Analysis of earthquakes in the distance range 40–70° and inferred lower mantle structure

About fifty earthquakes in the distance range 40–70° and azimuthal range 45–120° from the Celebes, Philippines, Mariana and Kurile Island regions, and recorded at Gauribidanur seismic array in southern India, were used in the present study. Measurements on slowness and apparent azimuths were made on the first 30 s of the short period P-wave trains using an adaptive processing technique. Analysis of this data set has revealed no strong evidence for any triplications in the travel-time curve over the ranges in question. The P-wave velocity increases continuously with an almost uniform gradient below 1000 km depth range and is in very close agreement with the JB model. Almost all the observed slowness values of the events were anomalously low and consistent suggesting that they are caused by some azimuthal dependent structure near the array.     

Measurement of apparent velocity and azimuth of seismic signals recorded at an array

A set of computer programs was written which enables one to determine automatically, the apparent velocity and azimuth of any portion of the seismic wave-train recorded at various seismic arrays. All that is required to use these programs is that the raw data be available on digital tape and that the user have access to any modern computer. The programs are written in Fortran IV and make use of the adaptive processing method whereby the arrival times of the wavefront at each sensor are accurately determined by cross-correlating the observed wavelet of interest with the corresponding wave on the beam trace. The new arrival times are then used to create a new and improved beam and the whole operation is repeated in an iterative manner until convergence takes place.     

Problems and discussion on Precambrian series of the Hesperic Massif (Western Iberian Peninsula)

In this paper, different Precambrian series of Hesperic Massif have been described, using some data taken from different bibliography and unpublished data by the authors. The relation among them have been discussed and also their problems stated.These Precambrian series are forming the anticlinorium nuclei of hercynian structure. The incomplete understanding of these series, as well as their occurrence in distant and isolated outcrops, give place to doubtful interpretations when traying to establish the stratigraphical sequence and he correlation among the different series.The discussion implied from the global study of these problems permit us, provisionally, to establish a general stratigraphy and a possible correlation among different units.All these series constitue an Upper Precambrian; within it three groups have been differentiated: lower group consisting of basic and ultrabasic complexes; intermediate group with a very important acid volcanism and derivated rocks, and finally upper group where pelitic schists and greywackes prevail.

---

Zusammenfassung Anhand von bereits bestehender Literatur und noch unveröffentlichten Forschungsergebnissen der Verfasser sollen die verschiedenen präkambrischen Serien des Hesperischen Massivs beschrieben, ihre Beziehung zueinander erörtert und die durch sie auftretenden Probleme behandelt werden. Alle diese Serien bilden Sattelkerne in den herzynischen Strukturen.Da wir bis heute nur über unvollständige Kenntnisse dieser Formationen verfügen und aufgrund ihres Vorkommens an weit voneinander entfernt liegenden Orten, treten bei dem Versuch, ihre Stratigraphie festzulegen und eine Wechselbeziehung zwischen den verschiedenen Serien herzustellen, eine Reihe von Problemen auf.Betrachtet man diese Probleme als Gesamtkomplex, ist es möglich, eine vorläufige Gesamt-Stratigraphie sowie eine wahrscheinliche Wechselbeziehung zwischen den verschiedenen Einheiten aufzuzeigen.Alle Serien gehören in das jüngere Präkambrium, das in drei Teile aufgegliedert werden kann: der unterste Teil wird aus basischen und ultrabasischen Komplexen gebildet, der mittlere Teil setzt sich aus bedeutenden sauren Vulkanismen und daraus hervorgegangenem Gestein zusammen, während der oberste Teil vor allem aus pelitischen Schiefern und Grauwacken besteht.

