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1.
Turbidity measurements by foreward scattering nephelometer have been regularly conducted on the north basin of Lake Lugano (Switzerland/Italy) since September 1992. In order to determine mass concentrations from these data, both, in-situ and laboratory calibration experiments have been performed in November and December 1992 on suspended matter of the hypolimnion. Results show:
- Mass concentration/turbidity ratios are different in the two turbidity zones examined due to variation in the optical signature of the suspended matter.
- Laboratory calibrations using suspended matter originating from the water depths of interest give representative results provided that physical and chemical alterations occuring during the particle transfer process remain negligible.
2.
Liparitic volcanism is a typical feature of the orogenic phase giving rise to the Kazakhstan, Middle Asia and Caucasus folded systems. The main characteristics of the liparitic volcanism common to these three regions are the following:
- Geo-structural zonation of the volcanic structures.
- Dismembered Moho surface within the volcanic structures.
- Synchronous, yet independent evolution of liparitic and andesitic volcanisms.
- Ignimbritic character of the liparitic volcanism.
- Lateral petrochemical zonation with some features common to the liparitic and andesitic rock series.
3.
László Szarka 《Surveys in Geophysics》1987,9(3-4):287-318
The paper gives a summary of geophysical aspects of man-made electromagnetic noise in the Earth as follows: - EM distortion effects of man-made constructions below and over the Earth's surface defined as ‘passive-noise’, - field observation of EM disturbances due to ‘active’ man-made sources, - EM source mechanism of some important active sources from a geophysical point of view, - efforts in order to improve the signal-to noise ratio by instrumental, methodological and dataprocessing ways, - application of man-made EM noise for geophysical prospecting. The paper is based on world-wide EM noise survey studies published mainly in geophysical journals. 相似文献
4.
J. Keller 《Bulletin of Volcanology》1969,33(3):942-959
Rhyolitic pumice deposits on some East Aegean Islands are the remnants of a tuff sheet which covered formerly more than 2500 km2. The rhyolites originated by melting of granitic crustal rocks. The petrological properties leading to this conclusion are as follows: -mineralogical composition of the pumice being 60 wt % of glass and 40 % of relictic granitic minerals (quartz, plagioclase, potash feldspar, biotite) in «phenocrysts» up to 1 cm Ø. -phenomena of strong corrosion, resorption and melting of all light colored «phenocrysts» in the rhyolitic pumice. -mineralogical and chemical identity between pumice and granitic xenolites found in great quantity in the pumice tuff. -structurally transitional types between pumice and the granites in different state of melting. -eutectic composition of the pumice glass for a pressure of 2 kb. 相似文献
5.
René Gächter 《Aquatic Sciences - Research Across Boundaries》1987,49(2):170-185
Data obtained from Lakes Baldegg and Sempach, two artificially mixed and oxygenated lakes, show that it is technically possible to significantly improve redox conditions, even in large eutrophic lakes. It is discussed why - the well-known release of phosphorus from anoxic sediments does not necessarily result from an abiotic reduction of phosphorus containing iron compounds, - net phosphorus retention by sediments is not simply linearly related to the phosphorus content of a lake, - artificial oxygenation of a previously anoxic hypolimnion does not permanently increase phosphorus retention capacity of lake sediments. From this it is concluded that improvement of hypolimnic redox conditions by lake internal measures such as aeration or oxygenation may accelerate the rate of recovery induced by a reduction of the external phosphorus loading, but that oxygenation per se will hardly be able to cause a reduction of trophic state. 相似文献
6.
