Method for determining fault activity in structural stable period

The invention relates to a method capable of accurately determining multi-stage active periods of a fault in a structural stable period. The method comprises the following steps of acquiring vertical principal stresses in different periods based on a vertical principal stress-depth relationship of a current stratum and stratum burial depths in different periods; determining the minimum principal stress in different periods based on the pressure-stress coupling relation of the current stratum and the stratum pressure and the vertical principal stress in different periods; based on the maximum principal stress, the minimum principal stress and the formation pressure in the different periods, the maximum effective principal stress and the minimum effective principal stress in the different periods being obtained; determining stress Moire circles in different periods based on the maximum effective principal stress and the minimum effective principal stress; based on the internal friction angle-burial depth relation of the current stratum and the stratum burial depths in different periods, critical fracture envelope lines in different periods being obtained; comparing the stress Moire circles at different periods with respective corresponding critical fracture envelope lines; and judging the opening and closing properties in different periods according to the position relationship between the stress Moire circle and the critical fracture envelope line.