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  • 1
    Keywords: Earthquake Prediction ; Simulation
    Description / Table of Contents: Vol. 157, 2000 spanning across disciplines and national boundaries gives cause for optimism. New participation in ACES to extend its existing synergies is welcomed. We wish to thank the scientific participants of The APEC Cooperation for Earthquake Simulation (ACES) and the contributors to this book. We express appreciation to the Australian, Chinese, Japanese and USA governments for supporting the establishment of ACES. We gratefully acknowledge funding support by the Australian government's Department of Industry, Science and Resources, The University of Queensland, Japan's Science and Technology Agency through its Research Organisation for Information Science and Technology, the Chinese Ministry of Science and Technology, and the National Science Foundation of China. We acknowledge with appreciation additional workshop sponsorship pro­ vided by SGI (Silicon Graphics). Special thanks to QUAKES team members (Tracy Paroz, David Place, Steffen Abe, Dion Weatherley and Steven Jaume) and Kim Olsen who provided assistance to the Editors. Peter Mora would also like to thank Evelyne Meier. REFERENCES I-st ACES Workshop Proceedings (1999), ed. Mora, P. (ACES, Brisbane, Australia, ISBN 1 86499 121 6), 554 pp. APEC Cooperation for Earthquake Simulation: http://quakes. earth. uq. edu. au/ACES ACES Inaugural Workshop: http://quakes. earth. uq. edu. au/ACES_ WS Raul Madariaga Peter Mora QUAKES Laboratoire de Geologie Department of Earth Sciences Ecole Normale Superieur The University of Queensland 24 Rue Lhomond 4072 Brisbane, Qld F-75231 Paris, Cedex 05 Australia France mora@earth. up. edu. au madariag@geologie. ens.
    Pages: Online-Ressource (VII, 567 Seiten)
    ISBN: 9783034876957
    Language: English
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  • 2
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Trace element concentration data can be used in a systematic way for the study of igneous processes by means of constructing models of such processes which satisfactorily account for the observations. We propose to treat the problem as an inverse problem. The concept of trace element paths (TEP) is introduced as a representation of the solution to the direct problem. The inverse problem consists of estimating, by a resolution of the equations, the various parameters of a model so as to provide a best fit to observed TEP. A detailed account of the theory is given in the case of equilibrium fractional crystallization. The estimated parameters are then those figuring in the Rayleigh distillation law, namely, 1) the initial concentrations of trace elements in the parental magma, 2) the bulk partition coefficients of the elements, and 3) the degree of crystallization corresponding to each sample of the magmatic suite analyzed. A slightly generalized maximum likelihood method is used to solve the linearized equation by a stable, iterative algorithm. Information theory is then shown to yield an account of the distribution and flow of information during the process of solving the inverse problem. The concept of Data Importances is generalized, and its use in optimizing the study justified. The technique is successfully applied to a synthetic data set, and then illustrated on a data set from Terceira (Azores). The results are used to refine the conclusions reached in part I, and permit a more detailed discussion of the model.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We thank the editors of GJI for the opportunity to respond to the comment in this issue by Kosarev, Petersen & Vinnik 11996: hereafter referred to as KPV), which disputes the historical and technical accuracy of the paper by Gurrola, Minster & Owens (1994; henceforth referred to as GMO).
