Recent variations in the general circulation as related to glacier retreat in northern Scandinavia

Summary A review is given of the investigations on variations in the general circulation in middle latitudes made byWillett andPetterssen. According toWillett a «high-index» type of circulation pattern with a strong zonal flow has probably caused the recent climatic improvement in the northern latitudes while the «low-index» type with meridional flow would create a cooling off in the same areas. According toPetterssen an other type of «low-index» pattern with a weak zonal flow and strong meridional exchange of air has been the essential cause of the warming up of the northern latitudes in Europe. This implies that the definition of the «low-index» type is not clear and gives rise to misunderstanding. Making use of our experience on glacier retreat in northern Scandinavia it is concluded that thePetterssen type of circulation more probably than the «high-index» type has caused the warming-up in the North Atlantic area from which the retreat of the glaciers has followed.     

Über die Bindung der Aerosolteilchen auf der Oberfläche der Wolkenelemente

Summary The importance ofStefan's flow by collection of insoluble aerosol particles on the surface of the evaporating droplets by condensation has recently been emphasized mainly in connection with the possible wash-out mechanism in the atmosphere. A simple theory is deduced for the collection efficiency of insoluble particles on droplets under theStefan's force and a comparision is made with the binding of aerosol particles byBrown's motion and microturbulence of air flow. In general we must take in account the influence ofStefan's flow by calculating the wash-out efficiency.     

The electrostatic force between a charged conducting sphere and a charged dielectric sphere in an arbitrarily oriented external electric field

Summary The electrostatic force between a charged conducting sphere and a charged dielectric sphere in a uniform, arbitrarily oriented external electric field is obtained and presented in terms of force coefficients which depend only on the relative geometry of the two spheres and the dielectric constants of the dielectric sphere and the medium. When the dielectric constant of the dielectric sphere is allowed to approach infinity, the resulting computed force agrees with that ofDavis (1964) for two conducting spheres, and when the external field and the charge on the dielectric sphere are set to zero, the resulting force agrees with that ofHall andBeard (1975) for a charged conducting sphere near an uncharged dielectric sphere.     

Coherency of rupture and seismic spectrum

In considering the seismic spectrum, one of the methods to incorporate irregularity of fault motion statistically is to introduce the concept of coherency of fracture. In a classic paper,Aki (1967) investigated the scaling law of seismic spectrum on the basis of a statistical model in which an exponentially decaying function is fitted to the autocorrelation function of the dislocation velocity. It is found, however, thatAki's model does not necessarily express irregular fault motion, but corresponds to a smooth dislocation. We show that an analytical function of dislocation velocity gives the same autocorrelation function and the same seismic spectrum as those ofAki's model. In actual fault motion, there is considerable evidence which indicates that the dislocation is not continuous and smooth over the whole fault plane, but is often segmented in several parts. In order to take into consideration this feature we introduce a generalized autocorrelation function of the dislocation velocity in which many coherent fractures smaller than the size of the fault dimension are included. It is shown that the more small-scale coherent fractures, the larger the seismic wave energy in the high frequency range.Kanamori andAllen (1986) showed that a large ratio of seismic wave energy relative to the seismic moment means a large effective stress drop. On the other hand, it is well known that when a fault plane is segmented in several parts, stress drop becomes large (e.g.,Madariaga, 1979;Rudnicki andKanamori, 1981). These two results are fused in our model, because we find that large seismic wave energy is obtained when the fault motion includes small-scale fractures.Kanamori andAllen (1986) also showed that there is a tendency for earthquakes with long repeat times to have a large effective stress drop. Our model implies that a fracture corresponding to earthquakes with long recurrence intervals is more complex, and the strength is large, as also suggested byCao andAki (1986) using a numerical simulation. It should be noted that to the zeroth order, an approximate scaling relation is observed among earthquakes, which means that a large earthquake consists of a relatively large-scale coherent fracture. This fact seems to suggest that the condition of occurrence of a large earthquake is related to the maturing of a source region in which a large coherent fracture becomes feasible.     

