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151.
152.
The fault parameters of the Guam earthquake of August 8, 1993 are estimated from seismological analyses, and the possibility of identifying the actual fault plane from tsunami waveforms is tested. The Centroid Moment Tensor solution of long-period surface waves shows one nodal plane shallowly dipping to the north and the other nodal plane steeply dipping to the south. The seismic moment is 3.5×1020 Nm and the corresponding moment magnitude is 7.7. The Moment Tensor Rate Function inversion ofP waves also yields a similar focal mechanism and seismic moment. The point source depth is estimated as 40–50 km.This earthquake generated tsunamis that propagated toward the Japanese coast along the Izu-Bonin-Mariana ridge system. The tsunamis are recorded on ocean bottom pressure gauges and tide gauges. Numerical computation of tsunamis shows that the computed waveforms from the two possible fault planes match well with the observed tsunami waveforms. The numerical computation also shows that the tsunami waveforms at Guam Island, just above the fault, should contain useful information regarding the identification of the actual fault plane. However, the current sampling rate of the tide gauges is so small that the records cannot help the identification. 相似文献
153.
154.
We have used a two dimensional radiative-chemical-transport model of the stratosphere to investigate the sensitivity of trace gas distributions to absorption of oxygen in the wavelength region 175–210 nm. Two different formulations for the Herzberg continuum absorption cross sections are used. The calculated transmission of ultra-violet light in the stratosphere is lower and higher than observed, depending on the choice of absorption cross section. For the higher transmission O3, ClO, and HO2 are found to be significantly increased in the lower stratosphere. Calculated O3 in the upper stratosphere, chlorofluorocarbons, N2O and odd-nitrogen are lower. The photolysis of oxygen is considerably faster at high latitudes implying that the photochemical recovery of depleted polar ozone is faster than currently assumed. 相似文献
155.
Jun-Ichi Matsuda Kenji Notsu Jun Okano Katsumi Yaskawa Leonard Chungue 《Tectonophysics》1984,104(1-2)
Sr isotopes and K-Ar ages were determined for volcanic rocks from three islands, Samoa, Rarotonga and Rurutu in the Austral-Gilbert-Marshall chain. We have established that Rurutu originated from the same “hot spot” as Tubuai and Raivavae in the Cook-Austral chain as indicated by its 11 m.y. K-Ar age and (
) ratios. The (
) ratios for Rurutu, Tubuai and Raivavae lie in the restricted range 0.7026–0.7035. K-Ar ages of all volcanic rocks from Samoa and Rarotonga are all less than 4 m.y. and their (
) ratios are much higher than those in Rurutu, Tubuai and Raivavae. These findings suggest that Samoa and Rarotonga did not originate in a single hot spot for the Cook-Austral islands. 相似文献
156.
Kenji Notsu Toshiya Mori Sandie Chanchah Do Vale Hiroyuki Kagi Takamori Ito 《Pure and Applied Geophysics》2006,163(4):825-835
Since the 8th century, more than seventeen eruptions have been recorded for the Mt. Fuji volcano, with the most recent eruption
occurring in 1707 (Hoei eruption). For the past 300 years the volcano has been in a quiescent stage and, since the early 1960s,
has exhibited neither fumarolic nor thermal activity. However, the number of low-frequency earthquakes with a hypocentral
depth of 10–20 km increased significantly beneath the northeastern flank of Mt. Fuji in 2000–2001, suggesting a possible resumption
of magmatic activity. In this study, diffuse CO2 efflux and thermal surveys were carried out in four areas of the volcano in 2001–2002 in order to detect possible signs of
the upward movement of deep magma. At all survey points, the CO2 efflux was below the detection limit with the exception of a few points with biological CO2 emission, and ground temperatures at a depth of 20–30 cm were below ambient, indicating no surface manifestations of gas
or heat emission. Should magma rise into the subsurface, the diffuse CO2 efflux would be expected to increase, particularly along the tectonically weakened lineation on the Mt. Fuji volcano, allowing
for the early detection of pre-eruptive degassing. 相似文献
157.
