Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “fault motion”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Comparison of GPS surveys with historical triangulation surveys in the southern California borderland

Global plate models predict about 56 mm/yr of motion between the North American and Pacific plates along the plate boundary in southern California, while geodetic and Holocene geological data suggest only 34 mm/yr on the San Andreas fault. Deformation in the Great Basin does not explain this discrepancy, and it has been suggested that faulting in the offshore of southern California could account for some of the discrepancy. Evidence of deformation in the offshore region of southern California is most abundant in the Santa Barbara Channel. Geological investigations of folding and faulting in this region, as well as earthquake investigations, indicate north-south shortening across the channel on the order of 10 to 20 mm/yr. The most rapid rates occur to the east of the channel in the Ventura Basin. South of the Santa Barbara Channel, though, evidence for deformation is limited to seismicity studies which are sparse. Seismic events are abundant in this area, but their implication for the amount of deformation in the offshore is unclear. GPS measurements made between June 1986 and May 1988 have been used to obtain vector positions for several stations at which historical first order triangulation observations were performed between the late 1800's and the mid 1900's between the coast of southern California and the nearby offshore islands. By comparing the spheroidal angles obtained from the GPS positions with the the previously observed triangulation data, shear strain rates can be calculated for the region using Frank's method. These results seem to suggest that shear strain deformation occurs in the offshore of southern California as a result of north to north-west shortening. That deformation is most active in the Santa Barbara Channel region and least active between Catalina and San Nicholas islands. Just how much of the missing plate motion can be accounted for by this deformation is not known at this time and will have to await further analysis.

Webb, Frank H.↗
NASA NTRS2010

Tectonics of the Outer Planet Satellites

Tectonic features on the satellites of the outer planets range from the familiar, such as clearly recognizable graben on many satellites, to the bizarre, such as the ubiquitous double ridges on Europa, the twisting sets of ridges on Triton, or the isolated giant mountains rising from Io's surface. All of the large and middle-sized outer planet satellites except Io are dominated by water ice near their surfaces. Though ice is a brittle material at the cold temperatures found in the outer solar system, the amount of energy it takes to bring it close to its melting point is lower than for a rocky body. Therefore, some unique features of icy satellite tectonics may be influenced by a near-surface ductile layer beneath the brittle surface material, and several of the icy satellites may possess subsurface oceans. Sources of stress to drive tectonism are commonly dominated by the tides that deform these satellites as they orbit their primary giant planets. On several satellites, the observed tectonic features may be the result of changes in their tidal figures, or motions of their solid surfaces with respect to their tidal figures. Other driving mechanisms for tectonics include volume changes due to ice or water phase changes in the interior, thermoelastic stress, deformation of the surface above rising diapirs of warm ice, and motion of subsurface material toward large impact basins as they fill in and relax. Most satellites exhibit evidence for extensional deformation, and some exhibit strike-slip faulting, whereas contractional tectonism appears to be rare. Io s surface is unique, exhibiting huge isolated mountains that may be blocks of crust tilting and foundering into the rapidly emptying interior as the surface is constantly buried by deposits from hyperactive volcanoes. Of the satellites, diminutive Enceladus is spectacularly active; its south polar terrain is a site of young tectonism, copious heat flow, and tall plumes venting into space. Europa's surface is pervasively tectonized, covered with a diverse array of exotic and incompletely understood tectonic features. The paucity of impact craters on Europa suggests that its tectonic activity is ongoing. Geysers on Triton show that some degree of current activity, while tectonic features that cross sparsely cratered terrain indicate that it may also be tectonically active. Ganymede and Miranda both exhibit ancient terrains that have been pulled apart by normal faulting. On Ganymede these faults form a global network, while they are confined to regional provinces on Miranda. Ariel, Dione, Tethys, Rhea, and Titania all have systems of normal faults cutting across their surfaces, though the rifting is less pronounced than it is on Ganymede and Miranda. Iapetus exhibits a giant equatorial ridge that has defied simple explanation. The rest of the large and middle-sized satellites show very little evidence for tectonic features on their surfaces, though the exploration of Titan's surface has just begun.

