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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Global positioning system reoccupation of early triangulation sites - Tectonic deformation of the Southern Coast Ranges

We study tectonic deformation in the Southern Coast Range, California. We use triangulation and astronomic azimuth data collected since 1875, trilateration since 1970, and global positioning system data collected from 1986 to 1987. Two modeling techniques have been used. An elastic block-fault model is applied to study the tectonic motion of the San Andreas Fault and the San Gregorio-Hosgri Fault. Station velocities are modeled to study regional deformations. Results show that the regional deformation is predominantly controlled by deep strike-slip motion along the San Andreas Fault, at a rate of 33 +/- 2 mm/yr. Deep slip along the San Gregorio-Hosgri Fault is about 0-4 mm/yr, assuming a locked suit to a depth of 20 km. Convergence normal to the San Andreas Fault in the Southern Coast Ranges is not greater than 0.02 microrad/yr.

Shen, Zheng-Kang↗
NASA NTRS1985

Dislocation model for aseismic fault slip in the transverse ranges of Southern California

Geodetic data at a plate boundary can reveal the pattern of subsurface displacements that accompany plate motion. These displacements are modelled as the sum of rigid block motion and the elastic effects of frictional interaction between blocks. The frictional interactions are represented by uniform dislocation on each of several rectangular fault patches. The block velocities and fault parameters are then estimated from geodetic data. Bayesian inversion procedure employs prior estimates based on geological and seismological data. The method is applied to the Transverse Ranges, using prior geological and seismological data and geodetic data from the USGS trilateration networks. Geodetic data imply a displacement rate of about 20 mm/yr across the San Andreas Fault, while the geologic estimates exceed 30 mm/yr. The prior model and the final estimates both imply about 10 mm/yr crustal shortening normal to the trend of the San Andreas Fault. Aseismic fault motion is a major contributor to plate motion. The geodetic data can help to identify faults that are suffering rapid stress accumulation; in the Transverse Ranges those faults are the San Andreas and the Santa Susana.

Cheng, A.↗
NASA NTRS2012

Recovery of Deep Moonquake Focal Mechanisms

Deep moonquakes are clustered not only in space but also in time: their recurrence times correspond to the durations of the anomalistic and draconic months, with some clusters preferring one of the two periods, while others are active with both periods. A key constraint for the understanding of the connection between the orbital motion of the Moon and its seismic activity is the focal mechanism: the orientation of the fault surface on which failure occurs during the quake. Due to the small aperture of the Apollo seismic network and the strong scattering of seismic waves within the lunar crust, the evaluation of P wave first motions to constrain the strike and dip of the fault planes is not feasible. Instead we evaluate the amplitude ratios of P and S waves. Seismograms are rotated into the P-SV-SH coordinate frame and amplitudes are determined as averages over short time windows after the arrival to reduce the impact of the scattering coda, which is independent of the source orientation. We allow for reversals of the fault motion, as observed for some clusters in previous studies, by taking into account the absolute amplitude only, without sign. An empirical site correction factor is applied to correct for amplitude distortions in the crust. We construct ensembles of fault plane solutions using an exhaustive grid search by accepting all orientations that reproduce the measured amplitude ratios within the observed standard deviations. Since all events of a given cluster are supposed to share the same fault plane, the combination of the individual inversion results further constrains the orientation. We evaluate 106 events from 25 different moonquake clusters. The most active cluster A001 contributes 37 events, while others contribute 1 to 9 events per cluster. Comparison of fault orientations with the variation of the tidal stress results in preferred orientations.