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In order to improve the signal-to-noise ratio of receiver function data, it is typical to stack receiver functions calculated from events at similar distances and back azimuths. We have adapted the velocity spectrum stacking (VSS) technique, used extensively in reflection seismology, to the receiver function method in order to stack data with different ray parameters, thereby improving further the signal-to-noise ratio. Perhaps more importantly, by producing the velocity spectrum stacks we take advantage of the differences in the shapes of the moveout curves of converted phases and reverberations to identify and separate the various phases and to infer velocity structure. By comparison of velocity spectrum stacks produced from the observed data at the IRIS/IDA broad-band station at Obninsk, Russia (OBN) with those produced from PREM synthetics we have identified Ps phases from the 400 and 670 km discontinuities. the P-to-S (Ps) converted phase from the 400 km discontinuity observed at OBN is much larger, compared with that of the 670 km discontinuity, than is predicted by PREM. This suggests a higher velocity contrast at 400 km than in PREM. By adapting a bootstrap method to assess the depth and velocity estimates determined by VSS, we find that the Ps phase from the 670 km discontinuity is best imaged with higher than PREM upper mantle P and S velocities and at a depth of 663 ± 3 km. We find no evidence of a 220 km discontinuity beneath OBN in these data.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2012-08-01
    Description: Improved near-field measurements of earthquake slip and deformation patterns have the potential for expanding our understanding of fault behavior and the relationship of active faulting to topography. Current techniques for obtaining these measurements—including field observation, Global Navigation Satellite Systems displacement estimation, and optical or radar remote sensing—have limitations that can be mitigated by the inclusion of results from differential airborne Light Detection and Ranging (LiDAR) analysis of the rupture zone. The 2005 airborne LiDAR survey of the southern San Andreas, San Jacinto, and Banning faults (the B4 survey) mapped 1100 km of the most seismically active fault systems in southern California for the purpose of providing a baseline for determining slip from a future earthquake. We used the B4 survey to develop a processing algorithm that yields rapid estimates of near-fault ground deformation using simultaneous cross correlation of both topography and backscatter intensity from pre-earthquake and simulated postearthquake LiDAR datasets. We show robust recovery of the direction and magnitude of an applied synthetic slip of 5 m in the horizontal and 0.5 m in the vertical within our area of study, with clear discrimination between areas with and without applied slip. We also successfully recovered more complex deformation from a modeled fault stepover in the same study area. Our results indicate that we should be able to recover slip to accuracies of better than 20 cm in the horizontal and 1 cm in the vertical, at a spatial resolution of ≤15 m for LiDAR datasets with sample densities as low as 0.5 points/m 2 .
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 6
    Publication Date: 2019-06-27
    Description: The inverse problem for gross earth data can be reduced to an undertermined linear system of integral equations of the first kind. A theory is discussed for computing particular solutions to this linear system based on the stochastic inverse theory presented by Franklin. The stochastic inverse is derived and related to the generalized inverse of Penrose and Moore. A Backus-Gilbert type tradeoff curve is constructed for the problem of estimating the solution to the linear system in the presence of noise. It is shown that the stochastic inverse represents an optimal point on this tradeoff curve. A useful form of the solution autocorrelation operator as a member of a one-parameter family of smoothing operators is derived.
    Keywords: MATHEMATICS
    Type: NASA. Ames Res. Center Math. of Profile Inversion; 12 p
    Format: text
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  • 7
    Publication Date: 2019-08-28
    Description: The first measurements are reported for a major earthquake by a continuously operating GPS network, the permanent GPS Genetic ARRY (PGGA) in southern California. The Landers and Big Bear earthquakes of June 28, 1992 were monitored by daily observations. Ten weeks of measurements indicate significant coseismic motion at all PGGA sites, significant postseismic motion at one site for two weeks after the earthquakes, and no significant preseismic motion. These measurements demonstrate the potential of GPS monitoring for precise detection of precursory and aftershock seismic deformation in the near and far field.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 361; 6410; p. 337-340.
    Format: text
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  • 8
    Publication Date: 2019-07-10
    Description: The topography of the Long Valley caldera, California, was sampled using airborne laser altimetry in 1993, 1995, and 1997 to test the feasibility of using airborne laser altimetry for monitoring deformation of volcanic origin. Results show the laser altimeters are able to resolve subtle topographic features such as a gradual slope and to detect small transient changes in lake elevation. Crossover and repeat pass analyses of laser tracks indicate decimeter-level vertical precision is obtained over flat and low-sloped terrain for altimeter systems performing waveform digitization. Comparisons with complementary, ground-based GPS data at a site close to Bishop airport indicate that the laser and GPS-derived elevations agree to within the error inherent in the measurement and that horizontal locations agree to within the radius of the laser footprint. A comparison of the data at two sites, one where no change and the other where the maximum amount of vertical uplift is expected, indicates approximately 10 cm of relative uplift occurred 1993-1997, in line with predictions from continuous GPS measurements in the region. Extensive terrain mapping flights during the 1995 and 1997 missions demonstrate some of the unique abilities of laser altimetry; the straightforward creation of high resolution, high accuracy digital elevation models of overflown terrain, and the ability to determine ground topography in the presence of significant ground cover such as dense tree canopies. These capabilities make laser altimetry an attractive technique for quantifying topographic change of volcanic origin, especially in forested regions of the world where other remote sensing instruments have difficulty detecting the underlying topography.
