On meteotsunamis around Tsushima Strait generated by the Baiu front

On July 15, 2009, a meteotsunami occurred over Tsushima Strait and flood damage was recorded on the west coast of Tsushima Island. This study investigated the meteorological systems related to that meteotsunami event using surface observation data, grid-point value data, and a mesoscale meteorological model. The mid-latitude trough in the mid-troposphere approached the moist air of the Baiu precipitation system, and a cold downdraft occurred over a wide area of western Japan. In the western Tsushima Strait, the warm, moist air of the lower atmosphere kept the front of the cold downdraft stationary. Around this area, an atmospheric gravity wave was generated continuously with the wave-conditional instability of the second kind mechanism and propagated toward Tsushima Island. The atmospheric gravity wave generated a pressure disturbance at sea level, which produced the meteotsunami. The frequency of the pressure disturbance using the numerical model had a peak in the 5- to 20-min period range, which corresponded with the peak frequency range of the observed tidal records.     

River Water Pollution in Developed and Developing Countries: Judge and Assessment of Physicochemical Characteristics and Selected Dissolved Metal Concentration

To compare water quality in rivers of developed and developing countries, a study based on physicochemical parameters and dissolved metals levels was conducted. Water samples were collected from selected sites in Dhaka, Bangladesh; Hokkaido and Osaka, Japan; Erdenet, Mongolia and West Java, Indonesia. Analysis of least significant differences revealed that most water quality parameters were within comparable low levels in both developed and developing countries. The dissolved metals concentrations were found to be similar and below those of water standards except for manganese and cadmium at every sampling point, and lead in Erdenet, Mongolia. Some metals showed high enrichment factors in the rivers of Osaka, Japan and Erdenet, Mongolia, indicating accumulation possibility of metals in the river‐bed sediments. High concentrations of dissolved organic carbon, Escherichia coli and dissolved metals suggested greater water pollution in some rivers of developing countries than in the rivers of Japan. Principal component analysis showed strong correlations between “dissolved organic carbon and chemical oxygen demand” and “conductivity and total dissolved solids” at each sampling point, and E. coli, nitrate (NO), nitrite (NO), and pH levels were found to be higher in the rivers of Dhaka and Erdenet. In addition, there were high levels of Al and Zn in West Java, Pb in Erdenet, and Mn, Fe, and Cr in the rivers of Dhaka and Japan. Based on pressures and impacts, it is evident that dissolved metal, organic, and fecal pollution in the rivers of developing countries are in somewhat dreadful condition in comparison with the rivers of developed country.     

Radial diffusion rate of planetesimals due to gravitational encounters

We study the rate of radial diffusion of planetesimals due to mutual gravitational encounters under Hill’s approximations in the three-body problem. Planetesimals orbiting a central star radially migrate inward and outward as a result of mutual gravitational encounters and transfer angular momentum. We calculate the viscosity in a disk of equal-sized planetesimals due to their mutual gravitational encounters using three-body orbital integrations, and obtain a semianalytic expression that reproduces the numerical results. We find that the viscosity is independent of the velocity dispersion of planetesimals when the velocity dispersion is so small that Kepler shear dominates planetesimals’ relative velocities. On the other hand, in high-velocity cases where random velocities dominate the relative velocities, the viscosity is a decreasing function of the velocity dispersion, and is found to agree with previous estimates under the two-body approximation neglecting the solar gravity. We also calculate the rate of radial diffusion of planetesimals due to gravitational scattering by a massive protoplanet. Using these results, we discuss a condition for formation of nonuniform radial surface density distribution of planetesimals by gravitational perturbation of an embedded protoplanet.     

