Config file: better explain when theoretical arrivals are used

Author: claudiodsf

sourcespec/configspec.conf

@@ -103,6 +103,10 @@ trace_units = option('auto', 'disp', 'vel', 'acc', default='auto')
 # TIME WINDOW PARAMETERS --------
 # P and S wave velocity (in km/s) for travel time calculation
 # (if None, the global velocity model 'iasp91' is used)
+# Theoretical P or S arrival times are used when a manual P or S pick is not
+# available, or when the manual P or S pick is too different from the
+# theoretical arrival (see 'p_arrival_tolerance' and 's_arrival_tolerance'
+# below).
 vp_tt = float(min=0, default=None)
 vs_tt = float(min=0, default=None)
 # As an alternative, a directory containing NonLinLoc travel time grids