Yesterday we were running along the extremely steep onshore escarpment(the one along the fault, which is just offshore). OK, we, being on a ship, were cruising along just offshore. The multibeam bathymetry display gives the slope of the seafloor on a display in real time and it was what looked to be 30 deg and more for a couple of hours. For offshore southern California, about 10 deg is steep. Maybe San Clemente Island escarpment is steeper than 10 deg; could be much more?

The steepness of the sea bottom makes the reflections from the chirp seismic come from the side, so the travel time is not what would be the case beneath the ship. The multibeam bathymetry by some magic black box (as far as I am concerned) directs beams of sound and can also tell which direction the reflections are coming back from, so the seafloor image is in the correct place. So, you get a rather severe mismatch between the 2 types of data which threw me for a loop yesterday.

OK, back to work.
Chris