A Step Towards Evaluation of the Seismic Response Reduction Factor in Multistorey Reinforced Concrete Frames

A seismic nonlinear time-history analysis was made for four-, six-, and eight-storey reinforced concrete buildings. These buildings were made as three-dimensional space frame structures with shear walls in both orthogonal directions. They have five bays with 4.8 m spacing each in the horizontal direction, and three bays with 4.2 m spacing each in the transversal direction. The frames were designed according to the Jordanian Seismic Code of practice for Seismic Zones 4, 3, 2, and 1 as proposed for Jordan by several authors. Time-history analysis was made using the El Centro (N-S) earthquake record of May 1940 as an actual earthquake excitation. The response reduction factor (R) that primarily consists of two factors that are the ductility reduction (Rµ) and the overstrength (), is obtained. It has been seen that the seismic zoning has a slight effect on the ductility reduction factor for different buildings, since it ranges from Zone 4 to Zone 1 as 2.37 to 2.52, 1.72 to 1.78, and 1.14 to 1.18 for four-, six-, and eight-storey buildings, respectively. Moreover, it is observed that, for different buildings and different seismic zones, the ductility reduction factor (Rµ) is slightly different from the system ductility factor (µ) especially for higher values of µ (i.e., Rµ µ). The response reduction factor, called overstrength (), was evaluated. The overstrength factor was found to vary with seismic zones (Z) , number of stories, and design gravity loads. However, the dependency on seismic zones was the strongest. The average overstrength of these buildings in Zones 4 and 1 was 2.61 and 6.94, respectively. The overstrength increased as the number of storeys decreased: overstrength of a four-storey building was higher than an eight-storey building by 36% in Zone 4, and 39% in Zone 1. Furthermore, buildings of the three heights had an average overstrength 165.9% higher in Zone 1 than in Zone 4. These observations have a significant implications for the seismic design codes which currently do not take into account the variation of the response reduction factor, R (i.e., ductility reduction factor times overstrength).     

Probabilistic seismic hazard zonation of Syria

Earthquake hazard maps for Syria are presented in this paper. The Peak Ground Acceleration (PGA) and the Modified Mercalli Intensity (MMI) on bedrock, both with 90% probability of not being exceeded during a life time of 50, 100 and 200 years, respectively are developed. The probabilistic PGA and MMI values are evaluated assuming linear sources (faults) as potential sources of future earthquakes. A new attenuation relationship for this region is developed. Ten distinctive faults of potential earthquakes are identified in and around Syria. The pertinent parameters of each fault, such as theb-parameter in the Gutenberg-Richter formula, the annual rate ₄ and the upper bound magnitudem ₁ are determined from two sets of seismic data: the historical earthquakes and the instrumentally recorded earthquake data (AD 1900–1992). The seismic hazard maps developed are intended for preliminary analysis of new designs and seismic check of existing civil engineering structures.     

Diffusion gradients in an eclogite xenolith from the Roberts Victor kimberlite pipe: (2) kinetics and implications for petrogenesis

In a bimineralic eclogite xenolith (sample JJG41) from the Roberts Victor kimberlite, compositional gradients in clinopyroxene are related to garnet exsolution. Two principal reactions involving clinopyroxene and garnet occur: (i) The net-transfer Al₂Si^-1Mg^-1 which is responsible for garnet growth according to the equation 2Di+Al₂Si^-1Mg^-1=Grossular+MgCa^-1 (reaction 1). This has created substantial compositional gradients in Al, Si and Mg within clinopyroxene. (ii) The exchange of Fe–Mg between garnet and clinopyroxene (reaction 2). During the stage of garnet growth (reaction 1) the lamellae crystallized sequentially as a result of a temperature decrease from around 1400 to 1200° C. This exsolution growth-stage was under the control of Al diffusion in clinopyroxene and at around 1200° C further growth of garnet lamellae became impeded by the sluggishness of Al diffusion in the clinopyroxene host. However, reaction 2 continued during further cooling down to about 1000° C; this temperature being inferred from the constant Fe–Mg partitioning at clinopyroxene-garnet interfaces for the whole set of lamellae. The initial clinopyroxene in JJG41 was probably formed by crystallization from a melt in Archaean time. The cessation of Fe–Mg exchange between garnet and clinopyroxene at about 1000° C may well predate the eruption of the eclogite in kimberlite at around 100 Ma. Kinetic models of reaction are examined for both reactions. Modelling of reaction 1, involving both diffusion and interface migration, allows several means of estimating the diffusion coefficient of Al in clinopyroxene; the estimates are in the range 10^-16-10^-20 cm²/s at 1200° C. These estimates bracket the experimentally determined data for Al diffusion in clinopyroxene, and from these experimental data a preferred cooling rate of about 300° C/Ma is obtained for the period of growth of garnet exsolution lamellae. A geospeedometry approach (Lasaga 1983) suitable for a pure-exchange process (reaction 2) is used to estimate the cooling rate in the later stages of the thermal history (after garnet growth); values 4–40° C/Ma are consistent with the shape of the Fe-diffusion gradients in the clinopyroxene. The extensive thermal history recorded by JJG41, including probable melt involvement at ca. 1400° C, demonstrates the complex evolution of rocks within the mantle. Whilst the notion of formation of mantle eclogites from subducted oceanic crust has become fashionable, it is clear that tracing eclogite geochemical and P-T characteristics backwards from their nature at the time of xenolith eruption, through high-temperature mantle events to the characteristics of the original subducted oceanic crust, will be very complex.     

