sentences:  suggested that unbending or thermal stresses in the upper 150 km of the slab may the primary cause of the seismicity.For northern IBM, used a refined earthquake relocation scheme to detect a DSZ between depths of 300 km and 400 km, which also has a spacing of 30 35 km between the upper and lower zones.They interpreted data from S to P converted phases and thermal modeling to propose that the DSZ results from transformational faulting of a metastable olivine wedge in the slab.