HOMOGENEOUS MAGNITUDE SYSTEM OF THE MAINLAND CHINA

Homogeneous magnitude system of the mainland China has been made from the data of SK instrumental network, using the method that together obtain earthquake magnitude, calibration function and correction of the site condition. Four new calibration functions have been obtained for P-wave PZ, PⅡ, and S-wave SH, SV from the distance of 2.5 to 100 degree. 21 corrections of the site condition are also obtained. The standard error of single station measurement of earthquake magnitude is about 0.21-0.23, utilizing the new calibration function and the corrections of site condition. The earthquake the magnitude of which is equal to or greater than 6.0 can be usually recorded by 16 stations. In this case, the standard error of average magnitude over the network is about 0.05. The body wave magnitude mSK, from SK instrumental measurement has a systematic difference to mb and mB, because mSK, mb and mB depend on instrument of measurement strongly. The principle of making mSK close to Ms is adopted.We have a suggestion of magnitude of displacement spectrum: the earthquake will be equal to each other at one frequency when their average displacement spectrum over on some focal reference sphere has the same value for P-wave (or S-wave). This magnitude scale has following advantage: 1. The magnitude of network on different region of all over world can be unified in view of it being absolute mechanical scale. 2. It has obvious meaning in physics. It can represent the size of earthquake and can be defined for any size and slow earthquakes as well as has no saturation trouble. 3. It can link up the current magnitude scale. 4. The measurement is easy and has less error for the displacement instrumental record.