T. Zsíros

SEISMIC HAZARD IN THE PANNONIAN REGION

Seismic hazard for single sites and hazard maps for the whole Pannonian region (44.0-50.0N; 13.0-28.0E) have been calculated. The hazard assessment was carried out using a probabilistic approach by incorporating a wide range of parameter values and viable interpretations that were consistent with the data. Alternative interpretations were described by branches of a logic tree. Each branch was weighted according to the ability of that interpretation to explain the available data. The resulting seismic hazard map describes expected shaking with a 475-year return period in terms of peak ground acceleration. Furthermore, some important contributors to seismic risk are highlighted, and a liquefaction hazard map is presented for the territory of Hungary.

Estimation of Macroseismic Focal Depth without Using Isoseismals

This paper describes a method which is able to estimate the macroseismic focal depth directly from the felt intensities instead of using the isoseismals. Based on the earthquakes of the Háromszék-Vrancea region and Italy, our study demonstrates that the method is capable to produce intermediate depth (90–125 km) and can be an alternative instrument beside the network determination.

Computer estimation of intensities: The 1985 Berhida, Hungary, earthquake

In this paper a computerized method for the intensity estimation from macroseismic observations is presented. The successive steps of the MSK intensity scale (2° to 10°) receives weights according to the observations marked on the earthquake questionnaires. These weights are summed for the individual scale steps. The distribution of these summed weights and their relation to an experimentally chosen function of the criterion make it possible to estimate the appropriate intensity value and its reliability. By computer evaluation of earthquake reports an objective comparison of estimated intensities given by different seismologists can be made, provided that uniform earthquake questionnaires are used. The application of this method will result in more homogeneous intensity data.

Focal Depth Estimation from Intensity Distribution

For the scarcity of data, isoseismal maps frequently cannot be drawn based on the intensity distributions of historic earthquakes. Therefore, the traditional focal depth estimations with isoseismals are out of question for such events. The method presented in this paper, instead of isoseismals, uses the discrete intensity distributions of earthquakes. The focal depth is determined from the observed intensities by the Kövesligethy model using a nonlinear least-squares method. The method is tested for 50 earthquakes and though the results are not satisfactory for intermediate Haromszék-Vrancea events and may be questionable to some crustal earthquakes, too, the method has the capability of depth estimation of historic earthquakes when isoseismals cannot be drawn. Even, when isoseismals are compiled, this method means a more objective solution, because of the subjective nature of isoseismals.

Earthquake magnitude relationships in the region of the Carpathian-Pannonian Basin

AbstractIn the region of the Carpathian-Pannonian Basin (44–50N; 13–28E) 81 earthquakes have moment magnitude (Mw); 61 of them are crustal events (focal depth <65 km) while 20 earthquakes belong to the intermediate focal depth region of the Vrancea (Romania) zone. For crustal events the regression of moment magnitude (Mw) on local magnitude (Ml) shows a better fit for large magnitudes using a second order equation against to a linear relationship, and the actual quadratic formula based on 61 events is the following:

Seismicity of the Western-Carpathians

\matrix{{{M_w} = 1.37( \pm 0.28) + 0.39( \pm 0.18){M_l} + 0.061( \pm 0.026)M_l^2} \cr {({M_w}:1.9 - 5.5;{M_l}:1.4 - 5.5).}\cr}

Seismicity of the Bánát region

In the intermediate focal depth Vrancea zone of the south-eastern bend of the Carpathians (44.5−46.5N; 25.5−28.0E) the number of body wave magnitudes is the largest one (20) among the local (8), the surface wave (14) and the duration (17) magnitudes. The linear relationship between the moment (Mw) and the body wave (Mb) magnitudes has the following form: