A unified scheme for processing GPS dual-band phase observations   总被引：3，自引：4，他引：3  

Burkhard Schaffrin  Yehuda Bock 《Journal of Geodesy》1988,62(2):142-160

A unified computational scheme is presented for sequential least-squares processing ofGPS dual-band carrier-beat-phase observations in network-mode positioning with orbit relaxation, and in orbit determination applications. This scheme is applicable to any spatial and temporal distribution of stations and satellites during a particularGPS experiment. Full covariance matrices can be specified for carrier-beat-phases and for weighted constraints on the ionosphere in order to improve phase ambiguity resolution. Physically meaningful choices for these covariance matrices are developed.  相似文献   

A demonstration of 1–2 parts in 107 accuracy using GPS     

Yehuda Bock  Richard I. Abbot  Charles C. Counselman III  Robert W. King 《Journal of Geodesy》1986,60(3):241-254

By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in10 ⁷ for every vector component. TheGPS-SLR difference was within6 parts in10 ⁸ in the horizontal coordinates, but83 mm in height.  相似文献   

Multi-resolution clustering analysis and 3-D visualization of multitudinous synthetic earthquakes     

Witold Dzwinel  David Yuen  Yoshihiro Kaneko  Krzysztof Boryczko  Yehuda Ben-Zion 《Visual Geosciences》2003,8(1):1-32

We use modern and novel techniques to study the problems associated with detection and analysis of multitudinous seismic events, which form the background for isolated great earthquakes. This new approach involves multivariate analysis of low and large magnitude events recorded in space over a couple of centuries in time. We propose here the deployment of the clustering scheme both for extracting small local structures and large-scale trends in synthetic data obtained from four numerically simulated models with: uniform properties (U), a Parkfield-type asperity (A), fractal brittle properties (F), and multi-size-heterogeneity fault zone (M). The mutual nearest neighbor (mnn) clustering scheme allows for extraction of multi-resolutional seismic anomalies in both the spatio-temporal and multi-dimensional feature space. We demonstrate that the large earthquakes are correlated with a certain pathway of smaller events. Visualization of the anomalies by using a recently introduced visualization package Amira reveals clearly the spatio-temporal relationships between clusters of small, medium and large earthquakes, indicating significant stress relaxation across the entire fault region. We demonstrate that this mnn scheme can extract distinct clusters of the smallest events, which precede and follow a singularly large magnitude earthquake. These clusters form larger spatio-temporal structures comprising a series of large earthquakes. The link between the large and medium magnitude events is not so clearly understood. Short-ranged correlations are dominated by strong spatio-temporal anomalies, thus reflecting the global seismic properties of the entire fault zone.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.  相似文献   

Bursting and quenching in massive galaxies without major mergers or AGNs     

Yuval Birnboim  Avishai Dekel  Eyal Neistein 《Monthly notices of the Royal Astronomical Society》2007,380(1):339-352

In this work, we study the formation and evolution of dark matter haloes by means of the spherical infalling model with shell-crossing. We present a framework to tackle this effect properly based on the numerical follow-up, with time, of that individual shell of matter that contains always the same fraction of mass with respect to the total mass. In this first step, we do not include angular momentum, velocity dispersion or triaxiality. Within this framework – named as the spherical shell tracker – we investigate the dependence of the evolution of the halo with virial mass, with the adopted mass fraction of the shell, and for different cosmologies. We find that our results are very sensitive to a variation of the halo virial mass or the mass fraction of the shell that we consider. However, we obtain a negligible dependence on cosmology. Furthermore, we show that the effect of shell-crossing plays a crucial role in the way that the halo reaches the stabilization in radius and the virial equilibrium. We find that the values currently adopted in the literature for the actual density contrast at the moment of virialization,  δ_vir  , may not be accurate enough. In this context, we stress the problems related to the definition of a virial mass and a virial radius for the halo. The question of whether the results found here may be obtained by tracking the shells with an analytic approximation remains to be explored.  相似文献   