Weber, Renee C.↗
NASA NTRS1993

Use of SPOT and ERS-1 SAR data to study the tectonic and climatic history of arid regions

In order to separate the effects of the different tectonic and climatic processes on the shapes of desert piedmonts, a modified conic equation was fitted to digital topographic data for individual alluvial fans in Death Valley (California, U.S.). The topographic data were obtained from a SPOT panchromatic stereo pair and from the airborne interferometric SAR (Synthetic Aperture Radar) (TOPSAR). The conic fit allows parameters for the epex position, slope, and radial curvature to be compared with unit age, uplift rate, and climatic conditions. Preliminary results indicate that slope flattens with age and radial curvature is concave up, but decreases with age. Work is continuing on correlation of fit residuals and apex position with fan unit age. This information will help in the determination of tectonic uplift rates and the climatic history of the western U.S. ERS-1 SAR images were used to study an area of western China where a large strike slip fault crosses a series of alluvial fans and stream valleys. Previous analysis of SPOT panchromatic images of the area shows that offsets fans and streams can be recognized. Measurement of the rate of motion of this fault will help in the overall model of deformation of the Asian tectonic plate in response to the collision of the Indian plate.

Farr, Tom G.↗
NASA NTRS2011

Relaxing USOS Solar Array Constraints for Russian Vehicle Undocking

With the retirement of Space Shuttle cargo delivery capability and the ten year life extension of the International Space Station (ISS) more emphasis is being put on preservation of the service life of ISS critical components. Current restrictions on the United States Orbital Segment (USOS) Solar Array (SA) positioning during Russian Vehicle (RV) departure from ISS nadir and zenith ports cause SA to be positioned in the plume field of Service Module thrusters and lead to degradation of SAs as well as potential damage to Sun tracking Beta Gimbal Assemblies (BGA). These restrictions are imposed because of the single fault tolerant RV Motion Control System (MCS), which does not meet ISS Safety requirements for catastrophic hazards and dictates 16 degree Solar Array Rotary Joint position, which ensures that ISS and RV relative motion post separation, does lead to collision. The purpose of this paper is to describe a methodology and the analysis that was performed to determine relative motion trajectories of the ISS and separating RV for nominal and contingency cases. Analysis was performed in three phases that included ISS free drift prior to Visiting Vehicle separation, ISS and Visiting Vehicle relative motion analysis and clearance analysis. First, the ISS free drift analysis determined the worst case attitude and attitude rate excursions prior to RV separation based on a series of different configurations and mass properties. Next, the relative motion analysis calculated the separation trajectories while varying the initial conditions, such as docking mechanism performance, Visiting Vehicle MCS failure, departure port location, ISS attitude and attitude rates at the time of separation, etc. The analysis employed both orbital mechanics and rigid body rotation calculations while accounting for various atmospheric conditions and gravity gradient effects. The resulting relative motion trajectories were then used to determine the worst case separation envelopes during the clearance analysis. Analytical models were developed individually for each stage and the results were used to build initial conditions for the following stages. In addition to the analysis approach, this paper also discusses the analysis results, showing worst case relative motion envelopes, the recommendations for ISS appendage positioning and the suggested approach for future analyses.

Menkin, Evgeny↗
NASA NTRS1986

A kinematic model of southern California

A kinematic model for southern California, based on late-Quaternary slip rates and orientations of major faults in the region, is proposed. Internally consistent motions are determined assuming that these faults bound rigid blocks. Relative to North America, most of California west of the San Andreas fault is moving parallel to the San Andreas fault through the Transverse Ranges and not parallel to the motion of the Pacific plate. The velocities of the blocks are calculated along several paths in southern California that begin in the Mojave Desert and end off the California coast. A path that crosses the western Transverse Ranges accumulates the accepted relative North America-Pacific plate velocity, whereas paths to the north and south result in a significant missing component of motion, implying the existence of a zone of active deformation in southern California.

Weldon, R.↗
NASA NTRS1987

Aseismic crustal deformation in the Transverse Ranges of southern California

Using geodetic data at a plate boundary, the subsurface displacements that accompany plate motion were modeled as the sum of rigid block motion and the elastic effects of frictional drag between blocks in a model consisting of 12 blocks and 27 rectangular fault patches. The block motion inferred from the geodetic data has the same order of magnitude as the geologic estimates, and for many faults the agreement was excellent. The model implies about 20 mm/y of crustal shortening normal to the trend of the San Andreas fault.

