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1.
Elisaveta Marekova 《Acta Geophysica》2012,60(3):858-873
The earthquake recurrence time distribution in a given space-time window is being studied, using earthquake catalogues from
different seismic regions (Southern California, Canada, and Central Asia). The quality of the available catalogues, taking
into account the completeness of the magnitude, is examined. Based on the analysis of the catalogues, it was determined that
the probability densities of the earthquake recurrence times can be described by a universal gamma distribution, in which
the time is normalized with the mean rate of occurrence. The results show a deviation from the gamma distribution at the short
interevent times, suggesting the existence of clustering. This holds from worldwide to local scales and for quite different
tectonic environments. 相似文献
2.
Elisaveta Marekova 《Acta Geophysica》2016,64(4):885-903
The earthquake inter-event time distribution is studied, using catalogs for different recent aftershock sequences. For aftershock sequences following the Modified Omori’s Formula (MOF) it seems clear that the inter-event distribution is a power law. The parameters of this law are defined and they prove to be higher than the calculated value (2–1/p). Based on the analysis of the catalogs, it is determined that the probability densities of the inter-event time distribution collapse into a single master curve when the data is rescaled with instantaneous intensity, R(t; M th ), defined by MOF. The curve is approximated by a gamma distribution. The collapse of the data provides a clear view of aftershock-occurrence self-similarity. 相似文献
3.
Analysis of the spatial distribution between successive earthquakes occurred in various regions in the world 总被引:1,自引:1,他引:0
Elisaveta Marekova 《Acta Geophysica》2014,62(6):1262-1282
The earthquake spatial distribution is being studied, using earthquake catalogs from different seismic regions (California, Canada, Central Asia, Greece, and Japan). The quality of the available catalogs, taking into account the completeness of the magnitude, is examined. Based on the analysis of the catalogs, it was determined that the probability densities of the inter-event distance distribution collapse into single distribution when the data is rescaled. The collapse of the data provides a clear illustration of earthquake-occurrence self-similarity in space. 相似文献
4.
Thomas Giesecke K.D. Bennett H. John B. Birks Anne E. Bjune Elisaveta Bozilova Angelica Feurdean Walter Finsinger Cynthia Froyd Petr Pokorný Manfred Rösch Heikki Seppä Spasimir Tonkov Verushka Valsecchi Steffen Wolters 《Quaternary Science Reviews》2011,30(19-20):2805-2814
Mid to high latitude forest ecosystems have undergone several major compositional changes during the Holocene. The temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers. Here we test the hypothesis that the timing of vegetation change was synchronous on a sub-continental scale, which implies a common trigger or a step-like change in climate parameters. Pollen diagrams from selected European regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed. The results show that the temporal pattern of vegetation change was significantly different from random. Times of change cluster around 8.2, 4.8, 3.7, and 1.2 ka, while times of higher than average stability were found around 2.1 and 5.1 ka. Compositional changes linked to the expansion of Corylus avellana and Alnus glutinosa centre around 10.6 and 9.5 ka, respectively. A climatic trigger initiating these changes may have occurred 0.5 to 1 ka earlier, respectively. The synchronous expansion of C. avellana and A. glutinosa exemplify that dispersal is not necessarily followed by population expansion. The partly synchronous, partly random expansion of A. glutinosa in adjacent European regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally. 相似文献
5.
A. Skopal S. Shugarov M. Vako P. Dubovský S.P. Peneva E. Semkov M. Wolf 《Astronomische Nachrichten》2012,333(3):242-255
We present new multicolour (UBVRCIC) photometric observations of classical symbiotic stars, EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, Draco C1, AG Peg, and AX Per, carried out between 2007.1 and 2011.9. The aim of this paper is to present new data of our monitoring programme, to describe the main features of their light curves (LC) and to point problems for their future investigation. The data were obtained by the method of the classical photoelectric and CCD photometry (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
We examined the behavior of different fractal dimensions when applied to study features of earthquake spatial distribution
on different types of data. We first examined simulated spatial fields of points of different clustering level, following
the so called Soneira-Peebles model. The model was chosen because it displays some similarity to the real clustering structure
of earthquakes occurring on hierarchically ordered faults. The analysis of the capacity, clustering and correlation dimensions
revealed that their behavior did not completely correlate with the clustering level of the simulated data sets. We also studied
temporal variations of the fractal coefficients, characterizing the spatial distribution of the 1999 İzmit-Düzce aftershock
sequence. The calculated coefficient values demonstrated analogous behavior like for the simulated data. They exposed different
variability in time, but for all of them a systematic fluctuation was observed before the occurrence of the Düzce earthquake.
Our analysis revealed that although fractal coefficients could be applied to measure earthquake clustering, they should be
used with caution, trying to figure out the best coefficient for a certain data set. 相似文献
7.
Elisaveta Marekova 《Studia Geophysica et Geodaetica》2011,55(2):203-212
Series of relatively large earthquakes in different regions of the Earth were studied. The study regions are characterized
by high seismic activity recorded at contemporary seismic networks. The main purpose of this investigation is to describe
analytically the seismic process in space and time. We consider statistical distributions of the distances and the time intervals
between consecutive earthquakes. The statistical distribution of the parameters describing consecutive seismic events is approximated
with suitable characteristic functions. The main purpose of this approach is to propose formal criteria for distinguishing
among different active tectonic areas in terms of their seismic activity. 相似文献
8.
Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146
dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg
was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope
archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735
Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1⋅m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0⋅m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1⋅m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical
plate archives is discussed briefly. 相似文献
9.
Results from optical photometric observations of the pre-main sequence star GM Cep are reported in the paper. The star is
located in the field of the young open cluster Trumpler 37—a region of active star formation. GM Cep shows a large amplitude
rapid variability interpreted as a possible outburst from EXor type in previous studies. Our data from BVRI CCD photometric observations of the star are collected from June 2008 to February 2011 in Rozhen observatory (Bulgaria) and
Skinakas observatory (Crete, Greece). A sequence of sixteen comparison stars in the field of GM Cep was calibrated in the
BVRI bands. Our photometric data for a 2.5 years period show a high amplitude variations ($\Delta V \sim2\mbox{$\Delta V \sim2\mbox{) and two deep minimums in brightness are observed. The analysis of collected multicolor photometric data shows the typical
of UX Ori variables a color reversal during the minimums in brightness. On the other hand, high amplitude rapid variations
in brightness typical for the Classical T Tauri stars also present on the light curve of GM Cep. Comparing our results with
results published in the literature, we conclude that changes in brightness are caused by superposition of both: (1) magnetically
channeled accretion from the circumstellar disk, and (2) occultation from circumstellar clouds of dust or from features of
a circumstellar disk. 相似文献
10.
The lightning activity and precipitation in two 3-hour time intervals in the grid boxes of 0.25 × 0.25° over East and Central Mediterranean during the summer of 2005 and 2006 are analysed. The results show that the frequency distribution of the precipitation amount is shifted towards larger values for the cases with lightning as compared with the cases without lightning. It was found that the number of cases with 3-hour accumulated rainfall greater than 10 mm was bigger when lightning occurred (65%) than when it was absent (35%). Investigation of diurnal and spatial distributions of lightning shows that the afternoon flash density peak is associated mainly with lightning over the land, which is in accordance with the results of earlier works. The early morning flash density peak is associated mainly with flashes over the sea. High correlation coefficients (0.89 during the morning hours and 0.98 during afternoon) were found between rain rate (mm/h) and average flash density (fl/km2) when flash density is averaged in logarithmic intervals of rain rate. 相似文献