This routine for calculating travel times for
 specific distances uses a set of precalculated
 tau-p tables for the iasp91 model stored as
  iasp91.hed, iasp91.tbl
 
 The source depth has to be specified and also
 the phase codes or keywords for the required branches
 ALL will give all available branches
 P  gives P-up,P,Pdiff,PKP, and PKiKP
 P+ gives P-up,P,Pdiff,PKP,PKiKP,PcP,pP,pPdiff,pPKP,
          pPKiKP,sP,sPdiff,sPKP, and sPKiKP
 S  gives S-up,S,Sdiff, and SKS
 S+ gives S-up,S,Sdiff,SKS,sS,sSdiff,sSKS,pS,pSdiff,
          and pSKS 
 basic gives P+ and S+ as well as 
          ScP, SKP, PKKP, SKKP, PP, and PKPPKP 
 
 or give a generic phase name
 
 You will have to enter a distance,
 if this is negative a new depth is calculated
 TO EXIT: give negative depth
 
 Enter desired branch control list at the prompts:
** Brnset:  the following phases have been selected -
              1  P       
              2  PKP       P       
              3  PKiKP   
Source depth (km):   
Enter delta:     delta    # code       time(s)    (min s)    dT/dD     dT/dh      d2T/dD2

   1.01    1  Pg          19.30   0  19.30    19.1192   1.11E-02  -5.18E-03
           2  Pb          19.97   0  19.97    17.0531  -7.86E-02  -6.30E-01
           3  Pn          20.86   0  20.86    13.7542  -1.20E-01  -8.05E-01
           4  PKiKP      993.89  16  33.89     0.0225  -1.72E-01   1.36E-02
 
Enter delta:  Source depth (km):