On coda waves of earthquakes

Summary Coda waves viz. the tail portion of an earthquake record have been observed and analysed byCarder, Macelwane and others. They showed that the periods of such waves increase with the increase of epicentral distances.Carder observed that these waves have very little transverse component so that these may be considered as of the type of Rayleigh waves. RecentlyOmote showed that the Coda waves contain three periodsT ₁,T ₂,T ₃ of whichT ₁ increases with epi-central distances as observed by previous observers. ButT ₂,T ₃ remain constant for all earthquakes from different epicentral distances.Omote tried to explain this phenomenon by considering that the surface of the earth consists of several layers andT ₂,T ₃ are free oscillation periods of the surface layers.T ₁ period has been explained bySezawa and also byJeffreys which has been shown byGutenberg. The author has attempted to explain the periodsT ₂,T ₃ by considering passage of cracks at the focal region. The Rayleigh wave character of Coda waves and low velocity of such waves have been explained.     

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.     

A consideration of Hayford's best fitting ellipsoid data using the differential change equations of Vening Meinesz

Summary The relations of the defining parameters of a geodetic system to the deflections of the vertical in this system given byVening Meinesz have been used in the computation of a best fitting ellipsoid. The data was that used byHayford in the computation of the resulting International Ellipsoid. Assuming the undulation (N ₀) at Meades Ranch to be zero, the results are: a=6,378,194 m and l/f=299.9. This a is much nearer to modern values than that of the Internaitonal Ellipsoid. If a flattening of 1/298.24 is fixed andN ₀=+3m,a=6,378,164 m which differs by one meter from a recent determination given byKaula.     

Die sogenannte «Moorschnecke»Leptobasis goesingense Palikein Pilzkonidium

Zusammenfassung Bau, Entwicklungsgeschichte (in Reinkulturen!) und ?kologie zeigen:Steinekkes ?Moorschnecke?, seineHelicosporium-Konidien,Leptobasis goesingense Palik undFortiea spirulina f. goesingense (Palik) Poljanskij geh?ren zusammen und stellen das Konidium einerHelicoonart dar. Es besteht keine Beziehung zuFortiea spirulina (Steinecke)J. De Toni.

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Summary Morphology, development (in pure cultures) and ecology show thatSteinecke’s ‘Moorschnecke’, hisHelicosporiumconidium,Leptobasis goesingense Palik andFortiea spirulina f.goesingense (Palik) Poljanskij belong together and represent the conidium of a species ofHelicoon. There is no connection to theFortiea spirulina (Steinecke)J. De Toni.

     

Beitrag zur Kenntnis der planktisch lebenden Ruderfusskrebse (Crustacea Copepoda) des Engstlensees (Berner Oberland)

Zusammenfassung Eine am 22. September 1969 im 1850 m hoch gelegenen Engstlensee gesammelte Planktonprobe enthielt zwei verschiedene Copepodenarten. Der Diaptomide ist ein Gield der GattungArctodiaptomus. Bereits 1885 ist er aus diesem Gew?sser als neue Artalpinus erw?hnt worden. Sp?tere Forscher haben ihn dann aber—wie alle ?hnlichen Populationen hochgelegener Alpenseen—mit der Speziesbacillifer Koelbel identifiziert. Nach den Ergebnissen vergleichender Untersuchungen des Verfassers istalpinus indessen doch als selbst?ndige Art zu bewerten, die hier zum erstenmal ausführlich beschrieben wird. DerCyclops des Engstlensees wird alsCyclops abyssorum tatricus (Kozminski, 1927) gekennzeichnet.

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Résumé Le 22 septembre 1969, l’auteur a effectué une récolte de faune pélagique dans l’Engstlensee. L’étude de cette récolte a permis de déterminer les deux Copépodes suivants:Arctodiaptomus alpinus (Imhof) etCyclops abyssorum tatricus (Kozminski). Tous les deux sont des Crustacés caractéristiques pour la faune pélagique de beaucoup de lacs élevés des Alpes. Jusqu’à présent, l’Arctodiaptomus alpinus a été nommébacillifer. Mais au cours d’une revision du ?groupebacillifer? du genreArctodiaptomus, l’auteur a constaté que ?bacillifer Koelbel? et ?alpinus Imhof? sont en réalité deux espèces différentes. Les résultats complets de cette revision seront publiés par un autre journal d’hydrobiologie.

