Detection of anomalous seismic phases by the wavelet transform   总被引：1，自引：0，他引：1  

Kiyoshi Yomogida 《Geophysical Journal International》1994,116(1):119-130

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Temperature changes over Eurasia during the late summer of 1979     

Ding Yihui  T. Iwashim  T. Murakami 《大气科学进展》1985,2(2):200-214

During the late summer of 1979, massive changes occurred in the distribution of temperature over Eur asia north of 15oN. At 300 hPa, zonal mean temperature averaged over Eurasia along 20o－25oN de-creased sharply around 23 August. An abrupt decrease in 300 hPa zonal mean temperature also occurred over extensive mid-latitude zones (40o－55oN) around 18 August, i. e., about 5 days prior to the monsoon withdrawal over South Asia.The intensity and location of N－S oriented, vertical overturning underwent significant changes over Eurasia during the transition from summer to fall. Near 20o－25oN, zonal mean updrafts weakened con-siderably during the transition period (18－27 August). Around 45oN, zonal mean downdrafts and the asso-ciated cooling (radiative) rate increased considerably during the transition period.Near 15oN, 300 hPa zonal mean temperature fluctuated nearly periodically with an approximate 40-day period. These fluctuations appear to be associated with a small imbalance between 40-day filtered adiabatic cooling (heating) and diabatic heating (cooling).  相似文献   

1979年印度夏季风活跃、中断和撤退时期欧亚上空风场和温度场的变化     

丁一汇  村上多喜雄 《气象学报》1984,42(2):198-210

本文对1979年夏季印度西南季风活跃、中断和撤退时欧亚地区大范围环流和温度场进行了分析。结果表明,该年季风活动的变率与欧亚中高纬环流形势的演变有明显关系。季风活跃期,高空西风带显著北移,西藏高原上空有高空反气旋环流建立、发展,苏联西部阻塞高压发展、维持;季风中断期,西藏高原西部有高空槽存在;苏联西部阻塞高压减弱、崩溃或有高空槽发展;季风的撤退也与东亚冷空气活动关系密切。  相似文献   

GPS radio holography as a tool for remote sensing of the atmosphere, mesosphere, and terrestrial surface from space     

Alexander Pavelyev  Yuei-An Liou  Christoph Reigber  Jens Wickert  Kiyoshi Igarashi  Klemens Hocke  Cheng-Yung Huang 《GPS Solutions》2002,6(1-2):100-108

GPS radio occultation (RO) signals are highly coherent and precise, and thus sufficient for holographic investigation of the atmosphere, ionosphere, and the Earth's surface from space. In principle, three-dimensional radio-holographic remote sensing is possible by using new radio holographic equations to retrieve the radio field within the atmosphere from a radio field known at some interface outside the atmosphere. A simplified two-dimensional form of the radio-holographic equations which are developed under an assumption of local spherical symmetry can be used to obtain two-dimensional radio images of the atmosphere and terrestrial surface. To achieve this, radio holograms recorded by a GPS receiver onboard a low earth orbit (LEO) satellite at two GPS frequencies can be used and focused synthetic aperture principle applied. Analysis of GPS/MET RO data is presented to show the effectiveness of a radio-holographic approach. It is shown that the amplitude of GPS radio signals (in addition to phase data) can be used to obtain detailed altitude profiles of the vertical gradient of refractivity in the atmosphere and electron density in the mesosphere. The results demonstrate the applicability of GPS radio holography for a detailed global study of the natural processes in the atmosphere and mesosphere. Electronic Publication  相似文献   

Crustal structure in and around the region of the 1995 Kobe Earthquake deduced from a wide-angle and refraction seismic exploration     

Takeshi Ohmura  Takeo Moriya  Chengshi Piao  Takaya Iwasaki  Toshikastu Yoshi  Shin'ichi Sakai  Tetsuya Takeda  Kaoru Miyashita  Humihito Yamazaki  Kiyoshi Ito  Akira Yamazaki  Yoji Shimada  Katsuya Tashiro  Hiroki Miyamachi 《Island Arc》2001,10(3-4):215-227

Abstract The 1995 Kobe (Hyogo-ken Nanbu) earthquake (M_JMA 7.2, M_w 6.9) occurred on Jan. 17, 1995, at a depth of 17 km, beneath the areas of southern part of Hyogo prefecture and Awaji Island. To investigate P-wave velocity distribution and seismological characteristics in the aftershock area of this great earthquake, a wide-angle and refraction seismic exploration was carried out by the Research Group for Explosion Seismology (RGES) . The profile including 6 shot points and 205 observations was 135 km in length, extending from Keihoku, Northern Kyoto prefecture, through Kobe, to Seidan on Awaji Island. The charge of each shot was 350–700 kg. The P-wave velocity structure model showed a complicated sedimentary layer which is shallower than 2.5 km, a 2.5 km-thick basement layer whose velocity is 5.5 km/s, overlying the crystalline upper crust, and the boundary between the upper and lower crust.
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed.  相似文献   

CodaQ as a combination of scattering and intrinsic attenuation: Numerical simulations with the boundary integral method     

Kiyoshi Yomogida  Rafael Benites 《Pure and Applied Geophysics》1996,148(1-2):255-268

Numerical modelling ofSH wave seismograms in media whose material properties are prescribed by a random distribution of many perfectly elastic cavities and by intrinsic absorption of seismic energy (anelasticity) demonstrates that the main characteristics of the coda waves, namely amplitude decay and duration, are well described by singly scattered waves in anelastic media rather than by multiply scattered waves in either elastic or anelastic media. We use the Boundary Integral scheme developed byBenites et al. (1992) to compute the complete wave field and measure the values of the direct waveQ and coda wavesQ in a wide range of frequencies, determining the spatial decay of the direct wave log-amplitude relation and the temporal decay of the coda envelope, respectively. The effects of both intrinsic absorption and pure scattering on the overall attenuation can be quantified separately by computing theQ values for corresponding models with (anelastic) and without (elastic) absorption. For the models considered in this study, the values of codaQ ^–1 in anelastic media are in good agreement with the sum of the corresponding scatteringQ ^–1 and intrinsicQ ^–1 values, as established by the single-scattering model ofAki andChouet (1975). Also, for the same random model with intrinsic absorption it appears that the singly scattered waves propagate without significant loss of energy as compared with the multiply scattered waves, which are strongly affected by absorption, suggesting its dominant role in the attenuation of coda waves.  相似文献   

Dislocation microstructures in naturally deformed silicate garnets   总被引：1，自引：0，他引：1  

Jun-ichi Ando  Kiyoshi Fujino  Toru Takeshita 《Physics of the Earth and Planetary Interiors》1993,80(3-4):105-116

Dislocation microstructures of naturally deformed silicate garnets and olivines in garnet-peridotites and silicate garnets in eclogites from four localities have been observed with a transmission electron microscope (TEM) to clarify the dislocation characteristics of silicate garnets. We have obtained the following results: (1) dislocation densities of garnets in all the garnet-peridotites (ρ = 10⁵−10⁷ cm⁻²) are always nearly an order of magnitude lower than those of co-existing olivines; (2) dislocation densities of garnets in eclogites (ρ = 10⁵−10⁸ cm⁻²) which are embedded in garnet-peridotites are almost an order of magnitude higher than those of garnets in the surrounding garnet-peridotites; (3) the dominant Burgers vector, b, of mainly edge dislocations in garnet is 100 for specimens with dislocation density ρ = 10⁵−10⁶ cm⁻², while b=1/2111 for specimens with ρ = 10⁷−10⁸ cm⁻². Result (1) indicates that the observed dislocations in garnets were formed by plastic deformation under the same stresses as for co-existing olivines, and that there is a similar relationship between applied stress and dislocation density for garnets as for olivines. Result (2) suggests that the stress concentration occurred around eclogites embedded in garnet-peridotites, and the resulting differential stress in garnets in eclogites was further elevated by the interlocking of neighboring hard garnet grains. Finally, result (3) indicates that the dominant Burgers vector of mainly edge dislocations in garnet changes from 100 to 1/2111 with increasing applied differential stress.  相似文献   