Mineralogy and physical nature of clay gouge

Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones. The 2-microns fractions in these fault gouges may compose a few percent to more than fifty percent of the total mass in the outcrops, and the mineralogy of the 2-microns fractions consists of a variety of clays (the common ones are montmorillonite, illite, kaolinite, chlorite, vermiculite and mixed-layer clays) and some quartz, feldspars, etc.Although we cannot yet conclude directly from the studies of gouges that similar gouges exist at depths where many large shallow earthquakes are generated, there is a strong possibility that they do, based on (1) available equilibrium data on various clays — for example, kaolinite has been found to exist at 4 kb and 375°C (±15°C) (Thompson, 1970) and montmorillonite + kaolite has been found to exist at 450°C and 4 kb (Velde, 1969); (2) the compatibility of laboratory velocity data in gouge (Wang et al., 1977) with those in a model for central California (Healy andPeake, 1975); (3) the capability of clays to undergo sudden earthquake-like displacements (Summers andByerlee, 1977); (4) the petrology of intrafault cataclastic rocks in old fault zones (Kasza, 1977); and (5) the compatibility of gouge mineralogy with the mineralogy of hydrothermal clay deposits.If clay gouges are indeed significant components of the fault zone at depth, then the mechanical properties of clays under confining pressures up to 4 kb are important in the behavior of faults. Very few experiments have been performed under such high pressures. But from the physical makeup of clays, we can infer that (1) the range of possible behavior includes stable sliding with vermiculite and montmorillonite (asByerlee andSummers, 1977, have proven) to stick-slip-like behavior with kaolinite, chlorite, etc.; (2) the absence or presence of water will greatly affect the strengths of gouges — it is possible that water may reduce the strength of gouge to a fairly small value.     

Hotspots,mantle convection and plate tectonics: A synthetic calculation

A model is developed that unifies vigorous hotspots with global-scale mantle convection and plate tectonics. The convection dynamics are assumed to generate flow patterns that emerge as closely packed polygonal cells in approaching the asthenosphere, and whose geometry is completely determined by a defining set of vigorous hotspots. Overlying viscously coupled rigid plates are driven with unique velocities (Euler vectors) at which the area integral of the shear forces is zero; these velocities are dynamically stable. The computed plate velocities, resulting from convection based on 15 hotspots, are compared with the velocities of plate motion models AM1-2 (Minster andJordan, 1978) and HS-NUVEL1 (Gripp andGordon, 1990), which combine transform fault geometries, magnetic anomalies and seismic data. The comparison shows a striking agreement for a majority of the plates. Geophysical implications of this numerical exercise are discussed.     

On the possible influence of meteoritic dust on rainfall

Summary This article comments on the statistical aspects of the calculations inBowen’s article on the influence of meteoritic dust on rainfall.Bowen seems to have neglected the phenomenon of self correlation in the series of rainfalls on successive days. This neglect made his conclusions rather significant, but when the self correlation is considered in the right way many of his results become insignificant and the question whether the meteoritic dust has the influence mentioned above remains unanswered. We applied the range and the so called constellation test. Especially stress is laid on the necessity of developing a coincidence test, which furnishes the probability of coinciding of peaks (one peak in one series, one peak in another one) even if the peaks are statistically unreal and of course the persistence ought to be considered. Three types of such a test were proposed. We also introduced a new way of tackling the problem stated byBowen. — SinceHannan published the numerical values of the serial correlation coefficients for Sydney (the rainstation used byBowen) we were able to give a more numerical basis to our critical remarks. Dr.C. Levert, Royal Netherlands Meteorological Institute,De Bilt (Holland).     

Rayleigh wave propagation in a two-layer anisotropic media

Summary The possibility of propagation of Rayleigh waves in an incompressible crust of constant density and rigidity varying exponentially with depth lying on a semi-infinite transversely isotropic base has been discussed in this paper. Frequency equation has been derived and numerical calculations are made. The result obtained in this case is compared with that ofNewlands [3]²) andDutta [4].     

Sull'analisi periodale dei diagrammi

Riassunto Dopo aver indicato un nuovo artificio per rendere più rapida la formazione di combinazioni selettive nella analisi periodale, si illustra un modello di analizzatore armonico che traduce con mezzi fotoelettrici gli schemi diLabrouste e diVercelli. Infine, si propone una variante costruttiva dell'analizzatore elettrico progettato dalLovera.

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Summary After having showed a new way by which the process for making the selective combinations used for periodical analysis is hastened, an harmonic analysing device which traducts with photoelectric means the schemes ofLabrouste andVercelli is illustrated. Further, a change in the construction ofLovera's electric analyser is proposed.