Cheng, Abe↗
NASA NTRS2004

Crustal Deformation and the Seismic Cycle across the Kodiak Islands, Alaska

The Kodiak Islands are located approximately 130 to 250 km from the Alaska-Aleutian Trench where the Pacific plate is underthrusting the North American plate at a rate of about 57 mm/yr. The southern extent of the 1964 Prince William Sound (${M-w}$ = 9.2) earthquake rupture occurred offshore and beneath the eastern portion of the Kodiak Islands. Here we report GPS results (1993-2001) from northern Kodiak Island that span the transition between the 1964 uplift region along the eastern coast and the region of coseismic subsidence further inland. The horizontal velocity vectors range from 22.9 $\pm$ 2.2 mm/yr at N26.3$\deg$W $\pm$ 2.5$\deg$, about 150 km from the trench, to 5.9 $\pm$ 1.3 mm/yr at N65.9$\deg$W $\pm$ 6.6$\deg$, about 190 km from the trench. Near the northeastern coast of Kodiak the velocity vector above the shallow, locked main thrust zone is between the orientation of PCFC-NOAM plate motion (N22$/deg$W) and the trench-normal (N3O$\deg$W). Further west, our geodetic results suggest the accumulation of shear strain that will be released eventually as left-lateral motion on upper plate faults such as the Kodiak Island fault. These results are consistent with the hypothesis that the difference between the Pacific-North American plate motion and the orientation of the down going slab would lead to 4-8 mm/yr of left-lateral slip. Short-term geodetic uplift rates range from 2 - 14 mm/yr, with the maximum uplift located near the axis of maximum subsidence during the 1964 earthquake. We evaluated alternate interseismic models for Kodiak to test the importance of various mechanisms responsible for crustal deformation rates. These models are based on the plate interface slip history inferred from earlier modeling of coseismic and post-seismic geodetic results. The horizontal (trench perpendicular) and vertical deformation rates across Kodiak are consistent with a model that includes the viscoelastic response to : (1) a downgoing Pacific plate interface that is locked at shallow depths,(2) coseismic slip in the 1964 and (3) interseismic creep below the seismogenic zone. The change in orientation of the horizontal velocity vector occurs down-dip from the locked main thrust zone. In southern Kodiak, the coseismic slip in the 1964 earthquake was smaller than in the northern Kodiak region; yet, the horizontal, interseismic velocities as a function of distance from the trench are comparable to those in northern Kodiak. Based on the earthquake history prior to, and following the 1964 earthquake, we hypothesize that the plate interface in southern Kodiak slips in more frequent large earthquakes than in northern Kodiak.

Sauber, Jeanne↗
NASA NTRS1988

Possible breakup of dark terrain on Ganymede by large-scale shear faulting

The questions of relative motions of large segments of Ganymede's lithosphere and of the effect of any motions on grooved terrain formation are reexamined. Resolvable furrows in both hemispheres were mapped in great detail using Voyager 1 and 2 images and U.S. Geological Survey controlled shaded-relief quadrangle maps. Estimates of the Galileo Regio and Marius Regio poles of furrow concentricity indicate a considerable westward offset of the Galileo Regio pole, suggesting the possibility of about 500-km of left-lateral offset of the two areas. There is evidence that shear deformation was concentrated along a major structural lineament which follows a small circle and encloses Galileo Regio, and that a smaller amount of distributed shear occurred across an adjacent 500- to 1500-km-wide band. The results indicate that either widespread shear strain or the shear's driving mechanism may have had a long-term effect on patterns of deformation of Ganymede's lithosphere.

