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NASA NTRS1991

Caldera-structure relationships in Kenya - Observations from satellite data

Maps were constructed showing lineaments displayed on four Landsat MSS images, to study volcanic-tectonic relationships in the Kenya segment of the Gregory or eastern sector of the East African rift system. Many of the mapped lineaments correlated well with fractures shown on geological maps. Selected lineaments, transverse to the rift trend, could be extrapolated to intersect rift faults at locations correlative with the locations of Kenya's seven volcanic calderas. The volcano-genetic difference between these intersections vs. similar intersections having no obvious relationship to any type of volcanic vent is not yet understood.

Blodget, Herbert W.↗

NASA NTRS1989

Intelligent hypertext manual development for the Space Shuttle hazardous gas detection system

This research is designed to utilize artificial intelligence (AI) technology to increase the efficiency of personnel involved with monitoring the space shuttle hazardous gas detection systems at the Marshall Space Flight Center. The objective is to create a computerized service manual in the form of a hypertext and expert system which stores experts' knowledge and experience. The resulting Intelligent Manual will assist the user in interpreting data timely, in identifying possible faults, in locating the applicable documentation efficiently, in training inexperienced personnel effectively, and updating the manual frequently as required.

Lo, Ching F.↗

NASA NTRS1999

Software Evolution and the Fault Process

In developing a software system, we would like to estimate the way in which the fault content changes during its development, as well determine the locations having the highest concentration of faults. In the phases prior to test, however, there may be very little direct information regarding the number and location of faults. This lack of direct information requires developing a fault surrogate from which the number of faults and their location can be estimated. We develop a fault surrogate based on changes in the fault index, a synthetic measure which has been successfully used as a fault surrogate in previous work. We show that changes in the fault index can be used to estimate the rates at which faults are inserted into a system between successive revisions. We can then continuously monitor the total number of faults inserted into a system, the residual fault content, and identify those portions of a system requiring the application of additional fault detection and removal resources.

Nikora, Allen P.↗

NASA NTRS2003

Secondary Fracturing of Europa's Crust in Response to Combined Slip and Dilation Along Strike-Slip Faults

A commonly observed feature in faulted terrestrial rocks is the occurrence of secondary fractures alongside faults. Depending on exact morphology, such fractures have been termed tail cracks, wing cracks, kinks, or horsetail fractures, and typically form at the tip of a slipping fault or around small jogs or steps along a fault surface. The location and orientation of secondary fracturing with respect to the fault plane or the fault tip can be used to determine if fault motion is left-lateral or right-lateral.

Kattenhorn, S. A.↗

NASA NTRS1990

Using Dynamic Sensitivity Analysis to Assess Testability

This paper discusses sensitivity analysis and its relationship to random black box testing. Sensitivity analysis estimates the impact that a programming fault at a particular location would have on the program's input/output behavior. Locations that are relatively \"insensitive" to faults can render random black box testing unlikely to uncover programming faults. Therefore, sensitivity analysis gives new insight when interpreting random black box testing results. Although sensitivity analysis is computationally intensive, it requires no oracle and no human intervention.

Voas, Jeffrey↗

NASA NTRS1985

Compressional environment in the location and orientation of planetary dorsa and terrestrial earthquake fault structures

Lunar mare ridges are not pure compressional ridges but their locations and orientations are most likely controlled by shear zones as seen from their Riedel-shear-like arrangements. On the Moon the crustal shortening has mostly taken place within mare areas but some young terra ridges are also to be seen indicating some crustal shortening also outside mare areas. This shortening has, however, not reached the same intensity as in the case of lobate scarp overthrusts on Mercury.

Raitala, J.↗

NASA NTRS1986

North American-Pacific relative plate motion in southern California from interferometry

VLBI measurements of baselines crossing the San Andreas fault zone in southern California have provided observational constraints on rates of elastic tectonic strain accumulation. The single site located near this fault (the JPL site) moves in a direction concordant with the Pacific plate motion vector but at approximately half the net rate relative to North America. This motion agrees approximately in amount with geologically determined displacement rates on the San Andreas fault alone but not with the local strike of the fault. When considered together with complementary geodetic data, these results suggest a complex relation between the short-term accumulation of elastic strain and its permanent accommodation on existing faults.

