Changed the model input file (unified_SLBM.txt) in two ways: (a) the constraint that gradients cannot be negative has been removed from the model input file and is now being imposed in the code. There can now be substantial negative gradients in the input file. (b) There are now 9 layers in the model where there were previously only 8. The 9 layers are:
The change is that there are now two versions of the MIDDLE_CRUST. MIDDLE_CRUST_N is the same as the previous MIDDLE_CRUST. MIDDLE_CRUST_G is a new layer that has the same depth as MIDDLE_CRUST_N but with P wave velocity 6.2 km/sec and S wave velocity of 3.5 km/sec. There are if statements in the code that select MIDDLE_CRUST_N for phases Pn and Sn and select MIDDLE_CRUST_G for Pg and Lg.
Implemented the LANL modification to the Zhao method that calculates travel times for mantle events.