The Mw 8.3 Illapel earthquake of Spetember 16, 2015, ruptured the Nazca-South America subduction zone for ~200 km along-strike distance. This rupture region is proximal to, but not contiguous with, the rupture regions of the 2010 Maule earthquake, which was extensively studied during the IMAD seismologic and geodetic deployments, and the 1985 Valpariaso, Chile, earthquake. We will deploy 32 seismometers in total to make local and regional recordings of aftershocks of the Illapel earthquake, for at least 5 months, in order to determine details of the main shock rupture extent and aftershock locations and mechanisms, to determine seismic velocity structure of the rupture region and overlying South America crust, and to estimate seismic attenuation and anisotropic structure of this portion of the Nazca-South America plate boundary. We will also attempt to characterize the apparent gap in seismicity between the 2010 M 8.8 and 1985 M>8 earthquake rupture regions (which lie immediately to the south of the gap) and the aftershock activity of the Illapel rupture zone.