Empirical relationships of earthquake magnitudes for local regions considering the active tectonic boundary areas

Local magnitude M_L and surface wave magnitude M_S are two widely used scales of earthquake magnitude, which usually need to be converted to each other using empirical equations. Due to a limit of data, and ignorance the difference in geological conditions, empirical equations based on historical earthquakes suffer from conversion errors in practice. Based on the historical earthquake data of 12 621 records with both M_L and M_S recorded in the past four decades, this paper derived the empirical conversion equations between M_L and M_S by regression analysis. Furthermore, empirical conversion equations were derived from the partitioned data for the 27 regions classified according to the secondary active tectonic boundary areas. The results show that the correlation between M_S and M_L is more significant after the magnitude data are partitioned, and the magnitudes that were converted with consideration of active tectonic boundaries showed lower conversion error.