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51.
A fault scarp in an urban area identified by LiDAR survey: A Case study on the Itoigawa–Shizuoka Tectonic Line, central Japan 总被引：2，自引：2，他引：0
A light detection and ranging (LiDAR) survey was conducted in a densely built-up area to generate a high-resolution digital elevation model (DEM) to look for active faults. The urban district of Matsumoto City in central Japan is located in a 3-km2 basin along the Itoigawa–Shizuoka Tectonic Line active fault system, one of Japanese onshore fault systems with the highest earthquake probability. A high-resolution DEM at a 0.5-m-grid interval was obtained after removing the effects of laser returns from buildings, clouds and vegetation. It revealed a continuous scarp, up to ~ 2 m in height. Borehole data and archaeological studies indicate the scarp was formed during the most recent faulting event associated with historical earthquakes. In addition, the fault scarp strongly supports that the urban district is in a pull-apart basin related to a fault step-over between two left-lateral strike-slip faults. Consequently, accurate interpretation of fault geometry is crucial to provide estimates of future surface deformation and to allow modeling of basin structure and strong ground motion. Thus, the LiDAR mapping survey in urban districts is effective for detailed active fault mapping in order to constrain basin structure and to forecast the exact location of surface rupturing associated with large earthquakes. 相似文献
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Heskett M Takada H Yamashita R Yuyama M Ito M Geok YB Ogata Y Kwan C Heckhausen A Taylor H Powell T Morishige C Young D Patterson H Robertson B Bailey E Mermoz J 《Marine pollution bulletin》2012,64(2):445-448
Plastic resin pellets collected from remote islands in the Pacific, Atlantic, and Indian Oceans and the Caribbean Sea were analyzed for polychlorinated biphenyls (PCBs), dichloro-diphenyltrichloroethane and its degradation products (DDTs), and hexachlorocyclohexanes (HCHs). Concentrations of PCBs (sum of 13 congeners) in the pellets were 0.1-9.9 ng/g-pellet. These were 1-3 orders of magnitude smaller than those observed in pellets from industrialized coastal shores. Concentrations of DDTs in the pellets were 0.8-4.1 ng/g-pellet. HCH concentrations were 0.6-1.7 ng/g-pellet, except for 19.3 ng/g-pellet on St. Helena, where current use of lindane is likely influence. This study provides background levels of POPs (PCBs<10 ng/g-pellet, DDTs <4 ng/g-pellet, HCHs <2 ng/g-pellet) for International Pellet Watch. Sporadic large concentrations of POPs were found in some pellet samples from remote islands and should be considered in future assessments of pollutants on plastic debris. 相似文献
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Kazunori Watanabe Koji Ono Keiichi Sakaguchi Akira Takada Hideo Hoshizumi 《Journal of Volcanology and Geothermal Research》1999,89(1-4)
Fugen-dake, the main peak of Unzen Volcano, began a new eruption sequence on November 17, 1990. On May 20, 1991, a new lava dome appeared near the eastern edge of the Fugen-dake summit. Small-scale, 104–106 m3 in volume, Merapi-type block and ash flows were frequently generated from the growing lava dome during May–June, 1991. These pyroclastic flows were accompanied by co-ignimbrite ash plumes that deposited ash-fall deposits downwind of the volcano. Three examples of co-ignimbrite ash-fall deposits from Unzen pyroclastic flows are described. The volume of fall deposits was estimated to be about 30% by volume of the collapsed portions of the dome that formed pyroclastic flows. This proportion is smaller than that described for other larger co-ignimbrite ash-fall deposits from other volcanoes. Grain size distributions of the Unzen co-ignimbrite ash-fall deposits are bi-modal or tri-modal. Most ashes are finer than 4 phi and two modes were observed at around 4–7 phi and 9 phi. They are composed mainly of groundmass fragments. Fractions of another mode at around 2 phi are rich in crystals derived from dome lava. Some of the fine ash component fell as accretionary lapilli from the co-ignimbrite ash cloud indicating either moisture or electrostatic aggregation. We believe that the co-ignimbrite ash of Unzen block and ash flows were formed by the mechanical fracturing of the cooling lava blocks as they collapsed and moved down the slope. These ashes were entrained into the convective plumes generated off the tops of the moving flows. 相似文献
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Information on the location and area for all MPAs in Japan was collected through a comprehensive survey targeting government officials and local stakeholders. It was verified that at least 1161 MPAs exist in Japan. Of these, 1055 are implemented in conjunction with fishery regulations in the form of no-take zones. More than 30% of the individual MPAs in Japan were established by self-imposed instruments agreed by members of fishery co-management organizations. It was suggested that the autonomous MPAs are not a product of simple altruism, but rather are logical extensions of the tenure system guaranteed by the government legal system. 相似文献
