The Bellingshausen Sea earthquake of February 5, 1977: Evidence for ridge-generated compression in the Antarctic plate     

Emile A. Okal 《Earth and Planetary Science Letters》1980,46(2):306-310

Body- and surface-wave data from a magnitude M_s = 6.4 event in the Bellingshausen Sea are used to infer a thrust fault mechanism, with compressional stress directed parallel to the vector of relative motion between Antarctica and the Pacific plate at the nearby ridge. The solution would not, on the other hand, be compatible with stress fields involving absolute plate motion, such as asthenospheric drag.  相似文献   

A surface-wave investigation of the rupture mechanism of the Gobi-Altai (December 4, 1957) earthquake     

Emile A. Okal 《Physics of the Earth and Planetary Interiors》1976,12(4):319-328

Long-period records of multiple Love waves from the 1957 earthquake in Mongolia (M_S = 8.0) at Pasadena are analysed and compared to synthetic seismograms, generated by the method of Kanamori. A fit in the time domain shows that the records are not consistent with the previous solution, achieved through a frequency-domain analysis of directivity by Ben-Menahem and Toksöz. The solution asks for a shorter rupture of 270 km at a velocity of 3.5 km/s. The focal parameters are constrained by updating all the reported first motion and are found to be: strike = 103°, dip = 53°, slip = 32°. A seismic moment of 1.8 · 10²⁸ dyn · cm is obtained. These figures are also consistent with a time-domain analysis of Love waves at Palisades and Strasbourg, and of Rayleigh waves at Pasadena, with a directivity study of Love waves at Pasadena, and with static deformation and isoseismal data. A discussion is given of the relation between moment, magnitude and rupture area, and a comparison is made with other events in the same region: it is concluded that this earthquake does not exhibit an “intra-plate” behavior, but rather compares better with “inter-plate” events, such as the great Assam earthquake.  相似文献   

De la vitesse de sédimentation des microbes dans l'eau du Léman prélevée dans le Petit-lac     

Emile Novel 《Aquatic Sciences - Research Across Boundaries》1969,31(1):150-156

Résumé L'auteur a étudié, dans des conditions expérimentales définies, la vitesse de sédimentation des bactéries appartenant à l'espèceEscherichia coli dans l'eau du Léman, puisée dans le Petit-lac. Théoriquement la durée de chute est de 16 heures et 40 minutes pour un mètre. L'on voit ainsi que pour atteindre le fond du Léman en sa plus grande profondeur un colibacille mettrait 256 jours et 18 heures si rien ne venait entraver sa descente.

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Zusammenfassung Unter definierten Versuchsbedingungen wurde die Sedimentationsgeschwindigkeit von Bakterien der ArtEscherichia coli aus dem Genfersee (Lac Léman) studiert, und zwar mit Material aus dem Petit Lac. Theoretisch betr?gt die Sinkzeit pro Meter 16 h 40 min. Daraus geht hervor, dass ein Colibazillus, sofern er unbehindert absinken kann, 256 h 18 min ben?tigt, um den Grund des Genfersees an seiner tiefsten Stelle zu erreichen.

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Etudes bactériologiques des eux du Léman,prélevées dans le Petit-Lac pendant les années 1960, 1961 et 1962     

Emile Novel 《Aquatic Sciences - Research Across Boundaries》1965,27(2):238-249

Conclusions Si l'on examine les chiffres, aussi bien du point de vue qualitatif (recherche des coliformes) que du point de vue quantitatif (nombre total des germes) de la période 1957 à 1962¹), on remarque une aggravation sensible de la situation bactériologique ces dernières années et, notamment surtout, en 1961 et 1962.

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Summary The examination of the figures with regard to the qualitative point of view (coliforms) as well as to the quantitative one (total number of germs) for the period of 1957 to 1962¹) reveals an aggravation of the bacterial situation in the last years and, especially, in 1961 and 1962.

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Zusammenfassung Bei der Prüfung der Zahlen, sowohl in qualitativer (Colibakterien) als auch in quantitativer Hinsicht (Total der vorhandenen Keime) wird für die Zeit von 1957 bis 1962¹) eine merkliche Verschlechterung der bakteriologischen Verh?ltnisse festgestellt. Dies gilt besonders für die letzten Jahre, vor allem aber für 1961 und 1962.

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Book review     

Emile A. Okal  Jeremy Bloxham  Barry Parsons  Leszek Czechowski  L. Czechowski  S. J. Gibowicz  Ursula B. Marvin  Richard Barakat  Jan Błęcki  Roberto Legnani  Stephen Warren 《Pure and Applied Geophysics》1988,127(1):161-180

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Introduction   总被引：1，自引：0，他引：1  

Emile A. Okal 《Pure and Applied Geophysics》1987,125(6):881-882

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The Gilbert Islands (Republic of Kiribati) earthquake swarm of 1981–1983     

Thorne Lay  Emile Okal 《Physics of the Earth and Planetary Interiors》1983,33(4):284-303

A major swarm of intraplate earthquakes at the southeastern end of the Gilbert Islands Chain (3.5°S, 177.5°E) commenced in December 1981 and lasted through March 1983. No seismicity had been reported in the historical record in this region prior to 1981, but during the swarm 217 events with m_b ? 4.0 were located by the NEIS, with 86 events having m_b ? 5.0. The source region is quite remote, and the uniform detection level for the NEIS is for m_b ? 4.8. A b-value of 1.35 is found for the swarm using the maximum likelihood method. Four events in the sequence were large enough (m_b = 5.6?5.9) to determine focal mechanisms teleseismically using body- and surface-wave analysis. These events are found to have a range of mechanisms, from predominantly thrust with a significant oblique component, to purely strike-slip. The compression axes are consistent for all four events, with horizontal orientation trending NNE-SSW. This orientation is perpendicular to the direction of plate motion. The events are located at depths between 15 and 20 km placing them deep in the oceanic crust or in the upper mantle. No obvious bathymetric feature can be related to the fault plane orientations, though there is an offset in the island chain near the epicenters. While some characteristics of the swarm suggest a magmatic origin, the nature of the focal mechanisms, the location of the swarm, and the large accumulated moment release of the sequence favor a tectonic origin.  相似文献   