    Keywords: Earth Resources and Remote Sensing
    Type: Remote Sensing of Active Volcanism; 249-264; Geophysical-Monograph-116
    Format: text
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  • 9
    Publication Date: 2019-07-10
    Description: The topography of the Long Valley caldera, California, was sampled using airborne laser altimetry in 1993, 1995, and 1997 to test the feasibility of using airborne laser altimetry for monitoring deformation of volcanic origin. Results show the laser altimeters are able to resolve subtle topographic features such as a gradual slope and to detect small transient changes in lake elevation. Crossover and repeat pass analyses of laser tracks indicate decimeter-level vertical precision is obtained over flat and low-sloped terrain for altimeter systems performing waveform digitization. Comparisons with complementary, ground-based CPS data at a site close to Bishop airport indicate that the laser and GPS-derived elevations agree to within the error inherent in the measurement and that horizontal locations agree to within the radius of the laser footprint. A comparison of the data at two sites, one where no change and the other where the maximum amount of vertical uplift is expected, indicates approximately 10 cm of relative uplift occurred 1993-1997, in line with predictions from continuous CPS measurements in the region. Extensive terrain mapping flights during the 1995 and 1997 missions demonstrate some of the unique abilities of laser altimetry; the straightforward creation of high resolution, high accuracy digital elevation models of overflown terrain, and the ability to determine ground topography in the presence of significant ground cover such as dense tree canopies. These capabilities make laser altimetry an attractive technique for quantifying topographic change of volcanic origin, especially in forested regions of the world where other remote sensing instruments have difficulty detecting the underlying topography.
    Keywords: Earth Resources and Remote Sensing
    Type: Remote Sensing of Active Volcanism; 249-263; Geophysical-Monograph-116
    Format: text
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  • 10
    Publication Date: 2019-07-13
    Description: Long Valley caldera, California, is a site of extensive volcanism, persistent seismicity, and uplift of a resurgent dome, currently at a rate of approximately 3 cm/year. Airborne laser altimetry was used to determine the surface topography of the region in 1993. A repeat mission occurred in 1995. Three different laser altimeters were flown, dubbed ATLAS, SLICER and RASCAL. Data processing consists of the combination of the aircraft trajectory and attitude data with the laser range, the determination of an atmospheric delay, laser pulse timing errors, laser system biases, and data geolocation to obtain the position of the laser spot on the ground. Results showed that using the ATLAS and SLICER instruments, the elevation of an overflown lake is determined to precisions of 3.3 cm and 2.9 cm from altitudes of 500 m and 3 km above the ground, and approximately 10 cm using the RASCAL instrument from 500 m above ground. Comparison with tide gauge data showed the laser measurements are able to resolve centimeter-level changes in the lake elevation over time. Repeat pass analysis of tracks over flat surfaces indicate no systematic biases affect the measurement procedure of the ATLAS and SLICER instruments. Comparison of GPS and laser-derived elevations of easily-identifiable features in the caldera confirm the horizontal accuracy of the measurement is within the diameter of the laser footprint, and vertical accuracy is within the error inherent in the measurement. Crossover analysis shows that the standard error of the means at track intersection points within the caldera and dome (i.e., where zero and close to the maximum amount of uplift is expected) are about 1 cm, indicating elevation change at the 3 cm/year level should be detectable. We demonstrate one of the powerful advantages of scanning laser altimetry over other remote sensing techniques; the straightforward creation of precise digital elevation maps of overflown terrain. Initial comparison of the 1993-1995 data indicates uplift occurred, but filtering is required to remove vegetation effects. Although research continues to utilize the full potential of laser altimetry data, the results constitute a successful demonstration that the technique may be used to perform geodetic monitoring of surface topographic change.
    Keywords: Earth Resources and Remote Sensing
    Type: SPIE (ISSN 0277-786X); 3222; 295-306
    Format: text
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