The in situ stress field of the Perth Basin, Australia

A total of 17 wells in the Perth Basin were interpreted to have 114 breakou ts covering a combined length of 3.2 km and a mean sigma (Hmax) orientation of 108 degreesN. The inferred mean orientation of sigma (Hmax) in the Pert h Basin is broadly consistent with that in the adjacent basement, Yilgarn B lock. The new data confirm that sigma (Hmax) orientation in the region is c onsistent with other stress indicators, different depths and different geol ogical provinces. The new data also confirm that the orientation of sigma ( Hmax) does not parallel the NNE direction of absolute plate velocity. Anoma lous north-south sigma (Hmax) orientations identified in a number of wells in the Perth Basin can be attributed to local structural effects.