Egill Hauksson, Crustal structure and seismicity distribution adjacent to the Pacific and North American plate boundary in southern California,  J. Geophys. Res., 105, 13,875-13,905, 2000.

This is the Vp/Vs ratio. The initial view is approximately to the north.   The values are linearly interpolated in depth onto a 1 km grid. The figure is plotted with a vertical exaggeration of about 5.