Introduction to special section on historical earthquakes     

Emile A. Okal 《Pure and Applied Geophysics》1992,139(1):1-1

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Phytoplankton production and nutrient distributions in a subtropical estuary: Importance of freshwater flow     

Michael C. Murrell  James D. Hagy  Emile M. Lores  Richard M. Greene 《Estuaries and Coasts》2007,30(3):390-402

The relationships between phytoplankton productivity, nutrient distributions, and freshwater flow were examined in a seasonal study conducted in Escambia Bay, Florida, USA, located in the northeastern Gulf of Mexico. Five sites oriented along the salinity gradient were sampled 24 times over the 28-mo period from 1999 to 2001. Water column profiles of temperature and salinity were measured along with surface chlorophyll and surface inorganic nutrient concentrations. Primary productivity was measured at 2 sites on 11 dates, and estimated for the remaining dates and sites using an empirical regression model relating phytoplankton net production to the product of chlorophyll, euphotic zone depth, and daily solar insolation. Freshwater flow into the system varied markedly over the study period with record low flow during 2000, a flood event in March 2001, and subsequent resumption of normal flow. Flushing times ranged from 1 d during the flood to 20 d during the drought. Freshwater input strongly affected surface salinity distributions, nutrient flux, chlorophyll, and primary productivity. The flood caused high turbidity and rapid flushing, severely reducing phytoplankton production and biomass accumulation. Following the flood, phytoplankton biomass and productivity sharply increased. Analysis of nutrient distributions suggested Escambia Bay phytoplankton alternated between phosphorus limitation during normal flow and nitrogen limitation during low flow periods. This study found that Escambia Bay is a moderately productive estuary, with an average annual integrated phytoplankton production rate of 290 g C m⁻² yr⁻¹.  相似文献   

M TSU : Recovering Seismic Moments from Tsunameter Records   总被引：1，自引：0，他引：1  

Emile A. Okal  Vasily V. Titov 《Pure and Applied Geophysics》2007,164(2-3):355-378

We define a new magnitude scale, M_TSU, allowing the quantification of the seismic moment M₀ of an earthquake based on recordings of its tsunami in the far field by ocean-bottom pressure sensors (``tsunameters') deployed in ocean basins, far from continental or island shores which are known to affect profoundly and in a nonlinear fashion the amplitude of the tsunami wave. The formula for M_TSU, M_TSU = log₁₀ M₀ − 20 = log₁₀ X (ω) + C_D^TSU + C_S^TSU + C₀, where X (ω) is the spectral amplitude of the tsunami, C_D^TSU a distance correction and C_S^TSU a source correction, is directly adapted from the mantle magnitude M_m introduced for seismic surface waves by Okal and Talandier. Like M_m, its corrections are fully justified theoretically based on the representation of a tsunami wave as a branch of the Earth's normal modes. Even the locking constant C₀, which may depend on the nature of the recording (surface amplitude of the tsunami or overpressure at the ocean floor) and its units, is predicted theoretically. M_TSU combines the power of a theoretically developed algorithm, with the robustness of a magnitude measurement that does not take into account such parameters as focal geometry and exact depth, which may not be available under operational conditions in the framework of tsunami warning. We verify the performance of the concept on simulations of the great 1946 Aleutian tsunami at two virtual gauges, and then apply the algorithm to 24 records of 7 tsunamis at DART tsunameters during the years 1994–2003. We find that M_TSU generally recovers the seismic moment M₀ within 0.2 logarithmic units, even under unfavorable conditions such as excessive focal depth and refraction of the tsunami wave around continental masses. Finally, we apply the algorithm to the JASON satellite trace obtained over the Bay of Bengal during the 2004 Sumatra tsunami, after transforming the trace into a time series through a simple ad hoc procedure. Results are surprisingly good, with most estimates of the moment being over 10²⁹ dyn-cm, and thus identifying the source as an exceptionally large earthquake.  相似文献   

Experimental determination of magnesium isotope fractionation during higher plant growth   总被引：1，自引：0，他引：1  

Emile B. Bolou-Bi  Anne Poszwa  Nathalie Vigier 《Geochimica et cosmochimica acta》2010,74(9):2523-6026