J. L. Cheminee 《Bulletin of Volcanology》1970,34(1):168-195
Concentrations in uranium, thorium and potassium were determined by gamma spectrometry in more than 100 samples of volcanic rocks from the material obtained during the French-Italian expedition in Dankalia (Afar-Ethiopia) (December 1967 – February 1968). These samples were taken from two geographically distinct areas: in the Erta Ale range, for basalts, K: 0,5%, U: 1,3 ppm, Th: 3,3 ppm, Th/U: 2,6. for alkaline rhyolites, U: 4,1 ppm, K: 2,3%, Th: 15,2 ppm, Th/U: 3,7. in the Pierre Pruvost massif, for acid rocks, K: 3,9%, U: 3,6 ppm, Th: 13,5 ppm, Th/U: 3,8. in the Borawlu centre, K: 2,8%, U: 4,6 ppm, Th: 14,7, Th/U: 3,4 for the rhyolites, K: 0,6%, U: 0,9 ppm, Th: 3,1 ppm for the basalts. on the Ethiopian high lands, for the Adigrate basaltic trap rocks, K: 0,6%, U: 0,6 ppm, Th: 1,1 ppm, Th/U: 1,7 and for the Axum zone of phonolitic pinnacles, K: 3,9%, U: 2,7 ppm, Th: 14,9 ppm, Th/U: 4,9. The Th/K and U/K ratios are particularly high compared with the usual data, except for the Pierre Pruvost massif which seems to be different from the others. The difference of Th/U ratios for basic rocks and acid rocks is meaningful. For the magma which gave the volcanism of the studied area, one can think of an evolution more especially connected with transfers of volatile elements. The strong correlations existing between potassium, uranium and thorium probably indicate the presence of groups which are distinct from a geochemical point of view in the Dankalia lavas. 相似文献
- the danakile depression (Erta Ale range, Pierre Pruvost massif, Alayta, Afdera, Borawlu).
- Ethiopian high lands (Adigrate — Axum).
Dash
7.
F. Sivardière T. Castelle G. Guyomarc'h L. Mérindol L. Buisson 《Surveys in Geophysics》1995,16(5-6):729-741
For two years, three French and Swiss laboratories have been making field observations and measurements on two high altitude slopes in a Northern French Alps site. The aim of this work is to study the functioning of the avalanche sites which, in their starting zones, undergo snow-transport by wind. The experimental site is located in the French Alps, at 2,800 m, above Grenoble. It is an open area, equipped with an automatic meteorological station and an altitude laboratory. The two slopes that are studied face East. One of them is artificially released but the other has a natural avalanche activity. The investigations concern: -snow deposition in avalanche starting zones; -temporal evolution of the snowpack characteristics; -avalanche release. For the field observations and measurements, continuous recording of the meteorological conditions on the site, photogrammetrical techniques and two snow depth profiles, as well as stratigraphical snow profiles and video are used. The computer modeling is based on existing computer models developed by the CEMAGREF-Nivologie (ELSA) and the CEN/Météo-France (SAFRAN-CROCUS-MEPRA), which analyse the snowpack and its stability. The field observations and measurements aim at improving snow-transport by wind modeling modules, in order to improve their whole analysis. 相似文献
8.
The Erta Ale range is the main volcanic unit in the Danakil rift. It is located along the axis of the northern part of the Depression, in a zone clearly related to the Red Sea rift. The detailed study of the tectonics, volcanism and petrographic succession of the whole range allows one to draw the following conclusions.
- A compl3te, tectonically controlled evolution is observed in the subaerial volcanism from simple fissure activity, to small shield volcanoes built along open fissures, and to more complex central volcanoes. The emitted products form a complete differentiation series from basalts to rhyolites, with a remarkably regular volume decrease from basic to silicic terms.
- The close relationships existing between petrological and volcanological evolution suggest that the magma fractionation has been realized at relatively shallow depth, at the emplacement level of magmatic reservoirs. The importance of a time factor in the differentiation processes in volcanic conditions is clearly stressed.
- All collected data strongly support the subcrustal origin of the whole volcanic series and the hypothesis of crustal separation with formation of new oceanic crust along the axis of the Northern Danakil Depression.
9.