Lyzenga, G. A.↗

NASA NTRS1990

Quantifying fault recovery in multiprocessor systems

Various aspects of reliable computing are formalized and quantified with emphasis on efficient fault recovery. The mathematical model which proves to be most appropriate is provided by the theory of graphs. New measures for fault recovery are developed and the value of elements of the fault recovery vector are observed to depend not only on the computation graph H and the architecture graph G, but also on the specific location of a fault. In the examples, a hypercube is chosen as a representative of parallel computer architecture, and a pipeline as a typical configuration for program execution. Dependability qualities of such a system is defined with or without a fault. These qualities are determined by the resiliency triple defined by three parameters: multiplicity, robustness, and configurability. Parameters for measuring the recovery effectiveness are also introduced in terms of distance, time, and the number of new, used, and moved nodes and edges.

Malek, Miroslaw↗

NASA NTRS1989

A model for the analysis of fault-tolerant signal processing architectures

This paper develops a new model, using matrices, for the analysis of fault-tolerant multiprocessor systems. The relationship between processors computing useful data, the output data, and the check processors is defined in terms of matrix entries. Unlike the matrix-based models proposed previously for the analysis of digital systems, this model uses only numerical computations rather than logical operations for the analysis of a system. Algorithms to evaluate the fault detection and location capability of the system are proposed which are much less complex than the existing ones. The new model is used to analyze some fault-tolerant architectures proposed for signal-processing applications.

Nair, V. S. S.↗

NASA NTRS1992

Lithospheric dynamics near plate boundaries

The progress report on research conducted between 15 Mar. - 14 Sep. 1992 is presented. The focus of the research during the first grant year has been on several problems broadly related to the nature and dynamics of time-dependent deformation and stress along major seismic zones, with an emphasis on western North America but with additional work on seismic zones in oceanic lithosphere as well. The principal findings of our research to date are described in the accompanying papers and abstract. Topics covered include: (1) Global Positioning System measurements of deformations associated with the 1987 Superstition Hills earthquake: evidence for conjugate faulting; (2) Global Positioning System measurements of strain accumulation across the Imperial Valley, California: 1986-1989; (3) present-day crustal deformation in the Salton Trough, southern California; (4) oceanic transform earthquakes with unusual mechanisms or locations: relation to fault geometry and state of stress in the lithosphere; and (5) crustal strain and the 1992 Mojave Desert earthquakes.

Solomon, Sean C.↗

NASA NTRS1992

Probabilistic evaluation of on-line checks in fault-tolerant multiprocessor systems

The analysis of fault-tolerant multiprocessor systems that use concurrent error detection (CED) schemes is much more difficult than the analysis of conventional fault-tolerant architectures. Various analytical techniques have been proposed to evaluate CED schemes deterministically. However, these approaches are based on worst-case assumptions related to the failure of system components. Often, the evaluation results do not reflect the actual fault tolerance capabilities of the system. A probabilistic approach to evaluate the fault detecting and locating capabilities of on-line checks in a system is developed. The various probabilities associated with the checking schemes are identified and used in the framework of the matrix-based model. Based on these probabilistic matrices, estimates for the fault tolerance capabilities of various systems are derived analytically.

Nair, V. S. S.↗

NASA NTRS2011

Strike-Slip Fault Patterns on Europa: Obliquity or Polar Wander?

Variations in diurnal tidal stress due to Europa's eccentric orbit have been considered as the driver of strike-slip motion along pre-existing faults, but obliquity and physical libration have not been taken into account. The first objective of this work is to examine the effects of obliquity on the predicted global pattern of fault slip directions based on a tidal-tectonic formation model. Our second objective is to test the hypothesis that incorporating obliquity can reconcile theory and observations without requiring polar wander, which was previously invoked to explain the mismatch found between the slip directions of 192 faults on Europa and the global pattern predicted using the eccentricity-only model. We compute predictions for individual, observed faults at their current latitude, longitude, and azimuth with four different tidal models: eccentricity only, eccentricity plus obliquity, eccentricity plus physical libration, and a combination of all three effects. We then determine whether longitude migration, presumably due to non-synchronous rotation, is indicated in observed faults by repeating the comparisons with and without obliquity, this time also allowing longitude translation. We find that a tidal model including an obliquity of 1.2?, along with longitude migration, can predict the slip directions of all observed features in the survey. However, all but four faults can be fit with only 1? of obliquity so the value we find may represent the maximum departure from a lower time-averaged obliquity value. Adding physical libration to the obliquity model improves the accuracy of predictions at the current locations of the faults, but fails to predict the slip directions of six faults and requires additional degrees of freedom. The obliquity model with longitude migration is therefore our preferred model. Although the polar wander interpretation cannot be ruled out from these results alone, the obliquity model accounts for all observations with a value consistent with theoretical expectations and cycloid modeling.

