BackgroundA comprehensive self-administered diet history questionnaire (DHQ: 150-item semi-quantitative questionnaire) and a brief self-administered DHQ (BDHQ: 58-item fixed-portion–type questionnaire) were developed for assessing Japanese diets. We compared the relative validity of nutrient intake derived from DHQ with that from the BDHQ, using semi-weighed 16-day dietary records (DRs) as reference.MethodsNinety-two Japanese women aged 31 to 69 years and 92 Japanese men aged 32 to 76 years completed a 4-nonconsecutive-day DR, a DHQ, and a BDHQ 4 times each (once per season) in 3 areas of Japan (Osaka, Nagano, and Tottori).ResultsNo significant differences were seen in estimates of energy-adjusted intakes of 42 selected nutrients (based on the residual method) between the 16-day DRs and the first DHQ (DHQ1) or between the DR and the first BDHQ (BDHQ1) for 18 (43%) and 14 (33%) nutrients, respectively, among women and for 4 (10%) and 21 (50%) nutrients among men. The median (interquartile range) Pearson correlation coefficients with the DR for energy-adjusted intakes of the 42 nutrients were 0.57 (0.50 to 0.64) for the DHQ1 and 0.54 (0.45 to 0.61) for the BDHQ1 in women; in men, the respective values were 0.50 (0.42 to 0.59) and 0.56 (0.41 to 0.63). Similar results were observed for the means of the 4 DHQs and BDHQs.ConclusionsThe DHQ and BDHQ had satisfactory ranking ability for the energy-adjusted intakes of many nutrients among the present Japanese population, although these instruments were satisfactory in estimating mean values for only a small number of nutrients.

[1] We compare the results of 2-D/3-D time-dependent models of small-scale convection under the island arc with the geophysical and geologic data observed in the NE Honshu subduction zone, northeast Japan. Assuming that the temperature anomalies have a close connection with the seismic anomalies, we may constrain the geometry of the low-viscosity wedge (LVW) overlying the slab, which may be produced by the water dehydrated from the subducting slab. Our preferred model predicts step-like low-velocity anomalies above the subducting slab rather than smooth anomalies subparallel to the subducting slab since the shallow nature of the LVW is required for the small-scale convection to occur at the back-arc end of the LVW. A movement of cold plumes generated at the back-arc end of the LVW may be related to a possible migration of volcanism from back-arc to volcanic front side. To be consistent with the observation, which may suggest the migration rate of $2 cm/yr, models require weak viscous couplings between the mantle wedge and the underlying subducting slab, whose speed of subduction is $10 cm/yr. Three-dimensional models showing 3-D temperature variation consist of fairly continuous and strong temperature anomalies (several hundreds of degrees) under the volcanic front and weak finger-like temperature anomalies (several tens of degrees) behind them, which are similar to the pattern of the seismic tomography. The timedependent behavior of the temperature field shows that the pattern of fingers flip-flops with a timescale equal to the ratio of the horizontal extent of the LVW to the migration speed of cold plumes. This change of pattern of fingers may have an important implication for understanding the past distribution of volcanism. Further studies related to (1) the detailed morphology of the low-velocity zone above the subducting slab, (2) the spatial and temporal evolution of volcanism, and (3) the dynamic 3-D model studies which selfconsistently determine the distribution of water/volatiles and the resultant weak rheology are important for checking the validity of our model or developing alternative models.