McKinnon, W. B.↗
NASA NTRS2011

Geodetic Strain Analysis Tool

A geodetic software analysis tool enables the user to analyze 2D crustal strain from geodetic ground motion, and create models of crustal deformation using a graphical interface. Users can use any geodetic measurements of ground motion and derive the 2D crustal strain interactively. This software also provides a forward-modeling tool that calculates a geodetic velocity and strain field for a given fault model, and lets the user compare the modeled strain field with the strain field obtained from the user s data. Users may change parameters on-the-fly and obtain a real-time recalculation of the resulting strain field. Four data products are computed: maximum shear, dilatation, shear angle, and principal components. The current view and data dependencies are processed first. The remaining data products and views are then computed in a round-robin fashion to anticipate view changes. When an analysis or display parameter is changed, the affected data products and views are invalidated and progressively re-displayed as available. This software is designed to facilitate the derivation of the strain fields from the GPS and strain meter data that sample it to facilitate the understanding of the strengths and weaknesses of the strain field derivation from continuous GPS (CGPS) and other geodetic data from a variety of tectonic settings, to converge on the "best practices" strain derivation strategy for the Solid Earth Science ESDR System (SESES) project given the CGPS station distribution in the western U.S., and to provide SESES users with a scientific and educational tool to explore the strain field on their own with user-defined parameters.

Kedar, Sharon↗
NASA NTRS1985

Tectonic rotations within the Rio Grande rift - Evidence from paleomagnetic studies

Paleomagnetic studies on Miocene Pliocene volcanic rocks from the Espanola basin of the Rio Grande rift, New Mexico, reveal directions discordant form the expected mean direction for North America. The Paliza Canyon Formation, Tschicoma Formation, and Lobato Basalt, all sampled in the Jemez Mountains west of the Pajarito fault zone, have mean declinations east of the expected mean. The Cerros del Rio volcanics, lying east of the Pajarito fault zone, have a westerly declination. Combined with published data on the Santa Fe Group sediments east of the fault zone, and the Valles Rhyolite, west of the fault zone, distinct rotations of the two areas are evident. The western block has rotated clockwise 12 deg, while the eastern block shows 16 deg of conter-clockwise motion. Differential rotations of 25-30 deg are calculated between the two blocks; 4 deg/m.y. is the minimum differential rotation for the past 5 m.y. Geologic explanations for these rotations include the opening of the Rio Grande rift in response to clockwise rotation of the Colorado Plateau and significant left slip along the Rio Grande rift.

Brown, L. L.↗
NASA NTRS1993

A fault-tolerant intelligent robotic control system

This paper describes the concept, design, and features of a fault-tolerant intelligent robotic control system being developed for space and commercial applications that require high dependability. The comprehensive strategy integrates system level hardware/software fault tolerance with task level handling of uncertainties and unexpected events for robotic control. The underlying architecture for system level fault tolerance is the distributed recovery block which protects against application software, system software, hardware, and network failures. Task level fault tolerance provisions are implemented in a knowledge-based system which utilizes advanced automation techniques such as rule-based and model-based reasoning to monitor, diagnose, and recover from unexpected events. The two level design provides tolerance of two or more faults occurring serially at any level of command, control, sensing, or actuation. The potential benefits of such a fault tolerant robotic control system include: (1) a minimized potential for damage to humans, the work site, and the robot itself; (2) continuous operation with a minimum of uncommanded motion in the presence of failures; and (3) more reliable autonomous operation providing increased efficiency in the execution of robotic tasks and decreased demand on human operators for controlling and monitoring the robotic servicing routines.

Marzwell, Neville I.↗
NASA NTRS1987

The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

The focus of the research was in two broad areas during the most recent 6 month period: the nature and dynamics of time-dependent deformation along major seismic zones, including the influence of irregularities in fault geometry on the earthquake cycles, and the processes contributing to the state of stress and rates of strain in plate interior regions. The principal findings of the research to date are described.

Solomon, Sean C.↗
NASA NTRS1991

The evolution of volcanism, tectonics, and volatiles on Mars - An overview of recent progress

Significant results of the 'Mars: Evolution of Volcanism, Tectonics, and Volatiles' (MEVTV) project are presented. The data for the project are based on geological mapping from the Viking images, petrologic and chemical analyses of SNC meteorites, and both mapping and temporal grouping of major fault systems. The origin of the planet's crustal dichotomy is examined in detail, the kinematics and formation of wrinkle ridges are discussed, and some new theories are set forth. Because the SNC meteorites vary petrologically and isotopically, the sources of the parental Martian magma are heterogeneous. Transcurrent faulting coupled with the extensional strains that form Valles Marineris suggest early horizontal movement of lithospheric blocks. A theory which connects the formation of the crustal dichotomy to the Tharsis region associates the horizontal motions with plate tectonics that generated a new lithosphere.

