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21.
Far-Field Tsunami Potential and a Real-Time Forecast System for the Pacific Using the Inversion Method 总被引:1,自引:0,他引:1
Estimating tsunami potential is anessential part of mitigating tsunami disasters. Weproposed a new method to estimate the far-fieldtsunami potential by assuming faultmodels on the Pacific Rim. We find thata tsunami that generates in the areas wherethere is no tsunami in the history can damagethe Japanese coast. This shows that it isimportant to estimate tsunami potential byassuming fault models other than the pastearthquake data.Another important activity to mitigate tsunamidisasters is to provide appropriatewarnings to coastal communities when dangerfrom a tsunami is imminent. We applied anew inversion method using wavelet transformto a part of the real-time tsunami forecastsystem for the Pacific. Because this inversionmethod does not require fault location, it ispossible to analyze a tsunami in real timewithout all seismic information. In order tocheck the usability of the system, anumerical simulation was executed assuming anearthquake at sea off Taiwan. The correlationcoefficient for the estimated initialwaveform to the assumed one was calculatedto be 0.78. It takes 90 min to capturetime-series waveform data from tsunamigauges and 5 sec to estimate the 2-D initialwaveform using the inversion method. After that,it takes 2 minutes to forecast thetsunami heights at the Japanese coast. Since thesum of these times is less than the 105minutes transit time of the tsunami fromTaiwan to Japan, it is possible to give a warningto the residents before the tsunami attacksthe Japanese coast. Comparing the tsunamiheights forecasted by this system with thosecalculated by the fault model, the averageerror was 0.39 m. The average error ofthe arrival time was 0.007 min. 相似文献
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23.
Neural Network-Based Estimation of Principal Metal Contents in the Hokuroku District,Northern Japan,for Exploring Kuroko-Type Deposits 总被引:7,自引:0,他引:7
Koike Katsuaki Matsuda Setsuro Suzuki Toru Ohmi Michito 《Natural Resources Research》2002,11(2):135-156
The Hokuroku district, extending over 40 × 40 km2 in northern Japan, is known to be dominated by kuroko-type massive sulfide deposits that have a genetic relation to submarine volcanic activity. The deposits are hosted in a specific stratigraphic zone of Miocene volcanic rocks. Because kuroko-type deposits are under exploration in several countries, it is important to integrate the geologic and geochemical data that have been accumulated in the Hokuroku district to characterize the distribution of deposits and produce a map of mineral potential. Thus, we collected data on multiple chemical components from 1917 rock cores at 143 drillhole sites and concentrated on components with relatively large amounts of data, which are SiO2, Al2O3, and Fe2O3 as major elements and Cu, Pb, and Zn as trace elements. Although frequencies of these data can be approximated by normal or lognormal distributions, spatial correlation structures cannot be extracted from the semivariograms of each component nor from the cross-semivariograms between two components of the major or minor elements. To handle such complexity, a spatial method of modeling content distribution, SLANS, is developed by applying a feedforward neural network. The principle of SLANS is to train a network repeatedly to recognize the relation between the data value and the location and lithology of a sample point. One-hundred outputs for each element are obtained by changing the numbers of neurons in a middle layer from 1 to 10 and sample data used for training from 3 to 12, and finally one output is selected based on the estimation precision of the network which is restricted near the target point. After constructing a geologic distribution model from the geological column classified into 25 rock codes, three-dimensional distributions of Cu, Pb, and Zn contents are estimated over the study area. The content models are considered to be valid because high-content zones are located on the known mine sites and the margins of ancient volcanoes or calderas. Some zones are distributed along strikes of major deep-seated fractures in the district. 相似文献
24.
C. Kaito Y. Ojima K. Kamitsuji O. Kido Y. Kimura H. Suzuki T. Sato T. Nakada Y. Saito C. Koike 《Meteoritics & planetary science》2003,38(1):49-57
Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite. 相似文献
25.
K. Koike M. Nakagawa H. Chihara M. Okada T. Awata J. Takada 《Planetary and Space Science》2006,54(4):325-330
Interstellar and circumstellar matter is known to be strongly irradiated by cosmic radiation and several types of cosmic ray particles. The effects of irradiation on simulated interstellar and circumstellar matter such as CaCO3, MgCO3, SiO2 and Al2O3 are investigated. Especially, thermoluminescence (TL) spectra after γ-ray and neutron irradiation are compared carefully. It is shown that the thermoluminescence after neutron irradiation appears significantly in the wavelength of blue region. On the reflectance in infrared region, the irradiation effect appears scarcely. 相似文献
26.