---

Resumen Se describen con datos bibliográficos e inéditos de los autores las distintas series precámbricas del Macizo Hespérico, discutiendo las relaciones entre ellas y planteando su problemática.Estos precámbricos forman núcleos anticlinoriales de las estructuras hercínicas. El incompleto conocimiento que hasta hoy se tiene de estos terrenos y su afloramiento en zonas distantes y aisladas, da lugar a problemas de interpretación, al intentar establecer una estratigrafía y una correlación entre las diferentes series.La discusión que se plantea al estudiar estos problemas globalmente, permite establecer provisionalmente una estratigrafía de conjunto y la posible correlación entre las diferentes unidades.Todas estas series constituyen un Precámbrico Superior en el que se han podido diferenciar 3 conjuntos:Uno inferior constituido por complejos básicos y ultrabásicos; otro medio con importantes volcanismos ácidos y rocas derivadas; y otro superior formado por esquistos pelíticos y grauvacas predominantemente.

---

Résumé Par des données bibliographiques et inedites les auteurs décrivent les differentes séries precambriènnes du Massif Hésperique, en discutant leurs rapports et en établissant leurs problèmes.Toutes ces séries se situent aux coeurs des anticlinaux dans les structures hercyniennes; leur connaissance insuffisante, aussi bien que leurs affleurements distants et isolés, causent des problèmes d'interprétation dés que l'on tente d'établir une stratigraphie générale et une corrélation entre les différentes séries.La discussion générale de ces problèmes nous a permis de définir une stratigraphie d'ensemble et la possibilité d'une corrélation des différentes unités.Toutes ces séries appartiennent au Précambrien Supérieur, qui comprend trois ensembles: Un ensemble inférieur formé de complexes basiques et ultrabasiques, un autre intermédiaire avec volcanites acides et roches dérivées et, finalement, un ensemble supérieur pélitique-grauvackeux.

---

. . .- , , , . , , . , : ; , , qa .

     

Gold mineralisation and alteration of Penakacherla schist belt, India, constraints on Archaean subduction and fluid processes

In the Dharwar Craton, southern India, gold deposits are found mostly along the six arcuate shear zones passing through late Archaean greenstone belts (2.7 Ga). One such shear zone complex extends for about 400 km within and along the Ramagiri–Hungund schist belt. The Penakacherla sector of this shear zone is excellently exposed, enabling a detailed investigation of synorogenic gold mineralisation and its relationship to associated hydrothermal alteration.Metamorphism and deformation under NE–SW compression associated with Archaean subduction processes converted mafic volcanic rocks into amphibolites and intermediate to felsic volcanic rocks into quartz mica schists. Continued compression generated a 50–100-m-wide shear zone complex consisting of mafic phyllonites. Advection of hydrothermal fluids through this shear zone and reaction between fluids and the mafic phyllonites resulted in a silicified, K-metasomatic assemblage mainly consisting of chlorite, amphibole, K-mica, plagioclase, ankerite, quartz, Fe-oxides, pyrite, chalcopyrite and arsenopyrite. Networks of quartz and carbonate veinlets, a few millimeters to a few centimeters thick, formed along the foliation planes giving rise to microscopic alteration envelope, in which individual veinlet systems are merged into one another to form a composite alteration system. Gold is found within these quartz veinlets, mafic phyllonites and at their mutual contacts.Hydrothermal fluids have modified the primary major, minor, trace and LREE compositions of host rocks such that their mutual behaviour became non-systematic. Some HFSE and HREE also show minor mobility but the overall REE pattern generally resembles that of the precursor mafic volcanic rocks. Mass and volume loss/gain by Si and Ca has made significant impact on Al, Ti and Zr abundances, which are generally immobile during hydrothermal alteration. However, element pairs such as Zr–Hf, V–Sc and Nb–Ta maintain primary inter-element ratios, although their absolute abundances are drastically diluted. Similarly, ΣREE in highly silicified and carbonatised samples are reduced, but patterns remain similar to those of relatively least altered mafic phyllonites with (La_N/Yb)_N between 1 and 3. In some samples, LREE enrichment is observed elevating in (La_N/Yb)_N from 3 to 11. Pathfinder elements and base metals such as As, Cd, Cu, Pb, Zn and Sb have been added along with the Au and Ag.δ¹³C of carbon varies from −16‰ to −21‰ suggesting a biogenic origin, whereas coexisting pyrite δ³⁴S ranges from 1‰ to 3‰, pointing towards the involvement of magmatic or average crustal sulphur. Overall concentrations of K, Rb, Sr, Ba, Nb, Ta, Ti, Cs, Cr, Co, V, Y and Sc and many of the ratios such as K/Rb, La/Sc, La/Yb indicate that metamorphism, devolatilisation and dehydration of an oceanic subducting slab might have partially contributed the mineralising fluids and generated the alteration assemblage observed in the host rocks. Fluid sources were mantle and greenstone belt dehydration and devolatilisation generating observed compositional and alteration diversity.     