Zimbelman, James R.↗
NASA NTRS1996

Transient Creep of a Composite Lower Crust: A Polymineralic Basis for Rapidly Evolving Postseismic Deformation Modes - 2

Postseismic horizontal strain and displacement following the June 28, 1992, Landers, California, earthquake (M(sub W) 7.3) is broad scale and cannot be explained solely by delayed afterslip located at the rupturing fault trace. Both the observed strain at Pifion Flat Observatory (PFO) and observed Global Positioning System receiver velocities evolve rapidly after the Landers-Big Bear earthquake sequence. The observed exponential decay of these motions, with timescales of 4-34 days, may reflect a soft creep rheology in the lower crust and brittle-ductile transition zone or even within the seismogenic crust itself. Here a simple model of a two-dimensional screw dislocation in a layered Maxwell viscoelastic Earth is employed in conjunction with a composite rheology to demonstrate that the short timescale transient response modes (approx. = 4-34 days) are consistent with the behavior of a biviscous lower crust. The lowest viscosity of this system is derivable from laboratory experimental data on the long-term creep of natural quarztites, and the highest viscosity is consistent with isostasy-related lower crustal flow in a continental extensional tectonic environment. The model predicts significant stress relaxation at the base of the seismogenic crust. Near the base of the seismogenic zone, and about 4 km away from the mainshock, the rate of predicted relaxation is of the order of 0.01 MPa/ d during the first 20 days of postseismic flow. Oblate spheroidal inclusions at 5% concentration levels that are both aligned and fairly flat in shape and that have a viscosity of 3-4 x 10(exp 15) Pa s are consistent with both the amplitude and decay time of horizontal crustal strain observed at PFO after the Landers mainshock. It is speculated that the structures exposed in cross sections and in seismic reflection profiles of the lower crust that have mylonitic associations are, in part, the cause of such rapid postseismic evolution in southeastern California. Unmylonitized quartz-rich rock at sufficiently elevated temperatures could also contribute to the rapid decay modes.

Ivins, Erik R.↗
NASA NTRS1989

Mapping small elevation changes over large areas - Differential radar interferometry

A technique is described, based on synthetic aperture radar (SAR) interferometry, which uses SAR images for measuring very small (1 cm or less) surface motions with good resolution (10 m) over swaths of up to 50 km. The method was applied to a Seasat data set of an imaging site in Imperial Valley, California, where motion effects were observed that were identified with movements due to the expansion of water-absorbing clays. The technique can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual displacements from seismic events, and prevolcanic swelling.

Gabriel, Andrew K.↗
NASA NTRS1995

Uplift of the Kenai Peninsula, Alaska, since the 1964 Prince William Sound earthquake

Using Global Positioning System (GPS) receivers, we reoccupied several leveling benchmarks on the Kenai Peninsula of Alaska which had been surveyed by conventional leveling immediately following the March 27, 1964, Prince William Sound earthquake (M(sub w) = 9.3). By combining the two sets of measurements with a new, high-resolution model of the geoid in the region, we were able to determine the cumulative 1993-1964 postseismic vertical displacement. We find uplift at all of our benchmarks, relative to Seward, Alaska, a point that is stable according to tide gauge data. The maximum uplift of about 1 m occurs near the middle of the peninsula. The region of maximum uplift appears to be shifted northwest relative to the point of maximum coseismic subsidence. If we use tide gauge data at Nikishka and Seward to constrain the vertical motion, then the observed uplift has a trenchward tilt (down to the southeast) as well as an arching component. To explain the observations, we use creep-at-depth models. Most acceptable models require a fault slip of about 2.75 m, although this result is not unique. If the slip has been continuous since the 1964 earthquake, then the average slip rate is nearly 100 mm/yr, twice the plate convergence rate. Comparing the net uplift achieved in 29 years with that observed over 11 years in an adjacent region southeast of Anchorage, Alaska, we conclude that the rate of uplift is decreasing. A further decrease in the uplift rate is expected as the 29-year averaged displacement rate is about twice the plate convergence rate and therefore cannot be sustained over the entire earthquake cycle.