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Oxygen isotopic compositions of chondrules: Implications for evolution of oxygen isotopic reservoirs in the inner solar nebula 总被引：1，自引：0，他引：1
Alexander N. Krot Hisayoshi Yurimoto Kevin D. McKeegan Laurie Leshin Marc Chaussidon Guy Libourel Miwa Yoshitake Gary R. Huss Yunbin Guan Brigitte Zanda 《Chemie der Erde / Geochemistry》2006,66(4):249-276
We review the oxygen isotopic compositions of minerals in chondrules and compound objects composed of a chondrule and a refractory inclusion, and bulk oxygen isotopic compositions of chondrules in unequilibrated ordinary, carbonaceous, enstatite, and Kakangari-like chondrites, focusing on data acquired using secondary ion mass-spectrometry and laser fluorination coupled with mass-spectrometry over the last decade. Most ferromagnesian chondrules from primitive (unmetamorphosed) chondrites are isotopically uniform (within 3–4‰ in Δ17O) and depleted in 16O (Δ17O>−7‰) relative to amoeboid olivine aggregates (AOAs) and most calcium–aluminum-rich inclusions (CAIs) (Δ17O<−20‰), suggesting that these classes of objects formed in isotopically distinct gaseous reservoirs, 16O-poor and 16O-rich, respectively. Chondrules uniformly enriched in 16O (Δ17O<−15‰) are exceptionally rare and have been reported only in CH chondrites. Oxygen isotopic heterogeneity in chondrules is mainly due to the presence of relict grains. These appear to consist of chondrules of earlier generations and rare refractory inclusions; with rare exceptions, the relict grains are 16O-enriched relative to chondrule phenocrysts and mesostasis. Within a chondrite group, the magnesium-rich (Type I) chondrules tend to be 16O-enriched relative to the ferrous (Type II) chondrules. Aluminum-rich chondrules in ordinary, enstatite, CR, and CV chondrites are generally 16O-enriched relative to ferromagnesian chondrules. No systematic differences in oxygen isotopic compositions have been found among these chondrule types in CB chondrites. Aluminum-rich chondrules in carbonaceous chondrites often contain relict refractory inclusions. Aluminum-rich chondrules with relict CAIs have heterogeneous oxygen isotopic compositions (Δ17O ranges from −20‰ to 0‰). Aluminum-rich chondrules without relict CAIs are isotopically uniform and have oxygen isotopic compositions similar to, or approaching, those of ferromagnesian chondrules. Phenocrysts and mesostases of the CAI-bearing chondrules show no clear evidence for 16O-enrichment compared to the CAI-free chondrules. Spinel, hibonite, and forsterite of the relict refractory inclusions largely retained their original oxygen isotopic compositions. In contrast, plagioclase and melilite of the relict CAIs experienced melting and 16O-depletion to various degrees, probably due to isotopic exchange with an 16O-poor nebular gas. Several igneous CAIs experienced isotopic exchange with an 16O-poor nebular gas during late-stage remelting in the chondrule-forming region. On a three-isotope diagram, bulk oxygen isotopic compositions of most chondrules in ordinary, enstatite, and carbonaceous chondrites plot above, along, and below the terrestrial fractionation line, respectively. Bulk oxygen isotopic compositions of chondrules in altered and/or metamorphosed chondrites show evidence for mass-dependent fractionation, reflecting either interaction with a gaseous/fluid reservoir on parent asteroids or open-system thermal metamorphism. Bulk oxygen isotopic compositions of chondrules and oxygen isotopic compositions of individual minerals in chondrules and refractory inclusions from primitive chondrites plot along a common line of slope of 1, suggesting that only two major reservoirs (gas and solids) are needed to explain the observed variations. However, there is no requirement that each had a permanently fixed isotopic composition. The absolute (207Pb–206Pb) and relative (27Al–26Mg) chronologies of CAIs and chondrules and the differences in oxygen isotopic compositions of most chondrules (16O-poor) and most refractory inclusions (16O-rich) can be interpreted in terms of isotopic self-shielding during UV photolysis of CO in the initially 16O-rich (Δ17O−25‰) parent molecular cloud or protoplanetary disk. According to these models, the UV photolysis preferentially dissociates C17O and C18O in the parent molecular cloud and in the peripheral zones of the protoplanetary disk. If this process occurs in the stability field of water ice, the released atomic 17O and 18O are incorporated into water ice, while the residual CO gas becomes enriched in 16O. During the earliest stages of evolution of the protoplanetary disk, the inner solar nebula had a solar H2O/CO ratio and was 16O-rich. During this time, AOAs and the 16O-rich CAIs and chondrules formed. Subsequently, the inner solar nebula became H2O- and 16O-depleted, because