The 1960 Chile earthquake: inversion for slip distribution from surface deformation

difference, and 16 determinations of horizontal strain provide an excellent view of the (quasi-)static source process of the great 1960 Chilean earthquake. These surface deformation data were employed in classical uniform slip fault models as well as more recently developed models that allow spatial variability of slip. The best uniform slip planar (USP) model is 850 km long, 130 km wide, and dips 20". Seventeen metres of fault displacement contributed to a USP moment of 9.4 x ld2 N m. The variable slip planar (VSP) model concentrates slip on a 900 km long, 150 km wide band parallel to the coast. Several peaks of slip with dimensions of 50-100 km appear in this band and are thought to represent major subduction zone asperities. Important fractures of the oceanic lithosphere bound the 1960 rupture and are offered as a potential source of fault segmentation within the Chilean subduction zone. The VSP moment for 1960 earthquake totals 9.5 x N m, about one fifth of the value estimated for the foreshock-mainshock sequence from seismic methods. Except for areas out to sea, geodetic resolution on the fault is fairly uniform. Thus, it is unlikely that slip missed by the network could increase the VSP moment much beyond 1.8