Introduction to “Historical and Recent Catastrophic Tsunamis in the World: Volume II. Tsunamis from 1755 to 2010”

Eighteen papers on past and recent destructive tsunamis are included in Volume II of the PAGEOPH topical issue “Historical and Recent Catastrophic Tsunamis in the World.” Three papers discuss deep-sea (DART) and coastal tsunami observations, warning systems and risk management in the Pacific Ocean. Four papers examine the 1755 Lisbon, 1964 Alaska, 2003 Algeria, and 2011 Haiti tsunamis. Four more papers, as well as some papers in Volume I, report on various aspects of the 2010 Chile tsunami. Two papers present some results of field survey and modelling investigation of the 2010 Mentawai, Indonesia, tsunami. Three papers report on modelling efforts of tsunami generation by earthquake and landslide, and of tsunami propagation. Finally, two papers discuss hazard assessment using a probabilistic approach.     

The spatial and seasonal distributions of air-transport origins to the Antarctic based on 5-day backward trajectory analysis

Transport of moisture-bearing air to the Antarctic is one of the important factors that control the mass balance of the ice sheet. Here, we investigate the distribution of air-parcel transport using a backward trajectory analysis over the entire Antarctic ice sheet, based on whether the air parcel was located inside or outside of Antarctica at 5 days before arrival. At this time, we considered the air from outside Antarctica to be moisture rich. Oceanic air was found to dominate in West Antarctica throughout the year, whereas air from inland was more prominently distributed around East Antarctica, especially in summer. In East Antarctica, there was a significant seasonal variation: air from inland dominated in summer, while air of oceanic origin dominated in winter. The distribution of air parcels that came from oceanic/inland sources was similar to the accumulation map (based on satellite data), which indicates that oceanic air parcels could be a substitute for moisture transport to the Antarctic. To determine the future impacts of climate change (e.g., sea level rise), more precise predictions of the variations in the surface mass balance will be required. Our results contribute towards the improved understanding of the spatial distributions of accumulation and aerosols found in Antarctic snow and ice cores.     

Geological setting of basaltic rocks in an accretionary complex,Khangai–Khentei Belt,Mongolia

We describe the mode of occurrence and geochemical characteristics of basalts, in the Khangai–Khentei belt in Mongolia, overlain by Middle Paleozoic radiolarian chert in an extensive accretionary complex. These basalts are greatly enriched in K, Ti, Fe, P, Rb, Ba, Th, and Nb in comparison to the composition of the mid‐ocean ridge basalts, indicative of within‐plate alkaline type. Ti/Y vs Nb/Y and MnO/TiO₂/P₂O₅ ratios of the basalts also suggest within‐plate affinities. Considering the geochemical characteristics as well as the conformable relationship with the overlying radiolarian chert, the alkaline basalts were clearly not continental but formed a pelagic oceanic island. The mode of occurrence and geochemistry of the basalts show that the alkaline basaltic volcanic activity had taken place to form an oceanic island in the Paleozoic pelagic region sufficiently far from continents to allow radiolarian ooze accumulation.     

The nationwide investigation of endocrine disruptors in sediment of harbours

Various types of endocrine disruptors or environmental hormones flow from their sources down into harbours through rivers and other watercourses, and are accumulated in sediment on the sea bottom. Tributyltin, which has been used as paint for ship bottoms, is considered one of the endocrine disruptors.In close cooperation with the other ministries and agencies, the Ports and Harbours Bureau of the Ministry of Land, Infrastructure and Transport carried out an investigation in 1999 to determine the actual condition of 12 endocrine disruptors in the sediment of 39 harbours, in order to gather fundamental data to be used in future examinations of policy. Furthermore, in 2000 the bureau chose seven harbours out of the above 39 harbours as subjects of an additional investigation regarding the surface distribution of endocrine disruptors in the harbour areas and the synchronistic change of accumulation of dioxin and other substances. As the result of the investigation regarding the surface distribution of endocrine disruptors accumulated in seven harbours, relatively high concentrations were measured in the innermost parts of harbours and the mouths of rivers. Synchronistic changes in the amount of dioxin and other substances accumulated in sediments of five harbours were determined. Small amounts of dioxin and other substances, including an especially small amount of coplanar-PCBs, were found in the layers formed before or around 1950. Relatively large amounts of these substances were measured in the upper layers formed during roughly 1960-1990, though no significant yearly differences in concentration could be identified. This result coincides with the facts that, during roughly 1960-1980, PCP and CNP were used as agricultural chemicals and full-scale production of PCBs started in 1960.     

