SIMULATION OF REALISTIC SYNTHETIC REFLECTION SEQUENCES1

It is useful to be able to calculate synthetic primary reflection sequences from which to generate synthetic seismic sections which can be used for testing new processing algorithms. However, these synthetic reflection sequences should closely match real properties found in recent studies. Using the ARMA(1,1) model resulting from such studies to describe the correlation (or spectral) structure of the sequences, and by matching moments up to fourth order (since the sequences are non-Gaussian in practice), realistic sequences can be generated. A simple scheme is provided which also eliminates the necessity of throwing away large numbers of simulated values at start-up. The procedure is illustrated on three real sequences and is seen to reproduce all the important features.     

Study ofP-wave velocity below moho

Summary Seismograms recorded during the Trans-Scandinavian Profile of 1969 at the stations Kajaani, Oulu, Maaselkä and Sodankylä are used to determine theP wave velocities for distances from 400 km to 1300 km. An apparent velocity of 8.50 km/s was found. After making a correction due to the curvature of the earth the velocity of about 8.40 km/s was obtained at an approximate depth of 80 km. Some comparisons are made with other results from Fennoscandian area.     

The petrology of chondrules in the sharps meteorite

Correlated petrographic and microprobe studies of 96 chondrules in the Sharps (H-3) chondrite indicate that chondritic material had a highly varied pre-accumulation history. Some chondrules, chiefly excentroradial and barred types, appear to be quenched droplets. Others, including most of the metal poor microporphyritic type, appear to have crystallized more slowly and are thought to be fragments of pre-existing rock. Although chondrules of all types show various effects similar to those produced by shock, such effects are most conspicuous in metal-rich chondrules and least conspicuous in spherical chondrules. It is concluded that shock was involved in the origin of chondrules and not simply a secondary effect.It is proposed that chondrules were formed by shock processes during the accumulation of nebular dust into asteroid-sized bodies. Olivine-rich microporphyritic chondrules are thought to be due to complete melting of large masses of target material; metal-rich chondrules represent shock melting and partial vaporization; and spherical, pyroxene-rich chondrules are interpreted as condensates from shock-generated vapor.     

On stresses and displacements due to a moving line load over the plane boundary of a heterogeneous elastic half-space

Summary The problem of concentrated line load moving with supersonic speed along the boundary of an isotropic heterogeneous medium has been solved as a plane strain problem. The stresses and displacements in the heterogeneous case considered are found to decay exponentially with distance.     

A terrestrial shear pattern?

The concept of the strain ellipsoid is applied to indicate a possible regular shear pattern of earthquake distribution over the Earth's surface. A simple model of the Earth is assumed in the form of a rotating sphere with a plastic interior and a thin, fragile, crust. On this basis rotation of the Earth generates an internal radial pressure at the equator equivalent to 1/300g causing a proportionate distortion of the spherical shell. The system is in dynamic equilibrium with an increase in gravity at the equator. The ellipsoid representing the distortion, has orthogonal principal axes corresponding to the principal strains while radial directions at 54°44 from the poles are unchanged in length and are thus possible axes of shear generating the same distortion. The Alpide region of earthquakes extending from Lisbon to Tokyo and restriction of earthquakes mainly to the broad band between latitudes 55°N or S are in support of the proposed view.Four unique sets of orthogonal shear systems have been identified which form a regular pattern with a definite symmetry with respect to the plane of the ecliptic. This suggests that the hoop stress at the Equator associated with Earth rotation may be triggered off by tidal forces and that earthquake prediction may well be possible. Other implications of this new approach are also discussed.     

Further notes on a feature of leaf and air temperatures

Summary This is a sequel to an earlier paper, in which it was pointed out that there is a tendency for the temperature of leaves of many well-watered plants, exposed to midday sunshine, to exceed the ambient temperature only when the latter is below a so-called equality temperature. Further evidence is presented here, again indicating that equality temperatures are often in the vicinity of 30°C.

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Zusammenfassung Der vorliegende Artikel stellt die Fortsetzung einer früheren Arbeit dar, in der dargelegt wurde, da? eine Tendenz dazu besteht, da\ die Temperature der Bl?tter vieler Pflanzen, denen hinreichend Wasser zur Verfügung steht und die der Mittagssonne ausgesetzt sind, nur dann h?her ist als die Umgebungstemperatur, wenn die letztere niedriger ist als die sogenannte „Gleichheitstemperatur”; das ist die Temperatur, bei der kein Flu? fühlbarer W?rme zwischen Blatt und Umgebung auftritt. Es werden Beispiele angeführt, die zeigen, da? die Gleichheitstemperatur nahe bei 30°C liegt.

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Résumé Le présent mémoire est la suite d'un précédent dans lequel on avait émis l'avis que la température des feuilles de bien des plantes exposées au soleil de midi ne dépassait la température ambiante que si cette dernière était inférieure à une certaine “température d'égalité” (Gleichheitstemperatur). Cette tendance ne se manifeste cependant que si les dites plantes disposent de suffisamment d'eau. La “température d'égalité” est celle à laquelle on ne constate pas de flux de chaleur sensible entre la feuille et le milieu ambiant. On donne ici des exemples supplémentaires qui montrent que cette “température d'égalité” est souvent proche de 30°C.

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With 5 Figures     

The nature of the 10 and 20 micrometer features in circumstellar dust shells

Photographic reduction techniques are compared using an iris photometer, GALAXY and PDS for measurement of two plates (B andV) of the globular cluster M15. The comparison shows that satisfactory results can be obtained by any of these methods in the outer areas of globular clusters, but in inner regions, due to crowding of stellar images and to the influence of the background density, the most appropriate technique is the procedure applied to PDS scans of the plates.     

Soil water dye tracing,with special reference to the use of rhodamine WT,lissamine FF and amino G acid

Three fluorescent dyes (Rhodamine WT, Lissamine FF and Amino G Acid) are compared for use in soil water tracing. Severe limitations are evident, but practical applications are possible. Background fluorescence, adsorption, desorption, pH and other non-adsorptive effects are reviewed in the contexts of soil column work and field tracing of soil water. Lissamine FF and Amino G Acid are to be preferred for soil column work because of their lower adsorption; Rhodamine WT exhibits higher adsorption but is useful in field situations where organic fluorescence backgrounds are high. Semi-quantitative work may be undertaken in soil columns once a priming and flushing procedure has been adopted.