Experimental and numerical analysis of container stack dynamics using a scaled model test

This paper describes an approach to simulate a seven-tier stack consisting of scaled model of a 20 ft ISO freight container and its linking connectors, denominated twist locks, subjected to dynamical load induced by its base. The physical (dimensions, mass, and moments of inertia) and structural (longitudinal, transversal and torsional stiffness) characteristics of the scaled models were decided based on two dimensionless numbers: ratios between gravity force and inertia force, and elastic force divided by inertia force, through experimental and numerical analysis. A series of experiments with controlled parameters were performed using a shaking table test to understand the effects of each variable in the container stack dynamics and present enough data to validate the numerical model. The results of this study indicate that the numerical model built is a promising tool for further study. Moreover, the model is able to predict conditions close to real situations faced by container stacks while storage on a ship's deck.     

Detection of Pacific tropical water variability by taut-line moorings in the western equatorial Pacific

This study uses temperature and salinity time series acquired with taut-line moorings in the western equatorial Pacific to investigate water mass behavior on the thermocline layer. Basically, it is insufficient to trace water mass variation by the original discrete depth coordinate data because of relatively high variability of density at fixed depth near the thermocline. A reconstruction method based on the density surface motion caused by tidal forcing was used to derive continuous profiles of temperature and salinity from vertically discrete measurements at fixed depths. This method can represent detailed vertical salinity structures and their variation, especially along the potential density surface of 24.8σ_θ, where the salinity maximum of South Pacific tropical water (SPTW) appeared. Variability around the 24.8σ_θ surface at each site was as large as that observed at the surface, which suggests a strong influence of SPTW behavior. High salinity along the 24.8σ_θ surface within the equatorial band of the western Pacific appeared during boreal fall-winter at sites far from New Guinea. In contrast, high salinity appeared near New Guinea during the boreal spring-summer. These features suggest the influence of the New Guinea Coastal Undercurrent. Over longer time scales, several higher salinity events were observed. The most pronounced salinity event occurred during 2007–2008. Interannual variation of the salinity anomaly along the 24.8σ_θ surface was negatively correlated with the Niño 3.4 sea surface temperature anomaly. A long-term salinity anomaly shift from negative to positive occurred around the end of 2002. The relationship with decadal variation in subtropical cell transport is also discussed.     

Reconstruction of the global lightning distribution from ELF electromagnetic background signals

The global lightning distribution has been obtained for the first time as the result of an inverse problem for the natural extremely low-frequency (ELF) electromagnetic background signals measured simultaneously at three stations: Lekhta (Karelia, Russia), Moshiri (Hokkaido, Japan), and West Greenwich (Rhode Island, USA). We employed a two-step technique consisting of: (1) inversion of ELF field spectra to a source distance distribution (distance profile) for each station of the network and (2) treating the obtained distance profiles as projections in the tomographic method. The structure of the source distance profiles reconstructed from experimental field spectra, varies during a day in a manner specific for each station, which can be explained generally by the temporal distribution of the sources in the tropical continental areas, so-called world thunderstorm centres (WTCs). The comparison of the obtained source distributions with the satellite data on lightning collected by Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) shows satisfactory agreement, which proves that our newly developed inversion technique is a suitable method for mapping global lightning.     

Fifteen years progress of the TRITON array in the Western Pacific and Eastern Indian Oceans

The Triangle Trans‐Ocean Buoy Network (TRITON) project by the Japan Agency for Marine-Earth Science and Technology began with deployment in the western tropical Pacific Ocean in 1998 and has shifted to steady, long-term observations since 1999. After on-site inter-comparison with the Autonomous Temperature Line Acquisition System mooring system of the Tropical Atmosphere and Ocean (TAO) array by the National Oceanic and Atmospheric Administration, the TRITON array became the international TAO/TRITON array in 2000 as a key component of the Global Ocean and Climate Observing Systems. The TAO/TRITON array took over from the TAO array, which was developed during the Tropical Ocean and Global Atmosphere program (1985–1994), and replaced the western part of TAO with new additional real-time measurements of salinity and ocean currents. In 2001, two TRITON moorings were deployed in the eastern Indian Ocean for capturing the eastern pole of the Indian Ocean Dipole. From this initiative, the Indian Ocean Observing System (IndOOS) was designed, and the Indian Ocean mooring array (Research Moored Array for Africa–Asian–Australian Monsoon Analysis and Prediction) was developed as a key component of IndOOS. In this paper, 15 years of progress in the TRITON project in the western Pacific and eastern Indian Oceans is reviewed with regards to scientific outcomes, technological development, and collaborations with international and domestic partners. Future directions for sustainable observation in the Pacific and Indian Oceans are also discussed.     

Variations in trace elements,isotopes, and organic geochemistry during the Hangenberg Crisis,Devonian–Carboniferous transition,northeastern Vietnam

The Hangenberg Crisis at the Devonian–Carboniferous boundary is known as a polyphase extinction event that affected more than 45 % of marine and terrestrial genera. As the cause of this event is still debated, analyses were carried out on sedimentary samples from the Devonian–Carboniferous Pho Han Formation in northeastern Vietnam to reconstruct the paleoenvironment around the time of this event using stable carbon isotopes; total sulfur; manganese; vanadium; molybdenum; and sedimentary organic matter, such as dibenzothiophenes, cadalene, and regular steranes. These geochemical signatures provide a high‐resolution redox history for this section and show that transgression‐driven high primary productivity, possibly enhanced by terrestrial input, caused severe oxygen depletion along the continental margin of the South China block during the Hangenberg Crisis.     

