GEK measurements in a shallow water region

Evidence for the applicability of GEK (Geomagnetic Electrokinetography) measurements to shallow water regions is provided from observations in the shelf region of the East China Sea. The reason for the effectiveness of GEK measurements in this case is investigated theoretically, and it is shown to be attributable to the existence of a thick conductive sedimentary layer. In addition, it is shown that low conductive basement rock can be regarded as a good conductor for GEK measurements if the current width is broad enough and if the ratio of current width to water depth is larger than the resistivity ratio of basement rock to sea water. This implies that barotropic tidal currents can be measured with GEK in any ocean on the earth if they have significant magnitudes.     

Scaling model experiments on propagation of electromagnetic waves using salt solution to simulate the Earth's crust: Loma Prieta and Kobe earthquakes

Propagation of electromagnetic (EM) waves from an earthquake focus in the conductive Earth has been investigated using 1/1,000,000 scaling models taking earth-ionosphere and ocean-Moho plane parallel-plate waveguides into account. Microwaves at a frequency, ω_m, a million times higher than that of seismic EM signal (SEMS), ω, were generated at the model focus. They are propagated in a salt solution modeling the earth's crust and reflected by ocean, fault planes, ionosphere and Moho plane all made by aluminum. Distribution of EM power was mapped by scanning a detector antenna over the model Earth's surface. The skin depth, δ, calculated by the exact skin depth equation, 1/δ=ω(μ/2)^1/2 [(1+(1/ωρ)²)^1/2 −1]^1/2 where dielectric constant, and permeability, μ are the same but resistivity, ρ, 10⁻⁶ times smaller than that of Earth, gave 10⁻⁶ times small skin depth validating the model scaling index. Images for evanescent and wave-ripple standing waves disturbed by normal, strike-slip and dip-slip conductive fault planes have been obtained using an aluminum plate. The co-circular contour map above the epicenter due to evanescence was pushed to the north east direction from the epicenter by the presence of ocean for the Loma Prieta earthquake, while to north direction for the Kobe earthquake. The intensity of EM ULF emissions for the Loma Prieta earthquake is discussed quantitatively.     

Simplified evaluation for swelling characteristics of bentonites

Bentonite is currently planned to be used as buffer and backfill materials for repositories of high-level nuclear waste because these materials must have the swelling characteristics to seal the waste. In the design for buffer and backfill materials, we must choose the adequate bentonite among many kinds of bentonite in the world. The database of the swelling characteristics of various bentonites and its evaluation will be available when we will select the adequate bentonite. For this purpose, this study performed the laboratory tests on the swelling pressure and swelling deformation of four kinds of bentonite produced in Japan and the United States. These bentonites have different physicochemical properties. This study investigated the characteristics of swelling pressure and swelling deformation from the viewpoint of the physicochemical properties of each bentonite. Furthermore, this study also proposed the simplified evaluation of swelling characteristics of various bentonites on the basis of microscopic analysis.     

Curvature derived from LiDAR digital elevation models as simple indicators of debris-flow susceptibility

To mitigate the damage caused by debris flows resulting from heavy precipitation and to aid in evacuation plan preparation, areas at risk should be mapped on a scale appropriate for affected individuals and communities. We tested the effectiveness of simply identifying debris-flow hazards through automated derivation of surface curvatures using LiDAR digital elevation models. We achieved useful correspondence between plan curvatures and areas of existing debris-flow damage in two localities in Japan using the analysis of digital elevation models(DEMs). We found that plan curvatures derived from 10 m DEMs may be useful to indicate areas that are susceptible to debris flow in mountainous areas. In residential areas located on gentle sloping debris flow fans, the greatest damage to houses was found to be located in the elongated depressions that are connected to mountain stream valleys. Plan curvaturederived from 5 m DEM was the most sensitive indicators for susceptibility to debris flows.     

