The Negev continental bridge: a chain in an intermodal transport system

This paper is a second follow-up discussion concerning the role, economic viability and operational characteristics of the Negev Continental Bridge in the fluid geo-political atmosphere of the Middle East. The two previous papers (Geoforum8, 29–32 and 311–318) discussed the viability of the Israeli Continental Bridge as an alternative to the Suez Canal. Now, two years after the Canal was re-opened for use by Israeli vessels, the annual amount of cargo movement across the Israeli land bridge is still growing, although it is less economical than the Suez Canal. It is thus suggested that there is a need to view the continental bridge as one part of a chain in an intermodal transport system.     

Quasi-static and Quasi-dynamic Modeling of Earthquake Failure at Intermediate Scales

We present a model for earthquake failure at intermediate scales (space: 100 m–100 km, time: 100 m/v _shear- 1000’s of years). The model consists of a segmented strike–slip fault embedded in a 3-D elastic solid as in the framework of Ben-Zion and Rice (1993). The model dynamics is governed by realistic boundary conditions consisting of constant velocity motion of the regions around the fault, static/kinetic friction laws with possible gradual healing, and stress transfer based on the solution of Chinnery (1963) for static dislocations in an elastic half-space. As a new ingredient, we approximate the dynamic rupture on a continuous time scale using a finite stress propagation velocity (quasi–dynamic model) instead of instantaneous stress transfer (quasi–static model). We compare the quasi–dynamic model with the quasi–static version and its mean field approximation, and discuss the conditions for the occurrence of frequency-size statistics of the Gutenberg–Richter type, the characteristic earthquake type, and the possibility of a spontaneous mode switching from one distribution to the other. We find that the ability of the system to undergo a spontaneous mode switching depends on the range of stress transfer interaction, the cell size, and the level of strength heterogeneities. We also introduce time-dependent log (t) healing and show that the results can be interpreted in the phase diagram framework. To have a flexible computational environment, we have implemented the model in a modular C++ class library.     

A unified scheme for processing GPS dual-band phase observations

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.     

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

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.     

Three-dimensional configuration and dynamics of the fresh–saline water interface near two saline lakes with different levels (Middle East)

A typical fresh–saline water interface in a coastal aquifer is characterized by saline-water circulation below the interface and freshwater flow above. Both flows are perpendicular to the shoreline. The flow pattern near two separated saline lakes is more complicated. For example, in the Middle East, the Dead Sea northern basin and the evaporation ponds of the Dead Sea Works are adjacent to each other but separated. The northern basin level is dropping by 1.1 m/year and the evaporation ponds’ levels are increasing by 0.2 m/year. The fresh–saline water interface in such situation is numerically simulated. Streamlines parallel or semiparallel to the shoreline are significant. Moreover, the fresh–saline water interface intrudes landward adjacent to the higher saline lake and is pushed lakeward adjacent to the lower saline lake. The simulation results support field observations showing that the interface migrates vertically at a faster rate relative to the changes in the water table and the lake levels.

     

The environment and evolution of an early egyptian urban center: Archaeological and geochemical investigations at hierakonpolis

We describe and summarize the results of new interdisciplinary techniques for recovering and analyzing historical and paleoenvironmental data from mid-Holocene archaeological and geological deposits in the modern Nile floodplain at the site of Hierakonpolis in Upper Egypt. Application of these techniques has produced the first stratigraphic link between historic (Early Dynastic) and late prehistoric (Predynastic) periods in the Nile Valley at a site which played a central role in the evolution of Egyptian civilization.     

A Unifying Phase Diagram for the Dynamics of Sheared Solids and Granular Materials

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.