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31.
As a result of the sea bottom survey of continental shelf northwest off Kyushu including Tsushima, Iki and Goto Islands which has been carried out by the Hydrographic Department of Japan, the following features of the area are revealed. Topographically, three groups of shelf channels, trending NE-SW, N-S and NW-SE respectively, are discovered and several small banks are found. Sand wave-like shapes are also seen in a seafloor about 200 m deep in the vicinity of Tsushima Straits. Geologically, remarkable tectonic lines characterized by faults and folding axes are confirmed and named Tsushima, Iki, Hirato and Goto Tectonic Lines. Several tectonic provinces can be defined by these tectonic lines. Each province consists of small geological blocks formed by indivisual tectonic movement such as tilting, uplifting and sinking. Such differential tectonic movement is often seen on the continental shelves around active island arc. In this area, these tectonics might be caused by activity of the Ryukyu Arc. This area may thus be a metastable portion existing between the northwestern Kyushu and the Asiatic continental block. The present submarine topography is probably closely related to these tectonics in addition to the eustatic sea-level changes in Quaternary age. 相似文献
32.
Rocket measurements of lower ionosphere electron density by propagation characteristics of VLF waves
The electron density profile in the lower ionosphere was determined from the right- and left-handed circularly polarized wave fields of a 40 kHz ground based signal observed by means of a rocket born receiver. Estimation of the electron density profile from 70 km up to 100 km was made under the condition for the values calculated by the full wave analysis to agree with the observed values. Results are presented for two rockets launched soon after sunset. 相似文献
33.
In the western subarctic North Pacific, a wind-driven cyclonic circulation, called the western subarctic gyre (WSAG), exists. We examined year-to-year changes of the gyre and hydrographic structures, applying the altimetry-based gravest empirical mode (AGEM) method to hydrographic and altimetric sea surface height (SSH) data, and relation to the in situ variation of the temperature minimum layer, i.e., the dichothermal layer, depth at station K2 (47° N, 160° E). The AGEM-based geostrophic volume transport and the streamfunction of the WSAG in the top 1000-dbar layer show that the gyre changes substantially. From the late 1990s to the mid-2000s, the gyre shrunk northward. Due to the shrinkage, the halocline bottom, which is equivalent to the top of the main pycnocline, deepens at K2 outside the central part of the gyre. The downward displacement of the dichothermal layer at K2 was found to be significantly related to that of the underlying halocline due to the northward shrinkage of the WSAG. 相似文献
34.
Variation of the southward interior flow of the North Pacific subtropical gyre,as revealed by a repeat hydrographic survey 总被引:2,自引:1,他引:1
Akira Nagano Hiroshi Ichikawa Yasushi Yoshikawa Shoichi Kizu Kimio Hanawa 《Journal of Oceanography》2012,68(2):361-368
Baroclinic variations of the southward flow in the interior region of the North Pacific subtropical gyre are presented with
five hydrographic sections from San Francisco to near Japan during 2004–2006. The volume transport averaged temperature of
the interior flow, which varies vigorously by a maximum of 0.8°C, is negatively correlated with the transport in the layer
of density 24.5–26.5σ
θ, associated with changes in the vertical current structure. Transport variation in this density layer is thus mainly responsible
for the thermal impact of the interior flow on the heat transport of the subtropical gyre. 相似文献
35.
Using magnetic data from the geostationary satellites of ATS 6 and SMS/GOES series, long-period geomagnetic pulsations, Psc 4 and Psc 5, associated with geomagnetic sudden commencements (SC's) were statistically analyzed. Local time and geomagnetic latitude dependence of the occurrence, and local time dependence of the period and the amplitude were examined for 218 SC's. For transverse Psc 5 pulsations which could be observed at all local times, the period was shorter and the amplitude was smaller near noon than in the morning and evening sides. Compressional Psc 5's, which were observed mainly from about 09.00 L.T. to midnight, had larger amplitude near noon. The period seemed to be longer near noon. As for Psc 4 pulsations the period tended to be shorter near noon. Psc 4's with the largest amplitude appeared near noon, but on the whole Psc 4's in the evening side had larger amplitude. The compressional Psc occurred more frequently near the geomagnetic equator (geomagnetic latitude ) than at higher latitude (). We suggest that the transverse Psc 5 pulsations can be considered to be magnetic field-line resonant oscillations excited by impulsive waves, while the compressional Psc 5's may be oscillations localized near the geomagnetic equator. 相似文献
36.
An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 1017.5 and 1020 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S0(600) to the primary energy is expressed as E (eV)=2.15×1017S0(600)1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρμ(600) (muon density above 1 GeV at 600 m from the core) vs. S0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 1015 to 1019 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy. 相似文献