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111.
Summary. Lg -wave observations at NORSAR from a sequence of explosions straddling the Central Graben in the North Sea, show that the phase is almost extinguished by passing through this structure. For models of the graben structure, based on seismic refraction experiments, with crustal thinning beneath a zone of thickened sediments, numerical modelling of Lg propagation shows very poor transmission. The inclusion of attenuation simulating the effects of scattering from faults and other complex structures further diminishes the transmittivity. The theoretical effect of a crustal pinch is to redistribute S energy over a wide range of groups velocities, a pattern that fits well with the observations.
Three components recordings at NORSAR of explosive charges fired in water covering a wide range of azimuths, show significant transverse components to the seismograms. The transverse energy builds up with travel time and for Lg is of the same order as the vertical component. These results are consistent with the theoretical prediction of progressive net transfer of energy from Rayleigh to Love modes as the wavetrain propagates through a three-dimensionally heterogeneous medium. 相似文献
Three components recordings at NORSAR of explosive charges fired in water covering a wide range of azimuths, show significant transverse components to the seismograms. The transverse energy builds up with travel time and for Lg is of the same order as the vertical component. These results are consistent with the theoretical prediction of progressive net transfer of energy from Rayleigh to Love modes as the wavetrain propagates through a three-dimensionally heterogeneous medium. 相似文献
112.
P.L. Dharmapriya Sanjeewa P.K. Malaviarachchi Leo M. Kriegsman K. Sajeev Andrea Galli Y. Osanai N.D. Subasinghe C.B. Dissanayake 《地学前缘(英文版)》2017,8(5):1115-1133
Here we report the occurrence of garnet porphyroblasts that have overgrown alternating silica-saturated and silica deficient microdomains via different mineral reactions. The samples were collected from ultrahigh-temperature (UHT) metapelites in the Highland Complex, Sri Lanka. In some of the metapelites, garnet crystals have cores formed via a dehydration reaction, which had taken place at silica-saturated microdomains and mantle to rim areas formed via a dehydration reaction at silica-deficient microdomains. In contrast, some other garnets in the same rock cores had formed via a dehydration reaction which occurred at silica-deficient microdomains while mantle to rim areas formed via a dehydration reaction at silica-saturated microdomains. Based on the textural observations, we conclude that the studied garnets have grown across different effective bulk compositional microdomains during the prograde evolution. These microdomains could represent heterogeneous compositional layers (paleobedding/laminations) in the precursor sediments or differentiated crenulation cleavages that existed during prograde metamorphism. UHT metamorphism associated with strong ductile deformation, metamorphic differentiation and crystallization of locally produced melt may have obliterated the evidence for such microdomains in the matrix. The lack of significant compositional zoning in garnet probably due to self-diffusion during UHT metamorphism had left mineral inclusions as the sole evidence for earlier microdomains with contrasting chemistry. 相似文献
113.
CCD photometry data of the T Tauri star H 187 are presented. They show that a new eclipse of this star began at the end of
2004. Since only one eclipse of this star has been observed previously with a duration of 3.5 years, our data indicate that
the eclipses of this object are periodic with a period P=4.9 years between eclipses. Thus, in terms of the absolute duration
of the eclipses and in terms of their relative length as a fraction of the period, H 187 is one of the most exotic objects
in the sky.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 529–534 (November 2005). 相似文献
114.
115.
A model is proposed that shows the relation of the block structure of the crust and earthquake sources (Sadovskii, 1979; Rodionov, 1979, 1984, 1994; Bugaev, 1999, 2011, 2014, 2015). The model can formalize how to assess the prediction of seismic regime parameters depending on the elastic limit and conditions and rate of deformation of the Earth’s crust. The spent nuclear fuel repository site in Olkiluoto (Finland) and a site in the area of the Krasnoyarsk Mining and Chemical Combine are considered as examples. It is demonstrated that the parameters of the prediction graphs limit the location of the points of magnitude repeatability graphs calculated for a site based on samples of earthquakes in the area according to different authors. This makes it possible to recommend predictive assessment of seismic regime parameters for stability monitoring of the seismic regime and safety analysis of a geological environment’s insulation properties for waste sites from the results of seismological monitoring and high-precision observations of modern movements of the Earth’s crust. 相似文献
116.
An experiment is reported in which heat was released as a passive tracer from an elevated lateral line source within a model plant canopy, with h s = 0.85 h c (h s and h c being the source and canopy heights, respectively). A sensor assembly consisting of three coplanar hot wires and one cold wire was used to measure profiles of mean temperature % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikamaana% aabaGaeqiUdehaaiaacMcaaaa!390C!\[(\overline \theta )\], temperature variance (Σθ 2), vertical and streamwise turbulent heat fluxes, and third moments of wind and temperature fluctuations. Conclusions were:
- Despite the very heterogeneous flow within the canopy, the observed dispersive heat flux (due to spatial correlation between time-averaged temperature and vertical velocity) was small. However, there is evidence from the plume centroid (which was lower than h s at the source) of systematic recirculating motions within the canopy.
- The ratio % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Wdm3aaS% baaSqaaiabeI7aXjaab2gacaqGHbGaaeiEaaqabaGccaGGVaWaa0aa% aeaacqaH4oqCaaWaaSbaaSqaaiaab2gacaqGHbGaaeiEaaqabaaaaa!41DF!\[\sigma _{\theta {\text{max}}} /\overline \theta _{{\text{max}}} \] (of maximum values on vertical profiles) decreased from 1 near the source to an asymptotic value of 0.4 far downstream, in good agreement with previous experimental and theoretical work for concentration fluctuations in the surface layer well above the canopy.