Montagne Pelée volcano (Martinique,in the French Lesser Antilles) hydrogeological system revealed by high-resolution helicopter-borne electromagnetic imagery     

Vittecoq  Benoit  Reninger  Pierre-Alexandre  Bellier  Vincent  Taïlamé  Anne-Lise  Nacimento  Laureen  Gros  Emile  Violette  Sophie 《Hydrogeology Journal》2023,31(5):1331-1352

Montagne Pelée, on the French island of Martinique, eastern Caribbean Sea, has been one of the deadliest volcanoes in the world, with 30,000 victims following the 1902 eruption. Thousands of people still live nearby, and this volcano is a strategic “water tank” for Martinique Island, providing 40% of the island’s water supply. This research aimed to better understand its hydrogeological functioning and the relationship with its complex volcanological evolution, taking advantage of a high-resolution helicopter-borne geophysical survey correlated with hydrogeological data from the boreholes and springs databases. Electromagnetic data, correlated with hydrogeological data, allowed for the identification of unsaturated zones, aquifers, and seawater intrusions, as well as the main geological units. In addition, data synthesised from pumping tests revealed that the older the unconsolidated pyroclastic deposits, the lower their hydraulic conductivity. The structural asymmetry between the northeastern and southwestern volcano flanks impacts its hydrogeological functioning. Consequently, the Montagne Pelée hydrogeological conceptual model is marked by several distinguishable aquifers. The upper perched aquifer within recent lava domes is directly involved in, and impacted by, phreatic eruptions, and it supports low flowrate springs. The remaining effective rainfall infiltrates to depth and recharges the hydrothermal system through vertical fractures. The other aquifers are categorized into three groups: northeastern, southeastern and southwestern flank aquifers. This research is a new step toward a better understanding of the Lesser Antilles volcanoes and more broadly of the central and proximal parts of the andesitic active volcanoes.

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Socotra Island,Yemen: field survey of the 2004 Indian Ocean tsunami     

Hermann M. Fritz  Emile A. Okal 《Natural Hazards》2008,46(1):107-117

The tsunami of 26th December 2004 severely affected Yemen’s Socotra Island with a death at a distance of 4,600 km from the epicenter of the Magnitude 9.0 earthquake. Yemen allowed a detailed assessment of the far-field impact of a tsunami in the main propagation direction. The UNESCO mission surveyed 12 impacted towns on the north and south shores covering from the east to the west tip of Socotra. The international team members were on the ground in Yemen from 11 to 19 October 2006. The team measured tsunami run-up heights and inundation distances based on the location of watermarks on buildings and eyewitness accounts. Maximum run-up heights were typically on the order of 2–6 m. Each measurement was located by means of global positioning systems (GPS) and photographed. Numerous eyewitness interviews were recorded on video. The tsunami impact on Socotra is compared with other locations along the shores of the Indian Ocean.  相似文献   

Magnesium Isotope Compositions of Natural Reference Materials   总被引：1，自引：0，他引：1  

Emile B. Bolou-Bi  Nathalie Vigier  Agnès Brenot  Anne Poszwa 《Geostandards and Geoanalytical Research》2009,33(1):95-109

This study presents a chemical protocol for the separation of Mg that is particularly adapted to alkali‐rich samples (granite, soil, plants). This protocol was based on a combination of two pre‐existing methods: transition metals were first removed from the sample using an AG‐MP1 anion‐exchange resin, followed by the separation of alkalis (Na, K) and bivalent cations (Ca²⁺, Mn²⁺ and Sr²⁺) using a AG50W‐X12 cation‐exchange resin. This procedure allowed Mg recovery of ～ 10 0 ± 8%. The [Σcations]/[Mg] molar ratios in all of the final Mg fractions were lower than 0.05. The Mg isotope ratios of eleven reference materials were analysed using two different MC‐ICP‐MS instruments (Isoprobe and Nu Plasma). The long‐term reproducibility, assessed by repeated measurements of Mg standard solutions and natural reference materials, was 0.14‰. The basalt (BE‐N), limestone (Cal‐S) and seawater (BCR‐403) reference materials analysed in this study yielded δ²⁶Mg mean values of ?0.28 ± 0.08‰, ?4.37 ± 0.11‰ and ?0.89 ± 0.10‰ respectively, in agreement with published data. The two continental rocks analysed, diorite (DR‐N) and granite (GA), yielded δ²⁶Mg mean values of ?0.50 ± 0.08‰ and ?0.75 ± 0.14‰, respectively. The weathering products, soil (TILL‐1) and river water (NIST SRM 1640), gave δ²⁶Mg values of ?0.40 ± 0.07‰ and ?1.27 ± 0.14‰, respectively. We also present, for the first time, the Mg isotope composition of bulk plant and organic matter. Rye flour (BCR‐381), sea lettuce (Ulva lactuva) (BCR‐279), natural hairgrass (Deschampsia flexuosa) and lichen (BCR‐482) reference materials gave δ²⁶Mg values of ?1.10 ± 0.14‰, ?0.90 ± 0.19‰, ?0.50 ± 0.22‰ and ?1.15 ± 0.27‰ respectively. Plant δ²⁶Mg values fell within the range defined by published data for chlorophylls.  相似文献