According to the distribution characteristics of in-situ stresses measured in the fault-block G around complex faults

in-situ stress field is simulated and estimated by establishing numerical model suitable for geological structure of the block G and applying the COFEM method(constrained optimization finite element method) based on the FEM method and the theory of constrained optimization. Simulating results fit with the distribution characteristics of the measurements. In addition

the influence of complex faults on regional in-situ stresses is analyzed by comparing the in-situ measurements with numerical results. It is shown that the distribution of in-situ stresses around faults is mainly affected by its near faults

and depends mainly on the scale of the fault and the distance from the near fault. Because of the influence of the faults

the distribution of in-situ stresses around faults is complicated

especially the terminal portion of faults

the distribution of in-situ stresses field can not be generated by some discrete measuring points. Three-dimensional numerical simulation is very important for us to analyze and estimate the in-situ stresses field.