The modified pseudo-depth section as a tool in resistivity and IP prospecting — A case history

Following the depths of investigation of different electrode arrays, given byRoy andApparao (1971) andRoy (1972), a modified pseudo-depth section was suggested for any array byApparao andSarma (1981) as a tool in resistivity and IP prospecting. The tool was used for the interpretation of IP and resistivity anomalies obtained in a virgin area—Jonnagiri village, Pattikonda Taluq, Kurnool district (A.P.) India. Two of the four bore holes recommended encountered sulphide mineralization, while the other two met with white altered ashy material at the position of the maximum anomaly contour in the depth sections. The drilling results prove the utility of the modified pseudosections in the interpretation of the field data.     

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.

     

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.     

Resolution of tidal high water anomaly

Summary As a preliminary calculation of the Equilibrium Theory of Tides, a fictitious Earth-Moon configuration is analyzed byThomson andTait [1]²), in which non-sphericity of oceans is attributed to the attraction exerted by a stationary Moon. A rise of level is found at the which Earth-Moon orbital motion is accounted. This feature, which is utterly contradictory to fact according toG. H. Darwin [2] prompted him to remark that the equilibrium theory is nearly as much wrong as possible, in respect to the time of high water. An elementary analysis is given which, in demonstrating an exactly opposite finding, suggests a manner of removing one of the long-standing obscurities of the Laplace theory, remarked upon byHough andAiry, and in recent times byC. Eckart [3].     

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.

     

Über ein neuartiges Prinzip der elektrischen Tiefensondierung

Zusammenfassung Fussend auf theoretischen Ergebnissen vonR. M. Foster undS. S. Stefanescu wird ein neuartiges Verfahren zur elektrischen Tiefensondierung bei horizontaler Schichtung vorgeschlagen. Dieses Verfahren arbeitet im Gegensatz zum bekanntenWenner-Verfahren und zum «Zentralinduktions-Verfahren» nachKoenigsberger nicht mit der Veränderung eines Längenparameters (Elektrodenabstand, Schleifenradius), sondern mit veränderlicher Frequenz bei unveränderter Position der Elektroden und Sonden. Einige Vorzüge werden genannt, die diese Methode in praktischer Hinsicht haben dürfte.

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Summary Taking reference of theoretical results ofR. M. Foster andS. S. Stefanescu, a new method of electrical depth-sounding refering to horizontal strata is proposed. This new way works contrary to the wellknown princip ofWenner and also to the «Zentral-Induktions-Verfahren» afterKoenigsberger not with a change of a length-parameter (electrode-distance and coilradius), but with changeable frequency at unchanged position of electrodes and sondes. A few advantages are described, which this method may have in practice.

     

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.     

Transient disturbance produced in an elastic half-space by impulsive shearing traction distributed over a circular region

The displacement produced in a semi-infinite, homogeneous, isotropic elastic medium by the application of shearing traction over a circular portion of the half-space has been evaluated in exact form by Cagniard's Technique (Cagniard, 1962;Gakenheimer andMiklowitz, 1969).     

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.     

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.     

Il primo problema fondamentale della Geodesia ampliato nel campo di Somigliana

Sommario Dopo aver richiamato l'ampliamento ad un campo potenziale spaziale delle formule diLegendre che risolvono il primo problema fondamentale della Geodesia, l'A. applica tali formule al caso del campo diSomigliana, che ammette l'ellissoide come una delle superfici equipotenziali della famiglia; tale applicazione rappresenta la più naturale estensione ad un campo tridimensionale delle classiche formule ellissoidiche superficiali, e si accorda con l'adozione internazionale del campo diSomigliana per tutte le speculazioni della Geodesia dinamica.

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Summary After having recalled the extension to a spatial potential field ofLegender's formulae solving the first fundamental problem in Geodesy, the author applies such formulae toSomigliana's field, which admits the ellipsoid as one of the equipotential surfaces of the family. Such application represents the most natural extension to a three-dimensional field of the classical ellipsoidal surface formulae, and agrees with the international adoption ofSomigliana's field in dynamic Geodesy.

     

On the Mathematical Analysis of an Elastic-gravitational Layered Earth Model for Magmatic Intrusion: The Stationary Case

In the early eighties Rundle (1980, 1981a,b, 1982) developed the techniques needed for calculations of displacements and gravity changes due to internal sources of strain in layered linear elastic-gravitational media. The approximation of the solution for the half space was obtained by using the propagator matrix technique. The Earth model considered is elastic-gravitational, composed of several homogeneous layers overlying a bottom half space. Two dislocation sources can be considered, representing magma intrusions and faults. In recent decades theoretical and computational extensions of that model have been developed by Rundle and co-workers (e.g., Fernández and Rundle, 1994a,b; Fernández et al., 1997, 2005a; Tiampo et al., 2004; Charco et al., 2006, 2007a,b). The source can be located at any depth in the media. In this work we prove that the perturbed equations representing the elastic-gravitational deformation problem, with the natural boundary and transmission conditions, leads to a well-posed problem even for varied domains and general data. We present constructive proof of the existence and we show the uniqueness and the continuous dependence with respect to the data of weak solutions of the coupled elastic-gravitational field equations.     