Isotopic evidence for trapped fissiogenic REE and nucleogenic Pu in apatite and Pb evolution at the Oklo natural reactor

A part of the boundary layer of reactor zone 10 at the Oklo natural reactor shows a unique petrologic texture, which contains high-grade uraninite and massive apatite concretions. In order to study distribution behavior of fission products around the boundary between the reactor zone and the wall rock and to clarify the relation of migration mechanisms of fission products with geochemical factors, in-situ isotopic analyses of Nd, Sm, Gd, Pb and U in uraninite and apatite from the sample were performed by Sensitive High Resolution Ion Microprobe (SHRIMP). Sm and Gd isotopic ratios of uraninite and apatite show evidence of neutron irradiation with fluence between 4.4-6.8×10¹⁹ n/cm². Judging from the isotopic anomalies of Nd and U, the apatite coexisting with the uraninite plays an important role in trapping fissiogenic LREE and nucleogenic ²³⁹Pu into the structure. Systematic Pb isotopic data from apatite, uraninite, galena and minium suggest the following chronological interpretations.

1.

The apatite formed 1.92±0.01 Ga ago and trapped fissiogenic light REE and nucleogenic ²³⁹Pu that migrated from the reactor during the criticality.

2.

The uraninite around the boundary between reactor and sandstone dissolved once 1.1∼1.2 Ga ago.

3.

Galena grains were formed by U-Pb mobilization in association with the intrusion of dolerite dyke 0.45∼0.83 Ga ago.

4.

Minium was derived from recent dissolution of galena under locally oxidizing conditions.

     

Integrated description of deformation modes in a sedimentary basin: A case study around a shallow drilling site in the Mizunami area, eastern part of southwest Japan

Abstract   Tectonic episodes in a sedimentary basin are described on the basis of an integrated study combining reflection seismic interpretation, drilling survey and paleomagnetism. A shallow inclined borehole penetrated a fault shown by reflection seismic and geological surveys in the Mizunami area, in the eastern part of southwest Japan. Paleomagnetic measurements were carried out on core samples successfully oriented using side-wall image logging of structural attitude. At six horizons, stable characteristic remanent magnetization (ChRM) was confirmed through thermal and alternating field demagnetization tests, which were carried by magnetite with minor amounts of high coercivity minerals, as revealed by experiments of stepwise acquisition of isothermal remanent magnetization. After correction of multiphase deformation inferred from borehole structural analysis, ChRM directions were combined with previous data and confirmed an easterly deflection reflecting the coherent clockwise rotation of the arc before the Middle Miocene. Compilation of reliable paleomagnetic data described differential rotation of the eastern part of southwest Japan raised by collision of the Izu–Bonin Arc since the Middle Miocene. The present study suggests that (i) the Mizunami area is adjacent to a highly deformed zone bounded by the Akaishi Tectonic Line (ATL), and (ii) forearc deformation of southwest Japan is localized around the ATL, which is quite different from gradual bending on the back-arc side without remarkable crustal break related to the collision event.     

Magma mixing recorded in intermediate rocks associated with high-Mg andesites from the Setouchi volcanic belt, Japan: implications for Archean TTG formation

Calc-alkaline intermediate rocks are spatially and temporally associated with high-Mg andesites (HMAs, Mg#>60) in Middle Miocene Setouchi volcanic belt. The calc-alkaline rocks are characterized by higher Mg# (strongly calc-alkaline trend) than ordinary calc-alkaline rocks at equivalent silica contents. Phenocrysts in the intermediate rocks have petrographical features such as: (1) coexisting reversely and normally zoned orthopyroxene phenocrysts in single rock; (2) sieve type plagioclase in which cores are mantled by higher An%, melt inclusion-rich zone; and (3) reversely zoned amphibole phenocrysts with opacite cores. In addition, mingling textures and magmatic inclusions were observed in some rocks. These petrographic features and the mineral chemistry indicate that magma mixing was the most important process in producing the strongly calc-alkaline rocks. The core composition of normally zoned orthopyroxene phenocrysts and the mantle composition of reversely zoned orthopyroxene phenocrysts have relatively high Mg# (85–90) in maximum. Although basaltic and high-Mg andesitic magmas are candidate as possible mafic end-member magmas, basaltic magma is excluded in terms of phenocryst assemblage and bulk composition. HMA magmas are suitable mafic end-member magmas that precipitated high Mg# (90) orthopyroxene, whereas andesitic to dacitic magma are suitable felsic end-members. In contrast, it is difficult to produce the strongly calc-alkaline trend through fractional crystallization from a HMA magma, because it would require removal of plagioclase together with mafic minerals from the early stage of crystallization, whereas the precipitation of plagiolase is suppressed due to the high water content of HMA magmas. These results imply that Archean Mg#-rich TTGs (>45–55), which are an analog of the strongly calc-alkaline rocks in terms of chemistry and magma genesis, can be derived from magma mixing in which a HMA magma is the mafic end-member magma, rather than by fractional crystallization from a HMA magma.     