Abstract:We review the evolution of late Cenozoic magmatism in the NE Japan arc, and examine the relationship between the magmatism and the crust-mantle structure. Recent studies reveal secular changes in the mode of magmatic activity, the magma plumbing system, erupted volumes and magmatic composition associated with the evolution of crust-mantle structures related to the tectonic evolution of the arc. The evolution of Cenozoic magmatism in the arc can be divided into three periods: the continental margin (66-21 Ma), the back-arc basin (21-13.5 Ma) and the island-arc period (13.5-0 Ma). Magmatic evolution in the back-arc basin and the island-arc periods appears to be related to the 2D to 3D change in the convection pattern of the mantle wedge related to the asthenosphere upwelling and subsequent cooling of the mantle. Geodynamic changes in the mantle caused back-arc basin basalt eruptions during the back-arc basin opening (basalt phase) followed by crustal heating and re-melting, which generated many felsic plutons and calderas (rhyolite/granite phase) in the early stage of the island-arc period. This was followed by crustal cooling and strong compression, which ensured vent connections and mixing between deeper mafic and shallower felsic magmas, erupting large volumes of Quaternary andesites (andesite phase).Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.The NE Japan arc is a typical island arc associated with a cold subduction zone. It is one of the most well-known island arcs on Earth and provides a useful model for our understanding of how subduction zones produce magmas, including andesites. The NE Japan arc is related to the westward

[1] Hydration and partial melting along subducting slabs can trigger Rayleigh-Taylor-like instabilities. We use 3-D petrological-thermomechanical numerical simulations to investigate small-scale convection and hydrous, partially molten, cold plumes formed in the mantle wedge in response to slab dehydration. The simulations were carried out with the I3ELVIS code, which is based on a multigrid approach combined with marker-in-cell methods and conservative finite difference schemes. Our numerical simulations show that three types of plumes occur above the slab-mantle interface: (1) finger-like plumes that form sheet-like structure parallel to the trench, (2) ridge-like structures perpendicular to the trench, and (3) flattened wavelike instabilities propagating upward along the upper surface of the slab and forming zigzag patterns parallel to the trench. The viscosity of the plume material is the main factor controlling the geometry of the plumes. Our results show that lower viscosity of the partially molten rocks facilitates the Rayleigh-Taylorlike instabilities with small wavelengths. In particular, in low-viscosity models (10 18 -10 19 Pa s) the typical spacing of finger-like plumes is about 30-45 km, while in high-viscosity models (10 20 -10 21 Pa s) plumes become rather sheet-like, and the spacing between them increases to 70-100 km. Water released from the slab forms a low-viscosity wedge with complex 3-D geometries. The computed spatial and temporal pattern of melt generation intensity above the slab is compared to the distribution and ages of volcanoes in the northeast Japan. Based on the similarity of the patterns we suggest that specific clustering of volcanic activity in this region could be potentially related to the activity of thermal-chemical plumes.

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The effects of multiple phase transitions on mantle convection are investigated by numerical simulations that are based on three-dimensional models. These simulations show that cold sheets of mantle material collide at junctions, merge, and form a strong downflow that is stopped temporarily by the transition zone. The accumulated cold material gives rise to a strong gravitational instability that causes the cold mass to sink rapidly into the lower mantle. This process promotes a massive exchange between the lower and upper mantles and triggers a global instability in the adjacent plume system. This mechanism may be cyclic in nature and may be linked to the generation of superplumes.

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Arc volcanism of the past 10 my in the northeast Honshu and Izu-Bonin Arcs shows several notable features. In the northeast Honshu Arc, the spatial distribution of volcanism exhibits several clusters elongated nearly perpendicular to the arc and the possible migration of volcanism from the back-arc side to the volcanic front side, at least, during the past 5 my. The pattern of clusters seems to have flip-flopped around 5 Ma. In the Izu-Bonin Arc, there are a series of across-arc seamount chains, in which volcanic activity occurred from ca 17 Ma to ca 3 Ma, similar to the clusters of the northeast Honshu Arc, although the recent active rifting occurs almost parallel to the arc. On the basis of studies of numerical modeling, these features might be explained, at least qualitatively, by the small-scale convection under the island arc. Several inferences can be made from our modeling results for the tectonics of the Izu-Bonin Arc. The angle of dip of subducting plate in the Izu-Bonin Arc might have increased. This can explain the disappearance of volcanism along the seamount chains and the recent along-arc volcanism with narrow rifting. The trend of seamount chains, which is oblique to the arc, might not be their intrinsic feature but rather a result of the lateral movement of the back-arc region after their formation. These inferences can be tested by the future detailed morphological and chronological studies of the Izu-Bonin Arc.