notes

su 的源代码库

There is a new model for this example - called syncline.
It's ok to have negative x-coordinates in the model, as is the case
here.  Also, in the geometry file a station can be refenced to a negative
x-coordinate (see file geometry5).  The integers describing the stations should
always be positive though, in other words, the minimum station number is 1.

It is generally a good idea to stay away from the very edges of the model.
So, if you must have a receiver at x = 0., then start the model at x < 0.