Two higher plant species (rye grass and clover) were cultivated under laboratory conditions on two substrates (solution, phlogopite) in order to constrain the corresponding Mg isotope fractionations during plant growth and Mg uptake. We show that bulk plants are systematically enriched in heavy isotopes relative to their nutrient source. The Δ²⁶Mg_plant-source range from 0.72‰ to 0.26‰ for rye grass and from 1.05‰ to 0.41‰ for clover. Plants grown on phlogopite display Mg isotope signatures (relative to the Mg source) ∼0.3‰ lower than hydroponic plants. For a given substrate, rye grass display lower δ²⁶Mg (by ∼0.3‰) relative to clover. Magnesium desorbed from rye grass roots display a δ²⁶Mg greater than the nutrient solution. Adsorption experiments on dead and living rye grass roots also indicate a significant enrichment in heavy isotopes of the Mg adsorbed on the root surface. Our results indicate that the key processes responsible for heavy isotope enrichment in plants are located at the root level. Both species also exhibit an enrichment in light isotopes from roots to shoots (Δ²⁶Mg_leaf-root = −0.65‰ and −0.34‰ for rye grass and clover grown on phlogopite respectively, and Δ²⁶Mg_leaf-root of −0.06‰ and −0.22‰ for the same species grown hydroponically). This heavy isotope depletion in leaves can be explained by biological processes that affect leaves and roots differently: (1) organo-Mg complex (including chlorophyll) formation, and (2) Mg transport within plant. For both species, a positive correlation between δ²⁶Mg and K/Mg was observed among the various organs. This correlation is consistent with the link between K and Mg internal cycles, as well as with formation of organo-magnesium compounds associated with enrichment in heavy isotopes. Considering our results together with the published range for δ²⁶Mg of natural plants and rivers, we estimate that a significant change in continental vegetation would induce a change of the mean river δ²⁶Mg that is comparable to analytical uncertainties.  相似文献   

GPS for real-time earthquake source determination and tsunami warning systems   总被引：1，自引：0，他引：1  

Geoffrey Blewitt  William C. Hammond  Corné Kreemer  Hans-Peter Plag  Seth Stein  Emile Okal 《Journal of Geodesy》2009,83(3-4):335-343

We identify the key design aspects of a GPS-based system (and in the future, GNSS-based systems) that could contribute to real-time earthquake source determination and tsunami warning systems. Our approach is based on models of both transient and permanent displacement of GPS stations caused by large earthquakes, while considering the effect of GPS errors on inverted earthquake source parameters. Our main conclusions are that (1) the spatial pattern, magnitude, and timing of permanent displacement of GPS stations can be inverted for the earthquake source and so predict the 3D displacement field of the ocean bottom, thus providing the initial conditions for tsunami models, and (2) there are no inherently limiting factors arising from real-time orbit and positioning errors, provided sufficient near-field GPS stations are deployed. This signal could be readily exploited by GPS networks currently in place, and will be facilitated by the IGS Real-Time Project as it comes to fruition.  相似文献   

Regional dispersion of first-order overtone Rayleigh waves     

Emile A. Okal  Bong-Gon Jo 《Geophysical Journal International》1983,72(2):461-481

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Solar abundance of praseodymium     

Emile Biémont  Nicolas Grevesse  Øivind Hauge 《Solar physics》1979,61(1):17-22

16 lines of Pr ii possibly present in the solar photospheric spectrum have been studied. When including hyperfine structure in synthetic calculations, investigations of 9 lines result in an abundance A _Pr = 0.71 ± 0.08 in the log A _H = 12.00 scale.  相似文献   

Ethnic coexistence in a pluralistic campus environment   总被引：1，自引：0，他引：1  

Emile Kok-Kheng Yeoh 《GeoJournal》2006,66(3):223-241

In Malaysia, ethnic segregation seems to have grown more and more pronounced at all levels of education, which may have in the main contributed to increasing occupational segregation by ethnicity when the graduates left to join the job market. Such trends may be disturbing given the effort the country has put in to promote interethnic understanding and reduce interethnic economic disparity since 1970. By critically investigating the dynamics of ethnic coexistence in the microcosm of the university campus environment, this paper provides statistical evidence to show how far the country has progressed in terms of ethnic relations since the watershed events of May 13, 1969; to what extent Malaysian multiethnic society is different now compared to the unmistakable racial “corporateness” and interethnic “separateness” that Furnivall observed in his classic study of 1948; and in what ways ethnic relations have been reshaped by three decades of affirmative action policies and the form of ethnic democracy adapted for this unique society.

Emile Kok-Kheng YeohEmail:

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Etude comparative,au point de vue quantitatif,de l'eau du réseau d'alimentation de la Ville de Genève durant l'année 1893 et durant l'année 1948     

Emile Novel 《Aquatic Sciences - Research Across Boundaries》1949,11(3-4):546-550

Résumé L'eau de consommation délivrée actuellement à la population genevoise et d'une richesse en germes nettement plus élevée que celle délivrée en 1893. L'augmentation du nombre des microorganismes est due, avant tout, à la pollution des canalisations dans lesquelles le plancton mort sert de substrat nutritif aux bactéries et leur permet de se multiplier dans l'eau des conduites.

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Zusammenfassung Das Trinkwasser der Stadt Genf weist heute eine auffallend h?here Keimzahl auf als im Jahr 1893. Dies ist auf die Verschmutzung der Kanalisationen zurückzuführen. In ihnen finden die Bakterien im abgestorbenen Plankton ein günstiges N?hrsubstrat, so da? sie sich in den Wasserleitungen vermehren.

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Sur le plancton du Rhône     

Emile André 《Aquatic Sciences - Research Across Boundaries》1926,3(3-4):259-266

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