Comparison between earthquake magnitudes determined by China seismograph network and US seismograph networks (I): Body wave magnitude

By using orthogonal regression method, a systematic comparison is made between body wave magnitudes deter-mined by Institute of Geophysics of China Earthquake Administration (IGCEA) and National Earthquake Informa-tion Center of US Geological Survey (USGS/NEIC) on the basis of observation data from China and US seismo-graph networks between 1983 and 2004. The result of orthogonal regression shows no systematic error between body wave magnitude mb determined by IGCEA and mb (NEIC). Provided that mb (NEIC) is taken as the bench-mark, body wave magnitude determined by IGCEA is greater by 0.2~0.1 than the magnitude determined by NEIC for M=3.5~4.5 earthquakes; for M=5.0~5.5 earthquakes, there is no difference; and for M≥6.0 earthquakes, it is smaller by no more than 0.2. This is consistent with the result of comparison by IDC (International Data Center).