Normal faulting and flexure in an elastic-perfectly plastic plate

An elastic-perfectly plastic plate model has been developed to analyze the flexure associated with normal faulting. The model consists of a thin layer, which is completely cut by a normal fault, overlying a fluid substratum. For a given applied bending moment at the fault, the relationship between the amount of displacement on the fault and the extent of the failure zone can be calculated. The model is applied to the Wasatch Front region in the eastern Basin and Range Province, USA to determine the correlation of its parameters with geological and geophysical data in the vicinity of a major normal fault, the Wasatch fault, along which there has been 3–4 km of Late Cenozoic uplift. In this region, most seismic activity occurs away from the Wasatch fault in a zone 30 km wide, roughly centered 30 km east of the fault. This activity occurs at depths of 15 km or less. In order to match the observations, the lithospheric layer must have a flexural rigidity of 0.5 to 1.1 · 10²² n-m and a yield stress of 1–2 kb and must have zero applied bending moment at the fault. The effective mechanical thickness of the lithosphere in this region is 20–25 km. These results indicate that the lithosphere in long-term mechanical studies in the eastern Basin and Range is thin and weak. Evaluating these results as compared to the seismic lithospheric thickness and temperature regime of the region produces some interesting correlations with studies in oceanic regions.     

Identification of regions enriched or depleted in radioelements through nondistributional analysis of aerial radiometric data

Throughout the aerial radiometric reconnaissance survey portion of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program, the identification of outliers (anomalies) was an important approach to locating regions with radio-element concentrations that are either higher or lower than expected. The method introduced herein to locate such regions involves three steps: selection of a high (or low) threshold for the variate of interest; use of the sample percentile to identify all points of interest; and movement of a window over the selected data to locate significant clusters of observations. These steps, applied to aerial radiometric ²¹⁴Bi (equivalent uranium) data collected over the Copper Mountain area in Wyoming, resulted in the identification of areas enriched in that variate.     

Heterogeneous shock-induced thermal radiation in minerals

A 500 channel optical imaging intensifying and spectral digital recording system is used to record the shock-induced radiation emitted from 406 to 821 nm from transparent minerals during the time interval that a shock wave propagates through the sample. Initial results obtained for single crystals of gypsum, calcite and halite in the 30 to 40 GPa (300 to 400 kbar) pressure range demonstrate greybody emission spectra corresponding to temperatures in the 3,000 to 4,000 K range and emissivities ranging from 0.003 to 0.02. In the case of gypsum and calcite, distinctive line spectra, are superimposed on the thermal radiation. The observed color temperatures are a factor of 2 to 10 greater than the Hugoniot temperature, calculable on the basis of continuum thermodynamics and equation of state models for the shock states achieved in the three minerals. These observed high temperatures are believed to be real. We conclude that we are detecting a large number of closed spaced high temperature shear-band regions immediately behind the shock front. A shear instability model, such as proposed independently by Grady (1977, 1980), Ananin et al. (1974), and Horie (1980), in which small zones of highly deforming and melted material are produced which are the source of the detected thermal radiation and have a fractional effective area approximately numerically equal to the measured emissivity, can be used to predict an effective emissivity of 0.0065 directly behind the shock front. If shear band instability arises from viscous flow processes, Grady's model and mineral thermal properties yield for the shocked mineral viscosities values in the range of 10⁹ to 10¹⁵ P immediately behind the shock front.     

A new approach for detecting and mapping sewage impacts

Increased nitrogen loading has been implicated in eutrophication occurrences worldwide. Much of this loading is attributable to the growing human population along the world's coastlines. A significant component of this nitrogen input is from sewage effluent, and delineation of the distribution and biological impact of sewage-derived nitrogen is becoming increasingly important. Here, we show a technique that identifies the source, extent and fate of biologically available sewage nitrogen in coastal marine ecosystems. This method is based on the uptake of sewage nitrogen by marine plants and subsequent analysis of the sewage signature (elevated delta 15N) in plant tissues. Spatial analysis is used to create maps of delta 15N and establish coefficient of variation estimates of the mapped values. We show elevated delta 15N levels in marine plants near sewage outfalls in Moreton Bay, Australia, a semi-enclosed bay receiving multiple sewage inputs. These maps of sewage nitrogen distribution are being used to direct nutrient reduction strategies in the region and will assist in monitoring the effectiveness of environmental protection measures.     

Distinct modes of bidecadal and multidecadal variability in a climate reconstruction of the last centuries from a South Pacific coral

The Rarotonga coral Sr/Ca time series (Linsley et al. in Science 290:1145–1148, 2000) provides a near-monthly resolved proxy record of South Pacific climate variability over the last ~300 years. Here we show that two distinct interdecadal, quasi-periodic time components with periods of ~80 and ~25 years can be identified in this time series by Singular Spectrum Analysis. Their associated spatial patterns in the global sea surface temperature (SST) field show notable differences. Whereas the multidecadal component is associated with a global SST pattern that was recently associated with solar forcing on multidecadal timescales, the bidecadal component is associated with a well known pattern of Pacific decadal to interdecadal SST variability.     

Quality control algorithms for rainfall measurements

One of the basic requirements for a scientific use of rain data from raingauges, ground and space radars is data quality control. Rain data could be used more intensively in many fields of activity (meteorology, hydrology, etc.), if the achievable data quality could be improved. This depends on the available data quality delivered by the measuring devices and the data quality enhancement procedures. To get an overview of the existing algorithms a literature review and literature pool have been produced. The diverse algorithms have been evaluated to meet VOLTAIRE objectives and sorted in different groups. To test the chosen algorithms an algorithm pool has been established, where the software is collected. A large part of this work presented here is implemented in the scope of the EU-project VOLTAIRE (Validation of multisensors precipitation fields and numerical modeling in Mediterranean test sites).     

Efficiency of heavy liquid separation to concentrate magnetic particles

Low-temperature rock magnetic measurements have distinct diagnostic value. However, in most bulk marine sediments the concentration of ferrimagnetic and antiferromagnetic minerals is extremely low, so even sensitive instrumentation often responds to the paramagnetic contribution of the silicate matrix in the residual field of the magnetometer. Analysis of magnetic extracts is usually performed to solve the problems raised by low magnetic concentrations. Additionally magnetic extracts can be used for several other analyses, for example electron microscopy or X-ray diffraction. The magnetic extraction technique is generally sufficient for sediments dominated by magnetite. In this study however, we show that high-coercivity components are rather underrepresented in magnetic extracts of sediments with a more complex magnetic mineralogy. We test heavy liquid separation, using hydrophilic sodium polytungstenate solution Na₆[H₂W₁₂O₄₀], to demonstrate the efficiencies of both concentration techniques. Low-temperature cycling of zero-field-cooled, field-cooled and saturation isothermal remanent magnetization acquired at room temperature was performed on dry bulk sediments, magnetic extracts, and heavy liquid separates of clay-rich pelagic sediments originating from the Equatorial Atlantic. The results of the thermomagnetic measurements clarify that magnetic extraction favours components with high spontaneous magnetization, such as magnetite and titanomagnetite. The heavy liquid separation is unbiased with respect to high- and low-coercive minerals, thus it represents the entire magnetic assemblage.