Murchie, Scott L.↗
NASA NTRS2013

Mars Science Laboratory CHIMRA/IC/DRT Flight Software for Sample Acquisition and Processing

The design methodologies of using sequence diagrams, multi-process functional flow diagrams, and hierarchical state machines were successfully applied in designing three MSL (Mars Science Laboratory) flight software modules responsible for handling actuator motions of the CHIMRA (Collection and Handling for In Situ Martian Rock Analysis), IC (Inlet Covers), and DRT (Dust Removal Tool) mechanisms. The methodologies were essential to specify complex interactions with other modules, support concurrent foreground and background motions, and handle various fault protections. Studying task scenarios with multi-process functional flow diagrams yielded great insight to overall design perspectives. Since the three modules require three different levels of background motion support, the methodologies presented in this paper provide an excellent comparison. All three modules are fully operational in flight.

sample processing↗
NASA NTRS1997

Structure and Kinematics of a Complex Crater: Upheaval Dome, Southeast, Utah

Two vastly different phenomena, extraterrestrial impact and salt diapirism, have been proposed for the origin of Upheaval Dome. Upheaval Dome is a about 2.5-km-diameter structural dome surrounded by a 5-km-diameter ring structural depression, which is in turn flanked by extensive, nearly flat-lying Colorado Plateau strata. Seismic refraction data and geologic mapping indicate that the dome originated by the collapse of a transient cavity formed by impact; data also show that rising salt has had a negligible influence on dome development. Evidence for this includes several factors: (1) a rare lag deposit of impactite is present; (2) fan-tailed fracture surfaces (shatter surfaces) and a few shattercones are present; (3) the top of the underlying salt horizon is at least 500 m below the center of the dome, with no exposures of salt in the dome to support the possibility that a salt diapir has ascended through it; (4) sedimentary strata in the center are significantly imbricated by top-to-the-center thrust faulting and are complexly folded; (5) top-to-the-center low-angle normal faults are found at the perimeter of the structure; and (6) clastic dikes are widespread. The scarcity of melt rocks and shock fabrics is attributed to approximately 0.5 km of erosion; the structures of the dome reflect processes of complex crater development at a depth of about 0.5 km below the crater floor. Based on mapping and kinematic analysis, we infer that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, largely resulted from this motion. In addition, we have detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding in the perimeter of the structure. Collectively, the observed deformation accounts for the creation of both the central uplift and the encircling ring syncline.

Kriens, B. J.↗
NASA NTRS2005

Quantifying Exact Motions Along Lineaments on Europa

Evaluating the precise motions along lineaments on the surface of Jupiter's icy moon, Europa, is a valuable tool for interpreting the development and history of lineaments of various morphologies. Such morphologies include strike-slip faults, dilational bands, ridges, and convergence zones. However, the exact mode of origin and kinematic behavior of these various lineaments are not obvious based on morphology alone. In fact, the apparent motions implied by displaced crosscut features can provide misleading indications of true motions along lineaments. Identifying the precise motions (combinations of sliding and opening/closing) is critical to the accurate characterization and interpretation of each of these lineament types. Lineaments of interest (i.e., those having displaced relatively older features in some manner) are identified on Galileo spacecraft images and measurements are made of the total offset, the separation, and relative orientations of crosscut features with respect to the lineament of interest. Specifically, by using these measured quantities and a series of trigonometric equations, the precise motions (i.e., dilation, convergence, strike-slip, or a combination of strike-slip and dilation or convergence) can be determined. These measurements are, however, limited by the resolution of the available images. This study focuses on motion analysis techniques for Europan lineaments and the precise characterization of fault-orthogonal and/or strike-slip motion along lineaments of varying morphologies. We highlight potential pitfalls of cursory analyses of motion indicators. For example, lineaments with obvious lateral offsets have typically been identified simply as strike-slip faults. This assumption may actually be incorrect, as fault-orthogonal motions may contribute to apparent lateral displacements (offsets or separations). Also, variability in the amount of fault motion along the trace length should theoretically be identifiable using the outlined technique. Strike-slip faults on Europa have conventionally been presumed to have a constant slip magnitude along their lengths; however, we posit that variable distributions of slip may be common, as is typical along terrestrial strike-slip faults.

