Analyzing the relation between earthquake and active fault based on the parameter optimization model

The gestation and occurrence of strong earthquake are closely related to fault activity, which are not only revealed by abundant experimentation and seismism but also proved by modern seismology. In the mainland of China, the correlation between earthquake activity and active fault is one of the bases for partitioning potential seismic sources, analyzing the seismotectonics and estimating location of strong earthquake. Due to nonuniformity of earth medium, instability of observation system and disturbance of environment etc, the variety of observational data is complicated, that is, there is no absolute "normal" or "abnormal", and seismic anomaly can be divided into many mutually exclusive "abnormal states". In different conditions of combined time-space-strength, determining the seismic anomaly by different monomial forecast method and its efficiency could be different due to the uncertainty of precursor itself or complexity of relation between precursor and earthquake gestation. In a "two-state" model, the difference could hardly be discovered and disposed in actual application. But in the "multi-state" model, the difference can be easily reflected and the optimal combination of forecasting parameters for a forecast method can also be determined easily. Based on the "multi-state" precursory model and the optimization method for parameters of earthquake forecast model under the condition of maximization of forecast efficiency, the relations of spatial location of earthquakes with M ≥ 6 and active faults in three seismic belts are analyzed. The results demonstrate that in the Hetao Seismic Belt, seismicity is mostly concentrated in the range of 20km along the fault, the optimization model can forecast the location of potential earthquake of M ≥ 6 near the faults with a relatively high accuracy, and the reliability value is 0. 5; while in the Qilan Mt Seismic Belt, the reliability only reaches 0. 14 when we use the model to estimate earthquakes within 30km range along the faults. The "multi-state" precursory model, the efficiency-evaluating model and the parameter selection of individual earthquake forecast model based on optimal efficiency are of certain revelatory and practicable meanings for developing knowledge about precursors, questing the laws of earthquake preparation and searching for optimal forecasting method.