ing within the downgoing plate, and appears to be assoeiated with segmentation of the subdueting plate produeed by forees related to the subduetion of the Louisville Ridge. To analyze fault plane heterogeneities in the northern Solomon Islands subdue- tion segment and their association with rupture eharaeteristics in general and the existenee of earthquake doublets in partieular, Xv and SCHWARTZ study in detail two sets of doublets, from 1974 and 1975, and then reloeate 85 underthrusting events in the area. The authors find that few smaller magnitude events overlap asperity regions, and that the majority of small magnitude underthrusting earth- quak es oeeupy a segment that has never experieneed a magnitude greater than 7.0 earthquake in the historie times. It will be of great value to soeiety when seismologists and geophysieists are able to monitor and prediet the pattern of geophysieal phenomena assoeiated with subduetion; this issue presents a modest step towards this goal. PAGEOPH, Vol. 140, No. 2 (1993) 0033 ~4553;93;020 183 ~ 28$1.50 + 0.20;0 (c) 1993 Birkhauser Verlag, Basel Slip Partitioning along Major Convergent Plate Boundaries 2 GUANG YU,l STEVEN G. WESNOUSKY,l and GORAN EKSTROM Abstract-Along plate boundaries characterized by oblique convergence, earthquake slip vectors are commonly rotated toward the normal of the trench with respect to predicted plate motion vectors. Consequently, relative plate motion along such convergent margins must be partitioned between displacements along the thrust plate interface and deformation within the foreare and back-are regions.