LOCAL MAGNITUDE SCALE ML EVALUATION FOR THE MAIN CRUSTAL SEISMIC ZONES OF ROMANIA

The seismic activity on the Romanian territory consists of both crustal and intermediate-depth earthquakes. The crustal seismicity is moderate and more scattered compared to the intermediate-depth one. In this paper we study the problem of homogeneous determination of local magnitude for earthquakes from the main seismic zones of Romania (Vrancea, Fagaras Mountains, Banat, Transylvania, Dobrogea and Romanian Plain). A waveforms database of digitally recorded data is used to derive new magnitude relations for different seismic areas of Romania. Wood Anderson amplitudes are computed from the available data and the maximum peak to-peak amplitudes are measured on the horizontal components of the broad-band sensors to define the local magnitude scale. The duration magnitude (M-D) is used as reference to calibrate the new magnitude scale based on amplitudes. The new coefficients are estimated through a multiple regression method. Our tests show that the new magnitude scale significantly improves the earthquake size evaluation and stability compared to the solution computed by present-day procedures at the National Institute for Earth Physics.