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51.
We report the statistical and wavelet analyses of the 21 May 2003 tsunami produced by an M w 6.8–6.9 thrust earthquake in the western Mediterranean Sea using 19 tide gauge records. The largest trough-to-crest wave height was 196 cm recorded at the Sant Antoni station in the lee of the incoming tsunami wave. Except at one station, the first wave was not the largest wave at all the analyzed stations, and the largest wave arrived several hours after the first arrival. In addition, the tsunami waves persisted for more than 1 day at most stations. As the spectra of coastal tide gauge stations are strongly influenced by topographic features, special care was taken here while interpreting the results of spectral and wavelet analysis. Our wavelet analysis shows that only a peak at around 23 min is persistent for long duration, and other peaks at 14, 30, 45, and 60 min appeared at short durations. The 23-min signal is possibly associated with the width of the source fault whereas the fault length contributed to the 45-min signal. Based on these dominant periods, the tsunami source dimensions are estimated as 95 km × 45 km. The statistical and wavelet analyses performed here provide some new insights into the characteristics of the tsunami that was generated and propagated in the western Mediterranean basin. 相似文献
52.
Vibrational density of states of the NaAlSi2O6 jadeite and NaAlSiO4 calcium ferrite (CF)-type, and SiO2 stishovite is calculated as a function of pressure up to 50 GPa using density functional perturbation theory. The calculated
frequencies are used to determine the thermal contribution to the Helmholtz free energy within the quasi-harmonic approximation
and to derive the equation of state and several thermodynamic properties of interest. A dissociation of jadeite into a mixture
of a CF-type phase and stishovite is predicted to occur at 23.4 GPa and 1,800 K with a positive Clapeyron slope of 2.8 MPa/K.
Elastic anisotropy for jadeite, the CF-type phase, and stishovite also computed clearly shows that stishovite and the CF-type
phase are the most anisotropic and isotropic in these three phases, respectively. 相似文献
53.
Gas was sampled regionally, including by drilling into faults, in the South Kanto gas-field around Tokyo Bay, Japan. Gas samples were collected from cores in a gas sampling container immediately after drilling. A value of δ13C1 = −44.3‰ was obtained for gas in the container and δ13C1 = −36.3‰ for seeping gas in a fault zone. However, typical CH4 in this dissolved-in-water gas-field is mainly depleted in 13C, and δ13C1 values range from −66‰ to −68‰ owing to microbial degradation of organic material. 13C-rich CH4 is so far uncommon in the South Kanto gas-field. Seepages were observed from the surface along the north–south fault zone. The natural gas is stored below the sandstone layer by impermeable mudstone underlying the boundary at a depth of 30 m. Gas seepages were not observed below a depth of 40 m. Gas rises along the fault zone dissolved-in-groundwater up to the shallow region and then separates from the groundwater. 13C-rich CH4 (adsorbed CH4) was found to have desorbed from drilled mudstone core samples taken at depths of 1400–1900 m in the main gas-production strata. Similarly, 13C-rich CH4 was found in black shale overlying the oceanic crust forming part of a sedimentary accretionary prism underling the Tokyo region. It also appears in the spring-water of spa wells, originating at a depth of 1200–1500 m along a tectonic line. Methane generated by microbial degradation of organic material through CO2 reduction in the South Kanto gas-field mainly originates as biogenic gas mixed with a small amount of 13C-rich CH4, derived from thermogenic gas without oil components in strata. It is assumed that 12C-rich CH4 is easily detached from core or pore water through gas production, whereas 13C-rich CH4 is strongly adsorbed on the surfaces of particles. The 13C-rich CH4 rises along the major tectonic line or up the 50 m wide normal fault zone from relatively deep sources in the Kanto region. 相似文献
54.
