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T. Morita Y. Sakawa Y. Kuramitsu H. Tanji H. Aoki T. Ide S. Shibata N. Onishi C. Gregory A. Diziere J. Waugh N. Woolsey Y. Sano A. Shiroshita K. Shigemori N. Ozaki T. Kimura K. Miyanishi R. Kodama M. Koenig H. Takabe 《Astrophysics and Space Science》2011,336(1):283-286
Collisionless shocks in counter-streaming plasmas, created by the high-power laser system Gekko XII HIPER, are investigated. The shock structure and density are measured by optical diagnostics such as shadowgraphy, interferometry, and streaked interferometry. The plasma density and temperature are estimated from self-emission measurements with visible light by streaked optical pyrometer and gated optical imager. Brightness temperatures are calculated considering the efficiency of the detectors, and electron temperatures are estimated. 相似文献
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Depositional environments of well‐sorted detrital limestone from the Minatogawa Formation in the southern part of Okinawa Island,the Ryukyu Archipelago,Japan 下载免费PDF全文
Well‐sorted detrital limestone is one of the typical lithofacies of the latest interval of the Pleistocene Ryukyu Group, which is exposed in the Ryukyu Archipelago in southwestern Japan. The depositional environments of the limestone are interpreted to be extremely shallow and to include back‐reef lagoons or moats and subaerial sand dunes. However, detailed micropaleontological analyses have not been performed on this limestone. In this study, the interpretation of the depositional environments and paleo‐water depths was improved by quantitative examination of foraminiferal assemblages for the well‐sorted detrital limestone of the Minatogawa Formation in the southern part of Okinawa Island. Thin sections of limestone collected from the Minatogawa (Horikawa) quarry were subjected to sedimentological and foraminiferal analyses. Comparison with modern foraminiferal distribution within the Ryukyu Archipelago indicates that back‐reef and fore‐reef dwelling foraminifers characterize the fossil assemblages from the well‐sorted detrital limestone (bioclastic grainstone). Three ratios of indicator foraminiferal taxa (ratios of back‐reef to fore‐reef taxa, planktonic foraminifers to Amphistegina lobifera and Amphistegina lessonii, and Calcarina gaudichaudii to other Calcarina species), as well as multivariate analyses suggest that the well‐sorted detrital limestone was deposited in fore‐reef setting shallower than 40 m in water depth. A comparable depth range was reconstructed from the coral assemblage in the associated coral limestone, suggesting that the Minatogawa Formation was deposited in a gently inclined ramp setting with patch reefs and/or fringing reefs. Stratigraphic changes in paleo‐water depth, together with evidence of several unconformities associated with paleosol layers suggest that there were repeated transgressions and regressions, with an amplitude up to several tens of meters, when the Minatogawa Formation was deposited. 相似文献
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Atsushi Suzuki Yusuke Yokoyama Hironobu Kan Kayo Minoshima Hiroyuki Matsuzaki Nozomu Hamanaka Hodaka Kawahata 《Quaternary Geochronology》2008,3(3):226-234
The Meiwa Tsunami, one of the largest tsunamis recorded in historical documents in Japan struck Ishigaki Island and neighboring islands of the Ryukyu Arc in April 1771 AD, killing more than 12 000 people. An enormous number of massive Porites coral boulders are scattered on the shore and in the reef moat of eastern Ishigaki Island. Although these boulders likely were cast ashore by the Meiwa Tsunami, a detailed examination has not yet been conducted. When the marine reservoir effect is taken into account, one of mode values of calibrated radiocarbon dates possibly corresponds to the time of the 1771 event. However, the range of calibrated radiocarbon ages indicates that the transport of the boulders cannot be ascribed solely to the tsunami. Oxygen isotope microprofiling, which indicates sea-surface temperature variation, was therefore conducted to further investigate the mechanism of transport. The results suggest that the skeletal growth of most coral colonies was interrupted in summer or autumn; hence, tropical storms and typhoons are also very likely to be agents of transport. Thus, by combining radiocarbon dating with oxygen isotope microprofiling to investigate Porites coral boulders, it is possible to separate paleotsunami boulders from those transported by storm events as far as tsunamis occurred during the non-storm season. 相似文献
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Radiated Energy of Great Earthquakes from Teleseismic Empirical Green’s Function Deconvolution 总被引:1,自引:0,他引:1
Annemarie S. Baltay Gregory C. Beroza Satoshi Ide 《Pure and Applied Geophysics》2014,171(10):2841-2862