Evidence for and implications of sedimentary diapirism and mud volcanism in the southern Utopia highland-lowland boundary plain, Mars

Several types of spatially associated landforms in the southern Utopia Planitia highland-lowland boundary (HLB) plain appear to have resulted from localized geologic activity, including (1) fractured rises, (2) elliptical mounds, (3) pitted cones with emanating lobate materials, and (4) isolated and coalesced cavi (depressions). Stratigraphic analysis indicates these features are Hesperian or younger and may be associated with resurfacing that preferentially destroyed smaller (<8 km diameter) impact craters. Based on landform geomorphologies and spatial distributions, the documented features do not appear to be specifically related to igneous or periglacial processes or the back-wasting and erosion of the HLB scarp. We propose that these features are genetically related to and formed by sedimentary (mud) diapirs that ascended from zones of regionally confined, poorly consolidated, and mechanically weak material. We note morphologic similarities between the mounds and pitted cones of the southern Utopia boundary plain and terrestrial mud volcanoes in the Absheron Peninsula, Azerbaijan. These analogs provide a context for understanding the geological environments and processes that supported mud diapir-related modification of the HLB. In southern Utopia, mud diapirs near the Elysium volcanic edifice may have resulted in laccolith-like intrusions that produced the fractured rises, while in the central boundary plain mud diapirs could have extruded to form pitted cones, mounds, and lobate flows, perhaps related to compressional stresses that account for wrinkle ridges. The removal of material a few kilometers deep by diapiric processes may have resulted in subsidence and deformation of surface materials to form widespread cavi. Collectively, these inferences suggest that sedimentary diapirism and mud volcanism as well as related surface deformations could have been the dominant Hesperian mechanisms that altered the regional boundary plain. We discuss a model in which detritus would have accumulated thickly in the annular spaces between impact-generated structural rings of Utopia basin. We envision that these materials, and perhaps buried ejecta of Utopia basin, contained volatile-rich, low-density material that could provide the source material for the postulated sedimentary diapirs. Thick, water-rich, low-density sediments buried elsewhere along the HLB and within the lowland plains may account for similar landforms and resurfacing histories.     

CaPtO3 as a novel post-perovskite oxide

Structural, morphological, magnetic, and thermal properties have been investigated for a novel post-perovskite oxide CaPtO₃ synthesized under high pressure. By comparing obtained structural parameters with those for known post-perovskite compounds, we argue that the chemical bond has a strong covalent character. Precise measurements of the Langevin susceptibility χ ₀ = −9.6 × 10⁻⁵ emu/mol and Debye temperature θ ∼ 470 K provide a good opportunity to confirm the reliability of first-principle calculations on predicting physical properties of the Earth’s D” layer.     

Decision-theoretic sensitivity analysis for reservoir development under uncertainty using multilevel quasi-Monte Carlo methods

At various stages of petroleum reservoir development, we encounter a large degree of geological uncertainty under which a rational decision has to be made. In order to identify which parameter or group of parameters significantly affects the output of a decision model, we investigate decision-theoretic sensitivity analysis and its computational issues in this paper. In particular, we employ the so-called expected value of partial perfect information (EVPPI) as a sensitivity index and apply multilevel Monte Carlo (MLMC) methods to efficient estimation of EVPPI. In a recent paper by Giles and Goda, an antithetic MLMC estimator for EVPPI is proposed and its variance analysis is conducted under some assumptions on a decision model. In this paper, for an improvement on the performance of the MLMC estimator, we incorporate randomized quasi-Monte Carlo methods within the inner sampling, which results in an multilevel quasi-Monte Carlo (MLQMC) estimator. We apply both the antithetic MLMC and MLQMC estimators to a simple waterflooding decision problem under uncertainty on absolute permeability and relative permeability curves. Through numerical experiments, we compare the performances of the MLMC and MLQMC estimators and confirm a significant advantage of the MLQMC estimator.     

Mechanism and future risk of slope instability induced by extreme rainfall event in Izu Oshima Island,Japan

Natural Hazards - A volcanic slope in Izu Oshima Island in Japan experienced a profound rain-induced disaster in October 2013. Since this slope had been stable for centuries except for minor...