     

Some hydrodynamic problems for a nepheloid zone

Summary A layer of a few hundred meters thickness with suspended matter (a nepheloid zone) was discovered byEwing andThorndike [4]³⁾ near the bottom on the continental slope of the North Atlantic. A downward pressure gradient is produced in this layer due to increment of water density with suspensoid. When only the Coriolis force balances with this pressure gradient, a bottom nepheloid current flows southwestward parallel to the depth contours with a velocity of about 10 (cm/sec) for a slope of one degree. The pressure gradient for fluid with locally variable density above a sloping bottom is treated and an extra term due to density gradient along the slope is derived. The vertical profiles of the nepheloid current with an effect on the vertical eddy viscosity are computed. Two kinds of vertical distributions of eddy viscosity are determined from the observed nepheloid distributions and used in the calculations: constant but different values at two layers and those increasing with height. The effect of the change of density along the bottom is treated by introducing dimensionless variables. Rossby number of the nepheloid current becomes about 10^–2 indicating inertia terms to be negligible. Rossby number of turbidity currents ranges from 2 (in a decaying area) to 5 (developing area), suggesting that inertia terms are more important than Coriolis terms. The trajectories of turbidity currents are computed from motion of a mass of mud under the Coriolis force and friction, and the results are applied to those inferred byHand andEmery [6] in the San Diego Through off California.LGO Contribution Number 925.     

Soil-structure interaction effects on an instrumented building

The paper highlights the use of fem and bi-directional lumped-mass-storey-stiffness numerical models for the study of the soil–structure interaction (ssi) effects on an instrumented building. Data on the structural response have been obtained through the project for seismic instrumentation of a 16-storey r/c cast-in-place dwelling building (Chisinau, Republic of Moldova) during a series of earthquakes (Gutenberg–Richter M _GR = 5.0−6.7). The effect of soil–structure interaction is clearly observed comparing the responses recorded on foundation and free-field. ssi becomes more pronounced for higher level of ground shaking amplifying the natural period of the structure and slightly suppressing high frequences on the foundation in comparison with the free-field motion.     

Inversion of source process and related studies of the Taiwan Strait earthquake using genetic algorithm

Applying genetic algorithm to inversion of seismic moment tensor solution and using the data of P waveform from digital network and initial motion directions of P waves of Taiwan network stations, we studied the moment tensor solutions and focal parameters of the earthquake of M=7.3 on 16 September of 1994 in Taiwan Strait and other four quakes of M _L≥5.8 in the near region (21°–26°N, 115°–120°E). Among the five earthquakes, the quake of M=7.3 on September 16, 1994 in Taiwan Strait is the strongest one in the southeastern coast area since Nan’ao earthquake of M=7.3 in 1918. The results show that moment tensor solution of M=7.3 earthquake is mainly double-couple component, and is normal fault whose fault plane is near NW. The strike of the fault plane resembles that of the distributive bands of earthquakes before the main event and fracture pattern shown by aftershocks. The tension stress axis of focal mechanism is about horizontal, near in NE strike, the compressive stress axis is approximately vertical, near in NWW strike. It seems that this quake is controlled by the force of Philippine plate’s pressing Eurasian plate in NW direction. But from the viewpoint of P axis of near vertical and T axis of near horizontal, it is a normal fault of strong tensibility. There are relatively big difference between focal mechanism solution of this quake and those of the four other strong quakes. The complexity of source mechanism solution of these quakes represents the complexity of the process of the strait earthquake sequences. Contribution No. 98A01001, Institute of Geophysics, State Seismological Bureau, China. The subject is supported and helped by Academician Yun-Tai CHEN, Profs. Qing-Yao HONG, Zhen-Xing YAO, Tian-Yu ZHENG, Yao-Lin SHI, Ji-An XU, Bo-Shou HUANG and colleague Mei-Jian AN, Xue-Reng DING, Rui-Feng LIU. De-Chong ZHANG and Ming Li provided the digital data warm-heartedly. Lin-Ying WANG offered us the catalogue of earthquakes in southeastern coastal area in China. Xi-Li WANG and Tong-Xia BAI provided us the issued annual reports data. The authors would like to express their gratitude to all of these people. This paper is sponsored by the National Natural Science Foundation of China and Scientific and Technological Commission of Shantou, Guangdong Province.     

