Abstract: The paper analyzed the deficiency of “binary state” (either abnormal or normal) earthquake precursory model and introduced the “multi-state” precursory model which refers to the fact that multi states of the abnormal of an earthquake forecast index exists. The efficiency evaluation method is put forward in the paper according to the “multi-state” precursory model. Based on the new concept, an optimization method for parameters of earthquake forecast model under the condition of maximization of forecast efficiency is developed. According to the general “multi-state” precursory model in which the forecast index can be in spatial, temporal, or spatial-temporal united domain, the model optimization method is applied to the North China and North-South Seismic Zone in China. The results demonstrate that optimization models to forecast location of potential earthquakes with M_S≥6 in relation to the latest (Q₃~Q₄) active faults are the region around the faults, whose widths are 20 km and 30 km respectively in the North China and South-North Seismic Zone in China. The corresponding forecast efficiency values are 0.42 and 0.34.

Key words: “Multi state” precursory mode, Earthquake forecast, Efficiency evaluation, Parameter optimization model