and estimate errors. The application of the procedure to three maria with prominent extensional features, Humorum, Orientale, and Serenitatis, gives values of T from about 40 + or - 10 to 50 + or - 10 km, and in each case the linearized matrix equation has an exact inverse.

Comer, R. P.↗
NASA NTRS1980

Tectonics and composition of Venus

The uncompressed density of Venus is a few percent less than the Earth. The high upper mantle temperature of Venus deepens the eclogite stability field and inserts a partial melt field. A thick basaltic crust is therefore likely. The anomalous density of Venus relative to the progression from Mercury to Mars may therefore have a tectonic rather than a cosmo-chemical explanation. There may be no need to invoke differences in composition or oxidization state.

Anderson, D. L.↗
NASA NTRS1980

Gravity fields of the terrestrial planets - Long-wavelength anomalies and tectonics

The paper discusses the gravity and topography data available for four terrestrial planets (earth, moon, Mars, and Venus), with particular emphasis on drawing inferences regarding the relationship of long-wavelength anomalies to tectonics. The discussion covers statistical analyses of global planetary gravity fields, relationship of gravity anomalies to elastic and viscoelastic models, relationship of gravity anomalies to convection models, finite strength, and isostasy (or the state of isostatic compensation). The cases of the earth and the moon are discussed in some detail. A summary of comparative planetology is presented.

Phillips, R. J.↗
NASA NTRS1980

New evidence for tectonic uplift in the Diablo Plateau region, West Texas

The National Geodetic Survey completed approximately 170 km of releveling in the Diablo Plateau-Salt Basin region during the fall of 1977. The survey was specifically designed to detect possible vertical crustal movements in the area. The new releveling measurements confirm contemporary uplift of the region and suggest that uplift has been continuous for the entire time the movements were monitored (1934-1977). Although the precise mechanism responsible for the observed uplift is unknown, it is almost certainly of tectonic origin. The pattern of uparching is perturbed at the Salt Basin graben, indicating 4.2 + or - 0.3 cm of subsidence relative to its margins between 1958 and 1977.

Reilinger, R.↗
NASA NTRS1980

Tectonic stress - Models and magnitudes

It is shown that global data on directions of principal stresses in plate interiors can serve as a test of possible plate tectonic force models. Such tests performed to date favor force models in which ridge pushing forces play a significant role. For such models the general magnitude of regional deviatoric stresses is comparable to the 200-300 bar compressive stress exerted by spreading ridges. An alternative approach to estimating magnitudes of regional deviatoric stresses from stress orientations is to seek regions of local stress either demonstrably smaller than or larger than the regional stresses. The regional stresses in oceanic intraplate regions are larger than the 100-bar compression exerted by the Ninetyeast Ridge and less than the bending stresses (not less than 1 kbar) beneath Hawaii.

Solomon, S. C.↗
NASA NTRS1980

The surface of Io - Geologic units, morphology, and tectonics

The geologic units, morphology and tectonics evident on a preliminary geological map obtained from best-resolution Voyager 1 images and a preliminary pictorial map of the surface of Io are discussed. Nine volcanic units are identified on the surface which are composed of mountain materials, intervent, layered and eroded layered plains, and wall and floor, pit crater flow, shield crater flow, fissure flow and crater cone units associated with volcanic vents, along with seven types of structural features. The cumulative volcanic crater size distribution of 170 Ionian vents with craters greater than 14 km is similar to that of impact craters on other solar system bodies, with a surplus of small craters and a preponderance of volcanic vents in the Io equatorial zone. The observed surface morphologies provide evidence for a mixture of silicates and sulfur as the dominant surface material. Lineaments and grabens are also apparent on the surface, in a common planetary grid pattern.

Schaber, G. G.↗
NASA NTRS1981

A possible dependence of tectonic strength on the age of the crust in Asia

In Asia, the intensity and style of active tectonics appears to depend on the age of the last orogenic activity. The shields have remained essentially undeformed during the India-Eurasian collision, but Paleozoic and Mesozoic orogenic belts apparently have been reactivated by this collision, with a suggestion of greater reactivation and more diffuse deformation of the younger belts. If the greater observed heat flow in regions of more recent orogenic activity reflects, at least in part, a greater heat flow from the mantle beneath the younger belts, then the temperatures in the mantle beneath the younger belts should be higher than beneath older belts and shields. Because of the strong dependence on temperature of the creep strength of minerals, particularly of olivine, the crust and mantle beneath the hotter, younger belts should be much weaker than those beneath older belts. This difference in temperature, and consequent difference in strength, may be the cause of the greater reactivation of younger belts.

Molnar, P.↗
NASA NTRS1981

Tectonics and evolution of Venus

Earlier data synthesized with data recently obtained by the Pioneer Venus Orbiter are analyzed with regard to general tectonics, interior, and long-term evolution of Venus. Comprehensive topographic maps, global properties of Venus, and variations in its gravity field are investigated, and bulk properties of Venus, earth, Mars, the sun, and chondritic meteorites relevant to planetary internal structure and evolution are studied. Although Venus was found to differ less than 30% from earth in comparing all important bulk properties, it appears to have evolved differently. It is noted that a slow rotation rate, the absence of a satellite, the virtual absence of a magnetic field, the dearth of water in the atmosphere, the abundance of primordial argon, and the high surface temperature, are properties in which Venus differs most from the earth. Further results showing the positive correlation of gravity and topography at all wavelengths and the apparent absence of any feature like an ocean indicate that Venus is a one-plate planet and its evolution apparently resembles that of Mars more than that of the earth.

Phillips, R. J.↗