Studio macrosismico del terremoto del Cansiglio (Friuli) del 18 Ottobre 1936

Riassunto È un terremoto già studiato su dati sismografici daP. Caloi che ha ottenuto una profondità ipocentrale di 18 Km. in disaccordo con i 37–51 calcolati con analoghi metodi per altri terremoti precedenti pure del Veneto. L'A. ha rideterminato la profondità ip. per il terremoto in questione con procedimento macrosismico, deducendo soltanto 4–5 Km. D'altra parte riesaminando i metodi delCaloi si è convinto che i suoi 18 Km. sono quanto mai incerti ed anche in forte contrasto col valore ottenuto pure microsismograficamente dalloSchmerwitz di 43 Km. Al riguardo l'A. ricorda e discute altre notevoli contraddizioni che intervengono in importanti questioni sismologiche.

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Summary The above mentioned earthquake was already investigated byP. Caloi only by seismographic data obtaining a depth of 18 Km., while others shocks in the same zone, investigated with similar methods, should have been originated in depths of 37–51 Km. Therefore, the A. has undertake a new determination using a macroseismic method and became a value of only 4–5 Km. The discrepance is particularly great on account of the value of 43 Km. obtained bySchmerwitz also with microseismic methods. The unreliability of similar results for the solution of some important seismologic problem is analised.

     

Computations of the tropospheric radiation budget in the Caribbean and Gulf of Mexico area for clear sky conditions

Summary Computations of solar heating and infrared cooling for clear sky conditions in the area of the Central American Seas are presented, as based on conventional radiosondes in 1960. Results are discussed with regard to latitude mean data available in the literature.Both solar heating and infrared cooling display the most pronounced latitudinal variation in winter, while the distribution is rather uniform in summer. Large heating rates are found in the lower layers over the Caribbean Sea. The infrared cooling shows maxima around 700 mb and below the 950 mb level, in both summer and winter. This contrasts withLondon's result, but agrees with a more recent study byDavis. Infrared cooling rates computed for clear sky conditions up to 500 mb are somewhat larger than the results form radiometer soundings in fall 1960 as reported byRiehl. Discrepancies betweenRiehl's data andLondon's latitude mean values appear to result essentially from different cloud conditions. The pattern of net cooling is in general consistent withLondon's latitude mean cross-sections for average cloudiness.Effective outgoing radiation in winter displays a decrease from the Caribbean Sea towards the cold interior of the North American Continent, while latitudinal contrasts vanish during the summer season. Computations compare well withBudyko's table andRiehl's estimate for fall 1960, while they are substantially lower thanLondon's data and estimates fromSverdrup's graph.

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Zusammenfassung Absorption von Sonnenstrahlung und langwellige Ausstrahlung für wolkenfreien Himmel wurden für den Bereich des Amerikanischen Mittelmeers berechnet, auf Grund herkömmlicher Radiosondenaufstiege im Jahre 1960. Die Ergebnisse werden mit Hinblick auf die in der Literatur verfügbaren Breitenkreismittelwerte diskutiert.Absorption von Sonnenstrahlung und langwellige Ausstrahlung ändern sich mit der geographischen Breite besonders stark im Winter, wogegen horizontale Unterschiede im Sommer weniger ausgeprägt sind. Eine relativ starke Absorption von Sonnenstrahlung scheint in den unteren Schichten über der Karibischen See stattzufinden. Die langwellige Ausstrahlung ist besonders stark um 700 mb und unterhalb des 950 mb-Niveaus, und zwar sowohl im Sommer wie im Winter. Das steht im Gegensatz zu den Ergebnissen vonLondon, stimmt aber mit einer neueren Studie vonDavis überein. Die für wolkenfreien Himmel berechnete langwellige Ausstrahlung bis hinauf zum 500 mb-Niveau ist etwas grösser als die aus Aufstiegen von Radiometersonden im Herbst 1960 gewonnenen Werte vonRiehl. Unterschiede zwischen den Daten vonRiehl und den Breitenkreismittelwerten vonLondon scheinen im wesentlichen aus unterschiedlichen Bewölkungsverhältnissen herzurühren. Die aus Absorption und langwelliger Ausstrahlung resultierenden Abkühlungsbeträge entsprechen im allgemeinen den vonLondon für mittlere Bewölkungsverhältnisse mitgeteilten mittleren Vertikalschnitten.Die effektive Ausstrahlung der Erdoberfläche zeigt im Winter eine Abnahme von der Karibischen See auf den dann kalten Nordamerikanischen Kontinent hin; Unterschiede mit der geographischen Breite verschwinden hingegen im Sommer. Die Berechnungen entsprechen den Tabellenwerten vonBudyko und den Abschätzungen vonRiehl für den Herbst 1960;London's Daten sowie Abschätzungen nach dem Nomogramm vonSverdrup hingegen sind deutlich höher.