Four volcanic units have been distinguished on the islanf of Fayal. In order of decreasing age, these are: the eastern rift, and products of the activity preceding the collapse of the caldera visible at the summit of the stratovolcano, characterized by an alkaline series: basalt-hawaiite-mugearite-trachyte; the products of the explosive and postcaldera activity where only evolved lavas occur (benmoreites and trachytes); the recent basaltic activity of the Horta region; the western fissural activity — recent and historical. The two last units are characterized by exclusively basaltic, frequently picritic, eruptions. The lava groups cannot be distinguished by chemical criteria and have thus been treated as a single suite. Ninety samples have been analysed by X-ray fluorescence, and the mineralogy of 6 representative specimens has been determined by microprobe. The data were used to work out the evolution of the lava. The series is shown to have been produced by crystal fractionation under moderate water pressure from an alkali basalt. Moderate fractionation of amphibole during the last stages allow the liquids to remain weakly undersaturated from initial basalts until final trachytes. Mineralogical and chemical diversity between the most evolved lavas, benmoreites and trachytes, is an evidence of the strong influence ofpH2O and/orfO2 on the composition of such residua. 相似文献
10.
Steam samples from six wells (Colombaia, Pineta, Larderello 57, Larderello 155, Gabbro 6, and Gabbro 1) in a south to north section across the Larderello geothermal field have been analyzed for inorganic and hydrocarbon gases and for oxygen-18 and deuterium of steam. The wells generally decrease in depth and increase in age toward the south. The steam samples are generally characterized by
- Total gas contents increasing south to north from 0.003 to 0.05 mole fraction;
- Constant CO2 (95±2 percent); near constant H2S (1.6±0.8), N2 (1.2±0.8), H2 (2±1), CH4 (1.2±1), and no O2 in the dry gas;
- Presence of numerous, straight chain and branched C2 to C6 hydrocarbons plus benzene in amounts independent of CH4 contents with highest concentrations in the deeper wells;
- Oxygen-18 contents of steam increasing south to north from ?5.0‰ to ?0.4‰ with little change in deuterium (?42±2‰).
- Decreasing gas contents with amount of production because the proportion of steam boiled from liquid water increases with production;
- Synthesis of CH4 from H2 and CO2 with CO2 and H2 produced by thermal metamorphism and rock-water reactions;
- Extraction of C2 to C6 hydrocarbons from rock organic matter;
- Either oxygen isotope exchange followed by distillation of steam from the north toward the south (2 plates at ～220°C) or mixture of deeper more-exchange waters from the north with shallow, less-exchanged recharging waters from the south.
11.
Microearthquake digital data collected at Campi Flegrei during the recent (1982–1985) ground uplift episode have been analyzed in order to infer source and medium seismic properties. The main results obtained from these analyses are:
- Hypocenter distribution and the size of the seismic zone do not change with time and do not depend on the ground uplift rate. Events occurred clustered in time with no simple causal relations between the cluster occurrences and their energy.
- Anelastic attenuation does not depend strongly on frequency, showing a constant pattern at high frequencies. The observed values of low and high frequency attenuation, due to the short source receiver distances, do not seriously affect the spectral content of signals radiated by the sources.
- A constant Brune stress drop pattern (～4–5 bars) as a function of seismic moment is observed. This indicates that the manner of fracturing is almost independent on magnitude of earthquakes (hypothesis of self-similarity (Aki, 1967)). Seismic processes in a prefractured medium can explain the observed small stress drop values.
- Focal mechanisms from moment tensor estimates show that radiation patterns are mostly well interpreted in terms of double couple source models.
- The scaling of peak ground motion parameters (A max andV max vs seismic moment) can be explained by an ω2 source model (constant stress drop) multiplied by an exponential function with a small decay parameter, which takes into account the measured attenuation.
12.
Federico Von Giovanoli André Lambert 《Aquatic Sciences - Research Across Boundaries》1985,47(2):159-178
Results obtained by means of an ultrasonic current meter in the plume of the Rhone river are summarized as follows:
- Currents of Rhone river water entering the lake were clearly discernible up to a distance of about 1 km from the river mouth. The interflow was observed at depth of 10 to 30 m.
- Interflow velocities decreased with increasing distance from the river mouth: from 40cm/s at a distance of 350 m to about 15 cm/s at 1 km.
- Short-term variations of current velocities and directions documented the highly turbulent nature of the interflow.
- The entering river water (inflow direction to the NNW) interfered with a persisting northeastward current of the lake water. At a distance of 1–2 km from the mouth the interflow gradually assumed the same direction, possibly due to deflection by Coriolis forces.
