Fits between observed (vertical bars represent picking uncertainties) and calculated (solid lines) traveltimes of OBH records for (a) model layers 6 and 7 and (b) model layers 8 and 9 using ray tracing and traveltime inversion as described in the text. Layers 6 and 7 represent upper to top of lower crust. Reflections and high-velocity (8.0–8.1 km s⁻¹) refraction arrivals indicate that the interface between model layer 8 and 9 represents the Moho. P-wave velocities are given in km s⁻¹. OBH positions are marked by solid circles. L1–L9 represent layer numbers.