Petrogenesis of A-type granites and origin of vertical zoning in the Katharina pluton, Gebel Mussa (Mt. Moses) area, Sinai, Egypt     

Y. Katzir  M. Eyal  B.A. Litvinovsky  B.M. Jahn  A.N. Zanvilevich  J.W. Valley  Y. Beeri  I. Pelly  E. Shimshilashvili 《Lithos》2007,95(3-4):208-228

The central pluton within the Neoproterozoic Katharina Ring Complex (area of Gebel Mussa, traditionally believed to be the biblical Mt. Sinai) shows a vertical compositional zoning: syenogranite makes up the bulk of the pluton and grades upwards to alkali-feldspar granites. The latters form two horizontal subzones, an albite–alkali feldspar (Ab–Afs) granite and an uppermost perthite granite. These two varieties are chemically indistinguishable. Syenogranite, as compared with alkali-feldspar granites, is richer in Ca, Sr, K, Ba and contains less SiO₂, Rb, Y, Nb and U; Eu/Eu* values are 0.22–0.33 for syenogranite and 0.08–0.02 for alkali-feldspar granites. The δ¹⁸O (Qtz) is rather homogeneous throughout the pluton, 8.03–8.55‰. The δ¹⁸O (Afs) values in the syenogranite are appreciably lower relative to those in the alkali–feldspar granites: 7.59–8.75‰ vs. 8.31–9.12‰. A Rb–Sr isochron (n = 9) yields an age of 593 ± 16 Ma for the Katharina Ring Complex (granite pluton and ring dikes).

The alkali–feldspar granites were generated mainly by fractional crystallization of syenogranite magma. The model for residual melt extraction and accumulation is based on the estimated extent of crystallization ( 50 wt.%), which approximates the rigid percolation threshold for silicic melts. The fluid-rich residual melt could be separated efficiently by its upward flow through the rigid clusters of crystal phase. Crystallization of the evolved melt started with formation of hypersolvus granite immediately under the roof. Fluid influx from the inner part of the pluton to its apical zone persisted and caused increase of P_H2O in the magma below the perthite granite zone. Owing to the presence of F and Ca in the melt, P_H2O of only slightly more than 1 kbar allows crystallization of subsolvus Ab–Afs granite. Abundance of turbid alkali feldspars and their ¹⁸O/¹⁶O enrichment suggest that crystallization of alkali-feldspar granites was followed by subsolvus fluid–rock interaction; the δ¹⁸O (Fsp) values point to magmatic origin of fluids.

The stable and radiogenic isotope data [δ¹⁸O (Zrn) = 5.82 ± 0.06‰, I_Sr = 0.7022 ± 0.0064, ε_Nd (T) values are + 3.6 and + 3.9] indicate that the granite magma was generated from a ‘juvenile’ source, which is typical of the rocks making up most of the Arabian–Nubian shield.  相似文献   

Spatiotemporal variations of crustal anisotropy from similar events in aftershocks of the 1999 M7.4 İzmit and M7.1 Düzce, Turkey, earthquake sequences     

Zhigang Peng †  Yehuda Ben-Zion 《Geophysical Journal International》2005,160(3):1027-1043

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A viscoelastic damage rheology and rate- and state-dependent friction   总被引：1，自引：0，他引：1  

Vladimir Lyakhovsky  Yehuda Ben-Zion  Amotz Agnon 《Geophysical Journal International》2005,161(1):179-190

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A Unifying Phase Diagram for the Dynamics of Sheared Solids and Granular Materials   总被引：1，自引：0，他引：1  

Yehuda Ben-Zion  Karin A. Dahmen  Jonathan T. Uhl 《Pure and Applied Geophysics》2011,168(12):2221-2237