Cohen, Steven↗
NASA NTRS1988

A physical model for earthquakes. I - Fluctuations and interactions. II - Application to southern California

The idea that earthquakes represent a fluctuation about the long-term motion of plates is expressed mathematically through the fluctuation hypothesis, under which all physical quantities which pertain to the occurance of earthquakes are required to depend on the difference between the present state of slip on the fault and its long-term average. It is shown that under certain circumstances the model fault dynamics undergo a sudden transition from a spatially ordered, temporally disordered state to a spatially disordered, temporally ordered state, and that the latter stages are stable for long intervals of time. For long enough faults, the dynamics are evidently chaotic. The methods developed are then used to construct a detailed model for earthquake dynamics in southern California. The result is a set of slip-time histories for all the major faults, which are similar to data obtained by geological trenching studies. Although there is an element of periodicity to the events, the patterns shift, change and evolve with time. Time scales for pattern evolution seem to be of the order of a thousand years for average recurring intervals of about a hundred years.

Rundle, John B.↗
NASA NTRS1990

Pacific-North America plate motions - New results from very long baseline interferometry

The state of Pacific-North America plate interaction is updated using newest VLBI measurements and newly developed rigid plate tectonic models. Particular attention is given to examining the extent of relative motion between the Pacific plate and the North America plate as measured from their stable interiors, the evidence of Pacific plate deformation off the central California coast, and the distribution of path integrated deformaton east of the San Andreas fault. The information obtained on these questions is discussed in the framework of implications for lithospheric rheology and earthquake hazard.

Ward, Steven N.↗
NASA NTRS1982

An aircraft sensor fault tolerant system

The design of a sensor fault tolerant system which uses analytical redundancy for the Terminal Configured Vehicle (TCV) research aircraft in a Microwave Landing System (MLS) environment was studied. The fault tolerant system provides reliable estimates for aircraft position, velocity, and attitude in the presence of possible failures in navigation aid instruments and onboard sensors. The estimates, provided by the fault tolerant system, are used by the automated guidance and control system to land the aircraft along a prescribed path. Sensor failures are identified by utilizing the analytic relationship between the various sensor outputs arising from the aircraft equations of motion.

Caglayan, A. K.↗
NASA NTRS1994

Failure tolerant operation of kinematically redundant manipulators

Redundant manipulators may compensate for failed joints with their additional degrees of freedom. In this paper such a manipulator is considered fault tolerant if it can guarantee completion of a task after any one of its joints has failed. This fault tolerance of kinematically redundant manipulators is insured here. Methods to analyze the manipulator's work space find regions inherently suitable for critical tasks because of their high level of failure tolerance. Constraints are then placed on the manipulator's range of motion to guarantee completion of a task.

Lewis, Christopher L.↗
NASA NTRS1986

Tectonic escape in the evolution of the continental crust

The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

Burke, K.↗
NASA NTRS1984

A Fault Tolerant System for an Integrated Avionics Sensor Configuration

An aircraft sensor fault tolerant system methodology for the Transport Systems Research Vehicle in a Microwave Landing System (MLS) environment is described. The fault tolerant system provides reliable estimates in the presence of possible failures both in ground-based navigation aids, and in on-board flight control and inertial sensors. Sensor failures are identified by utilizing the analytic relationships between the various sensors arising from the aircraft point mass equations of motion. The estimation and failure detection performance of the software implementation (called FINDS) of the developed system was analyzed on a nonlinear digital simulation of the research aircraft. Simulation results showing the detection performance of FINDS, using a dual redundant sensor compliment, are presented for bias, hardover, null, ramp, increased noise and scale factor failures. In general, the results show that FINDS can distinguish between normal operating sensor errors and failures while providing an excellent detection speed for bias failures in the MLS, indicated airspeed, attitude and radar altimeter sensors.

Caglayan, A. K.↗
NASA NTRS1982

Fault tolerant navigation in a Microwave Landing System environment

This paper describes the failure detection and isolation performance of a sensor fault tolerant system for the NASA Terminal Configured Vehicle (TCV) research aircraft in a Microwave Landing System (MLS) environment. The objective of the fault tolerant system is to detect failures in navigation-aid instruments and on-board sensors and to provide reliable estimates for the aircraft states in the possible presence of these sensor malfunctions. Analytic redundancy, which exists between the various sensor outputs due to the aircraft point mass equations of motion, is used to identify sensor failures. State estimates are used by an automatic guidance and control system to land the aircraft along a prescribed path.

Caglayan, A. K.↗