7.1.12 Location by grid search

Hypocenter can also locate an event by grid search. This can be quite time consuming but illustrates well the problem with local minima. Grid search can only be done for one event at a time using EEV command 'grid'.

Hypocenter is started up and will ask for the grid: Latitude and longitude range and grid spacing. A maximum of 71 points can be used in each direction. The point with the lowest RMS is found and the corresponding location and residual is printed on the screen. It is now optionally possible to plot the contours on the screen. The map coordinates used are as defined in SEISAN.DEF. Note that the grid search is using exactly the same parameters as Hypocenter. This includes all weights and phase types. The depth is fixxed to the depth given in the S-file header line. For more details and an example, see application note epi.pdf in INF.