Shunichi Sawada Yoshimichi Tsukamoto Kenji Ishihara 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):175-182
Multiple series of triaxial tests were carried out on unsaturated sandy soils subjected to irregular seismic excitation. To observe the volume changes of unsaturated soil specimens during undrained loading and subsequent process of drainage, the inner cell was newly installed inside the large triaxial cell. The soil samples tested were recovered from the construction site of a liquefied natural gas storage facility located in Tokyo Bay area. In the tests, the initial conditions of soil specimens were specified with the degrees of saturation Sr of 50, 75 and 100%. The soil specimens were anisotropically consolidated, and subjected to undrained irregular seismic excitation. The time history of irregular seismic excitation was the one obtained from one of the recent earthquakes in Japan. The drainage line was then opened to let the excess pore water drain out of soil specimens. The volume changes and residual shear strains of unsaturated soil specimens thus obtained are presented in the present paper. 相似文献
158.
M. Meftah D. Bolsée L. Damé A. Hauchecorne N. Pereira A. Irbah S. Bekki G. Cessateur T. Foujols R. Thiéblemont 《Solar physics》2016,291(12):3527-3547
Accurate measurements of the solar spectral irradiance (SSI) and its temporal variations are of primary interest to better understand solar mechanisms, and the links between solar variability and Earth’s atmosphere and climate. The SOLar SPECtrum (SOLSPEC) instrument of the Solar Monitoring Observatory (SOLAR) payload onboard the International Space Station (ISS) has been built to carry out SSI measurements from 165 to 3088 nm. We focus here on the ultraviolet (UV) part of the measured solar spectrum (wavelengths less than 400 nm) because the UV part is potentially important for understanding the solar forcing of Earth’s atmosphere and climate. We present here SOLAR/SOLSPEC UV data obtained since 2008, and their variations in three spectral bands during Solar Cycle 24. They are compared with previously reported UV measurements and model reconstructions, and differences are discussed. 相似文献
159.
Osamu Katoh Kazuyuki Teshima Osamu Abe Hitoshi Fujita Kuniaki Miyaji Kenji Morinaga Norihisa Nakagawa 《Journal of Oceanography》1996,52(4):491-507
In order to clarify detailed current structures over the continental shelf margin in the East China Sea, ADCP measurements were carried out in summers in 1991 and 1994 by the quadrireciprocal method (Katoh, 1988) for removing diurnal and semidiurnal tidal flows from observed flows, together with CTD measurements. We discussed the process of the Tsushima Current formation in the East China Sea. The Tsushima Current with a volume transport of 2 Sv (1 Sv=106 m3s–1) was found north of 31°N. A current with a volume transport of 0.4 Sv was clearly found along the 100 m isobath. Between the Kuroshio and the current along the 100 m isobath, southeastward component of velocity was dominant compared to northwestward one. Four eastward to southeastward currents were found over the sea bed shallower than 90 m depth. Total volume transport of these four currents was 1 Sv, and they seemed to be originated from the Taiwan Strait. Intrusion of offshore water into the inner shelf northwest of Amami Oshima was estimated to have a volume transport of 0.6 Sv. It is concluded that the Tsushima Current is the confluence of these currents over the continental shelf margin with the offshore water intruding northwest of Amami Oshima. 相似文献
160.
We have developed a flood water level estimation method that only employs satellite images and a DEM. The method involves three steps: (1) discriminating flood areas and identifying clumps of each flood area, (2) extracting the edges of the identified flood area using a buffering technique, and (3) performing spatial interpolation to transform the extracted elevation to flood water levels. We compared the estimated flood water levels with the observed ones. The RMSE using the RADARSAT was 1.99 and 1.30 m at river and floodplain points, respectively, whereas the RMSE using the MODIS was 4.33 and 1.33 m at the river and floodplain points, respectively. Given that most errors are attributed to the DEM, the method exhibited good performance. Furthermore, the method reproduced the flow directions and flood water level changes during the flooding period. Thus, we demonstrated that the characteristics of flood inundation can be understood even when ground observation data cannot be obtained. 相似文献