In this study, we determine the stress release from the 2003 Bam earthquake (Mw 6.6) by applying the stress inversion technique to focal mechanisms of 199 aftershocks. There is no evidence of significant surface faulting that can be used to study the faulting pattern of the Bam fault zone. Therefore, we applied two independent methods for identifying the faulting pattern in this zone: the instability criterion based on the analysis of orientations of nodal planes of focal mechanisms with respect to the regional stress, and the Fry method based on the analysis of spatial clus- tering of aftershock foci. The results show that the fault associated with the 2003 Bam earthquake is well oriented for shearing under the present-day regional stress. We identified four sets of faults with a close angular relation to the maximum horizontal com- pression (SHmax) that have been (re)activated. These faults include strike-slip (right lateral and left lateral), thrust, and normal faults that are oriented approximately oblique, perpendicular, and parallel relative to the SHmax, respectively. The direction of the SHmax is N31° E. Based on the results, we propose to apply the instability criterion and the Fry method to seismic data as two valuable and independent techniques in order to constrain the kinematic and active faulting in the area.

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