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Surface photometry of 23 ultraviolet excess galaxies from the two Byurakan surveys (FBS and SBS), selected to be blue compact dwarf candidates, has been made in B and R colors. A remarkable fraction of the sample exhibit a projected brightness distribution following the same de Vaucouleurs law as the bright spheroidal objects of the field (ellipticals and bulges of spirals). The other most frequent morphological type has an exponential brightness distribution, therefore similar to usual dwarf Magellanic irregulars. From their small absolute dimensions and average high effective surface brightness, the studied objects are indeed compact in the usual empirical sense.This article was presented as a report at the French-Armenian Colloquium (seeAstrofizika,
38, No. 4, 1995). Since it was submitted for publication slightly late, it was decided to include it in the present issue.Published in Astrofizika, Vol. 39, No. 1, pp. 91–100, January–March, 1996. 相似文献
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The spatio-temporal variation of seismicity in the southern Peru and northern Chile seismic gaps is analyzed with teleseismic data (m
b
5.5) between 1965 and 1991, to investigate whether these gaps present the precursory combination of compressional outer-rise and tensional downdip events observed in other subduction zones. In the outer-rise and the inner-trench (0 to 100 km distance from the trench) region, lower magnitude (5.0m
b
<5.5) events were also studied. The results obtained show that the gaps in southern Peru and northern Chile do not present compressional outer-rise events. However, both gaps show a continuous, tensional downdip seismicity. For both regions, the change from compressional to tensional regime along the slab occurs at a distance of about 160 km from the trench, apparently associated with the coupled-uncoupled transition of the interplate contact zone. In southern Peru, an increase of compressional seismicity near the interplate zone and of tensional events (5.0m
b
6.3) in the outer-rise and inner-trench regions is observed between 1987 and 1991. A similar distribution of seismicity in the outer-rise and inner-trench regions is observed with earthquakes (m
b
<5.5). In northern Chile there is a relative absence of compressional activity (m
b
5.5) near the interplate contact since the sequence of December 21, 1967. After that, only a cluster of low-magnitude compressional events has been located in the area 50 to 100 km from the trench. The compressional activity occurring near the interplate zone in both seismic gaps represents that a seismic preslip is occurring in and near the plate contact. Therefore, if this seismic preslip is associated with the maturity of the gap, the fact that it is larger in southern Peru than in northern Chile may reflect that the former gap is more mature than the latter. However, the more intense downdip tensional activity and the absence of compressional seismicity near the contact zone observed in northern Chile, may also be interpreted as evidence that northern Chile is seismically more mature than southern Peru. Therefore, the observed differences in the distribution of stresses and seismicity analyzed under simple models of stress accumulation and transfer in coupled subduction zones are not sufficient to assess the degree of maturity of a seismic gap. 相似文献
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Rodrigo Chi-Durán Diana Comte Marcos Díaz Jorge F. Silva 《Journal of Seismology》2017,21(5):1171-1184
In this work, new strategies for automatic identification of P- and S-wave arrival times from digital recorded local seismograms are proposed and analyzed. The database of arrival times previously identified by a human reader was compared with automatic identification techniques based on the Fourier transformation in reduced time (spectrograms), fractal analysis, and the basic matching pursuit algorithm. The first two techniques were used to identify the P-wave arrival times, while the third was used for the identification of the S-wave. For validation, the results were compared with the short-time average over long-time average (STA/LTA) of Rietbrock et al., Geophys Res Lett 39(8), (2012) for the database of aftershocks of the 2010 Maule M w = 8.8 earthquake. The identifiers proposed in this work exhibit good results that outperform the STA/LTA identifier in many scenarios. The average difference from the reference picks (times obtained by the human reader) in P- and S-wave arrival times is ～ 1 s. 相似文献
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Jean-Christophe Comte Rachel Cassidy Janka Nitsche Ulrich Ofterdinger Katarina Pilatova Raymond Flynn 《Hydrogeology Journal》2012,20(8):1569-1588
Groundwater flow in hard-rock aquifers is strongly controlled by the characteristics and distribution of structural heterogeneity. A methodology for catchment-scale characterisation is presented, based on the integration of complementary, multi-scale hydrogeological, geophysical and geological approaches. This was applied to three contrasting catchments underlain by metamorphic rocks in the northern parts of Ireland (Republic of Ireland and Northern Ireland, UK). Cross-validated surface and borehole geophysical investigations confirm the discontinuous overburden, lithological compartmentalisation of the bedrock and important spatial variations of the weathered bedrock profiles at macro-scale. Fracture analysis suggests that the recent (Alpine) tectonic fabric exerts strong control on the internal aquifer structure at meso-scale, which is likely to impact on the anisotropy of aquifer properties. The combination of the interpretation of depth-specific hydraulic-test data with the structural information provided by geophysical tests allows characterisation of the hydrodynamic properties of the identified aquifer units. Regionally, the distribution of hydraulic conductivities can be described by inverse power laws specific to the aquifer litho-type. Observed groundwater flow directions reflect this multi-scale structure. The proposed integrated approach applies widely available investigative tools to identify key dominant structures controlling groundwater flow, characterising the aquifer type for each catchment and resolving the spatial distribution of relevant aquifer units and associated hydrodynamic parameters. 相似文献
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A multifractal analysis of seismicity of three large earthquakes in Chile is made: the Central Zone 1985 (M W = 8.0), Antofagasta 1995 (M W = 8.1), and Maule 2010 (M W = 8.8) earthquakes. The analysis shows that the fractal dimension spectrum D q decreases with time before an earthquake. This fact suggests that the spatial distribution of seismic events could form a cluster before a main shock. 相似文献
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HI observations are presented for a new sample of 73 candidates BCDGs. HI emission has been detected from 36 and possible
emission from 11 galaxies. For detected galaxies HI radial velocities, HI line width measured at 50% and 20% of the maximum
intensity, HI fluxes, and HI masses are determined. The distributions of several parameters are given.
Translated from Astrofizika, Vol. 42, No. 2, pp. 203–218, April–June, 1999 相似文献