DESCRIPTION
     bw_relp is an earthquake location algorithm designed specif-
     ically  for  locating earthquakes at local and regional dis-
     tances using phase onset times and onset  azimuths  recorded
     by  relatively  sparse  network of three-component broadband
     stations.  An adaptive, migrating grid search  algorithm  is
     used  to  locate  the hypocenter.  The grid migrates and the
     mesh size shrinks as it homes in on the  global  minimum  in
     the  L**n  misfit parameter space.  The value of "n" in L**n
     is the norm (n = 2 is standard least-squares,  for  example)
     and  n  can  be  any  positive  real  number  (0 < n < Inf).
     bw_relp only requires forward model  calculations,  thus  it
     differs  from  most  commonly used earthquake location algo-
     rithms in that NO derivatives are  required.   This  greatly
     simplifies  the required computations, particularly for com-
     plex 2-D and 3-D velocity and azimuthal models.  The current
     implementation  of  bw_relp  uses  a  linear gradient over a
     halfspace velocity model  and  a  halfspace  azimuth  model.
     bw_relp  is  designed so that the user can easily supply the
     appropriate subroutines for calculating  phase  onset  times
     and azimuths using more complex models.