Earthquake source parameters and scaling relationships in Hungary (central Pannonian basin)

Abstract

Fifty earthquakes that occurred in Hungary (central part of the Pannonian basin) with local magnitude $M_\textrm{L}$ ranging from 0.8 to 4.5 have been analyzed. The digital seismograms used in this study were recorded by six permanent broadband stations and 20 short-period ones at hypocentral distances between 10 and 327 km. The displacement spectra for P- and SH-waves were analyzed according to Brune’s source model. Observed spectra were corrected for path-dependent attenuation effects using an independent regional estimate of the quality factor Q S . To correct spectra for near-surface attenuation, the κ parameter was calculated, obtaining it from waveforms recorded at short epicentral distances. The values of the κ parameter vary between 0.01 and 0.06 s with a mean of 0.03 s for P-waves and between 0.01 and 0.09 s with a mean of 0.04 s for SH-waves. After correction for attenuation effects, spectral parameters (corner frequency and low-frequency spectral level) were estimated by a grid search algorithm. The obtained seismic moments range from 4.21×1011 to 3.41×1015 Nm (1.7 ≤ M w ≤ 4.3). The source radii are between 125 and 1,343 m. Stress drop values vary between 0.14 and 32.4 bars with a logarithmic mean of 2.59 bars (1 bar = 105 Pa). From the results, a linear relationship between local and moment magnitudes has been established. The obtained scaling relations show slight evidence of self-similarity violation. However, due to the high scatter of our data, the existence of self-similarity cannot be excluded.