Surface properties of asteroids: A synthesis of polarimetry,radiometry, and spectrophotometry

The surface compositions of 110 asteroids are analyzed from statistically representative data sets of polarimetry as a function of phase angle, broad-band radiometry near 10 and 20 μm, and visible and near-infrared spectrophotometry. A comparison of albedos and diameters determined by polarimetry and radiometry shows that a modest upward revision of the radiometric albedo scale is needed and that a single law relating the slope of the polarization-phase curve to geometric albedo may not hold for very dark asteroids. We present reliable adopted albedos and diameters for 56 objects. Roughdi ameters for 52 additional objects are obtained from spectrophotometry using a correlation between albedo and color. Corrections for sampling bias permit investigation of asteroid compositions as a function of diameter, orbit, and other parameters.More than 90% of the minor planets fall into two broad compositional groups, defined by several optical parameters, designated by the symbols C and S. Comparisons with meteorite spectral albedo curves suggest that the two groups are compositionally similar to carbonaceous and stony-metallic meteorites, respectively. C-type asteroids predominate in the belt, especially in the outer half. An unusual distribution of compositions is found between 2.77 and 3.0 AU. Many S-type objects have diameters of 100–200 km; C-type objects are much more common at both larger and smaller sizes. Vesta is unique, being apparently the only differentiated asteroid remaining intact in the belt. The largest C-type objects are compositionally distinct from smaller ones and possibly are metamorphosed. We sketch some implications for meteoritics and for the early history of the solar system and point to the need for further systematic sampling of smaller and fainter objects by these three observational techniques.     

区域复合生态系统分析及其可持续发展对策

从系统物质循环角度分析了人类社会-经济-自然复合生态系统不可持续发展的原因是由于大量生产-大量消费-大量废弃的线性生产和消费模式耗用了大量资源，产生太多的废弃物，破坏了复合系统正常的物质代谢。提出系统调节，实现系统可持续发展的途径，包括控制人口增长，适度消费；调整复合系统生产链的数量结构和比例关系；建立协调的结构网络关系，构建循环型社会。     

The seismic hazard assessment of the Dead Sea rift, Jordan

The Dead Sea fault system and its branching faults represent one of the most tectonically active regions in the Middle East. The aim of this study is to highlight the degree of hazards related to the earthquake activities associated with the Dead Sea rift, in terms of speculating the possible future earthquakes. The present investigation mainly is based on available data and vertical crustal modeling of Jordan and the Dead Sea model for the Dead Sea basin with particular emphasis of the recent earthquake activities, which occurred on December 31st, 2003 (Mc = 3.7), February 11th, 2004 (strongest Mc = 4.9 R), and March 15th, 2004 (Mc = 4). The present research examines the location of the strong events and correlates them with the various tectonic elements in the area. The source mechanism of the main shock and the aftershock events is also examined. The analyses were based on the available short period seismogram data, which was recorded at the Natural Resources Authority of Jordan, Seismological Observatory. The seismic energy appears to have migrated from the south to the north during the period from December 31st up to March 12th, where the released seismic energy showed a migration character to the southern block of the eastern side of the Dead Sea, which led the seismic event to occur on March 15th.     

Nature minéralogique et rôle nutritionnel des argiles de sols céréaliers en région subhumide à semi-aride (Tunisie)

The cereal soils of the Northwest of Tunisia derive most of the time, from alluvial deposits or altered remains of carbonated and clayey rocks. Extraction of the clayey fraction permitted to reveal the presence of the following clayey minerals: kaolinite, illite, smectite, chlorite, as well as an illite–smectite interstratified layer, which is present in the deep horizons of the vertisol and in the isohumic soil. The presence of such types of clays shows that the evolution mechanism of soils is weathering of primary minerals inherited from the sedimentary rocks of the Northwest of Tunisia. These clays ensure to soils most of their cationic exchange capacity. Thanks to these clays, which have Ca⁺⁺, Mg⁺⁺ and K⁺ as exchangeable cations, the chemical fertility of these soils is ensured. It may be improved by increasing contents of organic matter, which is naturally few abundant in these soils. To cite this article: H. Ben Hassine, C. R. Geoscience 338 (2006).     

Structure of the earth's crust in Jordan from potential field data

Gravity and magnetic data were collected and used to study the crustal structure of Jordan. Three new geophysical maps of Jordan were created: a Moho discontinuity map, a crystalline basement surface map, and a map showing the lowest limit of magnetic blocks. Depths of the Curie Isotherm were also calculated. Results indicate that the depth to the Moho discontinuity in Jordan varies from 32 to 33 km in the northwest to 38 km in the southeast. The basement complex rocks outcrop on the surface in the southwest but lie at about 8 km in the northeast. The Curie Isotherm (585 °C) lies at a depth of about 10 km in the area east of the Dead Sea and dips southeastward towards the Al-Sirhan (Wadi Sirhan), southeast Jordan, where it is located at 35 km depth. Local isostasy of rock masses (blocks) in Jordan does not occur. Nevertheless, this does not rule out the possible existence of isostasy in a regional scale at greater depths within the mantle.