Abstract: The parameter C_v is available in describing the spatial inhomogeneity of earthquake precursory group. The validity of anomaly of C_v obtained from variety of observatory methods before earthquakes has been proved in a certain degree in earthquake forecast, however, the C_v value is not simply corresponding to the statistical distributions such as period, sub-period, Poisson, and clustering one et al. Based on review of research and application of C_v in the paper, further analysis is done on C_v value and its relation with the statistical distributions, especially to the problem existed in the application. The discussion is expected to be comprehensive in the physical implication of C_v . The discriminance to identify the anomaly of earthquake precursor group by using C_v is also provided in the paper.

Key words: Earthquake precursor group, Spatial inhomogeneity, C_v value, Spatial distribution, Earthquake forecast