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181.
182.
Palaeoseismological and archaeological analysis of a trench enabled us to estimate the Holocene slip rates on the East Helike Fault, flanking the south-western Gulf of Corinth. We recognized two major fault strands within the trench: the ‘north fault’ controls a succession of three colluvial wedges and the deposition of a 2.7 m thick sedimentary sequence. The ‘south fault’ controls the deposition of a 2.9-m thick brownish-red colluvium. Based on colluvial stratigraphy, radiocarbon dating of the sediments suggests that the slip rate was c. 0.3 mm yr−1 from 10 250 to c. 1400 bp , when it increased dramatically to c. 2.0 mm yr−1 after a strong earthquake event near 1400 bp . The faster slip rate evidently increased the sedimentation rate. 相似文献
183.
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185.
Steven G. Wallenhorst 《Solar physics》1982,79(2):333-341
Models of the solar corona which include the effects of hot downflowing material are considered. Temperature-height profiles of the quiet and flaring corona are derived, under the assumptions of hydrostatic equilibrium and that the dominant cause of transition region heating is due to the enthalpy of the downflowing matter. In addition, scaling laws for the lengths of coronal loops are derived. It is found that inclusion of the downward enthalpy flux leads to a loop scaling law for quiet Sun loops which does not differ appreciably from that of Rosner et al. (1978). However, inclusion of the effects of enthalpy flux lead to a scaling law for compact flare loops of L = (3.6 × 109)T
infc
sup0.55
cm, which predicts much smaller loop sizes than expected from the quiet Sun loop law; these predicted lengths, however, are in agreement with the observed small sizes of compact flare loops. 相似文献
186.
Major element compositional overlap exists between microspherules of different microtektite layers or strewnfields. For this reason, microspherules of similar composition cannot, a priori, be assumed to belong to the same microtektite event and those of different compositions cannot, a priori, be assumed to result from different events. Nevertheless, despite major element compositional overlap between microspherules of different strewnfields, multivariate factor analysis shows microtektites and related microspherules of three stratigraphically different late Eocene layers to follow recognizably different compositional trends. The microtektite population of the North American strewnfield (Globorotalia cerroazulensis Zone) follows compositionally well defined trends and is characterized by high concentrations of SiO2, Al2O3, and TiO2. The microspherule population of the slightly older crystal-bearing Globorotalia cerroazulensis Zone microspherule layer is more heterogeneous and characterized by microspherules which are relatively enriched in FeO and MgO and relatively impoverished in SiO2 and TiO2. The microspherule population of the oldest microspherule layer in the uppermost Globigerapsis semiinvoluta Zone is highly heterogeneous and characterized by microspherules which are relatively enriched in CaO and impoverished in Al2O3 and Na2O. Individual microspherules of this oldest late Eocene horizon often exhibit major element compositions similar to those of the lower Gl. cerroazulensis Zone layer and occasionally exhibit major element compositions similar to North American layer microtektites. Nevertheless, late Eocene microspherule occurrences can be assigned to appropriate late Eocene microtektite horizons on the basis of major element compositional trends. 相似文献
187.
Cluster analysis groups samples, but does not generally show gradations between clusters. To illustrate these relationships, principal-coordinate analysis and multidimensional scaling can be employed, but these methods may not be appropriate due to structural distortion. A minimum spanning tree (MST) computes a point-to-point path through the original matrix, and clusters are mapped on the MST diagram. The MST linkages, therefore, provide a natural continuum between the clusters, without distortion. Forty-six Silurian Tonoloway Limestone samples were analyzed for 16 sedimentary features indicative of subaerial exposure. Cluster analysis identified nine clusters which were reduced to five final, ordered groups by MST. 相似文献
188.
During the time period of November 1968 to March 1970, 259 15.4 GHz impulsive microwave bursts have been identified of which 147 had associated 2–12 Å soft X-ray bursts. Average durations, rise times, and decay times for the microwave bursts are 2.9 ± 2.4 min, 0.9 ± 0.8 min, and 2.2 ± 2.1 min, respectively.Total durations and decay times for the X-ray events display a wide range of values from a few minutes to several hours. Rise times for 50 % of the events fell in the range of 2 to 7 min. A significant fraction (32 %) of the X-ray events may exhibit a flux enhancement prior to the main outburst.For 85 % of the flare cases, the X-ray event begins simultaneously with or before the microwave event. In 91 % of the cases the X-ray event peaks later than the microwave event. The average delay is 3.0 ± 1.9 min with 50 % of cases in the range of 0 to 4 min.The X-ray flux increases are significantly correlated with the microwave flux, increases, having a correlation coefficient of 0.43 (> 99.9 % confident).This work was supported in part by the Office of Naval Research under contract NOOO14-68-A-0196-0009 and the National Aeronautics and Space Administration through grant NGL-16-001-002. 相似文献
189.
The dynamics of grain motion through gas are examined in terms of the injection of isotopically anomalous (compared to solar abundances) material into the early solar nebula. Calculations indicate that the injected grains cannot penetrate to the center of any of a range of reasonable configurations, suggesting the formation of an edge region enriched in injected material. Furthermore, the dynamical behavior of grains in turbulent flows indicates that pockets of grains can have some resistance to turbulent diffusion. The constraints developed here are used to delineate a set of consistent, injected-grain models for the origin of the isotopic anomalies in meteorite inclusions.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978. 相似文献
190.
The importance of sulfur dioxide emissions for climate change is now established, although substantial uncertainties remain.
This paper presents projections for future sulfur dioxide emissions using the MiniCAM integrated assessment model. A new income-based
parameterization for future sulfur dioxide emissions controls is developed based on purchasing power parity (PPP) income estimates
and historical trends related to the implementation of sulfur emissions limitations. This parameterization is then used to
produce sulfur dioxide emissions trajectories for the set of scenarios developed for the Special Report on Emission Scenarios
(SRES). We use the SRES methodology to produce harmonized SRES scenarios using the latest version of the MiniCAM model. The
implications, and requirements, for integrated assessment modeling of sulfur dioxide emissions are discussed. We find that
sulfur emissions eventually decline over the next century under a wide set of assumptions. These emission reductions result
from a combination of emission controls, the adoption of advanced electric technologies, and a shift away from the direct
end use of coal with increasing income levels. Only under a scenario where incomes in developing regions increase slowly do
global emission levels remain at close to present levels over the next century. Under a climate policy that limits emissions
of carbon dioxide, sulfur dioxide emissions fall in a relatively narrow range. In most cases, the relative climatic effect
of sulfur dioxide emissions decreases dramatically to a point where sulfur dioxide is only a minor component of climate forcing
by the end of the century. Ecological effects of sulfur dioxide, however, could be significant in some developing regions
for many decades to come. 相似文献