     

P in the shadow zone of the earth's core—Part I

Summary Regional variations have been indicated in the slope of theP travel-time curve in the shadow zone of the earth's core. Further study is needed since the uncertainties of the slope are large, especially for the observations from North American stations. There is no significant difference between themean slope of theP travel-time curve in the 95°102.9 range and those obtained byJeffreys, andJeffreys andBullen. However, there is a significant difference between themean slope in the 103° to 135° range as obtained in this study, and those obtained byJeffreys andBullen, and in a later revision byJeffreys. Themean travel-time curve ofP in the shadow zone of the earth's core should be lowered. A trial travel-time table is given with amean slope of 4.41 sec/deg. This table is in close agreement with the times obtained byGutenberg andRichter, and with the trial travel-times ofLehmann. Under the assumption of diffraction the longitudinal wave velocity has been determined to be 13.7 km/sec at the core-mantle boundary.This paper was presented at the Annual Meeting of the Seismological Society of America Reno, Nevada, 1966.     

Thermal regime of the Earth's outer core

Summary First an introduction into the dynamo problem and the core paradox is given. A novel theory of the volume dependence of Grüneisen's parameter is used for calculating the adiabatic temperatures on the assumption that the melting temperature of the material is reached at the boundary between the inner and outer cores of the Earth (IOB). On this condition, thermal convectionthroughout the outer core is impossible according to the melting-point curves ofKennedy andHiggins (1973) andLiu (1975), whereas it is permitted by that ofLeppaluoto (1972),Boschi (1975), andStacey (1977). Various possibilities of solving the core paradox are described.Mitt. d. ZIPE Nr. 682.     

Elektrische Aufladung Fallender Wassertropfen

Zusammenfassung Es wird die elektrische Aufladung einzelner, in ionisierter Luft frei fallender Wassertropfen experimentell untersucht, und zwar bei elektrischen Feldstärken zwischen 0 und 120 Volt/cm. Der Radius der untersuchten Wassertropfen beträgt 1.30 mm. Die elektrische Ladung wird durch Influenzring und hochohmige Röhrenvoltmeter in Verbindung mit Kathodenstrahloszillograph und Schleifenoszillograph gemessen. Es zeigt sich, dass der zeitliche Verlauf der Aufladung und die erreichte Grenzlandung mit der Theorie vonWhipple undChalmers in Einklang stehen. Auch zu der vonFrenkel angegebenen Theorie der Gewitterlektrizität durch Ionenabsorption wird eine experimentelle Aussage möglich.

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Summary The collecting of electrical charge by single waterdrops is experimentally examined. The drops fall freely through ionized air in the presence of electrical fields between 0 and 120 V/cm. Only drops with a radius of 1.30 mm are used. The electrical charge is measured by induction-ring and electronic amplifier previously described in connection with Cathode-Ray Oszillograph and recording Bifilar-Oszillograph. It is shown, that the rate of collecting of charge as well as the final charge gained are in accordance with the theory ofWhipple andChalmers. An experimental examination of the theorie of thunderstorm-electricity by ion absorption given byFrenkel becomes possible.

     

Sulla equazione differenziale di Schweydar relativa alle maree terrestri

Riassunto Viene riportata in forma riassuntiva e con alcune varianti lo svolgimento teorico seguito dalloSchweydar, considerando per la rigidità e per la densità interne, funzioni della profondità affatto generali, per giungere alla equazione differenziale del sesto ordine a coefficienti polinomiali per la marea. Vengono inoltre ricordati gli studi diprey e dell'A. su questo argomento.

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Summary The theoretical solvings bySchweydar are resumed, with some variations, considering general formulas for rigidity and internal density, to reach the differential equation of sixth degree with polynomial coefficients, for the tides.Prey's studies on this subject, and of the Author, are mentioned.

     

Seismicity of Bulgaria

Summary Using the concerning data of the Bulgarian earthquakes with magnitude greater 4 the seismicity of the period 1901–1965 was computed after a method byUllmann andMaaz and represented cartographically by isolines. The map lets us interpret the relation of the seismicity to the tectonic situation of Bulgaria. Further, the annual frequency of earthquakes of different magnitude basing on the same data is given.