- Current velocities showed considerable variations within a time scale in the order of hours at the same measuring position. The reasons for these fluctuations remain unclear. Possible causes may be lateral oscillations of the entering river water or its deviation by river mouth bars during periods of reduced river discharge. Variations of the discharge alone cannot explain these current fluctuations.
13.
For most previous geomagnetic surveys, the time variations of the observatory closest to the site of observation have been used for reduction. The accuracy of repeat station measurements depends upon the distance between the station and the observatory. Nowadays, the requirements for the accuracy of repeat station measurements are much higher, especially with respect to local secular variation anomalies. On the other hand, transportable variograph stations are available, by means of which time variations can be recorded closer to the station site. The reduction steps for this method are: - the stability of the base-line values of the variographs; - the question as to what degree a quiet night value represents the normal value at that time (e.g. influence of aD st field and/or other fields). A repeat station survey of the Federal Republic of Germany was carried out in 1982. During the same time, eleven stations recorded the time variations in that area. We discuss the aforementioned aspects by way of an example taken from this survey. 相似文献
- Reduction of measured values to the base-line of the nearby variograph station;
- Computation of the nearest quiet night value using the baseline of the variograph;
- Computation of the difference between this value and the corresponding one at the observatory.
14.
Some trace element data for volcanic rocks found at different levels, from Tertiary to Holocene, in south-eastern Sicily (Iblean Plateau and Mt. Etna) are presented and discussed in the present paper in order to better the information about the origin and relationships of the various rock types. Four groups of volcanic rocks have been recognized on the basis of their major element chemistry: 1) low-K tholeiites, 2) associated alkali basalts to nephelinites of the Iblean Plateau (Upper Pliocene to Lower Pleistocene), 3) the basal subalkaline lavas of Mt. Etna, and 4) the alkalic suite rocks that make up the bulk of the volcano. The distribution of Rb, Sr, Ni, Cr, Co, Cu, REE, Th and Sc suggests:
- an origin of the Iblean magmas by a different degree of partial melting of a Rb-poor and possibly slightly hetereogeneous mantle;
- quite distinct source compositions for the Etnean magmas, relative to those of the Iblean area, on the basis of their Rb and Sr contents;
- an origin of the alkalic rocks of Mt. Etna from independently generated magma(s) rather than by crystal fractionation of the Etnean subalkaline magmas or of a magma having the geochemical features of the Iblean alkali basalts; evidence for this is given by the distribution features of the incompatible elements showing an origin for these rocks from compositionally different parent magmas and/or an evolution under widely variable environmental conditions;
- the primary character for the chemical differences observed in some of the Etnean subalkaline rocks that can be accounted for by different physico-chemical conditions at their source rather than by crystal fractionation processes.
15.
Weiping Qin 《地震科学（英文版）》1992,5(1):177-185
This paper gives a complete commentary on some popular gradings which based on the 2×2 contingency table, for one—dimensional seismologic prediction. It contains:
- In view of the statistical correlation, the Wallen gradingV=√QS is the most equitable one amomg all gradings.
- Each one of the three gradings: Zhenchao Gu gradingS, Obuhov gradingQ and Shaoxie Xu gradingR, has its own inadequacy although they are so easy for use.
- A set of gradings can be derived fromV. The harmonic mean ofS andQ, H(S,Q) and the Hedike gradingS H are the members of this set. The order of some popular gradings are given in Theorem 5. 3.
- In view of the measure of the overlapping part a gradingW is introduced. Another set of gradings may be derived from it. The index of efficiencyh is the severest one among this set.
16.
Research on the principle and methodology of seismic zonation 总被引：1，自引：0，他引：1
Based on the cognizance of the temporal-spatial inhomogeneity of seismicity in North China, adopting the results of earthquake prediction in the past two decades and the currently used methods of seismic hazard analysis, and after some zonation trials in North China, some improvements on the zonation principle and methodology were made:
- Seismic zones were taken as statistic units where seismicity parameters were obtained. Tendency analysis was introduced. Earthquake annual average occurrence rates were estimated corresponding to the seismicity level in the future period;
- Average annual earthquake occurrence rates for a given magnitude interval of a specific seismic zone were assigned to potential sources considering the relative risk level among these sources. Thus, the risk of great earthquakes can be estimated.
