Calibration of the Local Magnitude Scale for Hungary

ABSTRACT The local magnitude for Hungary was calibrated based on 3490 seismograms of 422 crustal earthquakes recorded by 43 seismological stations in Hungary between 2016 and 2022. Following the suggestions of International Association of Seismology and Physics of the Earth’s Interior, the original Richter (1935) empirical attenuation relation can be written up as an overdetermined system of linear equations using the approach introduced by Hutton and Boore (1987). As a solution for the system of equations, the attenuation coefficients and station correction terms were obtained separately for the vertical and the horizontal components. The attenuation coefficients in the new scales characterize the local crustal response well. In Hungary, the amplitudes of the horizontal component show higher attenuation than the amplitudes of the vertical component. The station corrections are consistent with the geological features beneath the seismic stations and resulted in values between −0.48 and +0.32 for the vertical component and between −0.39 and 0.56 for the horizontal component. The event magnitudes computed with the new scales do not differ substantially in magnitude from those computed with the SeisComp3 software’s scale currently used in Hungary. However, the main improvement of the new scale is the reduction in variance between station magnitudes by 56.3%, using attenuation coefficients and station corrections. We suggest the use of the new vertical scale in the future.