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.     

Free and forced shallow-water oscillations in a rotating channel of parabolic cross-section

Free and forced oscillations of shallow water in an infinitely long rotating channel of parabolic cross-section are analyzed. The pure cross-channel oscillations ofChrystal (1905) and solutions for zero rotation first discussed byProudman (1925) andHidaka (1932) are special asymptotic solutions for the free modes of this model. However, for increasingly large, along-shore wave number, our solutions donot uniformly approach those ofReid (1958) andBall (1967) for a single shore-line and semi-infinite ocean. A method of computing eigen frequencies and eigen functions for the general problem is described, and a sufficient number of these are exhibited graphically to permit visualization of the transitions between the asymptotic regions.The forced problem consists of an incoming wave-train or surge generated at the center of the channel. Amplitude and transports near the shore are computed for a wide range of dimensionless incoming-wave frequencies and rotational frequencies.     

A simple formula for the second derivative method of interpretation

Summary Second derivative coefficients for various grid systems are derived followingPeters' andElkins' approaches. Two simple formulae, one for three dimensional bodies and the other for two dimensional bodies are also suggested. These utilise the average of the anomalies around a single circle and the anomaly at the central point.All the coefficient sets and the proposed simple formulae are applied to gravity fields of spheres and cylinders. Coefficients ofElkins' type derived with a weightage of 1/r ⁴ to all the circles gave excellent results in both the cases of spheres and cylinders, whereasPeters' coefficients without any weightage to the circles gave reliable results in case of cylinders only. The simple formulae suggested gave more accurate results than any of the above coefficient sets.     

On the propagation of plane waves in a porous visco-elastic material containing a fluid and deformed by a magnetic field

Summary In the present note, an attempt has been made to investigate the wave-motions in a poro-viscoelastic medium traversed by a static magnetic field, by using the equations ofMaxwell, and those ofBiot.     

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).     

Directional permeability of porous media to homogeneous fluids

Summary Investigations have shown that in groundwater- and oil-bearing strata there are preferential directions of flow that are often maintained over wide areas.Johnson & Hughes (1948, see Ref.) analysed a series of oil well cores by cutting them into small horizontal plugs and they obtained directional permeabilities which they plotted in the form of polar graphs. They were not able to give a physical explanation of this phenomenon. On the other hand, there exists a theory of permeability in which the latter is represented as a symmetric tensor. This theory has been developed byFerrandon (1948, see Ref.), but no experimental substantiation of it seems ever to have been attempted.In the present paper, the author undertakes to compare the two sets of findings. FromFerrandon's theory, the directional permeabilities (denoted byk) corresponding to the experiments ofJohnson & Hughes are calculated and it is shown thatk ^–1/2 if plotted as polar graph, should form an ellipse. The data ofJohnson & Hughes are then are drawn. In this manner, a substantiation of the tensor theory ofFerrandon is obtained.

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Zusammenfassung Untersuchungen der Permeabilität von Grundwasser und Erdöl führenden Gesteinsschichten haben gezeigt, dass dieselbe in vielen Fällen richtungsabhängig ist. Hierbei bleibt die Richtung extremaler Permeabilität oft über weite Gebiete konstant.Johnson & Hughes untersuchten eine Reihe von Bohrkernen von Oelquellen auf Richtungsabhängigkeit der Permeabilität. Hierzu schnitten sie aus denselben kleine, waagrechte Stücke, bestimmten deren Permeabilität und stellten das Ergebnis ihrer Messungen in der Form von Permeabilitätspolardiagrammen dar. Sie waren nicht im Stande, eine theoretische Erklärung der erhaltenen Kurven zu geben. Auf der anderen Seite existiert eine Theorie der Permeabilität, wobei die letztere als symmetrischer Tensor behandelt wird. Diese Theorie wurde vonFerrandon vorgeschlagen; es scheint aber, dass keine experimentelle Bestätigung davon je versucht worden ist.In der vorliegenden Arbeit vergleicht der Verfasser die zwei Typen von Untersuchungen. Nach derFerrandon'schen Theorie wird die «gerichtete» Permeabilität (mitk bezeichnet), die den Experimenten vonJohnson & Hughes entspricht, berechnet. Es wird gezeigt, dassk ^–1/2, als Polardiagramm dargestellt, die Gestalt einer Ellipse haben sollte. Die Resultate vonJohnson & Hughes werden dann in die Form vonk ^–1/2 umgerechnet und als entsprechende Polardiagramme dargestellt. In dieser Weise wird eine experimentelle Bestätigung der Tensortheorie vonFerrandon erhalten.

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Published by Permission of Imperial Oil Limited, Calgary, Alberta (Canada).     

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.     

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.