Coda-Q before and after the 1986 Andreanof Islands earthquake

Coda-Q values before and after the May 7, 1986 Andreanof Islands earthquake in the central Aleutian subduction zone were calculated from microearthquake seismograms on the basis of Aki's single backscattering model. Digital waveforms from 329 microeathquakes in 5.4 years before the mainshock and 40 aftershocks recorded by 11 stations of the Central Aleutians Seismic Network were utilized. Before the mainshock, coda-Q in the rupture zone west of the mainshock epicenter was 15% higher than theQ outside the rupture zone to the west. A lowQ in the region east of the mainshock epicenter is inferred, but lacks solid evidence. The highQ region accords with the part of the rupture zone where most seismic moment was released. During approximately two months after the mainshock, coda-Q in the rupture zone decreased about 10%. PrecursoryQ changes were not found in the 5.4 years before the mainshock. It is deduced that a coda-Q precursor, if it existed, was of small magnitude (<10%), or its duration was either shorter than one year or longer than four years.     

Some physical and chemical properties of lakes in north-eastern Norway

Summary Chemical and physical properties in 12 lakes in the north-easternmost part of Norway are studied. Geologically the lakes are situated on the pre-cambrian “Baltic shield”, with metamorphic and intrusive rocks that are not easily soluble. Vertical series of temperature, pH, O₂ and x₁₈ together with colour measurements and transparency indicate that the lakes are temperate and fundamentally oligotrophic, some with a dystrophic character. Some individual differences are discussed, with special reference to the surroundings, flow-through rate and morphometry. In accordance with the geology of the area the amount of electrolytes is small. Major ions (Ca, Mg, Na, K, HCO₃, SO₄ and Cl) are analysed. The greatest differences in the composition of these ions in the lakes are shown to be due mainly to the varying proximity to the sea and to geological differences. Rain is shown to be the most important factor in supplying major ions toat least some of the lakes. Individual variations are discussed, and comparisons are made with the ionic composition of water in other districts.

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Zusammenfassung An 12 im n?rdlichesten Teil von Norwegen, auf dem pr?kambrischen Baltischen Schild gelegenen Seen werden die chemischen und physikalischen Eigenschaften studiert. Das Einzugsgebiet besteht aus schwerl?slichem, metamorphem und intrusivem Gestein. Die vertikale Verteilung von Temperatur, pH, O₂ und x₁₈ samt Farbmessungen und Transparenz zeigt, dass die Seen dem temperierten Typus angeh?ren und im wesentlichen oligotroph sind, einige von dystrophem Charakter. Einige individuelle Unterschiede werden er?rtert mit besonderer Berücksichtigung der Umgebung, der Durchflutungszeit und der Morphometrie. In übereinstimmung mit der geologischen Beschaffenheit der Umgebung ist der Elektrolytgehalt neigdrig. Die dominierenden Ionen (Ca, Mg, Na, K, HCO₃, SO₄ und Cl) werden analysiert. Es wird nachgewiesen, dass die gr?ssten Unterschiede in der Zusammensetzung dieser Ionen in den Seen auf die verschiedene Entfernung vom Meer und auf geologische Unterschiede zurückzuführen sind. Für einige der Seen wird nachgewiesen, dass der Regen als wichtigster Faktor für ihre Versorgung mit Ionen anzusehen ist. Es werden individuelle Unterschiede er?rtert und Vergleiche mit der ionalen Zusammensetzung von Gew?ssern anderer Gegenden gezogen.

     

Isotopic composition of strontium in three basalt-andesite centers along the Lesser Antilles arc

Si⁸⁷/Sr⁸⁶ ratios have been determined for lavas and py lastic rocks from three basalt-andesite centers along the Lesser Antilles arc—Mt. Misery on the island of St. Kitts, Soufriere on the island of St. Vincent, and Carriacou, an island of The Grenadines. The average Si⁸⁷/Sr⁸⁶ content of these rocks is 0.7038 for Mt. Misery, 0.7041 for Soufriere, and 0.7053 for Carriacou. All the Sr⁸⁷/Sr⁸⁶ values from each center are the same within analytical uncertainty (±0.0002). The constancy of strontium isotopic data within each center supports the hypothesis that basalts and andesites for each specific center investigated are generated from the same source — in agreement with petrographic and major- and minor-element data. Strontium isotopic compositions and elemental concentrations, particularly of strontium and nickel, indicate that this source was mantle peridotite and that the relationship between the respective basalts and andesites is probably fractional crystallization.Publication authorized by the Director, U.S. Geological Survey.     

Some weak interaction processes in highly evolved stars

Some weak interaction processes which are important in stars whose central temperatures and densities exceed 10^9°K and 10⁶ gm/cm³ are discussed. Simple analytic expressions for reaction rates which are convenient for computer studies of the late stages of stellar evolution are given.Of the National Bureau of Standards and University of Colorado.     

The solar abundance of thorium and lead

Two new Th ii lines have been identified in the spectrum of the solar photosphere. The abundance derived from these lines together with the previously known Th ii line at 4019 Å, is log _Th = 0.85 ± 0.20 in the log _H = 12.00 scale. Analysis of three Pb i lines in the photospheric spectrum resulted in an abundance of log _pb = 1.90 ± 0.10. The solar Th/Pb ratio is: _Th/ _Pb = 0.09 _-0.005 ^0.09 .     

Two types of extremely short lasting decimetric bursts and their possible relation to processes in solar magnetic traps

High resolution spectral observations between 500 MHz and 550 MHz on 1972 October 25, revealed an emission event of special interest. The main feature was bursts with a single frequency duration of about 0.09 s and with a bandwidth of the same order of magnitude as the band covered by the spectrograph. The bursts occurred in showers' which lasted for one or two minutes and which were separated by quiet intervals of roughly the same length. Frequently the activity assumed a periodic nature. Periods between 0.1 s and 0.3 s were found. The most remarkable feature of the records was a very large number of bursts with the same duration as the wide band bursts, but showing a bandwidth of a mere 1–2 MHz.The wide band bursts may be plasma waves excited by proton streams trapped in coronal magnetic fields and the narrow band bursts may possibly be explained as perpendicular electrostatic electron cyclotron waves.