Badri Bhakta Shrestha Hajime Nakagawa Kenji Kawaike Yasuyuki Baba Hao Zhang 《Natural Hazards》2012,61(2):577-602
Experience shows that debris flows containing large woody debris (driftwood) can be more damaging than debris flows without
driftwood. In this study, the deposition process of debris flows carrying driftwood was investigated using numerical simulations
and flume experiments. Debris-flow trapping due to driftwood jamming in a slit-check dam was also investigated. A numerical
model was developed with an interacting combination of Eulerian expression of the debris flow and Lagrangian expression of
the driftwood, in which the fluctuating coordinates and rotation of the driftwood were treated stochastically. The calculated
shapes and thicknesses of a debris-flow fan and the positions and orientations of the deposited driftwood on a debris-flow
fan were consistent with experimental flume results. The jamming of driftwood in a slit-check dam was evaluated based on geometry
and probability. The simulated results of outflow discharge and the proportion of driftwood passed through the slit-check
dam also agreed with the experimental results. 相似文献
55.
Chemical characteristics of chromian spinel in plutonic rocks: Implications for deep magma processes and discrimination of tectonic setting 总被引:2,自引:0,他引:2
Shoji Arai Hidenobu Okamura Kazuyuki Kadoshima Chima Tanaka Kenji Suzuki Satoko Ishimaru 《Island Arc》2011,20(1):125-137
We summarize chemical characteristics of chromian spinels from ultramafic to mafic plutonic rocks (lherzolites, harzburgites, dunites, wehrlites, troctolites, olivine gabbros) with regard to three tectonic settings (mid‐ocean ridge, arc, oceanic hotspot). The chemical range of spinels is distinguishable between the three settings in terms of Cr# (= Cr/(Cr + Al) atomic ratio) and Ti content. The relationships are almost parallel with those of chromian spinels in volcanic rocks, but the Ti content is slightly lower in plutonics than in volcanics at a given tectonic environment. The Cr# of spinels in plutonic rocks is highly diverse; its ranges overlap between the three settings, but extend to higher values (up to 0.8) in arc and oceanic hotspot environments. The Ti content of spinels in plutonics increases, for a given lithology, from the arc to oceanic hotspot settings by mid‐ocean ridge on average. This chemical diversity is consistent with that of erupted magmas from the three settings. If we systematically know the chemistry of chromian spinels from a series of plutonic rocks, we can estimate their tectonic environments of formation. The spinel chemistry is especially useful in dunitic rocks, in which chromian spinel is the only discriminating mineral. Applying this, discordant dunites cutting mantle peridotites were possibly precipitated from arc‐related magmas in the Oman ophiolite, and from an intraplate tholeiite in the Lizard ophiolite, Cornwall. 相似文献
56.
Influence of flooding on groundwater flow in central Cambodia 总被引:2,自引:1,他引:1
Cambodia is affected by flooding from the Mekong, Tonle Sap and Bassac rivers every year, which harms human populations and
damages property, as well as alters the water quality in aquifer systems. The objective of this paper is to highlight the
effects of river flooding on groundwater flow using numerical simulation. A two-dimensional groundwater flow model coupled
with a groundwater recharge model was applied to the research area in central Cambodia. River level variation was included
in model processes, and flood areas and periods were assigned. The results showed that during flooding periods, floodwater
from the three rivers played an important role in recharging groundwater. During the dry season, Tonle Sap River received
groundwater supply from the northwest, and levels in the Bassac and Mekong River dropped to lower than the groundwater level.
This study improves understanding of the surface water and groundwater flow system in the study area. 相似文献
57.
Kenji Hirata Kenji Satake Yuichiro Tanioka Yohei Hasegawa 《Pure and Applied Geophysics》2009,166(1-2):77-96
In the southernmost Kuril Trench, the tsunami source regions vary their along-trench extent even among earthquakes occurring within the same segment. Recent studies suggest that the tsunami source of the 1952 Tokachi-oki earthquake (M 8.1) differs from but partially overlaps with that of the 2003 Tokach-oki earthquake (M 8.0). Furthermore, the along-trench extent among the earthquakes seems to differ between deep and shallow portions of the subduction interface. A seismic gap has been recognized along the deep subduction interface between the sources of the 1952 and 1973 earthquakes. We propose that the gap is now larger, including both shallow to deep portions of the interface between the 1973 and 2003 earthquakes. Variability in spatial extent of large subduction earthquakes in both along-trench direction and trench-normal direction makes it difficult to forecast future earthquakes in the southernmost Kuril Trench. 相似文献
58.
