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1.
The paper presents the results of Croatian earthquake catalogue revision for the period 1908–1992. The revised catalogue lists a total of 4853 events (4486 after 1908), of which 3700 are mainshocks. All primary data sources available to us (seismograms, phase onset time readings, macroseismic questionnaires…) were consulted in order to improve the quality and reliability of magnitude, intensity and location. Along with the most important earthquake parameters the catalogue contains entries that enable assessment of the reliability of location and bibliographic references. Using the temporal analysis of the maximum-likelihood estimate of the b -value in the frequency-magnitude relation, the catalogue is estimated to be complete for events with M ≥ 4.0 throughout the investigated period. The magnitude completeness threshold decreases to 3.8 after the middle of the century, and to about 3.6 in the last three decades. It is noted that the b-value variation with time is closely tied to the seismic activity, as well as that at present there seems to be a lack of seismic energy release corresponding to the M = 6.0–6.5 earthquake. 相似文献
2.
It is shown that the new definition1 of strong motion local magnitude M leads to stable estimates of magnitudes for earthquakes in Yugoslavia, with epicentral distances R <100 km and for 2.5 < M < 6.5. Tables with magnitudes computed using this new procedure are presented for all earthquakes contributing to the strong motion accelerogram files in EQINFOS for Yugoslavia.2 The similarity of our findings with the analogous analyses for California suggests new possibilities for relative calibration between various local magnitude scales, which are used in southeastern Europe, and ML in California. 相似文献
3.
Milan Herak 《Environmental Geology》1990,15(1):59-60
Relationships among tectogenetic karst types, major morphologic units, and environmental consequences are discussed. The development of urban centers and in-dustrial sites within the Dinaric Karst area without taking into account the above-mentioned parameters, require additional measures. This is necessary in order to avoid the pollution of groundwaters and karst springs used for water development.According to field experience and results of investigations, which were recently published, a reliable geotectonic interpretation needed for distinguishing orogenic and epi-oro-genic (epi-platform) karst terranes has usually been missing in analyses of karst morphology. This is important because the karst morphological features different in origin and distribution can be found in both types, respectively. 相似文献
4.
Herak Marijan Herak Davorka Markušić Snježana Ivančić Ines 《Studia Geophysica et Geodaetica》2001,45(3):251-266
The rate of aftershock occurrence after the M6 Ston-Slano (Croatia) earthquake is modeled as the Epidemic Type Aftershock Sequence (ETAS). Increase of the modeled cumulative number of aftershocks with time was fitted to observations by the least-squares criterion using the combined grid-search and Monte-Carlo approach. This enabled not only the estimation of the most probable ETAS parameters, but also the determination of their confidence limits, as well as the estimation of the bias between them. It has been found that the bias is significant for some of the parameter pairs, regardless of the threshold magnitude assumed. Residual analyses revealed that all strong aftershocks (M
L
4.5) occurred during the periods of normal to high aftershock activity. There were two periods of quiescence in the sequence, both of which were followed by a strong aftershock. 相似文献
5.
The territory of Croatia and neighboring regions is divided into 17 seismic source zones, considering available seismological
and geological data. On this basis, seismic hazard elements (seismicity rate, maximum magnitude, b-value, probabilities of
exceedance and return periods for a predefined set of magnitudes) are computed using the maximum likelihood method appropriate
for treating data-sets with variable completeness thresholds. The values of long term expected peak horizontal acceleration
obtained by using a combination of the deterministic and the probabilistic procedure are the highest in the Dubrovnik zone,
while the Zagreb zone has the highest earthquake hazard in the continental part of the country.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
—The paper presents results of experiments designed to measure the actual dynamic magnification of the Wiechert 1000 kg horizontal seismometer when excited by seismic waves. This is accomplished by comparing 51 digital records of seismic events recorded by the Wiechert and a well calibrated reference seismometer. The results obtained indicate that the magnification of the Wiechert seismometer is influenced by the interaction of its mass and frame, especially for high frequencies. This interaction has been modeled by considering a system of two coupled pendulums, yielding a theoretical dynamic magnification curve which exhibits main features of the observed magnification. The dis crepancy between the nominal and the actual response of the Wiechert seismograph may lead to errors in studies involving spectral analyses of recorded seismograms, and to overestimation of local earth quake magnitudes. 相似文献
7.
8.
Based on a large set of arrival times of the Pg phase reported by local and regional stations, we estimate azimuthal anisotropy of the Pg-wave velocity in focal volumes of the upper crust in NW Croatia. The method is based on analyses of the azimuthal dependence
of ratios of cumulative differences of arrival times and travel paths between foci of earthquake pairs, computed for rays
propagating within narrow azimuthal windows. The results clearly indicate the presence of anisotropy of 3.3% with the direction
of fast velocity (approximately NNE-SSW) coinciding with the direction of the maximum tectonic pressure as revealed by 23
available focal mechanisms and previous geological investigations. Although a large part of observed anisotropy can be explained
assuming that focal volumes are pervaded by a system of vertical extensive-dilatancy anisotropy (EDA) cracks aligned under
the influence of local tectonic stress field, there is indication that — to a smaller extent — some role was also played by
alignment of structural features in the region. 相似文献
9.
Ivo Allegretti Davorka Herak Marijan Herak Seweryn J. Duda 《Studia Geophysica et Geodaetica》2000,44(1):13-25
The magnitudes (M
S
, m
bP
, m
bS
) of the largest historical earthquakes which occurred in the first half of the 20
th
century, calculated on the basis of records of Wiechert horizontal seismographs in Göttingen (Germany) and Zagreb (Croatia), are compared with one another, as well as with the magnitudes reported in worldwide catalogues. Systematic trends are observed in the data regarding the temporal stability of magnitude estimations in Göttingen, as well as the apparent non-linearity of the instrument responsle in the case of the Wiechert seismograph in Zagreb. We were unable to clearly identify their causes – possible explanations include effects caused by the interaction of the seismometer's frame and mass, as well as local soil conditions, but nonhomogeneity of the reference catalogues cannot be ruled out. The results indicate that a careful re-examination and cross-checking of the reported magnitude figures for the earthquakes from the first half of the 20th century is required. 相似文献
10.
Peak acceleration attenuation relations for horizontal and vertical components are presented for the Dinarides region, based on 145 3-component accelerograms related to 46 earthquakes with local magnitudes of 4.5 or greater and with epicentral distances of less than 200 km as recorded on 39 recording sites in the greater Dinarides region. The attenuation functions were obtained by two-stage stratified regression on the local magnitude and epicentral distance as independent variables. The predicted peak acceleration values within the distance range covered by the data are comparable to the ones obtained for stiff-soil or rock sites when selected reference relations are used. The rather large average residuals are caused mostly by the lack of information on local site conditions and by the use of epicentral distance instead of fault distance. 相似文献