We present a simple unifying model that can be used to analyze, within a single framework, different dynamic regimes of shear deformation of brittle, plastic, and granular materials. The basic dynamic regimes seen in the response of both solids and granular materials to slowly increasing loading are scale-invariant behavior with power law statistics, quasi-periodicity of system size events, and persisting long term mode switching between the former two types of response. The model provides universal analytical mean field results on the statistics of failure events in the different regimes and distributed versus localized spatial responses. The results are summarized in a phase diagram spanned by three tuning parameters: dynamic strength change (weakening, neutral or strengthening) during slip events, dissipation of stress transfer (related to the void fraction in granular materials and damaged solids), and the ratio of shear rate over healing rate controlling the regaining of cohesion following failures in brittle solids. The mean field scaling predictions agree with experimental, numerical, and observational data on deformation avalanches of solids, granular materials, and earthquake faults. The model provides additional predictions that should be tested with future observation and simulation data.  相似文献   

Impact of textural patterns on modeled rock weathering rates and size distribution of weathered grains     

Yoni Israeli  Eyal Salhov  Simon Emmanuel 《地球表面变化过程与地形》2021,46(6):1177-1187

Rock texture has a critical influence on the way rocks weather. The most important textural factors affecting weathering are grain size and the presence of cracks and stylolites. These discontinuities operate as planes of mechanical weakness at which chemical weathering is enhanced. However, it is unclear how different rock textures impact weathering rates and the size of weathered grains. Here, we use a numerical model to simulate weathering of rocks possessing grain boundaries, cracks, and stylolites. We ran simulations with either synthetic or natural patterns of discontinuities. We found that for all patterns, weathering rates increase with discontinuity density. When the density was <~25%, the weathering rate of synthetic patterns followed the order: grid > honeycomb > Voronoi > brick wall. For higher values, all weathering rates were similar. We also found that weathering rates decreased as the tortuosity of the pattern increased. Moreover, we show that textural patterns strongly impact the size distributions of detached grains. Rocks with an initial monomodal grain size distribution produce weathered fragments that are normally distributed. In contrast, rocks with an initial log-normal size distribution produce weathered grains that are log-normally distributed. For the natural patterns, weathering produced lower modality distributions.  相似文献   

Parity and disparity between two Chama oysters: the reproductive biology of the Indo-Pacific C. pacifica Broderip,invasive to the Mediterranean Sea; and C. savignyi Lamy,indigenous to the Red Sea     

Dror Zurel  Uri Gophna  Yehuda Benayahu 《Marine Ecology》2012,33(3):261-271

The Indo-Pacific oyster Chama pacifica Broderip, 1835 (Mollusca, Bivalvia, Chamidae) is rarely found in the Northern Red Sea reefs of Eilat (Gulf of Aqaba), where it is outnumbered by its indigenous congener, Chama savignyi Lamy, 1921. The influx of Eritrean biota from the Red Sea into the Mediterranean Sea via the Suez Canal has led to the formation of massive Chama oyster beds along the Eastern Mediterranean shore. However, unlike the Northern Red Sea, the Eastern Mediterranean Chama beds are dominated by C. pacifica oysters, whereas C. savignyi is absent from this region. In an attempt to understand this difference in their respective distribution, the reproductive biology of both species was compared. Histological analysis of the male and female gonads, monitored monthly from March 2009 to August 2010 in both regions, revealed a similar reproductive cycle, comprising six stages: onset of gametogenesis, advanced gametogenesis, ripe, ready to spawn, spent and sexual rest. Female gonads demonstrated an additional, seventh stage – restoration, coinciding with inferred spawning of ripe gametes. Both species were found to be dioecious spawners, with a single, annual, temperature-dependent inferred spawning period. Chama pacifica was found to reproduce efficiently in maximal Mediterranean seawater temperatures not experienced by the Northern Red Sea Chama populations. This study demonstrates the high invasive potential of an oyster species despite its rarity in its source region.  相似文献