Rhoden, Alyssa Rose↗

NASA NTRS1985

Thermal regimes in the detachment fault environment as deduced from fluid inclusions

Extensional tectonism, which dominates middle- and late-Tertiary geology in western Arizona, southeastern California, and southern Nevada, is characterized by normal regionally extensive, low-angle detachment faults. The decollement movement of Fupper plate rocks relative to lower plate assemblages created extensive zones of dilatency, including synthetic and antithetic listric normal faults, tear faults, tectonic crush breccias, shatter breccias, and gash veins in lithologic units above and below the detachment. The tectonically enhanced permeability above and below the detachment fault permitted mass migration of large volumes of hydrothermal solutions along the fault zone during and following upper plate movement. Major quantities of MgO, CaO, K2O, FeO/Fe2O3, SiO2 and CO2 were added to rocks in and near the detachment and related structures. Also introduced were varying amounts of trace elements including Mn, Cu, S, Mo, Ba, Au, Pb, Zn, U and/or Ag. Minerals containing fluid incusions were collected from all of these loci at locations in detachment faulted terranes in western Arizona and southeastern California.

Beane, R. E.↗

NASA NTRS1992

Fault detection and bypass in a sequence information signal processor

The invention comprises a plurality of scan registers, each such register respectively associated with a processor element; an on-chip comparator, encoder and fault bypass register. Each scan register generates a unitary signal the logic state of which depends on the correctness of the input from the previous processor in the systolic array. These unitary signals are input to a common comparator which generates an output indicating whether or not an error has occurred. These unitary signals are also input to an encoder which identifies the location of any fault detected so that an appropriate multiplexer can be switched to bypass the faulty processor element. Input scan data can be readily programmed to fully exercise all of the processor elements so that no fault can remain undetected.

Peterson, John C.↗

NASA NTRS1992

Patterns of seismic activity preceding large earthquakes

A mechanical model of seismic faults is employed to investigate the seismic activities that occur prior to major events. The block-and-spring model dynamically generates a statistical distribution of smaller slipping events that precede large events, and the results satisfy the Gutenberg-Richter law. The scaling behavior during a loading cycle suggests small but systematic variations in space and time with maximum activity acceleration near the future epicenter. Activity patterns inferred from data on seismicity in California demonstrate a regional aspect; increased activity in certain areas are found to precede major earthquake events. One example is given regarding the Loma Prieta earthquake of 1989 which is located near a fault section associated with increased activity levels.

Shaw, Bruce E.↗

NASA NTRS1971

Plate convergence, transcurrent faults and internal deformation adjacent to Southeast Asia and the western Pacific

A model for oblique convergence between plates of lithosphere is proposed in which at least a fraction of slip parallel to the plate margin results in transcurrent movements on a nearly vertical fault which is located on the continental side of a zone of plate consumption. In an extreme case of complete decoupling only the component of slip normal to the plate margin can be inferred from underthrusting. Recent movements in the western Sunda region provide the most convincing evidence for decoupling of slip, which in this region is thought to be oblique to the plate margin. A speculative model for convergence along the margins of the Philippine Sea is constructed from an inferred direction of oblique slip in the Philippine region. This model requires that the triple point formed by the junction of the Japanese and Izu-Bonin trenches and the Nankai trough migrate along the Sagami trough.

Fitch, T. J.↗

NASA NTRS1973

ERTS Applications in earthquake research and mineral exploration in California

Examples that ERTS imagery can be effectively utilized to identify, locate, and map faults which show geomorphic evidence of geologically recent breakage are presented. Several important faults not previously known have been identified. By plotting epicenters of historic earthquakes in parts of California, Sonora, Mexico, Arizona, and Nevada, we found that areas known for historic seismicity are often characterized by abundant evidence of recent fault and crustal movements. There are many examples of seismically quiet areas where outstanding evidence of recent fault movements is observed. One application is clear: ERTS-1 imagery could be effectively utilized to delineate areas susceptible to earthquake recurrence which, on the basis of seismic data alone, may be misleadingly considered safe. ERTS data can also be utilized in planning new sites in the geophysical network of fault movement monitoring and strain and tilt measurements.

Abdel-Gawad, M.↗

NASA NTRS1975

Department of the Interior program

The remote sensing activities of the Department of Interior are summarized. The use of satellite imagery in land and water management is described. Specific topics discussed include: land use mapping, exploration and discovery of metal, oil, and gas deposits, location of geological faults, and repetitive monitoring of dynamic environmental phenomena related to water resources.

Balsley, J. R.↗