Haruko Sekiguchi Masayuki Yoshimi Haruo Horikawa Kunikazu Yoshida Sunao Kunimatsu Kenji Satake 《Journal of Seismology》2008,12(2):185-195
We studied the long-period ground motions in the Osaka sedimentary basin, Japan, which contains a 1- to 3-km thickness of
sediments and is the site of many buildings or construction structures with long-natural period. We simulated the broadband
ground motions likely to be produced by the hypothetical Nankai earthquake: the earthquake expected to give rise to the most
severe long-period ground motion within the basin. For the simulation, we constructed multiscale heterogeneous source models
based on the Central Disaster Management Council of Japan (CDMC) source model and adopted a hybrid computation method in which
long-period motion and short-period motion are computed using a 3-D finite difference method and the stochastic Green’s function
method, respectively. In computing long-period motions, we used a 3-D structure model of the crust and the Osaka sedimentary
basin. The ground motions are estimated to have peak velocities of 50–90 cm/s, prolonged durations exceeding 300 s, and long
predominant periods of 5–10 s in the area with great thickness of sediments. The predominant periods are in agreement with
an approximate evaluation by 4 H/V
s where H and V
s are the thickness of the sediment and the average S wave velocity, respectively. 相似文献
59.
Peter G. Brewer Edward T. Peltzer Gernot Friederich Izuo Aya Kenji Yamane 《Marine Chemistry》2000,72(2-4)
We have carried out a series of in situ experiments to investigate the formation of a CO2 hydrate (CO2:5.75 H2O) for the purpose of evaluating scenarios for ocean fossil fuel CO2 disposal with a solid hydrate as the sequestered form. The experiments were carried out with a remotely operated vehicle in Monterey Bay at a depth of 619 m. pH measurements made in close proximity to the hydrate–seawater interface showed a wide range of values, depending upon the method of injection and the surface area of the hydrate formed. Rapid injection of liquid CO2 into an inverted beaker to form a flocculant mass of hydrate resulted in pH initially as low as 4.5 within a few centimeters of the interface, decaying slowly over 1–2 h towards normal seawater values as dense CO2 rich brine drained from the hydrate mass. In a second experiment, slower injection of the liquid CO2 to produce a simple two-layer system with a near planar interface of liquid CO2 with a thin hydrate film yielded pH values indistinguishable from the in situ ocean background level of 7.6. Both field and laboratory results now show that the dissolution rate of a mass of CO2 hydrate in seawater is slow but finite. 相似文献
60.
Yuki Saito Peng K. Hong Takafumi Niihara Hideaki Miyamoto Kenji Fukumizu 《Meteoritics & planetary science》2020,55(1):193-206
The matching of asteroids and meteorites is a significant step toward a better understanding of the origin, structure, and history of the solar system. We propose a data‐driven approach for investigating common taxonomic structure between asteroids and meteorites; C‐, S‐, and V‐type for the former, and carbonaceous chondrite, ordinary chondrite, and howardite‐eucrite‐diogenite (HED) meteorite for the latter. In the numerical experiments, by checking whether the taxonomy information of meteorites improves classification for asteroid data, we examine the existence of common structure over the two domains. For this purpose, we compare the resultant accuracies of two clustering methods which are with/without the guidance of meteorite data. We observe that the guidance of meteorite taxonomy improves the accuracy for classifying asteroids, either with the reflectance spectra or major chemical compositions of meteorites. This fact serves as a piece of evidence that there is a common taxonomic structure and links between meteorites and asteroids, supporting a long‐standing hypothesis. 相似文献