The orientation of the stress axes within sinking slabs

In principle it should be possible to obtain information about the orientation of the stress axes within a sinking slab from the first motions observed at a single suitably placed seismic station. This idea is tested on the Tonga-Fiji-Kermadec Arc, using the short-period vertical seismograms from Port Moresby, and the orientations so obtained agree with those derived from fault plane solutions.