Abstract: This paper aims at main problems in measuring earthquake size in China. On the basis of clarifying the physical meaning of earthquake size, we firstly points out that the traditional magnitude scale M_L, m_b(m_B) and M_S which are defined by the source radiation energy E_R have some problems such as “overgeneralization”, “magnitude saturation” and “limitation” of M_L magnitude scale, as well as the uninterchangeable between magnitudes of different scales. The seismic moment M₀ derived from the “equivalent force” in the source area during the whole process of earthquake rupture is the most scientific measure of the earthquake size. In order to continue to use the term “magnitude” to describe the size of an earthquake, the moment magnitude scale M_W defined by M₀ not only solves problems in the traditional magnitude scale, but also applies to measure earthquakes with different sizes, different epicentral distances, and different focal depths. Therefore, it has been widely adopted by international seismology community in the past 20 years. Finally, we emphasize that promoting the measurement of earthquake size in line with international standards is an important basic work to advance the modernization of earthquake science and technology in China. It is not only conducive to the international communication and cooperation in earthquake science and technology, but also helpful to enhance the scientificity of earthquake prevention and disaster reduction.

Key words: Earthquake size, Magnitude of Earthquake, China