Geochemical characteristics of zircons in the Ashizuri A‐type granitoids: An additional granite topology tool for detrital zircon studies

Zircon is resistant to alteration over a wide range of geological environments, and isotopic ratios within the mineral provide constraints on ages and their parental magmas. Trace element compositions in zircon are also expected to reflect those of their parent magmas, and have a potential as essential indicators for their host rocks. Because most detrital zircons that accumulate at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. This study employs the conventional classification scheme of granites (I‐, S‐, M‐, and A‐types). To clarify geochemical characteristics of zircons in A‐type granites, trace element compositions of zircons extracted from the A‐type Ashizuri granitoids were examined. Zircons from the Ashizuri granitoids commonly show enrichments of heavy rare earth elements and positive Ce anomalies, indicating that these zircons were igneous in origin. In addition, zircons in these A‐type granites are characterized by enrichments of Nb, Y, Ta, Th, and U and strong negative Eu anomalies, which exhibit good positive correlations with those in their whole rocks. This fact indicates that these signatures in zircons reflect well those in their parental bodies and are useful in identifying zircons derived from A‐type granite. Based on compilations of available data, zircons from A‐type granites can be clearly discriminated from other‐types of granites within Nb/Sr–Eu anomaly, U/Sr–Eu anomaly, Nb/Sr–U/Sr, and Nb/Sr–Ta/Sr cross‐plots. All indices used in these diagrams were selected based on the geochemical features of both zircon and whole rock of A‐type granites. Application of these discrimination diagrams to detrital zircons will likely provide further insights. For example, some Hadean detrital zircons plot in similar fields to A‐type granites, implying the existence of A‐type magmatism in the Earth's earliest history.     

Depositional environments and maturity evaluated by biomarker analyses of sediments deposited across the Cenomanian–Turonian boundary in the Yezo Group,Tomamae area,Hokkaido, Japan

Biomarker analyses for evaluating maturity of organic matter and depositional environments such as redox conditions, were performed in sediments across the Cenomanian–Turonian boundary (CTB) in the Saku Formation of the Yezo Group distributed along the Shumarinai‐gawa River and the Omagari‐zawa River, both in the Tomamae area, Hokkaido, Japan. Maturity indicators using steranes and hopanes, show that organic matter in sediments from the Shumarinai‐gawa and Omagari‐zawa sections are of lower maturity than those from the Hakkin‐gawa section (Oyubari area). Moreover, the ββ hopane ratios clearly show that the maturity of the Shumarinai‐gawa samples is lower than that of the Omagari‐zawa samples. These variations in the maturity of organic matter presumably reflect the difference in their burial histories. The results for the pristane/phytane (Pr/Ph) ratios suggest that the Shumarinai‐gawa samples were deposited under dysoxic to anoxic environments across the CTB, while the depositional environments of the Omagari‐zawa samples were relatively oxic. By another paleoredox indicator using C₃₅ homohopanoids including a homohopene index (HHenI), higher values are observed in the Shumarinai‐gawa section, particularly in the horizons of the preceding period and an early stage of the first negative shift phase and the latest oceanic anoxic event 2 (OAE2) interval. These results suggest that the Shumarinai‐gawa samples record dysoxic to anoxic environments across the CTB. In contrast, the signals for the C₃₅ homohopanoid index values show a relatively oxic condition in the Omagari‐zawa section. The trends of stratigraphic variations in redox conditions are different from those in the OAE2 interval in the proto‐Atlantic and Tethys regions as reported previously. Hence, the redox variations in the Tomamae area were basically related to a local environmental setting rather than global anoxia. However, the prominent anoxic emphasis observed in the HHenI profile of the Shumarinai‐gawa section can be a distinctive, and possibly global, event in the North‐West Pacific just before the OAE2.     

Eocene extensional tectonics in the Amakusa region,northern Ryukyu arc

Paleogene surface tectonics in Japan is not well understood because of the paucity of onshore Paleogene stratigraphic records except for those from accretionary complexes. Paralic Paleogene formations remaining in SW Japan are usually so thin that it is difficult to decipher the tectonics from them. However, the Eocene paralic sedimentary package with a thickness of kilometers indicates syn-depositional tectonic subsidence by a few kilometers in the Amakusa archipelago, west of Kyushu Island. Thus, we made a detailed geological map of the Eocene formations in an area of ~50 square kilometers in the northwestern part of the archipelago. We identified NE-SW and NW-SE trending normal faults, most of which were recognized by previous researchers, and also discovered low-angle faults. NW-SE trending ones are known to be of the Miocene. NE-SW trending and low-angle normal faults are the oldest map-scale structures in the Eocene ones. It is not obvious within the above-mentioned area whether those normal faults are accompanied by growth strata. However, the significant southeastward thickening of the Eocene formations across the Amakusa archipelago suggests that they filled a large half graben with the basin margin fault along the eastern side of the archipelago. This basin model is consistent with the N-S to NW-SE transport directions of the low-angle and NE-SW trending normal faults. Since many NE-SW to EW trending Eocene grabens were formed in the offshore regions west of Kyushu Island and in the East China Sea, the Amakusa region was probably a northeastern branch of the rift system. The geologic structures and depositional ages of the Eocene formations indicate that the Eocene extensional tectonics removed the overlying strata to some extent for the high-P/T Takahama Metamorphic Rocks which crops out to the south of our study area.