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Analysing the areal distribution of earthquakes produced in the Carpathian Basin the conclusion can be drawn that only certain parts can be considered active along fracture lines, namely those parts which separate individually moving blocks. Generally accepted working theory states that if one fracture line ever generated an M-magnitude earthquake then at any point of the same line a similar or larger tremor may happen again. However, this principle is not supported by domestic experiences. In accordance with focal depths analysis we are going to verify that earthquakes were produced within more or less consolidated layers inside subsiding basins. Our analysis is aimed to explain the possible origin of earthquakes within small depth range and to point out the practical benefit of these investigations. We present also an analysis on the possible origin of „basin tremors” not taken so far into consideration and we offer a plausible explanation. Uncertainties of focal depth (hypocenter) determinations will also be given and we define relations between the focal depth (h), the magnitude (M), and the epicentral intensity (Io). The result will be presented in tables and comparison will be given between the focal depth data determined by us and by others. Finally viewpoints will be presented to help the recognition of earthquake foci and to set earthquake hazard determination on a real basis.

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The source parameters and dimensions of the three most important earthquakes (Komárom 1763, Io = IX EMS; Komárom 1783, Io = VII-VIII EMS; Mór 1810, Io = VIII EMS) of the area studied are estimated as follows     event                        focal depth   rupture area    max. displacement Jun. 28, 1763 Komárom   7.6 km     93 - 125 km2   29 - 35 cm Apr. 22, 1783 Komárom  11.5 km     18 -  36 km2   6 - 11 cm Jan. 14, 1810 Mór             5.0 km     18 -  45 km2   6 - 14 cm The average recurrence that we may expect an earthquake of M=2.7 every 1 year, an earthquake of M=4.0 every 10 years and an earthquake of M=5.3 every 100 years in this source zone. The probabilistic seismic hazard assessment predicts 1.4-2.0 m/cm2 peak ground accelerations, and 6.9-7.2 maximum (theoretical) earthquake intensity values with 10% chance of exceedance for an exposure time of 100 years in the area.

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In the seismic source zone of Bánát more than 600 earthquakes are known since 1773 among them six events with magnitude of 5.0–5.7 measured on the surface magnitude scale. The macroseismic reinterpretation of the April 2, 1901 earthquake yields epicentral intensity of VII on the European Macroseismic Scale, and a focal depth value of 12 km. Based on empirical relations the maximum rupture area is estimated as 50–55 km 2 and the maximum displacement along the fault is about 16 cm in the Bánát seismic zone due to the M S = 5.7 event occurred on July 12, 1991. The average recurrence that we may expect an earthquake of M ≥ 3.4 every 1 year, an earthquake of M ≥ 4.3 every 10 years and an earthquake of M ≥ 5.3 every 100 years in the studied source zone. The probabilistic seismic hazard assessment predicts 1.3–2.1 m/sec 2 peak ground accelerations, and 6.7–7.3 maximum (theoretical) earthquake intensity values with 10% chance of exceedance for an exposure time of 100 years in the region.

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In the small seismic source zone of Kecskemét 203 earthquakes are known between 1739 and 2006, and about 90 percent of them have a magnitude value not more than 3.0, however the strongest event on July 8, 1911 has 5.6 surface-wave magnitude. Concerning the latter earthquake the maximum (epicentral) intensity I = VIII (EMS) was observed in the area enclosed by Kecskemét, Katonatelep and Hetényegyháza locations. The quake caused significant damage to buildings (I ≥ VI EMS) on about 6 thousands square kilometres and was felt (I ≥ III EMS) on some 85 thousands square kilometres. The focal depth is estimated as 11 km directly from the individual intensity data points. During the earthquake liquefaction (sand crater) occurred in the epicentral area and some electromagnetic effects were also observed. Studying the source dimensions we conclude the rupture area is between 40 and 67 square kilometres and the maximum displacement along the fault is estimated to 14–20 centimetres for the Kecskemét earthquake of July 8, 1911. A probabilistic seismic hazard assessment predicts 1.1–1.5 m/s 2 peak ground accelerations, and 6.6–7.1 maximum (theoretical) earthquake intensity values with 10% chance of exceedance for an exposure time of 100 years in the studied area.