H. Suto H. Sogawa S. Tachibana C. Koike H. Karoji A. Tsuchiyama H. Chihara K. Mizutani J. Akedo K. Ogiso T. Fukui S. Ohara 《Monthly notices of the Royal Astronomical Society》2006,370(4):1599-1606
The infrared reflectivities of crystalline forsterite (Mg2 SiO4 ) were measured for the temperature range 295–50 K for each crystal axis, between wavenumber 5000 and 100 cm−1 . The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K. 相似文献
27.
28.
Identifying groundwater arsenic contamination mechanisms in relation to arsenic concentrations in water and host rocks 总被引:1,自引:1,他引:0
Leaching and oxidation of high arsenic (As) host rocks tend to be induced by circulation of deep geothermal waters, which
increase As concentration in shallow groundwater. The purpose of this study is to identify the mechanism of groundwater As
contamination in relation to leaching and oxidation along the border between the South Minahasa and Bolaang Mongondow districts,
North Sulawesi, Indonesia. This region contains Miocene sedimentary rock-hosted disseminated gold deposits associated with
hydrothermal alteration in a fault zone. Abnormally high As concentrations were observed in hot and cold springs and in surrounding
shallow groundwater for a total mineralization area of 8 × 10 km2. Two methods were adopted in this study: (1) microscopic and spectroscopic analyses of rock samples for mineral identification
and (2) geostatistics for spatial modeling of As concentrations in groundwater. Jarosite was identified as the chief fill
mineral in rock defects (cracks and pores). The presence of this mineral may indicate release of As into the environment,
as can occur as an alteration product derived from oxidation and leaching of pyrite, As-rich pyrite or sulfide minerals by
geothermal waters. Moreover, As concentrations in groundwater were estimated using geostatistics for spatial modeling. The
co-kriging map identified local anomalies in groundwater As concentrations over the permissible limit (10 ppb). Such anomalies
did not appear through ordinary kriging. Integration of the results indicates that As contamination in shallow groundwater
probably is controlled by heterogeneous distributions of jarosite and variations in intensity and extent of hydrothermal activities. 相似文献
29.
Characterization of the sediment composition of tidal flats and monitoring of their spatiotemporal changes has become an important part of the sustainable management of coastal environments. To accurately classify sediments through remote sensing, a comprehensive understanding of sediment reflectance spectra is indispensable. The present laboratory-based study explores the performance of the high spatial resolution (10?×?10 m) Advanced Land Observing Satellite (ALOS) launched in 2006. Relationships between reflectance spectra (bands 1 to 4) and four typical mass physical properties were investigated under wet and dry experimental conditions for intertidal sediments sampled near the Ba Lat Estuary in northern Vietnam. Reflectance in the near-infrared region corresponding to ALOS band 4 (0.76–0.89 μm) was found (1) to have a strong negative correlation with sand content (dry wt%) under both wet and dry conditions (linear correlation coefficient r?=?–0.7859 and –0.8094, respectively), (2) to increase with decreasing relative water content (%) in a given sediment type (r?=?–0.7748 to –0.9367 for mud, sandy mud, muddy sand, and sand), (3) to have a positive correlation with organic matter content (r?=?0.7610 and 0.6460 under wet and dry conditions for contents >0.20 dry wt%), and (4) to be insignificantly correlated with mineral composition assessed in terms of contents (wt%) of quartz, clay minerals, and mica group minerals. Positive relationships between reflectance and water content for the pooled data of all sediment types (r?=?0.6395) or organic matter content contrast with previous findings, and can be attributed to close interrelationships between these properties and the predominance of sand content as controlling factor of reflectance. This study clarifies that ALOS band 4 provides the most useful imagery for intertidal monitoring because its reflectance, as simulated using the laboratory data, shows the strongest correlation with sand content. In a next step, these experimental findings should be verified by identifying the reflectance relationships at satellite image scales, and also considering the effects of other tidal flat features on reflectance, such as microtopography and biological surface characteristics. 相似文献
30.