Variation of rare earth concentrations in pigeonitic and hypersthenic rock series from Izu-Hakone region,Japan

The abundances of rare earth elements in 5 each of aphyric volcanic rocks of pigeonitic and hypersthenic rock series from Izu-Hakone region have been determined by neutron activation analysis. Pigeonitic rock series show rare earth patterns with relative depletion of lighter rare earths (low lanthanum type) and large increase in rare earth abundances with differentiation. Hypersthenic rock series show higher lanthanum abundances (high lanthanum type) compared with pigeonitic rock series. The differences in rare earth patterns between two rock series are compatible with the theory of independent magmatic generation of these two series. Variation of rare earth patterns in both series have been examined by a model of magmatic differentiation based on the observed rare earth partition coefficients.     

Chemical fractionations in meteorites—X. Ureilites

Four ureilites (Dyalpur, Goalpara, Haverö, and Novo Urei) were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Rb, Re, Sb, Se, Te, Tl, and U. An attempt has been made to resolve the data into contributions from the parent ultramafic rock and the injected, carbon- and gas-rich vein material. Interelement correlations, supported by analyses of separated vein material (WANKE et al, 1972), suggest that the vein material is enriched about 10-fold in refractory Ir and Re over moderately volatile Ni and Au, and is low in volatiles except Ge, C, and noble gases. It appears to be a refractory-rich nebular condensate that precipitated carbon by surface catalytic reactions at ˜500K and trapped noble gases but few other volatiles. The closest known analogue is a Cr- and C-rich fraction from the Allende meteorite, highly enriched in heavy noble gases and noble metals. By analogy with Allende, the gas-bearing phase in ureilites may have been an Fe, Cr-sulfide.

The ultramafic rock contains siderophiles and chalcophiles (Ni, Au, Ge, S, Se) at ˜0.05 of Cl chondrite level, and highly volatile elements (Rb, Cs, Bi, Tl, Br, Te, In, Cd) at ˜0.01 Cl level. It probably represents the residue from partial melting of a C3V-like chondrite body, under conditions where phase separation was incomplete so that some liquid was retained. The vein material was injected into this rock at some later time.     

Spatio-temporal analysis of recent groundwater-level trends in the Red River Delta, Vietnam

A groundwater-monitoring network has been in operation in the Red River Delta, Vietnam, since 1995. Trends in groundwater level (1995?C2009) in 57 wells in the Holocene unconfined aquifer and 63 wells in the Pleistocene confined aquifer were determined by applying the non-parametric Mann-Kendall trend test and Sen??s slope estimator. At each well, 17 time series (e.g. annual, seasonal, monthly), computed from the original data, were analyzed. Analysis of the annual groundwater-level means revealed that 35?% of the wells in the unconfined aquifer showed downward trends, while about 21?% showed upward trends. On the other hand, confined-aquifer groundwater levels experienced downward trends in almost all locations. Spatial distributions of trends indicated that the strongly declining trends (>0.3?m/year) were mainly found in urban areas around Hanoi where there is intensive abstraction of groundwater. Although the trend results for most of the 17 time series at a given well were quite similar, different trend patterns were detected in several. The findings reflect unsustainable groundwater development and the importance of maintaining groundwater monitoring and a database in the Delta, particularly in urban areas.     

Calibration of the parameters for a hardening–softening constitutive model using genetic algorithms

The present paper introduces a genetic algorithm-based optimization technique to calibrate a nonlinear strain hardening–softening constitutive model for soils using five material parameters. The efficiency of the proposed technique is analyzed through the use of different GA techniques. The effects of elitism, crossover, and mutation, as well as population size, on the performance of the conventional GAs for this problem are investigated. Micro-genetic algorithms (mGAs) are chosen and tested for different population sizes. The mGAs with a population size of five yields the optimal parameter values after fewer function evaluations and capture the overall simulated or experimental behavior at every point in stress–strain and strain paths in triaxial compression. The proposed calibration technique is validated through comparison with the traditional calibration technique.