- The eddy diffusivity for heat from the line source (K HL ) increased, downstream of the source, to a nearly constant ‘far-field’ vertical profile. Within the canopy, the far-field K HL was an order of magnitude larger than K HP , the equivalent diffusivity for a plane source; well above the canopy, the two were equal. The time scale defined by (far-field K HL )/(vertical velocity variance) was independent of height within the canopy.
- Budgets for temperature variance, vertical heat flux and streamwise heat flux are remarkably similar to the equivalent budgets for an elevated line source in the surface layer well above the canopy, except in the lower part of the canopy in the far field, where vertical transport is much more important than in the surface layer.
- A random flight simulation of the mean height and depth of the temperature plume was generally in good agreement with experiment. However, details of the temperature and streamwise turbulent heat flux profiles were not correct, suggesting that the model formulation needs to be improved.
117.
Gisela Björse Richard H. W. Bradshaw Daniel B. Michelson 《Journal of Paleolimnology》1996,16(1):67-78
A method was developed to construct maps of former forest types based on regional pollen data in southern Sweden. The considered species were Alnus, Betula, Carpinus, Corylus, Fagus, Fraxinus, Juniperus, Picea, Pinus, Populus, Quercus, Salix, Tilia and Ulmus. A network of 37 regional pollen sites with high data quality from lakes and peat deposits were selected from Sweden south of 60 ° N. Pollen percentage values were calculated and converted into estimates of tree composition. For controlling the reliability of the reconstruction, the estimates from the core-tops were compared with present day forest inventory data, and local pollen diagrams were compared with the regional pollen diagrams. An inverse distance weighted interpolation algorithm was used to generate maps for each tree species distribution at 2000 BP, 1500 BP, 1000 BP, 500 BP and 0 BP. A supervised classification routine was implemented to generate nine different forest types common to the five studied time intervals. The maps show that the amounts and patterns of distribution of the species and the forest types have varied in a significant but systematic manner through time. The changes are due to human activities, migrational patterns and changes in climate. These maps will be of value as a basis for future landscape planning, forestry and conservation of biodiversity.This is the 20th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers. 相似文献
118.
M. G. Deminov G. F. Deminova G. A. Zherebtsov O. M. Pirog N. M. Polekh 《Geomagnetism and Aeronomy》2011,51(3):348-355
Results of statistical analysis of the properties of variability of F2-layer maximum parameters (critical frequency foF2 and the height hmF2) in quiet midlatitude ionosphere under low solar activity in the daytime (1000–1500 LT) and nighttime (2200–0300 LT) hours
are presented on the basis of Irkutsk station data for 2007–2008. It is found that the distribution density of δfoF2 could be presented as consisting of two distinctly different normal laws of this distribution, one of which corresponds
to weak (|δfoF2| < 10%) fluctuations in foF2 and the other corresponds to strong (30% > |δfoF2| > 10%) fluctuations. Weak fluctuations in foF2 to a substantial degree are related to ionospheric variability at times less of than 1–3 h and determine the δfoF2 variability in the daytime hours. Strong fluctuations in foF2 are mainly related to day-to-day variability of the ionosphere at a fixed local time, the variability increasing by approximately
a factor of 3 during the transition from day to night and determining the δfoF2 variability in the nighttime hours. The distribution density of ΔhmF2 is close to the normal distribution law. An interpretation of the different character of the distribution densities of δfoF2 and ΔhmF2 is given. 相似文献
119.
The processes of formation and distribution of the resources of fresh groundwater and surface water in the territory of Crimea Peninsula are considered. Water availability in the natural–historic and administrative regions of the republic is characterized. The proportions between different categories of groundwater resources are shown with their role in water supply to Crimea taken into account. The presentday development of groundwater resources is analyzed and the possible increase in water consumption meeting geoecological requirements is substantiated. 相似文献
120.
V. A. Panchenko V. A. Telegin V. G. Vorob’ev G. A. Zhbankov O. I. Yagodkina V. I. Rozhdestvenskaya 《Geomagnetism and Aeronomy》2018,58(2):229-236
The results of studying spread F obtained from the DPS-4 ionosonde data at the observatory of the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (Moscow) are presented. The methodical questions that arise during the study of a spread F phenomenon in the ionosphere are considered; the current results of terrestrial observations are compared with previously published data and the results of sounding onboard an Earth-satellite vehicle. The automated algorithm for estimation of the intensity of frequency spread F, which was developed by the authors and was successfully verified via comparison of the data of the digisonde DPS-4 and the results of manual processing, is described. The algorithm makes it possible to quantify the intensity of spread F in megahertz (the dFs parameter) and in the number of points (0, 1, 2, 3). The strongest spread (3 points) is shown to be most likely around midnight, while the weakest spread (0 points) is highly likely to occur during the daytime. The diurnal distribution of a 1–2 point spread F in the winter indicates the presence of additional maxima at 0300–0600 UT and 1400–1700 UT, which may appear due to the terminator. Despite the large volume of processed data, we can not definitively state that the appearance of spread F depends on the magnetic activity indices Kp, Dst, and AL, although the values of the dFs frequency spread interval strongly increased both at day and night during the magnetic storm of March 17–22, 2015, especially in the phase of storm recovery on March 20–22. 相似文献