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 determined by Institute of Geophysics of China Earthquake Administration (IGCEA) and National Earthquake Information Center of US Geological Survey (USGS/NEIC) on the basis of observation data from China and US seismograph networks between 1983 and 2004. The result of orthogonal regression shows no systematic error between body wave magnitude m(b) determined by IGCEA and m(b) (NEIC). Provided that mb (NEIC) is taken as the benchmark, body wave magnitude determined by IGCEA is greater by 0.2-0.1 than the magnitude determined by NEIC for M=3.5 similar to 4.5 earthquakes; for M=5.0 similar to 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).