Depth Estimation from Gravity Data Using the Maximum Entropy Method (MEM) and the Multi Taper Method (MTM)

The depth determination from the gravity data in frequency domain is carried out using the classical fast Fourier transform (FFT) method utilizing scaling properties of ensemble of anomalous source. The problem of calculating power spectrum from the FFT is well described in the literature. Here, the application of other high-resolution methods of power spectrum calculation, such as maximum entropy method (MEM) and multi-taper method (MTM) are explored to estimate depth to anomalous sources. At the outset, the FFT, the MEM and the MTM are tested on synthetic gravity data, generated for different types of synthetic models and then all these methods are applied to the field gravity data of the Bengal basin. The MTM with scaling is found to be superior for providing the detailed subsurface information rather than the MEM and the FFT methods in the case of synthetic as well as field examples.     

Groundwater irrigation and its implications for water policy in semiarid countries: the Spanish experience

Over the last decades, groundwater irrigation has become commonplace in many arid and semiarid regions worldwide, including Spain. This is largely a consequence of the advances in drilling and pumping technologies, and of the development of Hydrogeology. Compared with traditional surface water irrigation systems, groundwater irrigation offers more reliable supplies, lesser vulnerability to droughts, and ready accessibility for individual users. Economic forces influence the groundwater irrigation sector and its development. In Spain's Mediterranean regions, abstraction costs often amount to a very small fraction of the value of crops. In the inner areas, groundwater irrigation supports a more stable flow of farm income than rainfed agriculture. The social (jobs/m³) and economic (€/m³) value of groundwater irrigation generally exceeds that of surface water irrigation systems. However, poor groundwater management and legal controversies are currently at the base of Spain's social disputes over water. A thorough and transparent assessment of the relative socio-economic value of groundwater in relation to surface water irrigation might contribute to mitigate or avoid potential future conflicts. Enforcement of the European Union's Water Framework Directive may deliver better groundwater governance and a more sustainable use.

---

Resumen Durante las últimas décadas, la irrigación con agua subterránea se ha vuelto común en muchas regiones áridas y semiáridas alrededor del mundo, incluyendo a España. Ésta es en gran medida una consecuencia de los adelantos en las tecnologías de perforación y bombeo, y del desarrollo de la Hidrogeología. Comparada con los sistemas tradicionales de irrigación con agua superficial, la irrigación con agua subterránea ofrece suministros más fiables, la vulnerabilidad es menor a las sequías, y posee accesibilidad inmediata para los usuarios individuales. Las fuerzas económicas influyen el sector de irrigación con agua subterránea y su desarrollo. En las regiones mediterráneas de España, los costos de extracción suman a menudo una parte muy pequeña del valor de las cosechas. En las áreas internas, la irrigación con agua subterránea constituye un flujo más estable de ingresos para la granja, que la agricultura dependiente del agua lluvia. El valor social (empleos/m³) y económico (€/m³) de la irrigación con agua subterránea, generalmente excede a aquél con sistemas de irrigación de agua superficial. Sin embargo, la gestión pobre del agua subterránea y las controversias legales están actualmente en la base de las disputas sociales en España acerca del agua. Una evaluación completa y transparente del valor socio-económico relativo de agua subterránea respecto a la irrigación con agua superficial, podría contribuir mitigar o evitar los conflictos potenciales del futuro. La entrada en vigor del Marco Reglamentario de Agua de la Unión Europea, puede conllevar a una administración mejor del agua subterránea y a un uso más sostenible.