Gonadal histology and serum vitellogenin levels of bigeye tuna Thunnus obesus from the Northern Pacific Ocean--absence of endocrine disruption bio-indicators     

Hashimoto S  Kurihara R  Strüssmann CA  Yamasaki T  Soyano K  Hara A  Shiraishi H  Morita M 《Marine pollution bulletin》2003,46(4):459-465

Endocrine disrupting chemicals such as organochlorines have been detected in a large number of marine fish. Histological observation of the gonads, measurement of serum vitellogenin (VTG) level and of liver polychlorinated biphenyl (PCB) content were performed to evaluate the reproductive health and the contamination with endocrine disruptors in bigeye tuna Thunnus obesus, collected in the northern Pacific Ocean in 1999 and 2000. Abnormalities commonly found in species affected by endocrine disruptors such as the presence of oocytes in the testis or elevated serum VTG levels were not found in any of males examined. Both males and females had only small amounts of liver PCB content. The results suggest that currently there is little if any risk of organochlorine contamination or endocrine disruption of gonadal function in bigeye tuna from the northern Pacific Ocean. However, further studies are necessary to evaluate the health status of the open sea fishery resources.  相似文献   

Nutrients adsorption from seawater by new porous carrier made from zeolitized fly ash and slag     

Khelifi O  Kozuki Y  Murakami H  Kurata K  Nishioka M 《Marine pollution bulletin》2002,45(1-12):311-315

This study investigated the adsorption and precipitation of phosphate by blast furnace slag (BFS) separately.

In order to evaluate the adsorption capacity of BFS, BFS was treated before its use by acid. The authors aim to develop a new porous carrier to adsorb simultaneously ammonium and phosphate from seawater under eutrophic conditions. The current paper deals with a promising new approach to improve the utilization of some industrial solid wastes such as BFS and zeolite synthesized from fly ash [ZFA(Fe)] by their solidification to cylindrical porous carriers using a hydrothermal hot-pressing (HHP) method.

Attempts to produce porous carriers using an arranged HHP method with different porosities (24%, 40% and 52% (v/v)) were carried out. Physical properties of carriers such as porosity, compressive strength and height have been investigated. Laboratory studies showed strong evidence that the porous carrier was very selective towards phosphate and ammonium. The results demonstrated the role of porosity in enhancing phosphate and ammonium adsorption by the increase of the surface area per weight. The estimates of the parameters and the correlation coefficients according to the Freundlich equations revealed that adsorption was related to the porosity of carriers and phosphate and ammonium were adsorbed well on the carriers having large porosity.

The results suggested that developing carrier with high porosity was a promising way to enhance nutrients adsorption.  相似文献   

Role of H₂O and CO₂ Ices in Martian Climate Changes     

Tokuta YokohataMasatsugu Odaka  Kiyoshi Kuramoto 《Icarus》2002,159(2):439-448

In order to study the stability of martian climate, we constructed a two-dimensional (horizontal-vertical) energy balance model. The long-term CO₂ mass exchange process between the atmosphere and CO₂ ice caps is investigated with particular attention to the effect of planetary ice distribution on the climate stability. Our model calculation suggests that high atmospheric pressure presumed for past Mars would be unstabilized if H₂O ice widely prevailed. As a result, a cold climate state might have been achieved by the condensation of atmospheric CO₂ onto ice caps. On the other hand, the low atmospheric pressure, which is buffered by the CO₂ ice cap and likely close to the present pressure, would be unstabilized if the CO₂ ice albedo decreased. This may have led the climate into a warm state with high atmospheric pressure owing to complete evaporation of CO₂ ice cap. Through the albedo feedback mechanisms of H₂O and CO₂ ices in the atmosphere-ice cap system, Mars may have experienced warm and cold climates episodically in its history.  相似文献