Stress inversion from focal mechanism solution of Bam earthquake aftershocks (Iran, 2003)

摘要

Conventional inversion methods for in situ stress determination from fault slip data obtained from focal mechanism solutions, define the optimum stress as the maximum point of the object function. In this research, object functions are computed for a mesh of principal stress directions and stress ratios for fault slip data obtained from fault plane solution for aftershocks of Bam Earthquake in Iran, in 2003. Several stress state possibilities are found with close values of object function. To overcome this problem, a method is introduced in which the stress states with less than 5 percent difference with maximum value of the object function are selected and categorized according to their stress ratio. Significant stress states for each category are identified as high concentrated loci of principal stresses. The results obtained in this method are compared with results obtained from multiple inverse method which shows a close agreement.