---

Résumé Depuis les dernières décennies, l’irrigation avec l’eau souterraine est devenue commune dans plusieurs régions arides et semi-arides, incluant l’Espagne. Ceci est largement une conséquence due à l’avancement aux technologies de forages et des pompages, et au développement de l’Hydrogéologie. Comparé avec des systèmes traditionnels d’irrigation utilisant l’eau de surface, l’irrigation avec l’eau souterraine offre une technique d’alimentation plus fiable, une vulnérabilité à la sécheresse moins grande, et une accessibilité plus aisée pour chaque utilisateur. Les forces économiques influencent le secteur de l’irrigation par l’eau souterraine et son développement. Dans les régions de l’Espagne Méditerranéenne, les coûts d’exploitation représentent toujours une petite fraction de la valeur des cultures. Dans les régions intérieures, l’irrigation par l’eau souterraine supporte une agriculture plus stable et continue qu’une agriculture reposant sur l’eau de pluie. La valeur sociale (emploi/m³) et économique (€/m³) de l’irrigation avec l’eau souterraine, excède généralement celle des systèmes d’irrigation avec l’eau de surface. Néanmoins, des gestions pauvres de l’eau souterraine et des controverses légales sont couramment à la base de disputes sociales sur l’eau. Un bilan transparent et minutieux des valeurs relatives socio-économiques de l’eau souterraine en relation avec l’eau de surface d’irrigation, devrait contribuer à éviter de potentiels et futurs conflits. Un renforcement de la Directive Cadre de l’Union Européenne devrait apporter une meilleure gouvernance et un usage plus durable.

     

Spectral models for estimation of chlorophyll content, growth and yield of wheat crop

Field experiments were conducted during 1998–99 and 1999–2000 at research farm of the Department of Agricultural Meteorology, CCS Haryana Agricultural University, Hisar. Five wheat cultivars: WH 542, PBW 343, UP 2338, Raj 3765 and Sonak were sown on 25^th November, 10^th and 25^th December with four nitrogen levels viz., no nitrogen. 50, 100 and 150% of recommended dose. Leaf area index, dry matter at anthesis, final dry biomass and grain yield were recorded in all the treatments. Chlorophyll and wax contents of wheat leaves were estimated at different growth stages. Multiband spectral reflectance was measured using hand-held radiometer. Spectral indices such as simple ratio, normalized difference, transformed vegetation index, perpendicular vegetation index and greenness index were computed using the multiband spectral data. Values of all the spectral indices were maximum in 25 November sown crop with maximum dose of nitrogen (180 kg N ha^-1). PBW 343 showed higher values of all the spectral indices in comparison with other cultivars. The spectral indices recorded during maximum leaf area index stage were correlated with crop parameters. Using stepwise regression, empirical models for chlorophyll, leaf area index, dry biomass and yield prediction were developed. The ’R²’ values of these models ranged between 0.87 and 0.95.     

Quasi-static deformation of a layered half-space by a long strike-slip fault

Theoretical expressions for the surface displacement and shear stress caused by a long strike-slip dislocation in an elastic layer overlying an elastic half-space are derived and the correspondence principle is used to obtain the quasi-static response when the half-space is Maxwell-viscoelastic. Variation of the surface displacement and shear stress with horizontal distance is studied for various times and vertical extents of the fault. It is seen that the quasi-static response differs significantly from the corresponding elastic response.     

Inversion of gravity and magnetic anomalies over some bodies of simple geometric shape

The general expression for gravity and magnetic anomalies over thin sheets and sloping contacts may be expressed as a polynomial of the formFx ²+C₁Fx+C₂F+C₃x³+C₄x²+C₅x+C₆. The initial parameters of the source are obtained from the coefficientsC ₁, C₂,..., C₆ which may be solved by inverting a 6×6 matrix. The initial parameters are modified by successive iteration process using the difference formula until the root mean square error between the observed and calculated anomalies is a minimum. The regional background which may be in the form of a polynomial is estimated by the computer itself. This method is applied on a number of field anomalies and is found to yield reliable estimates of depth and other parameters of the source.