Imaging the Moho and V(p)/V(s) ratio in the western Superior Archean craton with wide angle reflections

A refraction/wide-angle reflection survey in northwestern Ontario investigated the Archean Superior Province of the Canadian Shield. Images of apparent Moho topography were produced from both the PmP and SmS Moho wide angle reflections. The average Moho depth is 41 km, and average P- and S-wave velocities 6.6 and 3.8 (±0.05) km/s respectively. The Moho dips southward from 39.5 to 42 km depth over roughly 400 km. From ratios of S and P travel times to the Moho, profiles of V_p/V_s were constructed. The average V_p/V_s ratios are 1.74 and 1.76 for on the E-W and N-S lines (Poisson's ratio σ = 0.253 and 0.262 respectively). V_p/V_s profiles show a sharp increase from west to east and a gradual increase from north to south, correlating with the distribution of more felsic continental crust and composite crust in the Western Superior.