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  • Author or Editor: M. Kiszely x
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In the seismological research it is very important to use a correct earthquake catalogue that provides a strong basis for indicating seismic sources and for developing seismotectonic models. Homogeneity is expected from the catalogue and desirable to indicate data that are derived from explosions. The spectral analysis provides means to discriminate explosions from earthquakes. The quarry-blasts have simpler spectra than earthquakes. We estimate coda attenuation Q c for quarry-blasts that occurred in Vértes mountains. It has been found that the coda decay rate Q c is significantly lower for quarry-blasts than for earthquakes. At 6 Hz and 10 Hz there are great differences between explosions and earthquakes.

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The annual, monthly, weekly and diurnal distribution of Carpathian and M≯7 earthquakes through out the world have been investigated together with the effect of the Moon. The annual distribution of the M≯7 earthquakes shows long-term stability. The monthly variation of seismic activity in case of Hungarian seismic events over the period from 1964 to 2004 shows remarkable maximum between May and October and a minimum between January and April. In the Carpathian dataset for 1964-2004 characteristic peak were found in the daily distribution around 13h and minimum at 8h and 18h (local time). There was no statistically significant lunar influence detected.

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The Carpathian Basin is situated in the territory between the Mediterranean area, which is seismically one of the active regions and the Carpathian Mountains belt. The temporal variation of seismicity is investigated on the example of three seismo-tectonically different regions: the Carpathian Basin, the Vrancea region and the Dinarides. The seismicity is analyzed since 1900 in order to investigate the existence of diurnal periodicities using hodographs. There are two different diurnal distributions opposing each other: maximum early morning dominates until the year 1963, followed by a period of time when earthquakes seem to occur more often around 13h local time mainly concerning the weak M M < 3.2 events. The midday maximum in the number of minor events may be caused by the inclusion of quarry blasts, but the diurnal geomagnetic variations correlate well with diurnal changes in earthquake activity. Duma and Rhuzin (2003) suppose that the current vortices induced by Sq variations in the lithospheric layer, flowing across the horizontal component of the geomagnetic field generate a torque which can be added to the tectonic loading stress (which have a maximum about noon) and may help trigger instability in a fault approaching the failure threshold.The spatial and temporal fractal structures of earthquakes were analyzed using the box counting method. The regions were divided into different size r of a square box and were counted the minimum number N ( r ) of boxes necessary to cover all the data. The recurrence times of earthquakes are shown to be a clustering process and are much higher in the Carpathian Basin. The earthquakes in these regions have self-similar structures. The slope of log N -log r function for Carpathian Basin breaks at about 20 km, which divides the range into two bands. This breaking at about 20 km maybe connected to the intrinsic weakness of the Carpathian Basin lithosphere.

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The Vértes Hills are interesting region in Hungary where small earthquakes with magnitude 2–3 exist among small quarry blasts in a noisy background. A seismological station PKSG (Gánt) works in the middle of Vértes Hills. The main purpose of this paper is to test the different discriminatory elements using the registrations of this single station.The diurnal discrimination of quarry blasts shows a peak time. My purpose is to focus onto these questionable earthquakes — happened in the peak time of the blasts — and be able to identify them.Every discriminant gave “1” if the event was considered to be a blast, and “0” if the event was considered to be an earthquake. The sum of these values shows the level of the separation. The classification of fifteen events was wrong. This is approximately 7 percentage of the dataset.It has been found that the spectral analysis and the correlation of spectra proved to be successful in the discrimination. One type of blast and five types of earthquakes are identified based on the correlation analysis of spectra of S-phases on the horizontal component. The result of the correlation analysis is that most of the spectrum of the blasts were very similar to each others. Correlation analysis has also showed that the big part of earthquakes could be classified into 5 groups. Earthquakes of each group concentrated on different places on the map. The maximum frequency and cepstrum analysis failed.

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The spatio-temporal patterns of the seismicity are shown. The earthquake occurrence is connected to the strain rate on the basis of Kostrov (1974) equation. It is shown that in the Pannonian Basin the seismic rates are 10-7-10-6. This values were derived from the local earthquake catalogues of the area of Komárom, Dunaharaszti (near Budapest) and Kecskemét.  It is shown that the earthquake occurrence in Hungary  has a well expressed diurnal periodicity.  Similar phenomenon was detected in the case of earthquakes of all Europe and in Turkey in case of weak (M L = 3.0) seismic events.

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