We expand on the empirical Green’s function deconvolution method of Ide et al. (2011) to estimate radiated energy for the six largest earthquakes worldwide over the last 10 years: 2011 M w 9.0 Tohoku-Oki, 2004 M w 9.1 Sumatra, 2010 M w 8.8 Maule, 2005 M w 8.7 Nias, 2007 M w 8.5 Bengkulu, and 2012 M w 8.6 off-Sumatra. Deconvolution of P, SV and SH components gives consistent energy results that are comparable to estimates found independently by other researchers. Apparent stress for the five great thrust earthquakes is between 0.4 and 0.8 MPa, while the 2012 off-Sumatra strike-slip earthquake has a higher apparent stress of 3 MPa, which is consistent with other studies that find a tendency for strike-slip events to be more energetic. Our results are within the spread of apparent stress from the wider global earthquake population over a large magnitude range. The azimuthal distribution of energy in each case shows signs of directivity, and in some cases, shows less energy radiated in the trench-ward direction, which may suggest enhanced tsunami potential. We find that eGfs as small as ~M 6.5 can be used for teleseismic deconvolution, and that an eGf-mainshock magnitude difference of 1.5 units yields stable results. This implies that M 8 is the minimum mainshock size for which teleseismic eGf deconvolution will work well. We propose that a database of eGf events could be used to calculate radiated energy and apparent stress of great, hazardous events in near real time, i.e., promptly enough that it could contribute to rapid response measures. 相似文献
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Castro-Correa Carmen-Paz Aldunce Ide Paulina Wyndham Vásquez Katherine Mena Maldonado Dania Pérez Tello Sonia 《Natural Hazards》2020,103(2):2427-2440
Natural Hazards - This article analyzes the impact of socio-natural disasters on social capital at a local level, studying the cases of the communities of Chañaral and Diego de Almagro after... 相似文献
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Alvaro de la Cámara C. R. Mechoso K. Ide R. Walterscheid G. Schubert 《Climate Dynamics》2010,35(6):965-975
The present paper examines the vortex breakdown and large-scale stirring during the final warming of the Southern Hemisphere
stratosphere during the spring of 2005. A unique set of in situ observations collected by 27 superpressure balloons (SPBs)
is used. The balloons, which were launched from McMurdo, Antarctica, by the Stratéole/VORCORE project, drifted for several
weeks on two different isopycnic levels in the lower stratosphere. We describe balloon trajectories and compare them with
simulations obtained on the basis of the velocity field from the GEOS-5 and NCEP/NCAR reanalyses performed with and without
VORCORE data. To gain insight on the mechanisms responsible for the horizontal transport of air inside and outside the well-isolated
vortex we examine the balloon trajectories in the framework of the Lagrangian properties of the stratospheric flow. Coherent
structures of the flow are visualized by computing finite-time Lyapunov exponents (FTLE). A combination of isentropic analysis
and FTLE distributions reveals that air is stripped away from the vortex’s interior as stable manifolds eventually cross the
vortex’s edge. It is shown that two SPBs escaped from the vortex within high potential vorticity tongues that developed in
association with wave breaking at locations along the vortex’s edge where forward and backward FTLE maxima approximately intersect.
The trajectories of three SPBs flying as a group at the same isopycnic level are examined and their behavior is interpreted
in reference to the FTLE field. These results support the concept of stable and unstable manifolds governing transport of
air masses across the periphery of the stratospheric polar vortex. 相似文献
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A simple theoretical model of atmospheric radiative equilibrium is solved analytically to help understand the energetics
of maintaining Earth's tropical and subtropical climate. The model climate is constrained by energy balance between shortwave
(SW) and longwave (LW) radiative fluxes. Given a complete set of SW and LW optical properties in each atmospheric layer, the
model yields a unique equilibrium-temperature profile. In contrast, if the atmospheric temperature profile and SW properties
are prescribed, the model yields essentially two distinct LW transmissivity profiles. This bimodality is due to a nonlinear
competition between the ascending and descending energy fluxes, as well as to their local conversion to sensible heat in the
atmosphere. Idealized slab models that are often used to describe the greenhouse effect are shown to be a special case of
our model when this nonlinearity is suppressed. In this special case, only one solution for LW transmissivity is possible.
Our model's bimodality in LW transmissivity for given SW fluxes and temperature profile may help explain certain features
of Earth's climate: at low latitudes the temperature profiles are fairly homogeneous, while the humidity profiles exhibit
a bimodal distribution; one mode is associated with regions of moist-and-ascending, the other with dry-and-subsiding air.
The model's analytical results show good agreement with the European Centre for Medium-Range Weather Forecasts' reanalysis
data. Sensitivity analysis of the temperature profile with respect to LW transmissivity changes leads to an assessment of
the low-latitude climate's sensitivity to the “runaway greenhouse” effect.
Received: 7 December 1999 / Accepted: 19 February 2001 相似文献