Transient SH-waves in a wedge-shaped layer

Summary. A generalized ray theory for transient SH -waves in a wedge-shaped layer over an elastic half-space is developed in this paper. The ray integrals for multiply reflected waves in the layer are derived in terms of two systems of coordinates and two sets of local wavenumbers, one along the free surface and the other along the sloped interface. All local wavenumbers are then transformed to a common wavenumber in all ray integrals which are evaluated by the Cagniard method. Results for the first motion approximation are in agreement with previous investigations.     

Waldsteinit

Ohne Zusammenfassung     

Optimal planning and operation of irrigation systems under water resource constraints in Oman considering climatic uncertainty

In this contribution, we introduce a stochastic framework for decision support for optimal planning and operation of water supply in irrigation. This consists of (1) a weather generator for simulating regional impacts of climate change on the basis of IPCC scenarios, (2) a tailor-made evolutionary optimization algorithm for optimal irrigation scheduling with limited water supply, (3) a mechanistic model for simulating water transport and crop growth in a sound manner, and (4) a kernel density estimator for estimating stochastic productivity, profit, and demand functions by a nonparametric method. As a result of several simulation/optimization runs within the framework, we present stochastic crop-water production functions (SCWPF) for different crops which can be used as a basic tool for assessing the impact of climate variability on the risk for the potential yield for specific crops and specific agricultural areas. A case study for an agricultural area in the Al Batinah region of the Sultanate of Oman is used to illustrate these methodologies. In addition, microeconomic impacts of climate change and the vulnerability of the agro-ecological system are discussed.     

Diversification of Livelihoods in a Society in Transition: A Case Study of Tibetan Communities in Southwest China

In recent years, large development and market integration programs have altered the socioeconomic structures and cultural identity of rural communities and ethnic minorities in Southwest China and influenced the management of natural resources. This article analyzes livelihood strategies in the Shuiluo Valley, a remote area of the Sino-Tibetan borderlands. Agricultural activities and the management of natural resources were studied in five villages of Muli Tibetan Autonomous County, Sichuan Province. Characteristic for rural societies in transition, livelihoods were found to be flexible, combining subsistence agriculture, off-farm employment, and the exploitation of both renewable and nonrenewable natural resources. Accessibility of villages did not influence household income and livelihood activities, and poorer households were not found to depend more on natural resources or on income from agriculture than wealthier households. The option of gold prospecting constitutes a major difference compared to more nontimber forest product-based livelihoods in adjacent areas of Southwest China.     

Generation and metamorphism of new crust in magmatic arcs: a case study from northern Chile

In a deep section of the Jurassic Andean arc, coastal Cordillera of northern Chile, south of Antofagasta, basic magmas from a mantle source accreted large masses of crust in an early stage of arc development. These gabbroic intrusions were isochemically metamorphosed at moderate pressures (≤ 5 kbar) and high temperatures (∼ 800°C) into uniform garnet-absent dino+ortho-pyroxene gneisses (granulites). Subsequently they were partly transformed into amphibolites ( T ≤ 700°C) during tectonically controlled access of fluid without major changes in whole rock chemistry. Locally migmatization occurs in the amphibolites. The metamorphic unit was diversified by enduring magmatic activity in the form of chemically distinct gabbroic and quartz dioritic intrusions. Formation and composition of continental crust might be a typical example for the deeper plutonic sections of this continental magmatic arc.     

Der Wert der Fusuliniden für Stratigraphische Vergleiche auf Grosse Entfernungen

Zusammenfassung Die Fusuliniden gestatten überraschend gute Zeitvergleiche in marinen Ablagerungen auf große Entfernungen, doch sollte stets die mit ihrer Hilfe gewonnene Stratigraphie durch die Ergebnisse, die mittels anderer Tiergruppen und der Pflanzen gewonnen wurden, geprüft werden.     

Ecotoxicity assessment of natural attenuation effects at a historical dumping site in the western Baltic Sea

During the late 1950s and early 1960s of the past century, industrial waste material highly enriched in various contaminants (heavy metals, PAHs) was dumped in the inner Mecklenburg Bay, western Baltic Sea. Large-scale shifts in the spatial distribution of heavy metals in surface sediments were mapped by geochemical monitoring in the mid-1980s and 12 years later in 1997. A further study in 2001 was designed to investigate the small-scale spatial distribution of contaminants inside, on top of, and around the historical dumping ground and to examine possible effects to benthic organisms (Arctica islandica, microbiological toxicity tests). The site is located within an area characterized by a discontinuous deposition of fine sediments, but net sedimentation rate of about 3mm/y led ultimately to a gradual coverage of the dumped material. During the first decades after the dumping, about half of the originally dumped material was already spread over the surrounding area as a result of sediment dynamics and re-suspension processes. Recent sediments of the historical dump site are still significantly enriched in heavy metals and PAHs. Microbiological toxicity test results were positive, though uptake of contaminants in mussels was found to deviate only slightly from that of a non-contaminated reference station due to a gradual dilution and decrease in bioavailability of the contaminants.     

Small Antarctic micrometeorites: A mineralogical and in situ oxygen isotope study

Abstract— We have investigated the texture, bulk chemistry, mineralogy, as well as the anhydrous minerals oxygen isotopic composition of 67 small Antarctic micrometeorites (AMMs) collected at Cap Prudhomme, Antarctica, and belonging to the currently poorly studied size fraction 25–50 μm. When compared to larger (50–400 μm) micrometeorites collected at the same site in Antarctica with the same techniques, no significant differences are found between the two populations. We therefore conclude that the population of Cap Prudhomme AMMs is homogeneous over the size range 25–400 μm. In contrast, small AMMs have different textures, mineralogy, and oxygen isotopic compositions than those of stratospheric interplanetary dust particles (IDPs). Because small AMMs (<50 μm) overlap in size with IDPs, the differences between these two important sources of micrometeorites can no longer be attributed to a variation of the micrometeorite composition with size. Physical biases introduced by the collection procedures might account for these differences.     

2.5D seismic velocity modelling in the south-eastern Romanian Carpathians Orogen and its foreland

The DACIA-PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August–September 2001, with the objective of obtaining new information on the deep structure of the external Carpathians nappe system and the architecture of the Tertiary/Quaternary basins developed within and adjacent to the Vrancea zone, including the rapidly subsiding Focsani Basin. The DACIA-PLAN profile is about 140 km long, having a roughly WNW–ESE direction, from near the southeast Transylvanian Basin, across the mountainous south-eastern Carpathians and their foreland to near the Danube River. A high resolution 2.5D velocity model of the upper crust along the seismic profile has been determined from a tomographic inversion of the DACIA-PLAN first arrival data. The results show that the data fairly accurately resolve the transition from sediment to crystalline basement beneath the Focsani Basin, where industry seismic data are available for correlation, at depths up to about 10 km. Beneath the external Carpathians nappes, apparent basement (material with velocities above 5.8 km/s) lies at depths as shallow as 3–4 km, which is less than previously surmised on the basis of geological observations. The first arrival travel-time data suggest that there is significant lateral structural heterogeneity on the apparent basement surface in this area, suggesting that the high velocity material may be involved in Carpathian thrusting.