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Zsíros T 1996: Macroseismic focal depth and intensity attenuation in the Carpathian region, Acta Geod. Geoph. Hung. , 31, 115--125. Macroseismic focal depth and intensity attenuation in the Carpathian region

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The source parameters and dimensions of the three most important earthquakes (Zsolna - Jan. 15, 1858, I o = VIII EMS; Jóko - Jan. 9, 1906, I o = VIII EMS; Jóko- Jan. 16, 1906, I o = VII-VIII EMS) of the area studied are estimated as follows: Event (Magnitude, Rupture area, Max. Displacement); Jan. 15, 1858 Zsolna (5.5 Ms, 22-36 km2, 8-11 cm); Jan. 9, 1906 Jóko (5.7 MS, 40-55 km2, 12-16 cm); Jan. 16, 1906 Jóko (5.3 MS, 12-24 km2,4-8 cm). The average recurrence that we may expect an earthquake of M = 2.3 every 1 year, an earthquake of M = 3.7 every 10 years and an earthquake of M = 5.1 every 100 years in this source zone. The probabilistic seismic hazard assessment predicts 1.2-1.7 m/sec2 peak ground accelerations, and 6.6-7.2 maximum (theoretical) earthquake intensity values with 10% chance of surpassing for an exposure time of 100 years in the area.

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In the region of the Carpathian-Pannonian Basin (44–50N; 13–28E) 81 earthquakes have moment magnitude (M w); 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 (M w) on local magnitude (M l) 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: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $\begin{gathered} M_w = 1.37( \pm 0.28) + 0.39( \pm 0.18)M_l + 0.061( \pm 0.026)M_l^2 \hfill \\ (M_w :1.9 - 5.5;M_l :1.4 - 5.5). \hfill \\ \end{gathered} $ \end{document}.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 (M w) and the body wave (M b) magnitudes has the following form: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $M_w = 1.20( \pm 0.08)M_b - 0.76( \pm 0.40)(M_w :4.1 - 7.7;M_b :3.8 - 7.3).$ \end{document}.The relationships of the different (M l, M s, M b, M d) magnitudes are also presented in the paper.

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The first scientific tools of earthquake investigations were provided by isoseismic maps. The present paper describes the formation and development of cartographic representation of macroseismic information. Study of old isoseismal maps is of importance in assessing the earthquake hazard. Unfortunately there are only few well documented events prior the epoch of instrumental seismology for which the earthquake parameters (i.e. magnitude, focal depth) and tectonic position can be estimated. In the same time important steps forward in development of seismology (e.g. use of time observations, seismic speed determinations, use of geological information, birth of engineering seismology) are connected with attempts of representation of macroseismic data on maps.

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The source parameters and dimensions of the tow strongest earthquakes (July 1, 1829, I o = VII-VIII EMS; October 15, 1834,  I o = IX EMS) in Érmellék area are estimated as follows  Date of the event     Focal depth     Magnitude    Rupture area          Max.                                                                                                       displacement July  01, 1829           21-33 km         5.5-5.7         33-55 km2        11-16 cm October 15, 1834     23-28 km         6.5-6.6        266-358 km2      74-90 cm  The average recurrence that we may expect an earthquake of M ≥ 0.7 every 1 year, an earthquake of M ≥ 2.9 every 10 years and an earthquake of M ≥ 5.0 every 100 years in this source zone. The probabilistic seismic hazard assessment predicts 1.1-1.4 m/cm2 peak ground accelerations, and 6.3-7.4 maximum (theoretical) earthquake intensity values with 10 % chance of exceedance for an exposure time of 100 years in the area.

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The investigations presented in this paper were aimed at empirical definition  of ground motion under Vrancea earthquakes.  They were based on the recorded accelerogrammes from the occurred strong Vrancea earthquakes of 1977, 1986 and 1990 obtained from the accelerographs installed in the territory of former Yugoslavia, Romania and Bulgaria. A methodological approach to empirical prediction of ground motion parameters under strong earthquake effects was developed and empirical attenuation laws of horizontal peak ground acceleration (PGA) were defined.  A new empirical mathematical model was applied. In this model the amplitudes of strong ground motion are in function of earthquake magnitude, epicentral distance, focal depth, azimuth of the instrument location in respect to  the radiation pattern and the ratio between the semi-axes of the seismic field  ellipse. Through the so called non-homogeneity function of the region, the model indirectly involves the effect of the focal mechanism and the non-homogeneity of the region through which the seismic waves propagate.  The mathematical model applied in these investigations contributed to the  empirical definition of the attenuation laws that play an important role in seismic  hazard analyses and hence in evaluation of the seismic hazard a country or a  region is exposed to.  The results obtained from these investigations are important not only for   Macedonia but for the entire Balkan region and beyond.  The presented methodology and the applied mathematical model of functional relationships are of a particular importance since they are different from the empirical models of strong ground motion that have so far been applied in the world.

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