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Herrn Prof. OttJaag zum 70. Geburtstag     

Isocystis pallida—keine Cyanophycee

Zusammenfassung Die Argumente, dieAnagnostidis undRathsack-Künzenbach zugunsten der Blaualgennatur von ?Isocystis pallida? anführen, sind hinf?llig, weil die Fortpflanzung obligat durch Knospung nach Art der Hefepilze, nicht durch Zweiteilung erfolgt, also die Pflanze grunds?tzlich anders als Blaualgen organisiert ist.

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Summary ‘Isocystis pallida’ is not a blue green alga, arguments against this statement expressed byAnagnostidis andRathsack-Künzenbach are not valid. In view of the obligatory budding of the cells, in manner of yeasts, instead of binary fission, the organism must be considered as a species of the genusTorulopsidosira.

     

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).     

On the various methods of deducing aerosol size distribution from diffusional decay measurements

Summary The value of three different methods for deducing aerosol size distribution from diffusional decay measurements — the exhaustion method proposed byPollak andMetnieks, the method byFuchs et al. and the method byNolan andScott — is investigated with numerical examples of known distributions and also by applying them to laboratory experiments. It was found that the exhaustion method and the method proposed byFuchs et al. are satisfactory for deducing the mean particle size and that none of the three methods is quite satisfactory for deducing dispersion of the distributions with higher accuracy.     

Hydrocarbon source systems and formation of gas fields in Sichuan Basin

The formation of large and middle gas fields in Sichuan Basin is investigated based on source wntrolling theory and hydrocarbon source systems. It is indicated that Є₁, S_l, P₁, P₂ and T₃ are the main source beds and Є₁/Z₂ d, C₂ h/S₁, P₁/P₂, P₂ ch/P₂, T_1,2/P,T3 x /T3 x are important hydrocarbon source systems in the basin. All these source systems are the prospective formations and exploration spaces of large and middle gas fields. It is also emphasized that hydrocarbon generation intensity is the most important geochemical factor to estimate large and middle gas fields. Project supported by the “85–102” Chinese National Key Science and Technology Project.     

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.     

Environmental mechanism of magnetic susceptibility changes of lacustrine sediments from Lake Hulun, China

The changes of magnetic susceptibility(κ) are correlated with those of corresponding sedimentological, geochemical, mineralogical and biological results, which verifies thatκ can be taken as one of the environmental proxies. However, usually the exact origin of magnetic signal is poorly understood, and is difficult to relate with the environmental evolution. Magnetic properties of material derived from the catchment and sedimentary environment may affect the accumulation, preservation, or authigenesis and diagenesis of magnetic minerals. In the Lake Hulun region in Inner Mongolia, it is found that muddy sediments, deposited during high water level period (corresponding to humid climate), have comparatively highκ values. In contrast, the sandy sediments, deposited during low water level period (corresponding to arid climate), have lowκ values. Detailed rock magnetic investigation confirms that detrital magnetite derived from volcanic rocks in the catchment exists in both muddy and sandy sediments. During high water level period, secondary ferrimagnetic iron sulphide was produced in muddy sediments under relatively reductive conditions. Ferrimagnetic iron sulphide, coexisting with detrital magnetite, predominates the magnetic properties of muddy sediments, resulting in increasingκ. This paper reveals the significance of authigenic ferrimagnetic iron sulphide produced after sediment deposition.     

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.     

Comparison of techniques that use the single scattering model to compute the quality factorQ from coda waves

Using simulated coda waves, the resolution of the single-scattering model to extract codaQ (Q _c ) and its power law frequency dependence was tested. The back-scattering model ofAki andChouet (1975) and the single isotropic-scattering model ofSato (1977) were examined. The results indicate that: (1) The inputQ _c models are reasonably well approximated by the two methods; (2) almost equalQ _c values are recovered when the techniques sample the same coda windows; (3) lowQ _c models are well estimated in the frequency domain from the early and late part of the coda; and (4) models with highQ _c values are more accurately extracted from late code measurements.     

A new measure of seismicity

Summary In this paper an attempt has been made to analyse the World shallow focus earth-quakes by the method ofGutenberg andRichter. Frequency-magnitude analysis of various earthquakes indicate that in the relation logN=a–b M, the ratio (b/a)^–1 satisfies fairly well the seismicity of a region and it is felt that this ratio may be used as a measure of seismicity for a given region.     

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.     

Zur Frage ionosphärisch-troposphärischer Beziehungen

Zusammenfassung Angeregt durch eine Arbeit vonS. Bauer wurde für ein sonnenfleckenarmes bzw.-reiches Jahr nach einer Korrelation zwischen derfoF2 bzw.h'F2 und Kaltfrontdurchgängen gesucht. Im Gegensatz zuBauer wurde keine Beziehung gefunden. Anschließend wurde nach einem Zusammenhang zwischen Ionosphärenstürmen und dem Luftdruck am Boden gefragt. Für den sonnenfleckenarmen Winter 1953/54 ergibt sich ein signifikantes Ergebnis.

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Summary Incited by a paper ofS. Bauer the A. tried to find a correlation betweenfoF2 orh'F2 and cold front passages for a year with a small respectively big number of sun-spots. Contrary toBauer no correlation was found. Further a connection between atmospheric pressure at the ground and ionospheric storms was undertaken. The result for the winter 1953/54 with a small number of sun-spots was significant.

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Vortrag gehalten auf die 6. Allgem. Versammlung der «Società Italiana di Geofisica e Meteorologia» (Genova: 10.–12. April 1958).     

Isocystis pallida—Blaualge oder hefeartiger Pilz?

Zusammenfassung Die vonWoronichin [29] alsIsocystis pallida beschriebene Cyanophycee, welche vonAnagnostidis [1] h?ufig in griechischen Thermalquellen gefunden wurde, hatGeitler [17] zu den hefeartigen Pilzen der GattungTorulopsidosira gestellt. Diesen Organismus, den wir in verschiedenen Thermen reelm?ssig angetroffen haben, (Griechenland, Ungarn, Schweiz) untersuchten wir an Hand umfangreicher Materialproben. Statistische und zellphysiologische Versuche sowie systematische Vergleiche führten uns zu dem Ergebnis, diesen Organismus alsI. pallida (Woronich.) bei den Cyanophyten zu belassen, bis biochemische Resultate seine Zugeh?rigkeit zu den Blaualgen in Frage stellen sollten.

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Summary The blue-green alga described byWoronichin [29] asIsocystis pallida and often found byAnagnostidis [1] in Greek hot springs has been classified byGeitler [17] among yeast-like fungi of the genusTorulopsidosira. This organism was regularly found in various hot springs (Greece, Hungary, Switzerland). Statistical and cytological tests, as well as systematical comparisons, led us to conclude that it should be classified asI. pallida (Woronich.) among the Cyanophyta until biochemical results should give cause to doubt that it belongs to the blue-green algae.

     

Case 27 thermal infrared anomaly precursor of impending earthquakes

People have already recognized the temperature increase anomaly before earthquakes, and studies have been made on this phenomenon (Wu, 1980;Wu et al., 1982;Geng, 1985). With the method of fixed-point network observation, only the timing temperature data limited to some sites can be obtained instead of dynamic evolution data of the temperature in a large area within the seismogenic range. However, it is advantageous to use the thermal infrared (IR) radiation measured by Meteosat to detect the ground temperature, because of the data accuracy, large area coverage, large amount of information, and the capability of capturing the time-space dynamic variation of the temperature increase before earthquakes. However relevant works on the relationship of the thermal IR anomaly measured by Meteosat to seismic activity are only found published in the Soviet Union (Gornuy et al., 1988). The authors used the thermal IR anomaly measured by Meteosat to monitor and tried to predict the earthquake of October 18, 1989 in Datong, Shanxi Province and other shocks, and obtained preliminary ideas and methods for carrying out predictions in this way.     

CodaQ as a combination of scattering and intrinsic attenuation: Numerical simulations with the boundary integral method

Numerical modelling ofSH wave seismograms in media whose material properties are prescribed by a random distribution of many perfectly elastic cavities and by intrinsic absorption of seismic energy (anelasticity) demonstrates that the main characteristics of the coda waves, namely amplitude decay and duration, are well described by singly scattered waves in anelastic media rather than by multiply scattered waves in either elastic or anelastic media. We use the Boundary Integral scheme developed byBenites et al. (1992) to compute the complete wave field and measure the values of the direct waveQ and coda wavesQ in a wide range of frequencies, determining the spatial decay of the direct wave log-amplitude relation and the temporal decay of the coda envelope, respectively. The effects of both intrinsic absorption and pure scattering on the overall attenuation can be quantified separately by computing theQ values for corresponding models with (anelastic) and without (elastic) absorption. For the models considered in this study, the values of codaQ ^–1 in anelastic media are in good agreement with the sum of the corresponding scatteringQ ^–1 and intrinsicQ ^–1 values, as established by the single-scattering model ofAki andChouet (1975). Also, for the same random model with intrinsic absorption it appears that the singly scattered waves propagate without significant loss of energy as compared with the multiply scattered waves, which are strongly affected by absorption, suggesting its dominant role in the attenuation of coda waves.     

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.