- The probabilistic spatial distribution function under the condition of magnitude interval was suggested to reflect the temporal and spatial inhomogeneity of seismicity.
- An orientation function in the seismic hazard analysis model was adopted, which reflects the real condition of earthquake foci in China.
17.
The spontaneous and evoked activity of electroreceptors were electrophysiologically studied. The results are:
- The spontaneous discharge rate ranged from 15 to 85 imp/s with a mode of 50 imp/s for 126 organs of 18 animals.
- By analysis of periodic histograms and interspike interval histograms of responses to sinusoidal electric stimulations, the frequency response characteristic was determined. The frequency response curve shows a band pass type, the band width ranged from 5 Hz to 30 Hz and the best frequency is around 15 Hz.
- The thresholds of responses for 47 organs were measured by injection of sinusoidal current into the organs. The threshold values were less than 0.1nA (61µV/cm) for 35 organs (74%), and less than 0.01nA (6.1 µV/cm) for the rest of 9 organs (19%).
18.
Characterization of and correction for cultural noise 总被引：2，自引：0，他引：2
Andreas Junge 《Surveys in Geophysics》1996,17(4):361-391
Surveys of time varying electromagnetic fields result in time series consisting of signals and noise, the latter defined as that part of the data which cannot be explained by a theory. Man-made contributions to noise can be subdivided into active and passive sources and are complex in character. As Szarka has treated this topic extensively in a recent review paper (Szarka, 1988), only a few further examples are presented here. Following discussion of noise correction in transient electromagnetic investigations which consists mainly of sophisticated stacking and filter procedures, several aspects of its correction in magnetotelluric and geomagnetic depth sounding data are considered. These include:
- The methods of treatment of single time series in the presence of visible noise—its detection, removal and sometimes replacement by data predicted from undisturbed intervals.
- The investigation of time series interrelations. This is mainly coherence based and—if possible—takes advantage of remote reference techniques.
- The examination of the statistical properties of the time series by regression analysis. This leads to the weighting of time segments of data in order to achieve unbiased and minimum variance estimates based on identically and independently Gaussian distributed residuals.
- The application of constraints. These can further improve the estimates' quality.
- The use of simultaneously recorded multistation data. This can contribute remarkably to noise suppression as well as to the treatment of non-uniform source fields.
- Leveraging and confidence limits. Problems relating to the former have not yet been solved satisfactorily while the Jacknife method seems to be an easy way of determining the latter.
19.
Andrea R. Ventling-Schwank Hans Jürg Meng 《Aquatic Sciences - Research Across Boundaries》1995,57(1):1-13
Using an acoustic system in a 9 m deep enclosure, the daily vertical distribution patterns of whitefish larvae were studied from hatching to the age of two months. Four patterns of daily vertical distribution and migration were observed in accordance to different developmental stages:
- Newly hatched larvae dispersed in the enclosure during the day and congregated at the water surface at night.
- After 2 weeks of age larvae stayed close to the water surface during day and night.
- At 15 to 18 mm length, larvae showed distinct vertical migration at dawn and dusk, they stayed close to the surface during the day and dispersed at night.
- At 28 mm length the depth pattern was reversed. These fish frequented greater depths during the day than at night.
20.
G. Budetta D. Condarelli M. Fytikas N. Kolios G. Pascale A. Rapolla E. Pinna 《Bulletin of Volcanology》1984,47(3):447-466
A program of geophysical research was carried out as a preliminary stage of study of the Santorini volcanic group. This area is of remarkable geothermal and volcanological interest, and the definition of a volcanological structural model is the starting point for an understanding of the local geodynamic processes. Gravity, magnetic and geoelectrical data proved that:
- the core of the volcanic edifice consists of a sedimentary-metamorphic basement;
- the basement is tectonically disturbed and a linear tectonic system produces a graben-type structure in the middle part of the area.