Vetter, J. C.↗
NASA NTRS1993

Plate tectonics and crustal deformation around the Japanese Islands

We analyze over a century of geodetic data to study crustal deformation and plate motion around the Japanese Islands, using the block-fault model for crustal deformation developed by Matsu'ura et al. (1986). We model the area including the Japanese Islands with 19 crustal blocks and 104 faults based on the distribution of active faults and seismicity. Geodetic data are used to obtain block motions and average slip rates of faults. This geodetic model predicts that the Pacific plate moves N deg 69 +/- 2 deg W at about 80 +/- 3 mm/yr relative to the Eurasian plate which is much lower than that predicted in geologic models. Substantial aseismic slip occurs on the subduction boundaries. The block containing the Izu Peninsula may be separated from the rigid part of the Philippine Sea plate. The faults on the coast of Japan Sea and the western part of the Median Tectonic Line have slip rates exceeding 4 mm/yr, while the Fossa Magna does not play an important role in the tectonics of the central Japan. The geodetic model requires the division of northeastern Japan, contrary to the hypothesis that northeastern Japan is a part of the North American plate. Owing to rapid convergence, the seismic risk in the Nankai trough may be larger than that of the Tokai gap.

Hashimoto, Manabu↗
NASA NTRS1974

A summary of ERTS data applications in Alaska

ERTS has proven to be an exceedingly useful tool for the preparation of urgently needed resource surveys in Alaska. For this reason the wide utilization of ERTS data by federal, state and industrial agencies in Alaska is increasingly directed toward the solution of operational problems in resource inventories, environmental surveys, and land use planning. Examples of some applications are discussed in connection with surveys of potential agricultural lands; mapping of predicted archaeological sites; permafrost terrain and aufeis mapping; snow melt enhancement from Prudhoe Bay roads; geologic interpretations correlated ith possible new petroleum fields, with earthquake activity, and with plate tectonic motion along the Denali fault system; hydrology in monitoring surging glaciers and the break-up characteristics of the Chena River watershed; sea-ice morphology correlated with marine mammal distribution; and coastal sediment plume circulation patterns.

Miller, J. M.↗
NASA NTRS1981

On the geodetic stability of the Goddard Optical Research Facility

Seismic observations of earthquakes and blasts, geologic analysis of Landsat images, and a search of the historical record was examined. However, no evidence for tectonic motion was found. Some faulting is present in the area but no evidence of seismic activity was found. No elastic resonances in the range from 0.3 to 15 Hz were found. It is concluded that, except for ground water induced changes, the facility is stable at least to the 0.5 cm level.

Webster, W. J., Jr.↗
NASA NTRS1990

Distributed deformation and block rotation in 3D

The authors address how block rotation and complex distributed deformation in the Earth's shallow crust may be explained within a stationary regional stress field. Distributed deformation is characterized by domains of sub-parallel fault-bounded blocks. In response to the contemporaneous activity of neighboring domains some domains rotate, as suggested by both structural and paleomagnetic evidence. Rotations within domains are achieved through the contemporaneous slip and rotation of the faults and of the blocks they bound. Thus, in regions of distributed deformation, faults must remain active in spite of their poor orientation in the stress field. The authors developed a model that tracks the orientation of blocks and their bounding faults during rotation in a 3D stress field. In the model, the effective stress magnitudes of the principal stresses (sigma sub 1, sigma sub 2, and sigma sub 3) are controlled by the orientation of fault sets in each domain. Therefore, adjacent fault sets with differing orientations may be active and may display differing faulting styles, and a given set of faults may change its style of motion as it rotates within a stationary stress regime. The style of faulting predicted by the model depends on a dimensionless parameter phi = (sigma sub 2 - sigma sub 3)/(sigma sub 1 - sigma sub 3). Thus, the authors present a model for complex distributed deformation and complex offset history requiring neither geographical nor temporal changes in the stress regime. They apply the model to the Western Transverse Range domain of southern California. There, it is mechanically feasible for blocks and faults to have experienced up to 75 degrees of clockwise rotation in a phi = 0.1 strike-slip stress regime. The results of the model suggest that this domain may first have accommodated deformation along preexisting NNE-SSW faults, reactivated as normal faults. After rotation, these same faults became strike-slip in nature.

Scotti, Oona↗
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↗