A method for determining both diffusion and sorption coefficients of rock medium within a few days by adopting a micro-reactor technique

Migration properties characterized by physico-chemical factors such as distribution coefficient (K_d) and diffusion coefficient (D_e) are of great concern in performance assessment of high-level radioactive waste disposal in a deep geologic environment. These coefficients are normally obtained with different sample geometries using conventional methods, i.e., crushed samples by the batch sorption method for K_d determination and block samples by the through-diffusion method for D_e. A size dependence on both K_d and D_e has been reported and an additional correction due to size difference is required to maintain consistency of the data set. A fast method was developed, hereafter referred to as the micro-channel method, to determine both the sorption coefficient (R_d) and D_e using non-crushed rock sample by adopting the micro-reactor technique. In this method, a radionuclide solution is injected into a micro-channel (20 mm length, 4 mm width, 160 μm depth), which is in contact with a plate-shaped rock sample. A part of the injected radionuclide can diffuse into the rock matrix and/or adsorb on the rock surface and this results in an inlet-outlet concentration difference. A breakthrough curve is easily obtained with a short observation period because the injection amount is extremely small and is comparable to that escaping by diffusion into the matrix. The breakthrough curve is analyzed by a two-dimensional diffusion-advection equation to evaluate R_d and D_e.In the present study, tritiated water (specific activity, 1.2 × 10⁴ Bq/mL; pH, 6) was injected into the micro-channel, and the breakthrough curve of ³H obtained. A series of experiments was carried out by changing the flow rate of the tritiated water (2.6 × 10⁻⁵–7.7 × 10⁻⁴ m/s). Rock samples were biotite granite from the Makabe area, Japan. The diffusion coefficient evaluated by least squares fitting to the numerical solutions (D_e = 1.5 × 10⁻¹¹ m²/s) agreed well with that obtained by the through-diffusion method (1.3 × 10⁻¹¹ m²/s). The breakthrough curve of Cs ([Cs] = 1.0 × 10⁻⁷ mol/L, pH 6) labeled with ¹³⁴Cs (specific activity adjusted to 4.9 × 10¹ Bq/mL) was also obtained. A nearly constant R_d value (5.5 × 10⁻² m³/kg) was found when the flow rate was less than 2.5 × 10⁻⁴ m/s. This implied that the sorption equilibrium is reached and K_d is obtained by the present method. This value was almost identical to K_d obtained by the batch sorption method (5.0 × 10⁻² m³/kg), but the testing period was very different; 1 day and 7 days, respectively. It is concluded that application of the micro-channel method provided advantages when compared with the conventional methods.     

Enzymatic Approach to Fungal Association with Arthropod Guts: A Case Study for the Crustacean Host, Nihonotrypaea harmandi, and Its Foregut Fungus, Enteromyces callianassae

Abstract. In the callianassid shrimp Nihonotrypaea harmandi (Bouvier 1901), the trichomycete fungus Enteromyces callianassae Lichtwardt 1961 occurs exclusively on the foregut lining. The enzymes from both the shrimp and the fungus apparently hydrolyze certain nitrogen and carbon compounds in detritus. The activities of various proteases and carbohydrases contained in the foregut juice were compared between fungus-infected shrimps collected from a sandflat in Kyushu, Japan (51 % infection rate) and uninfected shrimps from a nearby sandflat. The concentration of enzymatically hydrolyzable amino acids (EHAA) in sediment liberated by the foregut juice with fungi was slightly lower than that by 0.1 mg·ml^-1 proteinase-K and significantly higher than that by the foregut juice without fungi. In both foregut juices, substantial enzyme activities were recorded for proteinase(s), peptidases, amylase, cellulase and β-1,3-glucanase, and minimal ones for maltase and cellobiase. Of the commercial substrates examined, only in the case of the mixture of 16 kinds of dipeptides was a significantly higher enzyme activity in the foregut juice with fungi observed. In the process of EHAA liberation from sediment, peptidases secreted by the fungus most probably act as a supplement to the endogenous secretion by the shrimp. This may explain the higher shrimp growth rate recorded for the population with fungi. However, the significantly higher sediment EHAA concentration of the sandflat inhabited by this population versus the population without fungi could be another crucial factor explaining the site difference in shrimp growth rate.