ice-rich dust particles, which were depleted in 16O, agglomerated outside the snowline (5 AU), drifted rapidly towards the Sun and evaporated. During this time, which may have lasted for 3 Myr, most chondrules and the 16O-depleted igneous CAIs formed. We infer that most chondrules formed from isotopically heterogeneous, but 16O-depleted precursors, and experienced isotopic exchange with an 16O-poor nebular gas during melting. Although the relative roles of the chondrule precursor materials and gas–melt isotopic exchange in establishing oxygen isotopic compositions of chondrules have not been quantified yet, mineralogical, chemical, and isotopic evidence indicate that Type I chondrules may have formed in chemical and isotopic equilibrium with nebular gas of variable isotopic composition. Whether these variations were spatial or temporal are not known yet. 相似文献
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Assessment of digital camera-derived vegetation indices in quantitative monitoring of seasonal rice growth 总被引：4，自引：0，他引：4
Toshihiro Sakamoto Michio Shibayama Akihiko Kimura Eiji Takada 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):872-882
A commercially available digital camera can be used in a low-cost automatic observation system for monitoring crop growth change in open-air fields. We developed a prototype Crop Phenology Recording System (CPRS) for monitoring rice growth, but the ready-made waterproof cases that we used produced shadows on the images. After modifying the waterproof cases, we repeated the fixed-point camera observations to clarify questions regarding digital camera-derived vegetation indices (VIs), namely, the visible atmospherically resistant index (VARI) based on daytime normal color images (RGB image) and the nighttime relative brightness index (NRBINIR) based on nighttime near infrared (NIR) images. We also took frequent measurements of agronomic data such as plant length, leaf area index (LAI), and aboveground dry matter weight to gain a detailed understanding of the temporal relationship between the VIs and the biophysical parameters of rice. In addition, we conducted another nighttime outdoor experiment to establish the link between NRBINIR and camera-to-object distance. The study produced the following findings. (1) The customized waterproof cases succeeded in preventing large shadows from being cast, especially on nighttime images, and it was confirmed that the brightness of the nighttime NIR images had spatial heterogeneity when a point light source (flashlight) was used, in contrast to the daytime RGB images. (2) The additional experiment using a forklift showed that both the ISO sensitivity and the calibrated digital number of the NIR (cDNNIR) had significant effects on the sensitivity of NRBINIR to the camera-to-object distance. (3) Detailed measurements of a reproductive stem were collected to investigate the connection between the morphological feature change caused by the panicle sagging process and the downtrend in NRBINIR during the reproductive stages. However, these agronomic data were not completely in accord with NRBINIR in terms of the temporal pattern. (4) The time-series data for the LAI, plant length, and aboveground dry matter weight could be well approximated by a sigmoid curve based on NRBINIR and VARI. The results confirmed that NRBINIR was more sensitive to all of the agronomic data for overall season, including the early reproductive stages. VARI had an especially high correlation with LAI, unless yellow panicles appeared in the field of view. 相似文献
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Tomoko Sato Hiroto Takada Takehiko Yagi Hirotada Gotou Taku Okada Daisuke Wakabayashi Nobumasa Funamori 《Physics and Chemistry of Minerals》2013,40(1):3-10
We have investigated the high-pressure behavior of cristobalite in helium by powder X-ray diffraction. Cristobalite transformed to a new phase at about 8 GPa. This phase is supposed to have a molar volume of about 30 % larger than cristobalite, suggesting the dissolution of helium atoms in its interstitial voids. On further compression, the new phase transformed to a different phase which showed an X-ray diffraction pattern similar to cristobalite X-I at about 21 GPa. On the other hand, when the new phase was decompressed, it transformed to another new phase at about 7 GPa, which is also supposed to have a molar volume of about 25 % larger than cristobalite. On further decompression, the second new phase transformed to cristobalite II at about 2 GPa. In contrast to cristobalite, quartz did not show anomalous behavior in helium. The behavior of cristobalite in helium was also consistent with that in other mediums up to about 8 GPa, where the volume of cristobalite became close to that of quartz. These results suggest that dissolution of helium may be controlled not only by the density (amount of voids) but also by the network structure of SiO4 tetrahedra (topology of voids). 相似文献
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